Journal articles: 'Strain maintenance'

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Oskam, Linda, Gerard Venema, and Sierd Bron. "Plasmid maintenance inBacillus stearothermophilusis strain-dependent." FEMS Microbiology Letters 93, no. 3 (June 1992): 203–8. http://dx.doi.org/10.1111/j.1574-6968.1992.tb05098.x.

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Werren, J. H., and D. W. Loehlin. "Strain Maintenance of Nasonia vitripennis (Parasitoid Wasp)." Cold Spring Harbor Protocols 2009, no. 10 (October 1, 2009): pdb.prot5307. http://dx.doi.org/10.1101/pdb.prot5307.

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Jia, Honglei, Tianyou Chen, Shengwei Zhang, Xumin Sun, and Hongfang Yuan. "Effects of pressure maintenance and strain maintenance during compression on subsequent dimensional stability and density after relaxation of blocks of chopped corn straw." BioResources 15, no. 2 (April 1, 2020): 3717–36. http://dx.doi.org/10.15376/biores.15.2.3717-3736.

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Chopped corn straw is a viscoelastic material that can rebound after compression. Pressure maintenance and strain maintenance are two key processes that enhance the dimensional stability of post-compression straw blocks. To study the effects of stabilization processes on the dimensions of post-compression straw blocks, the authors comparatively explored the relationships of strain and stress with time during constant-speed compression (CC), constant-speed compression followed by strain maintenance (CCS), constant-speed compression followed by pressure maintenance (CCP), and constant-speed compression, pressure maintenance followed by strain maintenance (CCPS), and uncovered the reasons for these relationships. The Burgers constitutive model fit well to the data during the pressure maintenance stage (R2>0.990), and the effects of pressure maintenance on strain and dimensional stability of post-compression straw blocks were investigated. The Wiechert model B (R2>0.990) was the constitutive model that best represented the strain maintenance stage. Additionally, the effects of strain maintenance during CCS and CCPS on relaxation rate and dimensional stability of post-compression straw were compared. The relaxation density of post-compression straw blocks was compared among different stabilization processes. The relaxation density of post-compression straw blocks was the largest after CCPS, followed by CCS and CCP.

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Colijn, Caroline, Ted Cohen, and Megan Murray. "Latent Coinfection and the Maintenance of Strain Diversity." Bulletin of Mathematical Biology 71, no. 1 (December 10, 2008): 247–63. http://dx.doi.org/10.1007/s11538-008-9361-y.

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Stosic, Zorica, Milan Mitric, Ferenc Kiskarolj, Dusan Misic, and Ruzica Asanin. "Investigations of sensitivity to antibiotics of salmonella strain species originating from poultry from different epizootiological areas." Veterinarski glasnik 60, no. 1-2 (2006): 89–98. http://dx.doi.org/10.2298/vetgl0602089s.

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A total of 1666 samples were examined, of which 512 samples of parenchymatous organs of dead or deliberately sacrtificed animals, 60 samples of non-hatched fertilized eggs, 202 samples of feces, 652 samples of cloacal smears, 221 samples of smears from walls of maintenance objects, incubator stations, and transport vehicles, 19 samples of beddings and shavings. The samples originated from poultry farms and which were taken to a laboratory immediately on sampling and sown the same day. A total of 104 strains of Salmonella were isolated: 94 strains from samples of parenchymatous organs of dead chicks, 1 strain from non-hatched eggs, 3 strains from feces samples, 1 strain from samples of cloacal smears, 4 strains from samples of surface smears of maintenance objects and transport vehicles, and 1 strain from samples of beddings and shavings. Serological typization established the presence of the following serovarieties: Salmonella Enteritidis 79 strains, Salmonella Hartford 17 strains, Salmonella Typohimurium 5 strains, Salmonella Mbandaka 2 strains, and Salmonella Glostrup 1 strain. We examined the sensitivity of Salmonella strains to ampicillin, amoxicillin, gentamycin, streptomycin, neomycin, enrofloxacine, norfloxacine, flumequin, erythromycin, lincospectin, colistin, fluorphenicol, and a combination of sulphamethoxasole and trimethoprim. In S. Enteritidis strains, no resistence was established to colistin, fluorphenicol and sulphamethoxasole+trimethoprim, in fact, the sensitivity to these antibiotics and chemotherapeutics was 100%. Prevalence resitence of 0.96%, in only one strain, was established for enrofloxacine. A high prevalence resistence of 33.6% was established for neomycin, while prevalence resistence of 3.86% was established for the related aminoglycozide antibiotic gentamycin. The highest prevalence resistance in S.Hartford strains was established for erythromycin, 15.38%, and streptomycin, 7.6%. Resistence of S. Tyohimurium was established for flumequin and erythromycin in 1.9% strains. No resistance to antibiotics was established in the strains S. Mbandaka and S. Glostrup.

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DerdÃ¯Â¿Â½kovÃ¯Â¿Â½, MarkÃ¯Â¿Â½ta, VladimÃ¯Â¿Â½r DudiÃ¯Â¿Â½Ã¯Â¿Â½k, Brandon Brei, John S. Brownstein, Ira Schwartz, and Durland Fish. "Interaction and Transmission of Two Borrelia burgdorferi Sensu Stricto Strains in a Tick-Rodent Maintenance System." Applied and Environmental Microbiology 70, no. 11 (November 2004): 6783–88. http://dx.doi.org/10.1128/aem.70.11.6783-6788.2004.

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ABSTRACT In the northeastern United States, the Lyme disease agent, Borrelia burgdorferi sensu stricto, is maintained by enzoonotic transmission, cycling between white-footed mice (Peromyscus leucopus) and black-legged ticks (Ixodes scapularis). B. burgdorferi sensu stricto is genetically variable and has been divided into three major genotypes based on 16S-23S ribosomal DNA spacer (RST) analysis. To better understand how genetic differences in B. burgdorferi sensu stricto may influence transmission dynamics in nature, we investigated the interaction between an RST1 and an RST3 strain in a laboratory system with P. leucopus mice and I. scapularis ticks. Two groups of mice were infected with either BL206 (RST1) or B348 (RST3). Two weeks later, experimental mice were challenged with the opposite strain, while control mice were challenged with the same strain as that used for the primary infection. The transmission of BL206 and B348 from infected mice was then determined by xenodiagnosis with uninfected larval ticks at weekly intervals for 42 days. Mice in both experimental groups were permissive for infection with the second strain and were able to transmit both strains to the xenodiagnostic ticks. However, the overall transmission efficiencies of BL206 and B348 were significantly different. BL206 was more efficiently transmitted than B348 to xenodiagnostic ticks. Significantly fewer double infections than expected were detected in xenodiagnostic ticks. The results suggest that some B. burgdorferi sensu stricto strains, such as BL206, may be preferentially maintained in transmission cycles between ticks and white-footed mice. Other strains, such as B348, may be more effectively maintained in different tick-vertebrate transmission cycles.

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Bertuch, Alison A., and Victoria Lundblad. "EXO1 Contributes to Telomere Maintenance in Both Telomerase-Proficient and Telomerase-Deficient Saccharomyces cerevisiae." Genetics 166, no. 4 (April 1, 2004): 1651–59. http://dx.doi.org/10.1093/genetics/166.4.1651.

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Abstract Previous work in budding yeast has indicated that telomeres are protected, at least in part, from the action of Exo1, which degrades the C-rich strand of partially uncapped telomeres. To explore this further, we examined the consequences of Exo1-mediated activity in strains that lacked Ku, telomerase, or both. Loss of Exo1 partially rescued the telomere length defect in a yku80Δ strain, demonstrating that exonuclease action can directly contribute to telomere shortening. The rapid loss of inviability displayed by a yku80Δ est2Δ strain was also partially alleviated by an exo1Δ mutation, further supporting the proposal that Exo1 is one target of the activities that normally protect wild-type telomeres. Conversely, however, Exo1 activity was also capable of enhancing telomere function and consequently cell proliferation, by contributing to a telomerase-independent pathway for telomere maintenance. The recovery of recombination-dependent survivors that arose in a yku80Δ est2Δ strain was partially dependent on Exo1 activity. Furthermore, the types of recombination events that facilitate telomerase-independent survival were influenced by Exo1 activity, in both est2Δ and yku80Δ est2Δ strains. These data demonstrate that Exo1 can make either positive or negative contributions to telomere function and cell viability, depending on whether telomerase or recombination is utilized to maintain telomere function.

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Seppälä, Otto, Anssi Karvonen, E. Tellervo Valtonen, and Jukka Jokela. "Interactions among co-infecting parasite species: a mechanism maintaining genetic variation in parasites?" Proceedings of the Royal Society B: Biological Sciences 276, no. 1657 (October 28, 2008): 691–97. http://dx.doi.org/10.1098/rspb.2008.1229.

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Individuals of free-living organisms are often infected simultaneously by a community of parasites. If the co-infecting parasites interact, then this can add significantly to the diversity of host genotype×parasite genotype interactions. However, interactions between parasite species are usually not examined considering potential variation in interactions between different strain combinations of co-infecting parasites. Here, we examined the importance of interactions between strains of fish eye flukes Diplostomum spathaceum and Diplostomum gasterostei on their infectivity in naive fish hosts. We assessed the infection success of strains of both species in single-strain exposures and in co-exposures with a random strain of the other species. Parasite infection success did not consistently increase or decrease in the co-exposure treatment, but depended on the combinations of co-infecting parasite strains. This disrupted the relative infectivity of D. spathaceum strains observed in single-strain exposures. The infection success of D. gasterostei strains was independent of exposure type. These results suggest that interactions among parasite species may be strain specific and potentially promote maintenance of genetic polymorphism in parasite populations.

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Morris, Andrew, John P. Dear, Miltiadis Kourmpetis, Chris Maharaj, Amit Puri, and Alexander D. Fergusson. "Monitoring Creep Strain in Power Station Engineering Plant." Applied Mechanics and Materials 7-8 (August 2007): 31–36. http://dx.doi.org/10.4028/www.scientific.net/amm.7-8.31.

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Cost effective and reliable operation of a power station plant and achieving low carbon dioxide emissions can be very dependent on maintenance activities. Planning maintenance to minimise the down-time of the plant is a key cost factor. It is important to have the latest data as to the age and state of the components and parts at the time of plant shut down. Indeed, deciding on the best time to shut down the plant for maintenance can depend upon trends in these data. For steam pipes, the required ageing information is the creep strain rate. These creep strain data obtained at shut down provide key information as to the needed replacement of pipes to maintain reliable plant operation. This paper presents the E.ON UK ARCMAC creep strain measurement systems that are being further developed by Imperial College London with the use of DIC and other techniques.

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Kudva, Indira T., Julian Trachsel, Erika N. Biernbaum, and Thomas Casey. "Novel reusable animal model for comparative evaluation of in vivo growth and protein-expression of Escherichia coli O157 strains in the bovine rumen." PLOS ONE 17, no. 5 (May 26, 2022): e0268645. http://dx.doi.org/10.1371/journal.pone.0268645.

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Previously, we had demonstrated that Escherichia coli O157:H7 (O157) strain 86–24 expresses proteins involved in survival rather than virulence in vitro in rumen fluid from dairy cattle limit fed a maintenance diet. Here, we verified if this observation would be true for different O157 strains grown in vitro in rumen fluid from, and in vivo in the rumen of, animals on contrasting maintenance (high fiber) and lactation (high energy-protein) diets usually limit fed to dairy cattle. For the in vivo studies, an economical, novel, reusable and non-terminal rumen-fistulated animal model permitting simultaneous evaluation of multiple bacterial strains in the bovine rumen was developed. All experiments were conducted in duplicate using different animals to account for host-related variations. The O157 strains included, 86–24, EDL933 and the super shed SS-17. E. coli NalR (#5735), derived from a bovine intestinal commensal E. coli, was included as a control. As expected, diet influenced ruminal pH and volatile fatty acid (VFA) composition. The pH ranged from 6.2–7.0 and total VFA concentrations from 109–141 μM/ml, in animals fed the maintenance diet. In comparison, animals fed the lactation diet had a ruminal pH ranging between 5.18–6.0, and total VFA of 125–219 μM/ml. Strain dependent differences in O157 recovery from the rumen fluid of cattle fed either diet was observed, both in vitro and in vivo, with O157 strains 86–24 and EDL933 demonstrating similar survival patterns. Analysis of the O157 proteomes expressed in the rumen fluid/rumen verified previous observations of adaptive responses. Any difference in the adaptive response was mainly influenced by the animal’s diet and growth conditions (in vitro and in vivo) and not the O157 strain. These new insights into the O157 responses could help formulate modalities to control O157 across strains in cattle at all stages of husbandry.

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Matti, Katrin, Beatrice Bernardi, Silvia Brezina, Heike Semmler, Christian von Wallbrunn, Doris Rauhut, and Jürgen Wendland. "Characterization of Old Wine Yeasts Kept for Decades under a Zero-Emission Maintenance Regime." Fermentation 6, no. 1 (January 11, 2020): 9. http://dx.doi.org/10.3390/fermentation6010009.

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All laboratories dealing with microbes have to develop a strain maintenance regime. While lyophilization based on freeze-drying may be feasible for large stock centers, laboratories around the world rely on cryopreservation and freezing of stocks at −80 °C. Keeping stocks at these low temperatures requires investments of several thousand kW/h per year. We have kept yeast stocks for several decades at room temperature on agar slants in glass reagent tubes covered with vaspar and sealed with cotton plugs. They were part of the Geisenheim Yeast Breeding Center stock collection that was started in the 19th century, well before −80 °C refrigeration technology was invented. Of these stocks, 60 tubes were analyzed and around one-third of them could be regrown. The strains were typed by sequencing of rDNA PCR fragments. Based on BlastN analyses, twelve of the strains could be assigned to Saccharomyces cerevisiae, two to S. kudriavzevii, and the others to Meyerozyma and Candida. The strains were used in white wine fermentations and compared to standard wine yeasts Uvaferm/GHM (Geisenheim) and Lalvin EC1118. Even with added nitrogen, the strains exhibited diverse fermentation curves. Post-fermentation aroma analyses and the determination of residual sugar and organic acid concentrations indicated that some strains harbor interesting flavor characteristics, surpassing current standard yeast strains. Thus, old strain collections bear treasures for direct use either in wine fermentations or for incorporation in yeast breeding programs aimed at improving modern wine yeasts. Furthermore, this provides evidence that low-cost/long-term culture maintenance at zero-emission levels is feasible.

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Frost, Harold M. "Strain and other mechanical influences on bone strength and maintenance." Current Opinion in Orthopaedics 8, no. 5 (October 1997): 60–70. http://dx.doi.org/10.1097/00001433-199710000-00010.

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Wright, Paul H., and Paula J. Conneran. "Measuring Strain in Personal Relationships: A Refinement." Psychological Reports 64, no. 3_suppl (June 1989): 1321–22. http://dx.doi.org/10.2466/pr0.1989.64.3c.1321.

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A scale for measuring difficulty in maintenance of relationships appeared to assess strain associated with characteristics of one's partner. A new scale takes into account situational as well as personal sources of strain.

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Zymelka, Daniel, Kazuyoshi Togashi, and Takeshi Kobayashi. "Concentric Array of Printed Strain Sensors for Structural Health Monitoring." Sensors 20, no. 7 (April 2, 2020): 1997. http://dx.doi.org/10.3390/s20071997.

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Civil infrastructure is expanding around the world. The ever-growing trend toward urbanization drives the demand for new investments. However, the new constructions and gradual deterioration of those already existing, especially bridges, give rise to concerns about their proper maintenance. To improve safety and drive down maintenance costs of civil structures, there is a need for inexpensive sensing systems capable of reliable and automated monitoring. In this study, we present a new concept of thin-film strain sensors arranged in an array with a concentric layout that is incorporated into a flexible substrate sheet. The designed sensor array is intended to analyze strains in the proximity of round holes made at the crack tips, found in the investigated construction elements of civil structures. In this study, the performance of the sensor array was demonstrated using measurements taken on a highway bridge in one of the largest cities in Japan. We show that it can measure local strain distribution and indicate a region with risk for crack formation. The demonstrated results show new area of potential applications for the printed strain sensors in monitoring civil structures.

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Easter, Carla L., Helmut Schwab, and Donald R. Helinski. "Role of the parCBA Operon of the Broad-Host-Range Plasmid RK2 in Stable Plasmid Maintenance." Journal of Bacteriology 180, no. 22 (November 15, 1998): 6023–30. http://dx.doi.org/10.1128/jb.180.22.6023-6030.1998.

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ABSTRACT The par region of the stably maintained broad-host-range plasmid RK2 is organized as two divergent operons,parCBA and parDE, and a cis-acting site. parDE encodes a postsegregational killing system, andparCBA encodes a resolvase (ParA), a nuclease (ParB), and a protein of unknown function (ParC). The present study was undertaken to further delineate the role of the parCBA region in the stable maintenance of RK2 by first introducing precise deletions in the three genes and then assessing the abilities of the different constructs to stabilize RK2 in three strains of Escherichia coli and two strains of Pseudomonas aeruginosa. The intact parCBA operon was effective in stabilizing a conjugation-defective RK2 derivative in E. coli MC1061K and RR1 but was relatively ineffective in E. coli MV10Δlac. In the two strains in which the parCBA operon was effective, deletions in parB, parC, or bothparB and parC caused an approximately twofold reduction in the stabilizing ability of the operon, while a deletion in the parA gene resulted in a much greater loss ofparCBA activity. For P. aeruginosaPAO1161Rifr, the parCBA operon provided little if any plasmid stability, but for P. aeruginosaPAC452Rifr, the RK2 plasmid was stabilized to a substantial extent by parCBA. With this latter strain, parAand res alone were sufficient for stabilization. Thecer resolvase system of plasmid ColE1 and theloxP/Cre system of plasmid P1 were tested in comparison with the parCBA operon. We found that, not unlike what was previously observed with MC1061K, cer failed to stabilize the RK2 plasmid with par deletions in strain MV10Δlac, but this multimer resolution system was effective in stabilizing the plasmid in strain RR1. The loxP/Cre system, on the other hand, was very effective in stabilizing the plasmid in all threeE. coli strains. These observations indicate that theparA gene, along with its res site, exhibits a significant level of plasmid stabilization in the absence of theparC and parB genes but that in at least oneE. coli strain, all three genes are required for maximum stabilization. It cannot be determined from these results whether or not the stabilization effects seen with parCBA or thecer and loxP/Cre systems are strictly due to a reduction in the level of RK2 dimers and an increase in the number of plasmid monomer units or if these systems play a role in a more complex process of plasmid stabilization that requires as an essential step the resolution of plasmid dimers.

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Wang, Hen-Wei, Chun-Hui Chung, Tsung-Yong Ma, and Hin-chung Wong. "Roles of Alkyl Hydroperoxide Reductase Subunit C (AhpC) in Viable but Nonculturable Vibrio parahaemolyticus." Applied and Environmental Microbiology 79, no. 12 (April 5, 2013): 3734–43. http://dx.doi.org/10.1128/aem.00560-13.

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ABSTRACTAlkyl hydroperoxide reductase subunit C (AhpC) is the catalytic subunit responsible for the detoxification of reactive oxygen species that form in bacterial cells or are derived from the host; thus, AhpC facilitates the survival of pathogenic bacteria under environmental stresses or during infection. This study investigates the role of AhpC in the induction and maintenance of a viable but nonculturable (VBNC) state inVibrio parahaemolyticus. In this investigation,ahpC1(VPA1683) andahpC2(VP0580) were identified in chromosomes II and I of this pathogen, respectively. Mutants with deletions of these twoahpCgenes and their complementary strains were constructed from the parent strain KX-V231. The growth of these strains was monitored on tryptic soy agar–3% NaCl in the presence of the extrinsic peroxides H2O2andtert-butyl hydroperoxide (t-BOOH) at different incubation temperatures. The results revealed that bothahpCgenes were protective againstt-BOOH, whileahpC1was protective against H2O2. The protective function ofahpC2at 4°C was higher than that ofahpC1. The times required to induce the VBNC state (4.7 weeks) at 4°C in a modified Morita mineral salt solution with 0.5% NaCl and then to maintain the VBNC state (4.7 weeks) in anahpC2mutant and anahpC1 ahpC2double mutant were significantly shorter than those for the parent strain (for induction, 6.2 weeks; for maintenance, 7.8 weeks) and theahpC1mutant (for induction, 6.0 weeks; for maintenance, 8.0 weeks) (P< 0.03). Complementation with anahpC2gene reversed the effects of theahpC2mutation in shortening the times for induction and maintenance of the VBNC state. This investigation identified the different functions of the twoahpCgenes and confirmed the particular role ofahpC2in the VBNC state ofV. parahaemolyticus.

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Deleault, Andrea M., Nathan R. Deleault, Brent T. Harris, Judy R. Rees, and Surachai Supattapone. "The effects of prion protein proteolysis and disaggregation on the strain properties of hamster scrapie." Journal of General Virology 89, no. 10 (October 1, 2008): 2642–50. http://dx.doi.org/10.1099/vir.0.2008/002303-0.

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Native mammalian prions exist in self-propagating strains that exhibit distinctive clinical, pathological and biochemical characteristics. Prion strain diversity is associated with variations in PrPSc conformation, but it remains unknown precisely which physical properties of the PrPSc molecules are required to encipher mammalian prion strain phenotypes. In this study, we subjected prion-infected brain homogenates derived from three different hamster scrapie strains to either (i) proteinase K digestion or (ii) sonication, and inoculated the modified samples into normal hamsters. The results show that the strain-specific clinical features and neuropathological profiles of inoculated animals were not affected by either treatment. Similarly, the strain-dependent biochemical characteristics of the PrPSc molecules (including electrophoretic mobility, glycoform composition, conformational stability and susceptibility to protease digestion) in infected animals were unaffected by either proteolysis or sonication of the original inocula. These results indicate that the infectious strain properties of native prions do not appear to be altered by PrPSc disaggregation, and that maintenance of such properties does not require the N-domain (approximately residues 23–90) of the protease-resistant PrPSc molecules or protease-sensitive PrPSc molecules.

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Khachatryan, Artashes R., Thomas E. Besser, and Douglas R. Call. "The Streptomycin-Sulfadiazine-Tetracycline Antimicrobial Resistance Element of Calf-Adapted Escherichia coli Is Widely Distributed among Isolates from Washington State Cattle." Applied and Environmental Microbiology 74, no. 2 (November 26, 2007): 391–95. http://dx.doi.org/10.1128/aem.01534-07.

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ABSTRACT Association of specific antimicrobial resistance patterns with unrelated selective traits has long been implicated in the maintenance of antimicrobial resistance in a population. Previously we demonstrated that Escherichia coli strains with a specific resistance pattern (resistant to streptomycin, sulfadiazine, and tetracycline [SSuT]) have a selective advantage in dairy calf intestinal environments and in the presence of a milk supplement commonly fed to the calves. In the present study we identified the sequence of the genetic element that confers the SSuT phenotype and show that this element is present in a genetically diverse group of E. coli isolates, as assessed by macrorestriction digestion and pulsed-field gel electrophoresis. This element was also found in E. coli isolates from 18 different cattle farms in Washington State. Using in vitro competition experiments we further demonstrated that SSuT strains from 17 of 18 farms were able to outcompete pansusceptible strains. In a separate set of experiments, we were able to transfer the antimicrobial resistance phenotype by electroporation to a laboratory strain of E. coli (DH10B), making that new strain more competitive during in vitro competition with the parental DH10B strain. These data indicate that a relatively large genetic element conferring the SSuT phenotype is widely distributed in E. coli from cattle in Washington State. Furthermore, our results indicate that this element is responsible for maintenance of these traits owing to linkage to genetic traits that confer a selective advantage in the intestinal lumens of dairy calves.

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Tay, S. T. L., H. L. Jiang, and J. H. Tay. "Functional analysis of microbial community in phenol-degrading aerobic granules cultivated in SBR." Water Science and Technology 50, no. 10 (November 1, 2004): 229–34. http://dx.doi.org/10.2166/wst.2004.0651.

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Phenol-degrading aerobic granules were cultivated in a sequencing batch reactor with an influent phenol concentration of 500 mg l−1. Eight strains were isolated from aerobic granules to characterize the functional redundancy of the microbial community in the granules. The specific oxygen utilization kinetics show the eight strains possessed different phenol-degrading activities, with half-saturation constants (Ks) ranging from 0.4 to 70.5 mg phenol l−1. Two isolates belonging to dominant populations expressed differing functions. The first strain was linked to the function of phenol degradation as this strain has the highest phenol-degrading ability among all isolates, while the second strain was linked to the maintenance of the granule structure because of its strong self-flocculation activity. This study could be used to exploit the granule-based system for treating high-strength wastewaters.

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Rodrigues, Louise, Natalia Freitas, Bhaskar V. Kallakury, Stephan Menne, and Severin O. Gudima. "Superinfection with Woodchuck Hepatitis Virus Strain WHVNY of Livers Chronically Infected with Strain WHV7." Journal of Virology 89, no. 1 (October 15, 2014): 384–405. http://dx.doi.org/10.1128/jvi.02361-14.

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ABSTRACTThe determinants of the maintenance of chronic hepadnaviral infection are yet to be fully understood. A long-standing unresolved argument in the hepatitis B virus (HBV) research field suggests that during chronic hepadnaviral infection, cell-to-cell spread of hepadnavirus is at least very inefficient (if it occurs at all), virus superinfection is an unlikely event, and chronic hepadnavirus infection can be maintained exclusively via division of infected hepatocytes in the absence of virus spread. Superinfection exclusion was previously shown for duck HBV, but it was not demonstrated for HBV or HBV-related woodchuck hepatitis virus (WHV). Three woodchucks, which were chronically infected with the strain WHV7 and already developed WHV-induced hepatocellular carcinomas (HCCs), were superinfected with another WHV strain, WHVNY. Six weeks after the superinfection, the woodchucks were sacrificed and tissues of the livers and HCCs were examined. The WHVNY superinfection was demonstrated by using WHV strain-specific PCR assays and (i) finding WHVNY relaxed circular DNA in the serum samples collected from all superinfected animals during weeks one through six after the superinfection, (ii) detecting replication-derived WHVNY RNA in the tissue samples of the livers and HCCs collected from three superinfected woodchucks, and (iii) finding WHVNY DNA replication intermediates in tissues harvested after the superinfection. The results are consistent with the occurrence of continuous but inefficient hepadnavirus cell-to-cell spread and superinfection during chronic infection and suggest that the replication space occupied by the superinfecting hepadnavirus in chronically infected livers is limited. The findings are discussed in the context of the mechanism of chronic hepadnavirus infection.IMPORTANCEThis study aimed to better understand the determinants of the maintenance of chronic hepadnavirus infection. The generated data suggest that in the livers chronically infected with woodchuck hepatitis virus, (i) hepadnavirus superinfection and cell-to-cell spread likely continue to occur and (ii) the virus spread is apparently inefficient, which is consistent with the interpretation that a limited number of cells in the livers facilitates the spread of hepadnavirus. The limitations of the cell-to-cell virus spread most likely are mediated at the level of the cells and do not reflect the properties of the virus. Our results further advance the understanding of the mechanism of chronic hepadnavirus infection. The significance of the continuous but limited hepadnavirus spread and superinfection for the maintenance of the chronic state of infection should be further evaluated in follow-up studies in order to determine whether blocking the virus spread would facilitate the suppression of chronic hepadnavirus infection.

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SUZUKI, Tsuneyuki, Nobuko MORITA, Yoshio OHTA, and Tomoteru HIGASHIZAWA. "Maintenance of SHR Substrains and Development of a New Rat Strain." Proceedings of The Japanese Association of Animal Models for Human Diseases 3 (1987): 13–19. http://dx.doi.org/10.1538/expanim1985.3.13.

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Gupta, Sunetra, Martin C. J. Maiden, Ian M. Feavers, Sean Nee, Robert M. May, and Roy M. Anderson. "The maintenance of strain structure in populations of recombining infectious agents." Nature Medicine 2, no. 4 (April 1996): 437–42. http://dx.doi.org/10.1038/nm0496-437.

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Ruimerman, R., P. Hilbers, B. van Rietbergen, and R. Huiskes. "A theoretical framework for strain-related trabecular bone maintenance and adaptation." Journal of Biomechanics 38, no. 4 (April 2005): 931–41. http://dx.doi.org/10.1016/j.jbiomech.2004.03.037.

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Videau, Patrick, and Loralyn M. Cozy. "Anabaena sp. strain PCC 7120: Laboratory Maintenance, Cultivation, and Heterocyst Induction." Current Protocols in Microbiology 52, no. 1 (November 6, 2018): e71. http://dx.doi.org/10.1002/cpmc.71.

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Del Giudice, Francesco, Gian Maria Busetto, Martin S. Gross, Martina Maggi, Alessandro Sciarra, Stefano Salciccia, Matteo Ferro, et al. "Efficacy of three BCG strains (Connaught, TICE and RIVM) with or without secondary resection (re-TUR) for intermediate/high-risk non-muscle-invasive bladder cancers: results from a retrospective single-institution cohort analysis." Journal of Cancer Research and Clinical Oncology 147, no. 10 (March 6, 2021): 3073–80. http://dx.doi.org/10.1007/s00432-021-03571-0.

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Abstract Purpose (I) To evaluate the clinical efficacy of three different BCG strains in patients with intermediate-/high-risk non-muscle-invasive bladder cancer (NMIBC). (II) To determine the importance of performing routine secondary resection (re-TUR) in the setting of BCG maintenance protocol for the three strains. Methods NMIBCs who received an adjuvant induction followed by a maintenance schedule of intravesical immunotherapy with BCG Connaught, TICE and RIVM. Only BCG-naïve and those treated with the same strain over the course of follow-up were included. Cox proportional hazards model was developed according to prognostic factors by the Spanish Urological Oncology Group (CUETO) as well as by adjusting for the implementation of re-TUR. Results n = 422 Ta-T1 patients (Connaught, n = 146; TICE, n = 112 and RIVM, n = 164) with a median (IQR) follow-up of 72 (60–85) were reviewed. Re-TUR was associated with improved recurrence and progression outcomes (HRRFS: 0.63; 95% CI 0.46–0.86; HRPFS: 0.55; 95% CI 0.31–0.86). Adjusting for CUETO risk factors and re-TUR, BGC TICE and RIVM provided longer RFS compared to Connaught (HRTICE: 0.58, 95% CI 0.39–0.86; HRRIVM: 0.61, 95% CI 0.42–0.87) while no differences were identified between strains for PFS and CSS. Sub-analysis of only re-TUR cases (n = 190, 45%) showed TICE the sole to achieve longer RFS compared to both Connaught and RIVM. Conclusion Re-TUR was confirmed to ensure longer RFS and PFS in intermediate-/high-risk NMIBCs but did not influence the relative single BCG strain efficacy. When routinely performing re-TUR followed by a maintenance BCG schedule, TICE was superior to the other strains for RFS outcomes.

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Watt, Paul M., Ian D. Hickson, Rhona H. Borts, and Edward J. Louis. "SGS1, a Homologue of the Bloom's and Werner's Syndrome Genes, Is Required for Maintenance of Genome Stability in Saccharomyces cerevisiae." Genetics 144, no. 3 (November 1, 1996): 935–45. http://dx.doi.org/10.1093/genetics/144.3.935.

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Abstract The Saccharomyces cerevisiae SGS1 gene is homologous to Escherichia coli RecQ and the human BLM and WRN proteins that are defective in the cancer-prone disorder Bloom's syndrome and the premature aging disorder Werner's syndrome, respectively. While recQ mutants are deficient in conjugational recombination and DNA repair, Bloom's syndrome cell lines show hyperrecombination. Bloom's and Werner's syndrome cell lines both exhibit chromosomal instability. sgslΔ strains show mitotic hyperrecombination, as do Bloom's cells. This was manifested as an increase in the frequency of interchromosomal homologous recombination, intrachromosomal excision recombination, and ectopic recombination. Hyperrecombination was partially independent of both RAD52 and RAD1. Meiotic recombination was not increased in sgs1Δ mutants, although meiosis I chromosome missegregation has been shown to be elevated. sgs1Δ suppresses the slow growth of a top3Δ strain lacking topoisomerase 111. Although there was an increase in subtelomeric Y' instability in sgs1Δ strains due to hyperrecombination, no evidence was found for an increase in the instability of terminal telomeric sequences in a top3Δ or a sgs1Δ strain. This contrasts with the telomere maintenance defects of Werner's patients. We conclude that the SGS1 gene product is involved in the maintenance of genome stability in S. cermisiae.

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Maisnier-Patin, Sophie, Kurt Nordström, and Santanu Dasgupta. "RecA-Mediated Rescue of Escherichia coli Strains with Replication Forks Arrested at the Terminus." Journal of Bacteriology 183, no. 20 (October 15, 2001): 6065–73. http://dx.doi.org/10.1128/jb.183.20.6065-6073.2001.

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ABSTRACT The recombinational rescue of chromosome replication was investigated in Escherichia coli strains with the unidirectional origin oriR1, from the plasmid R1, integrated within oriC in clockwise (intR1 CW) or counterclockwise (intR1 CC) orientations. Only theintR1 CC strain, with replication forks arrested at the terminus, required RecA for survival. Unlike the strains with RecA-dependent replication known so far, theintR1 CC strain did not require RecBCD, RecF, RecG, RecJ, RuvAB, or SOS activation for viability. The overall levels of degradation of replicating chromosomes caused by inactivation of RecA were similar in oriC andintR1 CC strains. In theintR1 CC strain, RecA was also needed to maintain the integrity of the chromosome when the unidirectional replication forks were blocked at the terminus. This was consistent with suppression of the RecA dependence of theintR1 CC strain by inactivating Tus, the protein needed to block replication forks at Ter sites. Thus, RecA is essential during asymmetric chromosome replication for the stable maintenance of the forks arrested at the terminus and for their eventual passage across the termination barrier(s) independently of the SOS and some of the major recombination pathways.

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Zitomersky, Naamah Levy, Michael J. Coyne, and Laurie E. Comstock. "Longitudinal Analysis of the Prevalence, Maintenance, and IgA Response to Species of the Order Bacteroidales in the Human Gut." Infection and Immunity 79, no. 5 (March 14, 2011): 2012–20. http://dx.doi.org/10.1128/iai.01348-10.

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ABSTRACTBacteroidalesspecies are the most abundant Gram-negative bacteria of the human intestinal microbiota. These bacteria evolved to synthesize numerous capsular polysaccharides (PS) that are subject to phase variation. InBacteroides fragilis, PS synthesis is regulated so that only one of the eight PS biosynthesis loci is transcribed at a time in each bacterium. To determine if the bacteria evolved this unusual property to evade a host IgA response, we directly studied the human fecal ecosystem. We performed a longitudinal analysis of the abundantBacteroidalesspecies from 15 healthy adults at four intervals over a year. For this study, we used bacterial culture to perform analyses not accurate with DNA-based methods, including quantification of total viableBacteroidalesbacteria, strain maintenance, and IgA responses. AbundantBacteroidalesisolates were identified to the species level using multiplex PCR and 16S rRNA gene sequencing. Arbitrarily primed PCR was used for strain typing. IgA responses to endogenous strains carried over the year were analyzed, and the orientations of the invertible PS locus promoters from the ecosystem were quantified. Subjects consistently harbored from 5 × 108to 8 × 1010Bacteroidalesbacteria/g of feces. Within the cohort, 20 differentBacteroidalesspecies were detected at high concentrations.Bacteroides uniformiswas the most prevalent; however, abundantBacteroidalesspecies varied between subjects. Strains could be maintained over the year within the ecosystem at high density. IgA responses were often not induced and did not correlate with the elimination of a strain or major changes in the orientations of the capsular PS locus promoters.

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Kloos, Julia, João A. Gama, Joachim Hegstad, Ørjan Samuelsen, and Pål J. Johnsen. "Piggybacking on Niche Adaptation Improves the Maintenance of Multidrug-Resistance Plasmids." Molecular Biology and Evolution 38, no. 8 (March 24, 2021): 3188–201. http://dx.doi.org/10.1093/molbev/msab091.

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Abstract The persistence of plasmids in bacterial populations represents a puzzling evolutionary problem with serious clinical implications due to their role in the ongoing antibiotic resistance crisis. Recently, major advancements have been made toward resolving this “plasmid paradox” but mainly in a nonclinical context. Here, we propose an additional explanation for the maintenance of multidrug-resistance plasmids in clinical Escherichia coli strains. After coevolving two multidrug-resistance plasmids encoding resistance to last resort carbapenems with an extraintestinal pathogenic E. coli strain, we observed that chromosomal media adaptive mutations in the global regulatory systems CCR (carbon catabolite repression) and ArcAB (aerobic respiration control) pleiotropically improved the maintenance of both plasmids. Mechanistically, a net downregulation of plasmid gene expression reduced the fitness cost. Our results suggest that global chromosomal transcriptional rewiring during bacterial niche adaptation may facilitate plasmid maintenance.

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Vasconcelos, Ana Tereza R., Henrique B. Ferreira, Cristiano V. Bizarro, Sandro L. Bonatto, Marcos O. Carvalho, Paulo M. Pinto, Darcy F. Almeida, et al. "Swine and Poultry Pathogens: the Complete Genome Sequences of Two Strains of Mycoplasma hyopneumoniae and a Strain of Mycoplasma synoviae." Journal of Bacteriology 187, no. 16 (August 15, 2005): 5568–77. http://dx.doi.org/10.1128/jb.187.16.5568-5577.2005.

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ABSTRACT This work reports the results of analyses of three complete mycoplasma genomes, a pathogenic (7448) and a nonpathogenic (J) strain of the swine pathogen Mycoplasma hyopneumoniae and a strain of the avian pathogen Mycoplasma synoviae; the genome sizes of the three strains were 920,079 bp, 897,405 bp, and 799,476 bp, respectively. These genomes were compared with other sequenced mycoplasma genomes reported in the literature to examine several aspects of mycoplasma evolution. Strain-specific regions, including integrative and conjugal elements, and genome rearrangements and alterations in adhesin sequences were observed in the M. hyopneumoniae strains, and all of these were potentially related to pathogenicity. Genomic comparisons revealed that reduction in genome size implied loss of redundant metabolic pathways, with maintenance of alternative routes in different species. Horizontal gene transfer was consistently observed between M. synoviae and Mycoplasma gallisepticum. Our analyses indicated a likely transfer event of hemagglutinin-coding DNA sequences from M. gallisepticum to M. synoviae.

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Kato, Junichi, Junya Amie, Yoshinori Murata, Akio Kuroda, Atsushi Mitsutani, and Hisao Ohtake. "Development of a Genetic Transformation System for an Alga-Lysing Bacterium." Applied and Environmental Microbiology 64, no. 6 (June 1, 1998): 2061–64. http://dx.doi.org/10.1128/aem.64.6.2061-2064.1998.

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ABSTRACT Four marine bacteria, Alteromonas sp. strains A27, A28, A29, and A30, that lyse the diatom Skeletonema costatumNIES-324 were isolated from coastal seawater samples. They were also able to lyse the diatoms Thalassiosira sp. andEucampia zodiacs and the raphidophycean flagellateChattonella antiqua. Cryptic indigenous plasmids, designated pAS28 and pAS29, were detected in Alteromonassp. strains A28 and A29, respectively. These plasmids appeared to be similar based on size and restriction site analysis. A shuttle vector that replicates in Escherichia coli andAlteromonas sp. strain A28 was constructed by fusing pAS28 and E. coli vector pCRIIc. The 16-kbp chimeric plasmid, designated pASS1, had the ability to transform strain A28 at a frequency of 106 transformants per μg of DNA. Deletion analysis of pASS1 showed that the 4.7-kbEcoRI-HindIII region of pAS28 was essential for plasmid maintenance in strain A28. ThisEcoRI-HindIII fragment contained an open reading frame which appeared to encode a 708-amino-acid protein.

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Rahman, MM, M. Salah Uddin, S. Zaman, MA Saleh, AE Ekram, P. Farhana, and MH Razu. "Comparative study on growth and morphological characteristics of a wild type strain Rhizobium spp. (RCA-220) and a genetically engineered E. coli BL21." Journal of Bio-Science 20 (January 18, 2014): 75–82. http://dx.doi.org/10.3329/jbs.v20i0.17718.

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Context: Comparison between a wild type strain Rhizobium spp. (RCA-220) and a genetically modified strain E. coli BL21 in context of growth features. Objective: To observe the comparative growth characteristics of a genetically modified E. coli BL21 and an isolated wild type strain Rhizobium spp. (RCA-220). Materials and Methods: Different kinds of investigations were accomplished in both Luria-Bertani (LB) liquid and semi-solid media to observe the growth and maintenance of these strains. For the isolation of Rhizobium spp. selective Yeast Extract Manitol Agar (YEMA) was used. Colony morphology, pH, temperature, carbon source, salt concentration and light were taken under consideration and optimized for growth characteristics. Results: For the strain E. coli BL21, the maximum growth rate was 1.9 at incubation time 72 h, pH 7.2, temperature 37°C (optimized) while for Rhizobium spp. the growth rate was significantly higher (OD 2) at pH 6.8, temperature 28°C (optimized). Among all used carbon sources, strains grown in the medium supplemented with peptone showed rapid and good performance. So, peptone was proved as the best carbon source for both strains. The maximum growths of these strains were observed at 0g/100ml NaCl salt concentration. RCA-220 strain was comparatively more tolerable to salt than E. coli BL21 strain. In this work, E. coli BL21 showed rapid and good performance in presence of light while Rhizobium spp. showed better performance in absence of light. Statistical analysis showed that the growth rate of Rhizobium spp. was significantly higher than E. coli BL21. Conclusion: From the experimental results, it can be concluded that naturally obtained microbial strains were stable and could tolerate any stress condition where the modified strains lose their growth capability and the overall growth performances were reduced or slowed down than the wild type strain. DOI: http://dx.doi.org/10.3329/jbs.v20i0.17718 J. bio-sci. 20: 75-82, 2012

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Ghosh, Enakshi, and Chandish R. Ballal. "Diapause induction and termination in Indian strains of Trichogramma chilonis (Hymenoptera: Trichogrammatidae)." Canadian Entomologist 149, no. 5 (August 9, 2017): 607–15. http://dx.doi.org/10.4039/tce.2017.35.

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AbstractThe role of temperature in diapause induction was studied as a mode of long-term storage of Trichogramma chilonis (Ishii) (Hymenoptera: Trichogrammatidae). Three different strains of this widely used biocontrol agent (T. chilonis Nilgiris strain, T. chilonis Kodaikanal strain, and T. chilonis 15 °C strain) reared on the factitious host Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) were used for this experiment. Except T. chilonis laboratory strain, all the other strains could successfully undergo diapause at their pre-pupal stage. Maximum percentage of healthy pre-pupae were recorded in the three strains by providing a pre-storage temperature of 10 °C for 35 days with eight hours of photophase wherein 75–87% could enter into diapause. Further, at a maintenance temperature of 5 °C with 24 hours of scotophase, diapause could be maintained. Diapause could be terminated after six months of storage with 23–36% of adult emergence. However, there was significant reduction in longevity and parasitism rate of the emerged adults. Considering superior biological parameters, 95 days of storage (including pre-storage duration) could provide around 60% adult emergence. Successful long-term storage of T. chilonis strains through diapause induction can facilitate commercial insectaries in stockpiling this biocontrol agent for large-scale field releases. This is the first study on successful induction and termination of diapause in T. chilonis strains and evaluating their performance attributes.

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Campen, Matthew J., Yugo Tagaito, Jianguo Li, Alexander Balbir, Clarke G. Tankersley, Phillip Smith, Alan Schwartz, and Christopher P. O’Donnell. "Phenotypic variation in cardiovascular responses to acute hypoxic and hypercapnic exposure in mice." Physiological Genomics 20, no. 1 (December 15, 2004): 15–20. http://dx.doi.org/10.1152/physiolgenomics.00197.2003.

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The impact of genetic variation on cardiovascular responses to hypoxia and hypercapnia is not well understood. Therefore, we determined the acute changes in systemic arterial blood pressure (PSA) and heart rate (HR) in seven strains of commonly used inbred mice exposed to acute periods of hypoxia (10% O2), hypercapnia (5% CO2), and hypoxia/hypercapnia (10% O2 + 5% CO2) during wakefulness. Hypercapnia induced an essentially homogeneous response across strains, with PSA maintained at or slightly above baseline and with HR exhibiting a typical baroreceptor-mediated bradycardia. In contrast, exposure to hypoxia elicited a marked heterogeneity in cardiovascular responses between strains. The change in PSA during hypoxia ranged from maintenance of normotension in the FVB/J strain to profound hypotension of ∼30 mmHg in the DBA/2J strain. HR responses were highly variable between strains during hypoxia, and with the exception of the DBA/2J strain that exhibited significant bradyarrhythmias and consequent hypotension, the HR responses were unrelated to changes in PSA. The PSA response to combined hypoxia/hypercapnia represented a balance of the hypertension of hypercapnia and the hypotension of hypoxia in six of the seven strains. In the FVB/J strain, combined hypoxia/hypercapnia produced a hypertensive response that was greater than that of hypercapnia alone. These results suggest that genetic background affects the cardiovascular response to hypoxia, but not hypercapnia.

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Balsalobre, Luz, María José Ferrándiz, Gabriela de Alba, and Adela G. de la Campa. "Nonoptimal DNA Topoisomerases Allow Maintenance of Supercoiling Levels and Improve Fitness ofStreptococcus pneumoniae." Antimicrobial Agents and Chemotherapy 55, no. 3 (December 20, 2010): 1097–105. http://dx.doi.org/10.1128/aac.00783-10.

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ABSTRACTFluoroquinolones, which target gyrase and topoisomerase IV, are used for treatingStreptococcus pneumoniaeinfections. Fluoroquinolone resistance in this bacterium can arise via point mutation or interspecific recombination with genetically related streptococci. Our previous study on the fitness cost of resistance mutations and recombinant topoisomerases identified GyrAE85K as a high-cost change. However, this cost was compensated for by the presence of a recombinant topoisomerase IV (parCandparErecombinant genes) in strain T14. In this study, we purified wild-type and mutant topoisomerases and compared their enzymatic activities. In strain T14, both gyrase carrying GyrAE85K and recombinant topoisomerase IV showed lower activities (from 2.0- to 3.7-fold) than the wild-type enzymes. These variations ofin vitroactivity corresponded to changes ofin vivosupercoiling levels that were analyzed by two-dimensional electrophoresis of an internal plasmid. Strains carrying GyrAE85K and nonrecombinant topoisomerases had lower (11.1% to 14.3%) supercoiling density (σ) values than the wild type. Those carrying GyrAE85K and recombinant topoisomerases showed either partial or total supercoiling level restoration, with σ values being 7.9% (recombinant ParC) and 1.6% (recombinant ParC and recombinant ParE) lower than those for the wild type. These data suggested that changes acquired by interspecific recombination might be selected because they reduce the fitness cost associated with fluoroquinolone resistance mutations. An increase in the incidence of fluoroquinolone resistance, even in the absence of further antibiotic exposure, is envisaged.

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Uemura, H., and R. B. Wickner. "Suppression of chromosomal mutations affecting M1 virus replication in Saccharomyces cerevisiae by a variant of a viral RNA segment (L-A) that encodes coat protein." Molecular and Cellular Biology 8, no. 2 (February 1988): 938–44. http://dx.doi.org/10.1128/mcb.8.2.938-944.1988.

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For the maintenance of "killer" M1 double-stranded RNA in Saccharomyces cerevisiae, more than 30 chromosomal genes are required. The requirement for some of these genes can be completely suppressed by a cytoplasmic element, [B] (for bypass). We have isolated a mutant unable to maintain [B] (mab) and found that it is allelic to MAK10, one of the three chromosomal MAK genes required for the maintenance of L-A. The heat curing of [B] always coincided with the loss of L-A. To confirm that [B] is located on L-A, we purified viral particles containing either L-A or M1 from strains with or without [B] activity and transfected these purified particles into a strain which did not have either L-A or M1. The transfectants harboring L-A and M1 from a [B] strain showed the [B] phenotype, but the transfectants with L-A and M1 from a [B-o] strain did not show the [B] phenotype. Furthermore, the transfectants having L-A from a [B] strain and M1 from a [B-o] strain also showed the [B] phenotype. Therefore, we concluded that [B] is a property of a variant of L-A. In the transfection experiment, we also proved that the superkiller phenotype of the [B] strain is a property of L-A and that L-A with [B] activity can maintain a higher copy number of M1 regardless of the source of M1 viruslike particles. These data suggest that MAK genes whose mutations are suppressed by [B] are concerned with the protection of M1 (+) single-stranded RNA or the formation of M1 viruslike particles and that an L-A with more efficient production of M1 viruslike particles can completely dispense with the requirement for those MAK genes.

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Uemura, H., and R. B. Wickner. "Suppression of chromosomal mutations affecting M1 virus replication in Saccharomyces cerevisiae by a variant of a viral RNA segment (L-A) that encodes coat protein." Molecular and Cellular Biology 8, no. 2 (February 1988): 938–44. http://dx.doi.org/10.1128/mcb.8.2.938.

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For the maintenance of "killer" M1 double-stranded RNA in Saccharomyces cerevisiae, more than 30 chromosomal genes are required. The requirement for some of these genes can be completely suppressed by a cytoplasmic element, [B] (for bypass). We have isolated a mutant unable to maintain [B] (mab) and found that it is allelic to MAK10, one of the three chromosomal MAK genes required for the maintenance of L-A. The heat curing of [B] always coincided with the loss of L-A. To confirm that [B] is located on L-A, we purified viral particles containing either L-A or M1 from strains with or without [B] activity and transfected these purified particles into a strain which did not have either L-A or M1. The transfectants harboring L-A and M1 from a [B] strain showed the [B] phenotype, but the transfectants with L-A and M1 from a [B-o] strain did not show the [B] phenotype. Furthermore, the transfectants having L-A from a [B] strain and M1 from a [B-o] strain also showed the [B] phenotype. Therefore, we concluded that [B] is a property of a variant of L-A. In the transfection experiment, we also proved that the superkiller phenotype of the [B] strain is a property of L-A and that L-A with [B] activity can maintain a higher copy number of M1 regardless of the source of M1 viruslike particles. These data suggest that MAK genes whose mutations are suppressed by [B] are concerned with the protection of M1 (+) single-stranded RNA or the formation of M1 viruslike particles and that an L-A with more efficient production of M1 viruslike particles can completely dispense with the requirement for those MAK genes.

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Hiltunen, J. K., F. Okubo, V. A. S. Kursu, K. J. Autio, and A. J. Kastaniotis. "Mitochondrial fatty acid synthesis and maintenance of respiratory competent mitochondria in yeast." Biochemical Society Transactions 33, no. 5 (October 26, 2005): 1162–65. http://dx.doi.org/10.1042/bst0331162.

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Mitochondrial FAS (fatty acid synthesis) of type II is a widely conserved process in eukaryotic organisms, with particular importance for respiratory competence and mitochondrial morphology maintenance in Saccharomyces cerevisiae. The recent characterization of three missing enzymes completes the pathway. Etr1p (enoyl thioester reductase) was identified via purification of the protein followed by molecular cloning. To study the link between FAS and cell respiration further, we also created a yeast strain that has FabI enoyl-ACP (acyl-carrier protein) reductase gene from Escherichia coli engineered to carry a mitochondrial targeting sequence in the genome, replacing the endogenous ETR1 gene. This strain is respiratory competent, but unlike the ETR1 wild-type strain, it is sensitive to triclosan on media containing only non-fermentable carbon source. A colony-colour-sectoring screen was applied for cloning of YHR067w/RMD12, the gene encoding mitochondrial 3-hydroxyacyl-ACP dehydratase (Htd2/Yhr067p), the last missing component of the mitochondrial FAS. Finally, Hfa1p was shown to be the mitochondrial acetyl-CoA carboxylase.

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Torchia, Timothy E., and James E. Hopper. "GENETIC AND MOLECULAR ANALYSIS OF THE GAL3 GENE IN THE EXPRESSION OF THE GALACTOSE/MELIBIOSE REGULON OF SACCHAROMYCES CEREVISIAE." Genetics 113, no. 2 (June 1, 1986): 229–46. http://dx.doi.org/10.1093/genetics/113.2.229.

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ABSTRACT During the galactose adaptation period of a Saccharomyces cerevisiae strain bearing a naturally occurring gal3 allele, we found a longer induction lag and slower rate of accumulation of GAL10 and MEL1 RNAs compared to wild-type strains. A strain of genotype gal3 gal1 gal7 is noninducible for MEL1 gene expression, but this expression block is bypassed by overexpression of the GAL4 gene or by deletion of the GAL80 gene, either of which causes a constitutive phenotype. An otherwise wild-type strain that bears a chromosomal gal3 gene disruption mutation does not produce wild-type GAL3 RNA and exhibits induction comparable to a strain bearing the naturally occurring gal3. Based on this array of results, we conclude that the GAL3 gene product executes its function at a point before GAL4 mediated transcription of the GAL1-10-7 and MEL1 genes. Thus, the data are consistent with the previously advanced hypothesis that the GAL3 gene product functions to synthesize the inducer or coinducer molecule. In experiments in which the presence of either the plasmid-carried cloned GAL3 gene or the plasmid-carried cloned GAL1-10-7 genes allows MEL1 induction of a gal3 gal1 gal7 cell, we find that loss of the plasmid results in the shutoff of MEL1 expression even when galactose is continuously present. Either GAL3 function or GAL1-10-7 functions are therefore required for both the initiation and the maintenance of the induced state. Since the strains bearing either the naturally occurring gal3 allele or the gal3 disruption (null) allele do induce, the plasmid loss experiments indicate the existence of two completely independent induction initiation-maintenance pathways, one requiring GAL3 function, the other requiring GAL1-10-7 function. Finally, Northern blot analysis reveals two major GAL3 transcripts that differ in size by approximately 500 nucleotides.

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Weber, Markus F., Gabriele Poxleitner, Elke Hebisch, Erwin Frey, and Madeleine Opitz. "Chemical warfare and survival strategies in bacterial range expansions." Journal of The Royal Society Interface 11, no. 96 (July 6, 2014): 20140172. http://dx.doi.org/10.1098/rsif.2014.0172.

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Dispersal of species is a fundamental ecological process in the evolution and maintenance of biodiversity. Limited control over ecological parameters has hindered progress in understanding of what enables species to colonize new areas, as well as the importance of interspecies interactions. Such control is necessary to construct reliable mathematical models of ecosystems. In our work, we studied dispersal in the context of bacterial range expansions and identified the major determinants of species coexistence for a bacterial model system of three Escherichia coli strains (toxin-producing, sensitive and resistant). Genetic engineering allowed us to tune strain growth rates and to design different ecological scenarios (cyclic and hierarchical). We found that coexistence of all strains depended on three strongly interdependent factors: composition of inoculum, relative strain growth rates and effective toxin range. Robust agreement between our experiments and a thoroughly calibrated computational model enabled us to extrapolate these intricate interdependencies in terms of phenomenological biodiversity laws. Our mathematical analysis also suggested that cyclic dominance between strains is not a prerequisite for coexistence in competitive range expansions. Instead, robust three-strain coexistence required a balance between growth rates and either a reduced initial ratio of the toxin-producing strain, or a sufficiently short toxin range.

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Sumitani, M., A. M. Cabral, L. C. Michelini, and E. M. Krieger. "In vivo adaptive responses of the aorta to hypertension and aging." American Journal of Physiology-Heart and Circulatory Physiology 273, no. 1 (July 1, 1997): H96—H103. http://dx.doi.org/10.1152/ajpheart.1997.273.1.h96.

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To investigate the dynamic behavior of the aorta of freely moving rats during the maintenance of hypertension, a longitudinal study was performed in renal hypertensive (Goldblatt 1 kidney, 1 clip) rats aged 3, 6, and 9 mo in which hypertension was maintained for 1, 3, and 6 mo, respectively. The pulsatile caliber of the thoracic aorta was measured (electrolytic strain gauge chronically implanted) simultaneously with aortic pressure under basal conditions and during transient changes of blood pressure. Aortic thickness was determined postmortem by morphometry. Establishment of hypertension (179 +/- 5 mmHg) by increasing the stress developed by the aorta caused increases in the resting values of caliber (20%), thickness (21%), and strain (95%); the maintenance of hypertension for a 6-mo period caused a further increase in thickness (58% vs. age-matched normotensive aortas) but not in aortic caliber and strain, the subsequent alterations of which were due only to growth/aging. Although different calibers, thicknesses, and dynamic strains were presented, the stress-strain relationship during transient blood pressure changes was similar for all hypertensive and normotensive groups with the exception of renal hypertensive rats aged 6 mo, which presented a steeper relationship (a large transitory increase in aortic distensibility was observed at that age). Dynamic adaptive responses of the aorta to hypertension compensate for geometric changes in such a way as to maintain a near-constant distensibility. It was concluded that, in contrast to the extrathoracic vessels, the adaptive responses of the aorta to hypertension were directed to maintain its compliance without changing the distensibility and stress-strain relationship, contributing to partially counterbalance the increased pressure and the decreased compliance of the more peripheral components of the arterial tree.

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Morozov, Konstantin, Arkady Shabarov, Anton Kuranov, Nikita Belyakov, Boris Zuyev, Dmitriy Vlasenko, Dmitriy Demekhin, and Eugene Bakhtin. "Geodynamic monitoring and its maintenance using modeling by numerical and similar materials methods." E3S Web of Conferences 129 (2019): 01012. http://dx.doi.org/10.1051/e3sconf/201912901012.

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The paper describes the fundamental issues of deformation monitoring systems and instrumental methods for measuring the stress-strain state of the rock massif based on the use of three-component strain sensors developed by specialists from the University of Mines and Avangard OJSC. One of the main tasks of the developed systems is the prediction and prevention of possible dynamic manifestations of rock pressure in rockburst-hazardous deposits.

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Fujio, Yoshihisa, Masamichi Nakajima, and Anna Alexandrovna Barinova. "Decrease of the Effective Population Size during Maintenance of the Guppy Strain." Fisheries science 65, no. 3 (1999): 362–66. http://dx.doi.org/10.2331/fishsci.65.362.

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Nikonorov, Yu M., and G. V. Benkovskaya. "The mechanisms of lifespan polymorphism maintenance in the house fly laboratory strain." Advances in Gerontology 4, no. 3 (July 2014): 163–68. http://dx.doi.org/10.1134/s2079057014030059.

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Odds, F. C., A. D. Davidson, M. D. Jacobsen, A. Tavanti, J. A. Whyte, C. C. Kibbler, D. H. Ellis, M. C. J. Maiden, D. J. Shaw, and N. A. R. Gow. "Candida albicans Strain Maintenance, Replacement, and Microvariation Demonstrated by Multilocus Sequence Typing." Journal of Clinical Microbiology 44, no. 10 (October 1, 2006): 3647–58. http://dx.doi.org/10.1128/jcm.00934-06.

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Yuan, Yongliang. "Fatigue Analysis of Mobile Maintenance Platform Based on Ansys Workbench." MATEC Web of Conferences 175 (2018): 03048. http://dx.doi.org/10.1051/matecconf/201817503048.

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In order to investigate the performance of the mobile maintenance platform, Ansys Workbench was used to analyze the strength analysis of the mobile maintenance platform. The deformation, stress, and strain were obtained. The fatigue module was used to analyze the fatigue of the mobile maintenance platform and the fatigue life based on the cumulative fatigue damage theory. The simulation results show that the strength of the mobile maintenance platform is sufficient, and its lifetime is as high as 19.8 years. The mobile maintenance platform has a large space for optimization and this paper provides a basis for future structural optimization design.

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Del Giudice, Francesco, Rocco Simone Flammia, Benjamin I. Chung, Marco Moschini, Benjamin Pradere, Andrea Mari, Francesco Soria, et al. "Compared Efficacy of Adjuvant Intravesical BCG-TICE vs. BCG-RIVM for High-Risk Non-Muscle Invasive Bladder Cancer (NMIBC): A Propensity Score Matched Analysis." Cancers 14, no. 4 (February 10, 2022): 887. http://dx.doi.org/10.3390/cancers14040887.

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Background: Intravesical immunotherapy with bacillus Calmette–Guerin (BCG) is the standard therapy for high-risk non-muscle invasive bladder cancer (NMIBC). The superiority of any BCG strain over another could not be demonstrated yet. Methods: Patients with NMIBCs underwent adjuvant induction ± maintenance schedule of intravesical immunotherapy with either BCG TICE or RIVM at two high-volume tertiary institutions. Only BCG-naïve patients and those treated with the same strain over the course of follow-up were included. One-to-one (1:1) propensity score matching (PSM) between the two cohorts was utilized to adjust for baseline demographic and tumor characteristics imbalances. Kaplan–Meier estimates and multivariable Cox regression models according to high-risk NMIBC prognostic factors were implemented to address survival differences between the strains. Sub-group analysis modeling of the influence of routine secondary resection (re-TUR) in the setting of the sole maintenance adjuvant schedule for the two strains was further performed. Results: 852 Ta-T1 NMIBCs (n = 719, 84.4% on TICE; n = 133, 15.6% on RIVM) with a median of 53 (24–77) months of follow-up were reviewed. After PSM, no differences at 5-years RFS, PFS, and CSS at both Kaplan–Meier and Cox regression analyses were detected for the whole cohort. In the sub-group setting of full adherence to European/American Urology Guidelines (EAU/NCCN), BCG TICE demonstrated longer 5-years RFS compared to RIVM (68% vs. 43%, p = 0.008; HR: 0.45 95% CI 0.25–0.81). Conclusion: When routinely performing re-TUR followed by a maintenance BCG schedule, TICE was superior to RIVM for RFS outcomes. However, no significant differences were detected for PFS and CSS, respectively.

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Souza, Lucas Santana, Yasuhiko Irie, and Shigetoshi Eda. "Black Queen Hypothesis, partial privatization, and quorum sensing evolution." PLOS ONE 17, no. 11 (November 30, 2022): e0278449. http://dx.doi.org/10.1371/journal.pone.0278449.

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Microorganisms produce costly cooperative goods whose benefit is partially shared with nonproducers, called ‘mixed’ goods. The Black Queen Hypothesis predicts that partial privatization has two major evolutionary implications. First, to favor strains producing several types of mixed goods over nonproducing strains. Second, to favor the maintenance of cooperative traits through different strains instead of having all cooperative traits present in a single strain (metabolic specialization). Despite the importance of quorum sensing regulation of mixed goods, it is unclear how partial privatization affects quorum sensing evolution. Here, we studied the influence of partial privatization on the evolution of quorum sensing. We developed a mathematical population genetics model of an unstructured microbial population considering four strains that differ in their ability to produce an autoinducer (quorum sensing signaling molecule) and a mixed good. Our model assumes that the production of the autoinducers and the mixed goods is constitutive and/or depends on quorum sensing. Our results suggest that, unless autoinducers are costless, partial privatization cannot favor quorum sensing. This result occurs because with costly autoinducers: (1) a strain that produces both autoinducer and goods (fully producing strain) cannot persist in the population; (2) the strain only producing the autoinducer and the strain producing mixed goods in response to the autoinducers cannot coexist, i.e., metabolic specialization cannot be favored. Together, partial privatization might have been crucial to favor a primordial form of quorum sensing—where autoinducers were thought to be a metabolic byproduct (costless)—but not the transition to nowadays costly autoinducers.

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Krzywinska, Elzbieta, Jaroslaw Krzywinski, and Jeffrey S. Schorey. "Naturally occurring horizontal gene transfer and homologous recombination in Mycobacterium." Microbiology 150, no. 6 (June 1, 2004): 1707–12. http://dx.doi.org/10.1099/mic.0.27088-0.

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Acquisition of genetic information through horizontal gene transfer (HGT) is an important evolutionary process by which micro-organisms gain novel phenotypic characteristics. In pathogenic bacteria, for example, it facilitates maintenance and enhancement of virulence and spread of drug resistance. In the genus Mycobacterium, to which several primary human pathogens belong, HGT has not been clearly demonstrated. The few existing reports suggesting this process are based on circumstantial evidence of similarity of sequences found in distantly related species. Here, direct evidence of HGT between strains of Mycobacterium avium representing two different serotypes is presented. Conflicting evolutionary histories of genes encoding elements of the glycopeptidolipid (GPL) biosynthesis pathway led to an analysis of the GPL cluster genomic sequences from four Mycobacterium avium strains. The sequence of M. avium strain 2151 appeared to be a mosaic consisting of three regions having alternating identities to either M. avium strains 724 or 104. Maximum-likelihood estimation of two breakpoints allowed a ∼4100 bp region horizontally transferred into the strain 2151 genome to be pinpointed with confidence. The maintenance of sequence continuity at both breakpoints and the lack of insertional elements at these sites strongly suggest that the integration of foreign DNA occurred by homologous recombination. To our knowledge, this is the first report to demonstrate naturally occurring homologous recombination in Mycobacterium. This previously undiscovered mechanism of genetic exchange may have major implications for the understanding of Mycobacterium pathogenesis.

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Alleman, Mary, and Michael Freeling. "THE Mu TRANSPOSABLE ELEMENTS OF MAIZE: EVIDENCE FOR TRANSPOSITION AND COPY NUMBER REGULATION DURING DEVELOPMENT." Genetics 112, no. 1 (January 1, 1986): 107–19. http://dx.doi.org/10.1093/genetics/112.1.107.

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ABSTRACT The Mu transposon of maize exists in a highly mutagenic strain called Robertson's Mutator. Plants of this strain contain 10-50 copies of the Mu element, whereas most maize strains and other plants have none. When Mutator plants are crossed to plants of the inbred line 1S2P, which does not have copies of Mu, the progeny plants have approximately the same number of Mu sequences as did their Mutator parent. Approximately one-half of these copies have segregated from their parent and one-half have arisen by transposition and are integrated into new positions in the genome. This maintenance of copy number can be accounted for by an extremely high rate of transposition of the Mu elements (10-15 transpositions per gamete per generation). When Mutator plants are self-pollinated, the progeny double their Mu copy number in the first generation, but maintain a constant number of Mu sequences with subsequent self-pollinations. Transposition of Mu and the events that lead to copy number maintenance occur very late in the development of the germ cells but before fertilization. A larger version of the Mu element transposes but is not necessary for transposition of the Mu sequences. The progeny of crosses with a Mutator plant occasionally lack Mutator activity; these strains retain copies of the Mu element, but these elements no longer transpose.

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Journal articles on the topic 'Strain maintenance'

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