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1
Phoenix, Vernon R., Kurt O. Konhauser e F. Grant Ferris. "Experimental study of iron and silica immobilization by bacteria in mixed Fe-Si systems: implications for microbial silicification in hot springs". Canadian Journal of Earth Sciences 40, n. 11 (1 novembre 2003): 1669–78. http://dx.doi.org/10.1139/e03-044.
Testo completoAbstract (sommario):
The immobilization of silica and iron by the bacteria Bacillus subtilis was monitored in controlled microcosms to elucidate the role iron may play in aiding bacterial silicification in hot springs. Silica and iron immobilization was monitored as a function of bacterial concentration, iron concentration, and silica concentration (both undersaturated and oversaturated with respect to amorphous silica). Results demonstrate that bacterial cells do immobilize more Fe than bacteria-free systems in solutions with iron concentrations [Formula: see text]50 ppm Fe. However, as iron concentrations increase, the difference between Fe immobilization in bacterial and bacteria-free systems decreases as non-bacterially mediated precipitation processes dominate. Additionally, bacterial systems that had immobilized more Fe compared with bacteria-free systems did not immobilize more silica than bacteria-free systems. By comparing molar ratios of (silica in solution)/(bacterially bound Fe), it is evident that insufficient iron is bound to the bacterial surface to act as an effective salt bridge for silica sorption. This appears to be because much of the iron is immobilized by non-bacterially mediated precipitation of phases such as Fe(OH)3 and poorly ordered hydrous iron silicates. It follows that in silica-enriched hot springs, silica and iron immobilization processes are significantly dominated by non-bacterially mediated precipitation. Any bacterially mediated processes are exceedingly small and outside the resolution of these experiments.
2
Kupka, Daniel, Michal Lovás e Vladimir Šepelák. "Deferrization of Kaolinic Sand by Iron Oxidizing and Iron Reducing Bacteria". Advanced Materials Research 20-21 (luglio 2007): 130–33. http://dx.doi.org/10.4028/www.scientific.net/amr.20-21.130.
Testo completoAbstract (sommario):
Iron oxidizing bacteria Acidithiobacillus ferrooxidans, iron reducing bacteria Acidiphilium spp. and their mixture were applied for leaching of iron impurities from quartz sand. The bacterial leaching was carried out in order to decrease the amount of colouring iron oxides and to improve the technological properties of the raw material. Mineralogical analysis confirmed the presence of siderite, iron-bearing muscovite and various amorphous and crystalline forms of iron oxides occurring both free and coating siderite and quartz particles. Mössbauer spectroscopy revealed various oxidation and magnetic states of iron ions, with the prevalence of reduced ionic species. Highest extraction of iron was achieved with pure culture of iron-reducing bacteria with ferrous iron as dominant species in the leaching liquor. Surprisingly, iron oxidizing bacteria caused passivation of the surface of iron-bearing minerals, resulting in the depression of iron leaching in comparison with abiotic control. Ferric iron was major species in the leaching solution containing the mixed culture of iron-oxidizing and iron-reducing bacteria. The mixture was far less efficient in iron extraction than pure culture of iron-reducing bacteria.
3
Tang, Kam W., e Hans-Peter Grossart. "Iron effects on colonization behavior, motility, and enzymatic activity of marine bacteria". Canadian Journal of Microbiology 53, n. 8 (agosto 2007): 968–74. http://dx.doi.org/10.1139/w07-059.
Testo completoAbstract (sommario):
Iron availability in the ocean has been shown to affect the growth and production of phytoplankton and free-living bacteria. A large fraction of marine bacteria are specialized in colonizing and living on particles and aggregates, but the effects of iron limitation on these bacteria are not fully known. We conducted laboratory experiments to study the effects of iron availability on particle colonization behavior, motility, and enzymatic activities of 4 strains of marine bacteria. Iron depletion reduced the bacterial particle colonization rate by 1.7%–43.1%, which could be attributed to reduced swimming speeds in 2 of the 4 strains. Protease activity was not affected by iron availability. However, attached bacteria did show higher protease activities than their free counterparts. Our results suggest that iron limitation in the ocean could in some cases reduce bacteria–particle interactions by reducing bacterial motility and colonization rate.
4
Page, Malcom G. P. "The Role of Iron and Siderophores in Infection, and the Development of Siderophore Antibiotics". Clinical Infectious Diseases 69, Supplement_7 (13 novembre 2019): S529—S537. http://dx.doi.org/10.1093/cid/ciz825.
Testo completoAbstract (sommario):
Abstract Iron is an essential nutrient for bacterial growth, replication, and metabolism. Humans store iron bound to various proteins such as hemoglobin, haptoglobin, transferrin, ferritin, and lactoferrin, limiting the availability of free iron for pathogenic bacteria. However, bacteria have developed various mechanisms to sequester or scavenge iron from the host environment. Iron can be taken up by means of active transport systems that consist of bacterial small molecule siderophores, outer membrane siderophore receptors, the TonB-ExbBD energy-transducing proteins coupling the outer and the inner membranes, and inner membrane transporters. Some bacteria also express outer membrane receptors for iron-binding proteins of the host and extract iron directly from these for uptake. Ultimately, iron is acquired and transported into the bacterial cytoplasm. The siderophores are small molecules produced and released by nearly all bacterial species and are classified according to the chemical nature of their iron-chelating group (ie, catechol, hydroxamate, α-hydroxyl-carboxylate, or mixed types). Siderophore-conjugated antibiotics that exploit such iron-transport systems are under development for the treatment of infections caused by gram-negative bacteria. Despite demonstrating high in vitro potency against pathogenic multidrug-resistant bacteria, further development of several candidates had stopped due to apparent adaptive resistance during exposure, lack of consistent in vivo efficacy, or emergence of side effects in the host. However, cefiderocol, with an optimized structure, has advanced and has been investigated in phase 1 to 3 clinical trials. This article discusses the mechanisms implicated in iron uptake and the challenges associated with the design and utilization of siderophore-mimicking antibiotics.
5
Tang, Yu Lan, Wei Bin Wu, Ya Ting He, Jin Xiang Fu e Xiao Lan Wang. "Low-Temperature Domestication of an Iron and Manganese Oxidizing Bacteria". Advanced Materials Research 374-377 (ottobre 2011): 826–30. http://dx.doi.org/10.4028/www.scientific.net/amr.374-377.826.
Testo completoAbstract (sommario):
Abstract.One superior iron and manganese bacteria were separated from the stable operation of porcelain granular BAF filters of removing iron, manganese and ammonia. The bacteria was domesticated at low temperature. By analyzing the sample water containing iron and manganese in the role of iron and manganese bacteria which was not domesticated and domesticated at different temperature, observing the Iron and manganese concentration with time going on, studying the bacteria’s removal of iron and manganese property and the domesticated effect. Studies show that: the selected bacteria with 1% bacterial liquid at proper temperature within 48h ,the removal rate of iron and manganese was 75% and 35% respectively;After domesticated at low temperature, the removal rate of the iron and manganese domesticated bacteria at 10°C was improved 0.4 and 2 times more than the before domesticated; The iron and manganese domesticated bacteria at 10°C did not grow at 4°C,but the bacteria’s removal rate was better than the bacteria cultured at 30°C,and the iron removal rate was improved from 23% to 35%,the manganese removal rate was improved from 5% to 11%.
6
Xing, Weijia, Yue Zhan, Lei Yang e Lei Yan. "Iron Biomineralization Performed by Iron-Cycling Bacteria and Magnetotactic Bacteria". ACTA SCIENTIFIC MICROBIOLOGY 1, n. 3 (1 marzo 2018): 28–29. http://dx.doi.org/10.31080/asmi.2018.01.0024.
Testo completo
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Kuznetsova, D. A., V. A. Rykova e O. N. Podladchikova. "Bacterial Siderophores: Structure, Functions, and Role in the Pathogenesis of Infections". Problems of Particularly Dangerous Infections, n. 3 (29 ottobre 2022): 14–22. http://dx.doi.org/10.21055/0370-1069-2022-3-14-22.
Testo completoAbstract (sommario):
This review systematizes and analyzes the data published over the past decade, devoted to the study of low-molecular-weight high affinity iron chelators – siderophores. Siderophores, which are found in bacteria, fungi and mammals, are able to extract iron from insoluble inorganic compounds, and in the host organism – from complexes with proteins that perform the function of nonspecific protection of mammals from infections. The extracted iron is delivered to cells through surface protein receptors specific for each siderophore, as well as various protein transport systems that make up membranes. Siderophores play an important role in virulence in pathogenic bacteria, performing many functions in the host organism, in addition to providing microbes with iron and other biological metals. They participate in the storage of excess iron, toxic to cells, protect bacteria from reactive oxygen compounds, compete for iron with phagocytes, and have a harmful effect on host cells, acting as secreted bacterial toxin in some cases. Bacterial siderophores perform a signaling function and regulate both, their own synthesis and the synthesis of other virulence factors. Many pathogenic bacteria produce several siderophores that are active under different conditions, against various sources of iron in the host organism and at different stages of infectious process. The review presents the results of the experimental studies aimed at elucidating the structure and diverse functions of bacterial siderophores, the mechanisms of their biosynthesis and regulation of expression, as well as the role of these molecules in the physiology and virulence of pathogenic bacteria. Special emphasis is put on siderophores of bacteria causing particularly dangerous infections.
8
Ebrahiminezhad, Alireza, Zahra Manafi, Aydin Berenjian, Sedigheh Kianpour e Younes Ghasemi. "Iron-Reducing Bacteria and Iron Nanostructures". Journal of Advanced Medical Sciences and Applied Technologies 3, n. 1 (22 maggio 2017): 9. http://dx.doi.org/10.18869/nrip.jamsat.3.1.9.
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Liu, Zhuoming, Scott Reba, Wei-Dong Chen, Suheel Kumar Porwal, W. Henry Boom, Robert B. Petersen, Roxana Rojas, Rajesh Viswanathan e L. Devireddy. "Regulation of mammalian siderophore 2,5-DHBA in the innate immune response to infection". Journal of Experimental Medicine 211, n. 6 (26 maggio 2014): 1197–213. http://dx.doi.org/10.1084/jem.20132629.
Testo completoAbstract (sommario):
Competition for iron influences host–pathogen interactions. Pathogens secrete small iron-binding moieties, siderophores, to acquire host iron. In response, the host secretes siderophore-binding proteins, such as lipocalin 24p3, which limit siderophore-mediated iron import into bacteria. Mammals produce 2,5-dihydroxy benzoic acid, a compound that resembles a bacterial siderophore. Our data suggest that bacteria use both mammalian and bacterial siderophores. In support of this idea, supplementation with mammalian siderophore enhances bacterial growth in vitro. In addition, mice lacking the mammalian siderophore resist E. coli infection. Finally, we show that the host responds to infection by suppressing siderophore synthesis while up-regulating lipocalin 24p3 expression via TLR signaling. Thus, reciprocal regulation of 24p3 and mammalian siderophore is a protective mechanism limiting microbial access to iron.
10
Akinbosede, Daniel, Robert Chizea e Stephen A. Hare. "Pirates of the haemoglobin". Microbial Cell 9, n. 4 (4 aprile 2022): 84–102. http://dx.doi.org/10.15698/mic2022.04.775.
Testo completoAbstract (sommario):
Not all treasure is silver and gold; for pathogenic bacteria, iron is the most precious and the most pillaged of metallic elements. Iron is essential for the survival and growth of all life; however free iron is scarce for bacteria inside human hosts. As a mechanism of defence, humans have evolved ways to store iron so as to render it inaccessible for invading pathogens, such as keeping the metal bound to iron-carrying proteins. For bacteria to survive within humans, they must therefore evolve counters to this defence to compete with these proteins for iron binding, or directly steal iron from them. The most populous form of iron in humans is haem: a functionally significant coordination complex that is central to oxygen transport and predominantly bound by haemoglobin. Haemoglobin is therefore the largest source of iron in humans and, as a result, bacterial pathogens in critical need of iron have evolved complex and creative ways to acquire haem from haemoglobin. Bacteria of all cell wall types have the ability to bind haemoglobin at their cell surface, to accept the haem from it and transport this to the cytoplasm for downstream uses. This review describes the systems employed by various pathogenic bacteria to utilise haemoglobin as an iron source within human hosts and discusses their contribution to virulence.
11
Timofeeva, Anna M., Maria R. Galyamova e Sergey E. Sedykh. "Bacterial Siderophores: Classification, Biosynthesis, Perspectives of Use in Agriculture". Plants 11, n. 22 (12 novembre 2022): 3065. http://dx.doi.org/10.3390/plants11223065.
Testo completoAbstract (sommario):
Siderophores are synthesized and secreted by many bacteria, yeasts, fungi, and plants for Fe (III) chelation. A variety of plant-growth-promoting bacteria (PGPB) colonize the rhizosphere and contribute to iron assimilation by plants. These microorganisms possess mechanisms to produce Fe ions under iron-deficient conditions. Under appropriate conditions, they synthesize and release siderophores, thereby increasing and regulating iron bioavailability. This review focuses on various bacterial strains that positively affect plant growth and development through synthesizing siderophores. Here we discuss the diverse chemical nature of siderophores produced by plant root bacteria; the life cycle of siderophores, from their biosynthesis to the Fe–siderophore complex degradation; three mechanisms of siderophore biosynthesis in bacteria; the methods for analyzing siderophores and the siderophore-producing activity of bacteria and the methods for screening the siderophore-producing activity of bacterial colonies. Further analysis of biochemical, molecular–biological, and physiological features of siderophore synthesis by bacteria and their use by plants will allow one to create effective microbiological preparations for improving soil fertility and increasing plant biomass, which is highly relevant for sustainable agriculture.
12
RAWLS, REBECCA. "Pumping Iron, Bacteria-style". Chemical & Engineering News Archive 80, n. 9 (4 marzo 2002): 13. http://dx.doi.org/10.1021/cen-v080n009.p013a.
Testo completo
13
Budzikiewicz, Herbert. "Iron Acquisition and Iron Transport by Bacteria". Frontiers in Natural Product Chemistry 1, n. 1 (1 gennaio 2005): 89–98. http://dx.doi.org/10.2174/1574089054583786.
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Mathews, Salima, Ranjeet Kumar e Marc Solioz. "Copper Reduction and Contact Killing of Bacteria by Iron Surfaces". Applied and Environmental Microbiology 81, n. 18 (6 luglio 2015): 6399–403. http://dx.doi.org/10.1128/aem.01725-15.
Testo completoAbstract (sommario):
ABSTRACTThe well-established killing of bacteria by copper surfaces, also called contact killing, is currently believed to be a combined effect of bacterial contact with the copper surface and the dissolution of copper, resulting in lethal bacterial damage. Iron can similarly be released in ionic form from iron surfaces and would thus be expected to also exhibit contact killing, although essentially no contact killing is observed by iron surfaces. However, we show here that the exposure of bacteria to iron surfaces in the presence of copper ions results in efficient contact killing. The process involves reduction of Cu2+to Cu+by iron; Cu+has been shown to be considerably more toxic to cells than Cu2+. The specific Cu+chelator, bicinchoninic acid, suppresses contact killing by chelating the Cu+ions. These findings underline the importance of Cu+ions in the contact killing process and infer that iron-based alloys containing copper could provide novel antimicrobial materials.
15
Zhu, Mingang, Marianne Valdebenito, Günther Winkelmann e Klaus Hantke. "Functions of the siderophore esterases IroD and IroE in iron-salmochelin utilization". Microbiology 151, n. 7 (1 luglio 2005): 2363–72. http://dx.doi.org/10.1099/mic.0.27888-0.
Testo completoAbstract (sommario):
The siderophore salmochelin is produced under iron-poor conditions by Salmonella and many uropathogenic Escherichia coli strains. The production of salmochelin, a C-glucosylated enterobactin, is dependent on the synthesis of enterobactin and the iroBCDEN gene cluster. An E. coli IroD protein with an N-terminal His-tag cleaved cyclic salmochelin S4 to the linear trimer salmochelin S2, the dimer salmochelin S1, and the monomers dihydroxybenzoylserine and C-glucosylated dihydroxybenzoylserine (salmochelin SX, pacifarinic acid). The periplasmic IroE protein was purified as a MalE–IroE fusion protein. This enzyme degraded salmochelin S4 and ferric-salmochelin S4 to salmochelin S2 and ferric-salmochelin S2, respectively. In E. coli, uptake of ferric-salmochelin S4 was dependent on the cleavage by IroE, and independent of the FepBDGC ABC transporter in the cytoplasmic membrane. IroC, which has similarities to ABC-multidrug-resistance proteins, was necessary for the uptake of salmochelin S2 from the periplasm into the cytoplasm. IroE did not function as a classical binding protein since salmochelin S2 was taken up in the absence of a functional IroE protein. IroC mediated the uptake of iron via enterobactin in a fepB mutant. IroE was also necessary in this case for the uptake of ferric-enterobactin, which indicated that only the linear degradation products of enterobactin were taken up via IroC. PfeE, the Pseudomonas aeruginosa IroE homologue, was cloned, and its enzymic activity was shown to be very similar to that of IroE. It is suggested that homologues in other bacteria are also periplasmic IroE-type esterases of siderophores.
16
Osadebe, Anwuli U., Dorcas C. Olorondu e Gideon C. Okpokwasili. "Environmental and Microbial Influences on Corrosion of Selected Types of Petroleum Industry Steel". Environment and Natural Resources Journal 19, n. 4 (1 giugno 2021): 310–19. http://dx.doi.org/10.32526/ennrj/19/2021004.
Testo completoAbstract (sommario):
This study explored the influence of brackish water sediment, mangrove swamp sediment, clayey/lateritic soil, and river water (freshwater) sediment on the corrosion rates of carbon, mild, and stainless steels and the species of sulphate reducing bacteria (SRB) and iron bacteria associated with the process. The material loss following burial of the steel samples for a 9-month period was assessed. Standard and specialised microbiological techniques were employed in the characterisation of the bacterial species. Qualitative assessment for corrosion was done via optical microscopy and macroscopy. Corrosion was highest on steel buried in brackish water sediment and lowest in that from river water sediment. Carbon steel was the most susceptible to corrosion while stainless steel was the most resistant. Sulphite, sulphide, nitrate and phosphate concentrations had a strong impact on corrosion rates. Thiobacillus, Leptothrix and Gallionella dominated amongst the iron bacteria while Desulfobacter and Desulfovibrio dominated amongst the SRB. There were significant differences in corrosion rates and bacterial abundance from one environment to the other. Iron bacteria showed greater abundance than SRB across the different environments and steel types. Iron bacteria counts, however, did not correlate positively with corrosion rates. The findings suggest that oil industry facilities in brackish water environments are more liable to corrosion than those located in fresh water ecosystems.
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Finlayson-Trick, Emma CL, Jordie AJ Fischer, David M. Goldfarb e Crystal D. Karakochuk. "The Effects of Iron Supplementation and Fortification on the Gut Microbiota: A Review". Gastrointestinal Disorders 2, n. 4 (26 settembre 2020): 327–40. http://dx.doi.org/10.3390/gidisord2040030.
Testo completoAbstract (sommario):
Iron supplementation and fortification are used to treat iron deficiency, which is often associated with gastrointestinal conditions, such as inflammatory bowel disease and colorectal cancer. Within the gut, commensal bacteria contribute to maintaining systemic iron homeostasis. Disturbances that lead to excess iron promote the replication and virulence of enteric pathogens. Consequently, research has been interested in better understanding the effects of iron supplementation and fortification on gut bacterial composition and overall gut health. While animal and human trials have shown seemingly conflicting results, these studies emphasize how numerous factors influence gut microbial composition. Understanding how different iron formulations and doses impact specific bacteria will improve the outcomes of iron supplementation and fortification in humans. Furthermore, discerning the nuances of iron supplementation and fortification will benefit subpopulations that currently do not respond well to treatment.
18
Golonka, Rachel, Beng San Yeoh e Matam Vijay-Kumar. "The Iron Tug-of-War between Bacterial Siderophores and Innate Immunity". Journal of Innate Immunity 11, n. 3 (2019): 249–62. http://dx.doi.org/10.1159/000494627.
Testo completoAbstract (sommario):
Iron is necessary for the survival of almost all aerobic organisms. In the mammalian host, iron is a required cofactor for the assembly of functional iron-sulfur (Fe-S) cluster proteins, heme-binding proteins and ribonucleotide reductases that regulate various functions, including heme synthesis, oxygen transport and DNA synthesis. However, the bioavailability of iron is low due to its insolubility under aerobic conditions. Moreover, the host coordinates a nutritional immune response to restrict the accessibility of iron against potential pathogens. To counter nutritional immunity, most commensal and pathogenic bacteria synthesize and secrete small iron chelators termed siderophores. Siderophores have potent affinity for iron, which allows them to seize the essential metal from the host iron-binding proteins. To safeguard against iron thievery, the host relies upon the innate immune protein, lipocalin 2 (Lcn2), which could sequester catecholate-type siderophores and thus impede bacterial growth. However, certain bacteria are capable of outmaneuvering the host by either producing “stealth” siderophores or by expressing competitive antagonists that bind Lcn2 in lieu of siderophores. In this review, we summarize the mechanisms underlying the complex iron tug-of-war between host and bacteria with an emphasis on how host innate immunity responds to siderophores.
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Appenzeller, Brice M. R., Carolina Yañez, Frederic Jorand e Jean-Claude Block. "Advantage Provided by Iron for Escherichia coli Growth and Cultivability in Drinking Water". Applied and Environmental Microbiology 71, n. 9 (settembre 2005): 5621–23. http://dx.doi.org/10.1128/aem.71.9.5621-5623.2005.
Testo completoAbstract (sommario):
ABSTRACT The presence of iron, used both as a nutrient and as an electron acceptor, was demonstrated to give an advantage to Escherichia coli bacteria in drinking water. Slight additions of ferrous sulfate to water with initial low iron concentrations led to a significant increase in the number of E. coli bacteria. The presence of ferric oxide in water under anaerobic conditions increased bacterial cultivability.
20
Ong, Cheryl-Lynn Y., Adam J. Potter, Claudia Trappetti, Mark J. Walker, Michael P. Jennings, James C. Paton e Alastair G. McEwan. "Interplay between Manganese and Iron in Pneumococcal Pathogenesis: Role of the Orphan Response Regulator RitR". Infection and Immunity 81, n. 2 (26 novembre 2012): 421–29. http://dx.doi.org/10.1128/iai.00805-12.
Testo completoAbstract (sommario):
ABSTRACTStreptococcus pneumoniae(the pneumococcus) is a major human pathogen that is carried asymptomatically in the nasopharynx by up to 70% of the human population. Translocation of the bacteria into internal sites can cause a range of diseases, such as pneumonia, otitis media, meningitis, and bacteremia. This transition from nasopharynx to growth at systemic sites means that the pneumococcus needs to adjust to a variety of environmental conditions, including transition metal ion availability. Although it is an important nutrient, iron potentiates oxidative stress, and it is established that inS. pneumoniae, expression of iron transport systems and proteins that protect against oxidative stress are regulated by an orphan response regulator, RitR. In this study, we investigated the effect of iron and manganese ion availability on the growth of aritRmutant. Deletion ofritRled to impaired growth of bacteria in high-iron medium, but this phenotype could be suppressed with the addition of manganese. Measurement of metal ion accumulation indicated that manganese prevents iron accumulation. Furthermore, the addition of manganese also led to a reduction in the amount of hydrogen peroxide produced by bacterial cells. Studies of virulence in a murine model of infection indicated that RitR was not essential for pneumococcal survival and suggested that derepression of iron uptake systems may enhance the survival of pneumococci in some niches.
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Luptakova, Alena, e E. Macingova. "Sorption of Copper Ions by Biogenic Iron Sulphides". Advanced Materials Research 20-21 (luglio 2007): 631–34. http://dx.doi.org/10.4028/www.scientific.net/amr.20-21.631.
Testo completoAbstract (sommario):
Biogenic iron sulphides are excellent adsorbents for various heavy metals ions. Consequently, they have practical application for the elimination of heavy metals from waste waters. One of the principles for the iron sulphides preparation is the application of sulphatereducing bacteria. This biological-chemical method is based on the ability of these bacteria to reduce sulphates to hydrogen sulphide, which binds with the ferrous cations to form insoluble precipitates – iron sulphides. Under certain bacterial growth conditions biogenic iron sulphides can be magnetic. The aim of this work is to study the possibility of using SRB for the preparation of iron sulphides, which were used subsequently in the framework of sorption tests to eliminate copper ions from model solutions.
22
Ahmed, Ayaz, e Shahana Kazmi. "Siderophore Production and its Role as Therapeutic Agent". Microbiological & Immunological Communications 1, n. 01 (31 dicembre 2022): 21–33. http://dx.doi.org/10.55627/mic.001.01.0181.
Testo completoAbstract (sommario):
Siderophores are iron chelators, which are produced by bacteria under iron-deficient conditions required for their growth. Therefore, siderophores can be used as a carrier to direct drugs into the bacteria and kill them. The present study was designed to screen siderophore production using different bacteria using an iron-deficient medium and its synergistic capability to kill drug-resistant bacteria. Siderophore under iron-deprived condition was evaluated by chrome azurol S (CAS) assay. Whereas, broth micro-dilution method and checkerboard assay were used to determine the antimicrobial properties of selected drugs or epigallocatechin gallate (EGCG) individually or in combination with synthetic siderophore. Results demonstrated that the entire tested microorganisms produced siderophore under the iron-deprived condition as evidenced by orange halo zones in CAS agar plates. Gram-negative bacteria produced more siderophores as reflected by orange color with bacterial zone inhibition of 17-22mm as compared to Gram-positive bacteria (13-15mm). As compared to antibiotics and EGCG, acetohydroxamic acid (aHa; synthetic siderophore) showed no antibacterial properties (1500 - 6500 µg/ml). The synergism of aHa with tetracycline, ceftriaxone, and EGCG (FIC index <0.5) against S. typhi, methicillin-resistant and sensitive Staphylococcus aureus, and E. coli were evident. In conclusion, siderophore may be considered a potential candidate to design different combination therapy against emerging antimicrobial-resistant pathogens.
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Liu, Xing Yu, Ming Jiang Zhang, Yi Bin Li, Zi Ning Wang e Jian Kang Wen. "In Situ Bioremediation of Tailings by Sulfate Reducing Bacteria and Iron Reducing Bacteria: Lab- and Field-Scale Remediation of Sulfidic Mine Tailings". Solid State Phenomena 262 (agosto 2017): 651–55. http://dx.doi.org/10.4028/www.scientific.net/ssp.262.651.
Testo completoAbstract (sommario):
To research the remediation efficiency of sulfate reducing bacteria and iron reducing bacteria on heavy metals, the remediation experiments of laboratory-scale and field-scale were conducted respectively with chalcopyrite tailings and 3 hectares lead-zinc sulfides mine tailings. The ion concentration of exudate was determined using inductively coupled plasma atomic emission spectroscopy, and key bacterial strains were investigated by real-time PCR. The laboratory-scale experiment of chalcopyrite tailings indicated pH of exudate rose to neutral, penetration time of exudate significantly increased, redox potential and dissolved iron notably decreased, and black metal sulfides were formed during remediation by sulfate reducing bacteria and iron reducing bacteria. The field-scale lead-zinc sulfides mine tailings remediation results indicated that the concentration of dissolved heavy metals in exudate decreased, and the growth of both moss and plants were promoted.
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Suzuki, Tomoko, Hideki Hashimoto, Nobuyuki Matsumoto, Mitsuaki Furutani, Hitoshi Kunoh e Jun Takada. "Nanometer-Scale Visualization and Structural Analysis of the Inorganic/Organic Hybrid Structure of Gallionella ferruginea Twisted Stalks". Applied and Environmental Microbiology 77, n. 9 (4 marzo 2011): 2877–81. http://dx.doi.org/10.1128/aem.02867-10.
Testo completoAbstract (sommario):
ABSTRACTThe so-called Fe/Mn-oxidizing bacteria have long been recognized for their potential to form extracellular iron hydroxide or manganese oxide structures in aquatic environments. Bacterial species belonging to the genusGallionella, one type of such bacteria, oxidize iron and produce uniquely twisted extracellular stalks consisting of iron oxide-encrusted inorganic/organic fibers. This paper describes the ultrastructure ofGallionellacells and stalks and the visualized structural and spatial localization of constitutive elements within the stalks. Electron microscopy with energy-dispersive X-ray microanalysis showed the export site of the stalk fibers from the cell and the uniform distribution of iron, silicon, and phosphorous in the stalks. Electron energy-loss spectroscopy revealed that the stalk fibers had a central carbon core of bacterial exopolymers and that aquatic iron interacted with oxygen at the surface of the carbon core, resulting in deposition of iron oxides at the surface. This new knowledge of the structural and spatial associations of iron with oxygen and carbon provides deeper insights into the unique inorganic/organic hybrid structure of the stalks.
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Gehrer, Clemens M., Alexander Hoffmann, Richard Hilbe, Philipp Grubwieser, Anna-Maria Mitterstiller, Heribert Talasz, Ferric C. Fang et al. "Availability of Ferritin-Bound Iron to Enterobacteriaceae". International Journal of Molecular Sciences 23, n. 21 (28 ottobre 2022): 13087. http://dx.doi.org/10.3390/ijms232113087.
Testo completoAbstract (sommario):
The sequestration of iron in case of infection, termed nutritional immunity, is an established strategy of host defense. However, the interaction between pathogens and the mammalian iron storage protein ferritin is hitherto not completely understood. To better characterize the function of ferritin in Gram-negative infections, we incubated iron-starved cultures of Salmonella Typhimurium and knockout mutant strains defective for major iron uptake pathways or Escherichia coli with horse spleen ferritin or ionic iron as the sole iron source. Additionally, we added bovine superoxide dismutase and protease inhibitors to the growth medium to assess the effect of superoxide and bacterial proteases, respectively, on Salmonella proliferation and reductive iron release. Compared to free ionic iron, ferritin-bound iron was less available to Salmonella, but was still sufficient to significantly enhance the growth of the bacteria. In the absence of various iron acquisition genes, the availability of ferritin iron further decreased. Supplementation with superoxide dismutase significantly reduced the growth of the ΔentC knockout strain with holoferritin as the sole iron source in comparison with ionic ferrous iron. In contrast, this difference was not observed in the wildtype strain, suggesting that superoxide dismutase undermines bacterial iron uptake from ferritin by siderophore-independent mechanisms. Ferritin seems to diminish iron availability for bacteria in comparison to ionic iron, and its iron sequestering effect could possibly be enhanced by host superoxide dismutase activity.
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Chathoth, Kanchana, Louis Fostier, Bénédicte Martin, Christine Baysse e Fabrice Mahé. "A Multi-Skilled Mathematical Model of Bacterial Attachment in Initiation of Biofilms". Microorganisms 10, n. 4 (23 marzo 2022): 686. http://dx.doi.org/10.3390/microorganisms10040686.
Testo completoAbstract (sommario):
The initial step of biofilm formation is bacteria attachment to biotic or abiotic surfaces and other bacteria through intra or interspecies interactions. Adhesion can be influenced by physicochemical conditions of the environment, such as iron. There is no available mathematical model of bacterial attachment giving realistic initiation rather than random adhesion. We describe a simple stochastic attachment model, from the simplest case in two dimensions with one bacterial species attaching on a homogeneous flat surface to more complex situations, with either several bacterial species, inhomogeneous or non-flat surfaces, or in three dimensions. The model depends on attachment probabilities (on the surface, laterally, or vertically on bacteria). Effects of each of these parameters were analyzed. This mathematical model is then applied to experimental oral microcolonies of Porphyromonas gingivalis, Streptococcus gordonii, and Treponema denticola, either as mono-, two, or three species, under different iron concentrations. The model allows to characterize the adhesion of three bacterial species and explore the effect of iron on attachment. This model appears as a powerful tool for initial attachment analysis of bacterial species. It will enable further modeling of biofilm formation in later steps with biofilm initialization more relevant to real-life subgingival biofilms.
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Miot, Jennyfer, Karim Benzerara, Martin Obst, Andreas Kappler, Florian Hegler, Sebastian Sch�dler, Camille Bouchez, Fran�ois Guyot e Guillaume Morin. "Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria". Applied and Environmental Microbiology 75, n. 17 (10 luglio 2009): 5586–91. http://dx.doi.org/10.1128/aem.00490-09.
Testo completoAbstract (sommario):
ABSTRACT Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (α-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a mixture of lipids and polysaccharides or of lipopolysaccharides. The iron and the organic carbon contents of these fibers are linearly correlated at the 25-nm scale, which in addition to their texture suggests that these fibers act as a template for mineral precipitation, followed by limited crystal growth. Moreover, we evidence a gradient of the iron oxidation state along the mineralized fibers at the submicrometer scale. Fe minerals on these fibers contain a higher proportion of Fe(III) at cell contact, and the proportion of Fe(II) increases at a distance from the cells. All together, these results demonstrate the primordial role of organic polymers in iron biomineralization and provide first evidence for the existence of a redox gradient around these nonencrusting, Fe-oxidizing bacteria.
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Miot, Jennyfer, Karim Benzerara, Guillaume Morin, Andreas Kappler, Sylvain Bernard, Martin Obst, Céline Férard et al. "Iron biomineralization by anaerobic neutrophilic iron-oxidizing bacteria". Geochimica et Cosmochimica Acta 73, n. 3 (febbraio 2009): 696–711. http://dx.doi.org/10.1016/j.gca.2008.10.033.
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Saavedra, Albert, e Eduardo Cortón. "Leaching of Pyrite by Acidithiobacillus ferrooxidans Monitored by Electrochemical Methods". Solid State Phenomena 262 (agosto 2017): 541–44. http://dx.doi.org/10.4028/www.scientific.net/ssp.262.541.
Testo completoAbstract (sommario):
The aim of this work was to use electrochemical methods, capable to follow the corrosion of minerals, in order to monitor the progressive attack of the bacteria on the mineral. The assay was performed in a three electrode cell, with pyrite as the working electrode. The tests were performed in the absence and presence of iron; when present it was in low concentration. In order to compare the bacterial attack with other conditions, the study was conducted in three systems: live bacteria in culture media, dead bacteria in culture media, and sterile culture media, used as a control. The initial bacterial concentration was 106 bact.mL-1. To follow the process, current and corrosion potential were calculated. Live bacteria system showed a continuous increase of current with respect to the incubation time, being up to 4-times higher in the condition with iron (the corrosion current is related to the increase of the mineral area, produced by the bacterial attack, which was corroborated identifying by SEM the bacterial fingerprint on the mineral). Dead bacteria and sterile culture medium showed no current increase with respect to time. In addition, voltammetric studies shown that in live bacteria system the surface area increased when the biofilm was present. Whereas, in the dead bacteria system only the presence of some organic compounds interacting with the mineral was detected. The controls (sterile culture medium) showed the presence of iron hydroxides complexes and elemental sulfur, product of chemical leaching and the initial phase of a passivation process. With this study we demonstrated that the leaching process can be monitored by electrochemical methods, where the process of bacterial-mineral interaction could be followed, and also simultaneously identifying the initial processes of passivation. Our work can be useful for the development of a device for the in situ monitoring of biomining processes.
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Guan, Le Luo, Kaneo Kanoh e Kei Kamino. "Effect of Exogenous Siderophores on Iron Uptake Activity of Marine Bacteria under Iron-Limited Conditions". Applied and Environmental Microbiology 67, n. 4 (1 aprile 2001): 1710–17. http://dx.doi.org/10.1128/aem.67.4.1710-1717.2001.
Testo completoAbstract (sommario):
ABSTRACT More than 60% of species examined from a total of 421 strains of heterotrophic marine bacteria which were isolated from marine sponges and seawater were observed to have no detectable siderophore production even when Fe(III) was present in the culture medium at a concentration of 1.0 pM. The growth of one such non-siderophore-producing strain, alpha proteobacterium V0210, was stimulated under iron-limited conditions with the addition of an isolated exogenous siderophore,N,N′-bis (2,3-dihydroxybenzoyl)-O-serylserine from aVibrio sp. Growth was also stimulated by the addition of three exogenous siderophore extracts from siderophore-producing bacteria. Radioisotope studies using 59Fe showed that the iron uptake ability of V0210 increased only with the addition of exogenous siderophores. Biosynthesis of a hydroxamate siderophore by V0210 was shown by paper electrophoresis and chemical assays for the detection of hydroxamates and catechols. An 85-kDa iron-regulated outer membrane protein was induced only under iron-limited conditions in the presence of exogenous siderophores. This is the first report of bacterial iron uptake through an induced siderophore in response to exogenous siderophores. Our results suggest that siderophores are necessary signaling compounds for growth and for iron uptake by some non-siderophore-producing marine bacteria under iron-limited conditions.
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Norton, Cheryl D., e Mark W. LeChevallier. "A Pilot Study of Bacteriological Population Changes through Potable Water Treatment and Distribution". Applied and Environmental Microbiology 66, n. 1 (1 gennaio 2000): 268–76. http://dx.doi.org/10.1128/aem.66.1.268-276.2000.
Testo completoAbstract (sommario):
ABSTRACT This pilot study compares the compositions of bacterial biofilms in pipe networks supplied with water containing either high levels of biodegradable organic matter (BOM) or low levels of BOM (conventionally or biologically treated, respectively). The Microbial Identification System for fatty acid analysis was utilized in this study to identify a large number of organisms (>1,400) to determine population changes in both conventionally and biologically treated water and biofilms. Data generated during this study indicated that suspended bacteria have little impact on biofilms, and despite treatment (conventional or biological), suspended microbial populations were similar following disinfection. Prechlorination with free chlorine resulted not only in reduced plate count values but also in a dramatic shift in the composition of the bacterial population to predominately gram-positive bacteria. Chlorination of biologically treated water produced the same shifts toward gram-positive bacteria. Removal of assimilable organic carbon by the biologically active filters slowed the rate of biofilm accumulation, but biofilm levels were similar to those found in conventionally treated water within several weeks. Iron pipes stimulated the rate of biofilm development, and bacterial levels on disinfected iron pipes exceeded those for chlorinated polyvinyl chloride pipes. The study showed that the iron pipe surface dramatically influenced the composition, activity, and disinfection resistance of biofilm bacteria.
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Schryvers, Anthony B., e Guido C. Gonzalez. "Receptors for transferrin in pathogenic bacteria are specific for the host's protein". Canadian Journal of Microbiology 36, n. 2 (1 febbraio 1990): 145–47. http://dx.doi.org/10.1139/m90-026.
Testo completoAbstract (sommario):
Transferrin receptors detected by a solid-phase binding assay were shown to be specific for the host's transferrin in the representative bacterial pathogens Neisseria meningitidis (human), Pasteurella haemolytica (bovine), and Actinobacillus pleuropneumoniae (porcine). Consistent with the receptor specificity, iron-deficient bacteria were only capable of utilizing transferrin from the host as a source of iron for growth. Key words: iron, transferrin, receptor.
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Arcos Arango, Yamilet, Judith Betancur Urhan, Gustavo Peñuela e Néstor Jaime Aguirre. "Relationship between soluble forms of iron and manganese and the presence of oxidizing bacteria of both elements in the dam Riogrande II-Don Matías (Antioquia, Colombia)". Revista Facultad de Ingeniería Universidad de Antioquia, n. 55 (1 marzo 2013): 45–54. http://dx.doi.org/10.17533/udea.redin.14713.
Testo completoAbstract (sommario):
From August 2006 to March 2008 presence of bacteria associated with the oxidation of iron and manganese was determined in the euphotic zone limit (LZF) and in the bottom of the hipolimnio (HF) in seven seasons of Riogrande II Dam reservoir depending on the availability of these metals. A water temperature, dissolved oxygen, pH, redox potential and electrical conductivity were measured in situ. At the bottom of hipolimnio with levels of dissolved oxygen ≤ 4 mgL-1 only were found iron oxidizing bacteria compatible with Gallionella sp, and Sphaerotilus sp, Beggiatoa sp . Final estimates for the bacterial population were conducted in culture media and the selective and specific recognition through morphological observations on wet mounts and colors. The largest number of these bacteria was found on the arm of Rio Grande (E4) in which levels of soluble iron were above 1.4 mgL-1. We found no presence of manganese-oxidizing bacteria.
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Arezes, João, Grace Jung, Victoria Gabayan, Erika Valore, Tomas Ganz, Yonca Bulut e Elizabeta Nemeth. "Hepcidin-Induced Hypoferremia Is a Host-Defense Mechanism Against Siderophilic Bacteria". Blood 122, n. 21 (15 novembre 2013): 176. http://dx.doi.org/10.1182/blood.v122.21.176.176.
Testo completoAbstract (sommario):
Abstract Introduction The iron-regulatory hormone hepcidin, a 25 amino acid peptide secreted by hepatocytes, is greatly increased during infection or inflammation, causing hypoferremia. Hypoferremia during infections has been proposed as a host defense mechanism that evolved to restrict iron availability for pathogen growth but specific support for this hypothesis has been lacking. Hereditary hemochromatosis, an iron overload disease caused by hepcidin deficiency, is associated with greatly increased risk of infections with siderophilic pathogens such as Vibrio vulnificus and Yersinia enterocolitica. Hepatic iron overload, high plasma iron concentrations and impaired hypoferremic response to infection could contribute to the susceptibility of hereditary hemochromatosis patients to infections with siderophilic bacteria. In this study we investigated the role of hepcidin-induced hypoferremia in murine resistance to Vibrio vulnificus infection. Methods In order to examine the effect of iron stores, plasma iron concentrations and inflammatory hypoferremia on susceptibility to infection, we iron-depleted or iron-loaded wild type (WT) and hepcidin KO (Hamp1-/-) mice by dietary manipulations: WT mice were fed low (4 ppm) or high (10,000 ppm) iron diets, and hepcidin KO mice were fed low (4 ppm) or standard (270 ppm) iron diets. The mice were infected with V. vulnificus(CMCP6 strain) by subcutaneous administration. We analyzed survival, CFU counts in blood and tissues, as well as iron and inflammatory parameters. In addition, we tested the host-protective effect of acute hypoferremia induced by the minihepcidin PR73, a hepcidin agonist developed in our laboratory. Results As expected, V. vulnificus growth and resulting host mortality was greatly enhanced in iron-loaded as compared to iron-depleted mice, in both WT and Hamp1-/- groups. Comparing WT to Hamp1-/- mice, both iron-loaded and iron-depleted Hamp1-/- mice had much higher mortality than either iron-loaded or iron-depleted WT when given the same number of bacteria. Relative to the number of injected bacterial CFU, Hamp1-/- mice had much higher post-infection bacterial counts in blood, liver and spleen. Furthermore, Hamp1-/- mice did not develop hypoferremia during infection whereas WT mice responded to the infection by acutely increasing plasma hepcidin concentration (within 6 h) and lowering serum iron (Table 1). To isolate the role of hypoferremia, we next compared iron-loaded WT mice to iron-depleted Hamp1-/- mice. Despite identical baseline serum iron concentrations (WT 65±4 vs Hamp1-/- 69±7 μM) and lower hepatic iron stores of Hamp1-/- (WT 425±109 vs Hamp1-/- 112±81 μg/g, p<0.001), iron-depleted Hamp1-/- mice were still much more susceptible to V. vulnificus infection than iron-loaded WT mice, with 1000-fold lower number of bacteria needed for lethal infection (1x103 CFU for Hamp1-/- vs 1x106 CFU for WT), suggesting that hepcidin-dependent hypoferremia is critical for the control of V. vulnificus infection. Experimental induction of hypoferremia in Hamp1-/- mice by the administration of the minihepcidin PR73 prior to infection abated mortality from a lethal dose of V. vulnificus (Table 2) and dramatically reduced bacterial burden in blood and tissues. Minihepcidin treatment was life-saving even when administered 3 h after infection to iron-overloaded Hamp1-/- mice (Figure 1). Conclusion Reactive hepcidin-induced hypoferremia after V. vulnificus infection restricts bacterial growth and helps protect the host from acute mortality. Timely administration of hepcidin agonists to hepcidin-deficient subjects may protect against morbidity and mortality from infections with siderophilic microorganisms. Disclosures: Ganz: Intrinsic LifeSciences: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees. Nemeth:Intrinsic LifeSciences: Equity Ownership, Membership on an entity’s Board of Directors or advisory committees.
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Poiata, Antoniea, Alexandru Vlahovici, Dorina-Emilia Creanga e Petronela Tupu. "Fluorescent bacteria detecting iron loading". International Journal of Environmental Analytical Chemistry 85, n. 12-13 (15 ottobre 2005): 993–1000. http://dx.doi.org/10.1080/03067310500151235.
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Ratledge, Colin, e Lynn G. Dover. "Iron Metabolism in Pathogenic Bacteria". Annual Review of Microbiology 54, n. 1 (ottobre 2000): 881–941. http://dx.doi.org/10.1146/annurev.micro.54.1.881.
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Pakulski, J. Dean, Richard B. Coffin, Cheryl A. Kelley, Sonya L. Holder, Roswell Downer, Peter Aas, M. Maille Lyons e Wade H. Jeffrey. "Iron stimulation of Antarctic bacteria". Nature 383, n. 6596 (settembre 1996): 133–34. http://dx.doi.org/10.1038/383133b0.
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Yarlott, Nelson. "Iron Bacteria Still Bugging Operators". Opflow 26, n. 12 (dicembre 2000): 3–11. http://dx.doi.org/10.1002/j.1551-8701.2000.tb02287.x.
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Prabhakar, Pranav Kumar. "Bacterial Siderophores and Their Potential Applications: A Review". Current Molecular Pharmacology 13, n. 4 (2 novembre 2020): 295–305. http://dx.doi.org/10.2174/1874467213666200518094445.
Testo completoAbstract (sommario):
The bacterial infection is one of the major health issues throughout the world. To protect humans from the infection and infectious agents, it is important to understand the mechanism of interaction of pathogens along with their susceptible hosts. This will help us to develop a novel strategy for designing effective new drugs or vaccines. As iron is an essential metal ion required for all the living systems for their growth, as well, it is needed by pathogenic bacterial cells for their growth and development inside host tissues. To get iron from the host tissues, microbes developed an iron-chelating system called siderophore and also corresponding receptors. Siderophores are low molecular weight organic complex produced by different strains of bacteria for the procurement of iron from the environment or host body under the iron deficient-conditions. Mostly in the environment at physiological pH, the iron is present in the ferric ionic form (Fe3+), which is water- insoluble and thus inaccessible for them. Such a condition promotes the generation of siderophores. These siderophores have been used in different areas such as agriculture, treatment of diseases, culture the unculturable strains of bacteria, promotion of plant growth, controlling phytopathogens, detoxification of heavy metal contamination, etc. In the medical field, siderophores can be used as “Trojan Horse Strategy”, which forms a complex with antibiotics and also delivers these antibiotics to the desired locations, especially in antibiotic-resistant bacteria. The promising application of siderophore-based use of antibiotics for the management of bacterial resistance can be strategies to be used.
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Sandrini, Sara M., Raminder Shergill, Jonathan Woodward, Remya Muralikuttan, Richard D. Haigh, Mark Lyte e Primrose P. Freestone. "Elucidation of the Mechanism by Which Catecholamine Stress Hormones Liberate Iron from the Innate Immune Defense Proteins Transferrin and Lactoferrin". Journal of Bacteriology 192, n. 2 (9 ottobre 2009): 587–94. http://dx.doi.org/10.1128/jb.01028-09.
Testo completoAbstract (sommario):
ABSTRACT The ability of catecholamine stress hormones and inotropes to stimulate the growth of infectious bacteria is now well established. A major element of the growth induction process has been shown to involve the catecholamines binding to the high-affinity ferric-iron-binding proteins transferrin (Tf) and lactoferrin, which then enables bacterial acquisition of normally inaccessible sequestered host iron. The nature of the mechanism(s) by which the stress hormones perturb iron binding of these key innate immune defense proteins has not been fully elucidated. The present study employed electron paramagnetic resonance spectroscopy and chemical iron-binding analyses to demonstrate that catecholamine stress hormones form direct complexes with the ferric iron within transferrin and lactoferrin. Moreover, these complexes were shown to result in the reduction of Fe(III) to Fe(II) and the loss of protein-complexed iron. The use of bacterial ferric iron uptake mutants further showed that both the Fe(II) and Fe(III) released from the Tf could be directly used as bacterial nutrient sources. We also analyzed the transferrin-catecholamine interactions in human serum and found that therapeutically relevant concentrations of stress hormones and inotropes could directly affect the iron binding of serum-transferrin so that the normally highly bacteriostatic tissue fluid became significantly more supportive of the growth of bacteria. The relevance of these catecholamine-transferrin/lactoferrin interactions to the infectious disease process is considered.
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Patel, Priyanka, Shreyas Bhatt, Hardik Patel e Meenu Saraf. "Iron chelating bacteria: a carrier for biofortification and plant growth promotion". Journal of Biological Studies 3, n. 3 (1 dicembre 2020): 111–20. http://dx.doi.org/10.62400/jbs.v3i3.5309.
Testo completoAbstract (sommario):
Biofortification is the process by which the nutritional quality of food crops is improved through agronomic practices, conventional plant breeding, or modern biotechnology to focus on malnourishment in developing countries. Under iron restricted environment certain bacteria (iron chelating bacteria) produced iron chelating molecules called as siderophore. This review gives an overview of Need for biofortification, Plant growth promoting rhizobacteria, Plant growth promoting consortia, importance of iron for human health, uptake of iron in plants, iron chelating (siderophore producing) bacteria as plant growth promotor, siderophore, generalized mechanism for siderophore-mediated iron transport in bacteria and the possible approaches to enhancing iron content in plants by implementing iron chelating bacteria as biotechnological carrier for increasing plant nutrition, yield and quality.
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Corbari, L., M. A. Cambon-Bonavita, G. J. Long, F. Grandjean, M. Zbinden, F. Gaill e P. Compère. "Iron oxide deposits associated with the ectosymbiotic bacteria in the hydrothermal vent shrimp Rimicaris exoculata". Biogeosciences Discussions 5, n. 2 (24 aprile 2008): 1825–65. http://dx.doi.org/10.5194/bgd-5-1825-2008.
Testo completoAbstract (sommario):
Abstract. The Rimicaris exoculata shrimp is considered a primary consumer that dominates the fauna of most Mid-Atlantic Ridge (MAR) hydrothermal ecosystems. These shrimps harbour in their gill chambers an important ectosymbiotic community of chemoautotrophic bacteria associated with iron oxide deposits. The structure and elemental composition of the minerals associated with these bacteria have been investigated by using X-ray microanalyses, light microscopy, and transmission, environmental scanning and scanning transmission electron microscopy. The nature of the iron oxides in shrimps obtained from the Rainbow vent field at 36°14.0' N, has also been determined by Mössbauer spectroscopy. This multidisciplinary approach has revealed that the three step-levels of mineral crust found in the Rimicaris exoculata shrimps consist of heavy concretions formed by nanoparticles of two-line ferrihydrite intermixed with minor inorganic SiO2, (Ca,Mg)SO4, and (Ca,Mg)3(PO4)2 minerals that may stabilise the ferrihydrite form of iron oxides. Morphological observations on the bacteria have revealed their close interactions with these minerals and, thus, indicate the biogenic origin of the iron oxide deposits. The evolution of the bacterial density in the three mineral crust levels is related to the amount of the iron deposits and it is proposed that the lower crust level is the most likely region for the location of the iron-oxidizing bacteria.
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Heinrichs, Jon H., LaVette E. Gatlin, Charles Kunsch, Gil H. Choi e Mark S. Hanson. "Identification and Characterization of SirA, an Iron-Regulated Protein from Staphylococcus aureus". Journal of Bacteriology 181, n. 5 (1 marzo 1999): 1436–43. http://dx.doi.org/10.1128/jb.181.5.1436-1443.1999.
Testo completoAbstract (sommario):
ABSTRACT The acquisition of iron by pathogenic bacteria is often a crucial step in establishing infection. To accomplish this, many bacteria, including Staphylococcus aureus, produce low-molecular-weight iron-chelating siderophores. However, the secretion and transport of these molecules in gram-positive organisms are poorly understood. The sequence, organization, and regulation of genes involved in siderophore transport are conserved among gram-negative bacteria. We used this information to identify a putative siderophore transport locus from an S. aureus genomic sequence database. This locus contains three predicted open reading frames with a high degree of homology to genes involved in siderophore uptake in several bacterial species, in particular the cbrlocus of the plant pathogen Erwinia chrysanthemi. The first gene in the locus, which we have designated sir for staphylococcal iron regulated, encodes a putative lipoprotein with a molecular mass of 37 kDa. The open reading frame is preceded by a 19-bp region of dyad symmetry with homology for operator sequences controlling iron-regulated expression of genes in other bacteria. Fur titration experiments indicate that this region of dyad symmetry is sufficient for Fur-dependent regulation in Escherichia coli. The expression of this gene was repressed, in a dose-dependent manner, by the addition of iron to the S. aureus culture medium. sir-encoded proteins may be involved in iron acquisition in vivo and therefore may be targets for antimicrobial agents.
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Goss, Christopher H., Yukihiro Kaneko, Lisa Khuu, Gail D. Anderson, Sumedha Ravishankar, Moira L. Aitken, Noah Lechtzin et al. "Gallium disrupts bacterial iron metabolism and has therapeutic effects in mice and humans with lung infections". Science Translational Medicine 10, n. 460 (26 settembre 2018): eaat7520. http://dx.doi.org/10.1126/scitranslmed.aat7520.
Testo completoAbstract (sommario):
The lack of new antibiotics is among the most critical challenges facing medicine. The problem is particularly acute for Gram-negative bacteria. An unconventional antibiotic strategy is to target bacterial nutrition and metabolism. The metal gallium can disrupt bacterial iron metabolism because it substitutes for iron when taken up by bacteria. We investigated the antibiotic activity of gallium ex vivo, in a mouse model of airway infection, and in a phase 1 clinical trial in individuals with cystic fibrosis (CF) and chronicPseudomonas aeruginosaairway infections. Our results show that micromolar concentrations of gallium inhibitedP. aeruginosagrowth in sputum samples from patients with CF. Ex vivo experiments indicated that gallium inhibited key iron-dependent bacterial enzymes and increased bacterial sensitivity to oxidants. Furthermore, gallium resistance developed slowly, its activity was synergistic with certain antibiotics, and gallium did not diminish the antibacterial activity of host macrophages. Systemic gallium treatment showed antibiotic activity in murine lung infections. In addition, systemic gallium treatment improved lung function in people with CF and chronicP. aeruginosalung infection in a preliminary phase 1 clinical trial. These findings raise the possibility that human infections could be treated by targeting iron metabolism or other nutritional vulnerabilities of bacterial pathogens.
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Anzaldi, Laura L., e Eric P. Skaar. "Overcoming the Heme Paradox: Heme Toxicity and Tolerance in Bacterial Pathogens". Infection and Immunity 78, n. 12 (2 agosto 2010): 4977–89. http://dx.doi.org/10.1128/iai.00613-10.
Testo completoAbstract (sommario):
ABSTRACT Virtually all bacterial pathogens require iron to infect vertebrates. The most abundant source of iron within vertebrates is in the form of heme as a cofactor of hemoproteins. Many bacterial pathogens have elegant systems dedicated to the acquisition of heme from host hemoproteins. Once internalized, heme is either degraded to release free iron or used intact as a cofactor in catalases, cytochromes, and other bacterial hemoproteins. Paradoxically, the high redox potential of heme makes it a liability, as heme is toxic at high concentrations. Although a variety of mechanisms have been proposed to explain heme toxicity, the mechanisms by which heme kills bacteria are not well understood. Nonetheless, bacteria employ various strategies to protect against and eliminate heme toxicity. Factors involved in heme acquisition and detoxification have been found to contribute to virulence, underscoring the physiological relevance of heme stress during pathogenesis. Herein we describe the current understanding of the mechanisms of heme toxicity and how bacterial pathogens overcome the heme paradox during infection.
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Li, Yongchao, Xiaoxian Hu e Bozhi Ren. "Treatment of antimony mine drainage: challenges and opportunities with special emphasis on mineral adsorption and sulfate reducing bacteria". Water Science and Technology 73, n. 9 (1 febbraio 2016): 2039–51. http://dx.doi.org/10.2166/wst.2016.044.
Testo completoAbstract (sommario):
The present article summarizes antimony mine distribution, antimony mine drainage generation and environmental impacts, and critically analyses the remediation approach with special emphasis on iron oxidizing bacteria and sulfate reducing bacteria. Most recent research focuses on readily available low-cost adsorbents, such as minerals, wastes, and biosorbents. It is found that iron oxides prepared by chemical methods present superior adsorption ability for Sb(III) and Sb(V). However, this process is more costly and iron oxide activity can be inhibited by plenty of sulfate in antimony mine drainage. In the presence of sulfate reducing bacteria, sulfate can be reduced to sulfide and form Sb2S3 precipitates. However, dissolved oxygen and lack of nutrient source in antimony mine drainage inhibit sulfate reducing bacteria activity. Biogenetic iron oxide minerals from iron corrosion by iron-oxidizing bacteria may prove promising for antimony adsorption, while the micro-environment generated from iron corrosion by iron oxidizing bacteria may provide better growth conditions for symbiotic sulfate reducing bacteria. Finally, based on biogenetic iron oxide adsorption and sulfate reducing bacteria followed by precipitation, the paper suggests an alternative treatment for antimony mine drainage that deserves exploration.
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Al-Rawi, Marwa amin, Nada H. A. L. Al-Mudallal e Ali A. Taha. "Iron Oxide Nanoparticles as Anti-Virulence Factors of Gram-positive and Gram-negative Bacteria". SAR Journal of Pathology and Microbiology 4, n. 04 (11 agosto 2023): 48–57. http://dx.doi.org/10.36346/sarjpm.2023.v04i04.003.
Testo completoAbstract (sommario):
Background: Due to their extensive use in medical therapy, iron oxide nanoparticles have recently attracted the attention of researchers in the field of increasing multi-resistance properties in bacterial pathogens. Because iron oxide nanoparticles have a high specific surface area, they can interact with bacterial surface structures and exhibit significant antibacterial activity. Objective: The current work, determined the effect of a novel anti-virulence factor agent which was created from iron oxide nanoparticles against selected gram-positive and gram-negative variant bacterial strains that were isolated and identified from elderly Iraqi patients with urinary tract infections. Methods: Seven bacterial strains (three gram-positive and four gram-negative) were tested for their (biofilm, adhesion, and hemolysis) activity using the quantitative test-tube method, glass-slide method, and by determining the hemolysis ability of bacterial isolates against previously prepared RBC, respectively. The highest virulence factors formation bacterial isolates were chosen to determine the effect of Iron-oxide nanoparticles. Previously prepared and characterized Iron- oxide nanoparticles were used as anti- (biofilm, adhesion, and hemolysis) by using specific Bacterial-Fe3O4 NPs complex with different concentrations. The Results: All these bacteria expressed their virulence factors, the highest-level biofilm formation abilities were detected in Proteus mirabilis and Staphylococcus aureus, and the highest-level adhesion activity was observed in Enterococcus faecalis and Pseudomonas aeruginosa while the highest-level hemolysis activities on human RBC were determined in Micrococcus luteus and E. coli. The effects of (Fe3O4) nanoparticles against the highest virulence factors bacterial isolates shows an increases in the biofilm formation abilities of S. aureus and P. mirabilis as well as for standard bacterial strains the anti-biofilm formation ability of (Fe3 O4) NPs against gram-positive S. aureus, Proteus mirabilis, and standard gram-negative bacteria demonstrated an in-decrease biofilm formation ability of these bacteria effective at (5000 and 10000 µg/ml). The anti-adhesion ability of (Fe3 O4) NPs against gram-positive Enterococcus faecalis, and gram-negative Pseudomonas aeruginosa determined no effect on the adhesion abilities of gram-positive and negative bacteria atall concentrations (250, 400, 500, 750 and 1000µg/ml) Finally, the effect of different concentrations of iron oxide nanoparticles on the hemolysis ability of Micrococcus luteus and Escherichia coli on RBC was determined, the highest hemolysis inhibition level was estimated in 1000 µg/ml and the less inhibition in 500 µg/ml as compared with control.
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Seppänen, Harri. "Biological Treatment of Groundwater in Basins with Floating Filters–II. The Role of Microorganisms in Floating Filters". Water Science and Technology 20, n. 3 (1 marzo 1988): 185–87. http://dx.doi.org/10.2166/wst.1988.0097.
Testo completoAbstract (sommario):
The role of certain types of bacteria is quite decisive in the formation of iron and manganese precipitates. Bacteria and other organisms participate in the precipitation of soluble iron and manganese in many different ways. The production of hydrogen peroxide seems to be an important phase in the formation of the precipitates. Bacteria produce hydrogen peroxide as an intermediate or an end product of metabolic processes (Gorlenko etal., 1983). Iron and manganese bacteria are typical gradient organisms, growing in a sharp gradient between oxidized and reduced environments. Iron precipitating types are oligotrophic and manganese precipitating types need higher concentrations of organic compounds. Manganese precipitating bacteria are eutrophic. Iron bacteria are sessile, and grow attached to the solid surfaces of filter media. Typical iron and manganese precipitating bacteria in groundwaters are Gallionella, Leptothrix, and Metallogenium.
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Pi, Hualiang, e John D. Helmann. "Ferrous iron efflux systems in bacteria". Metallomics 9, n. 7 (2017): 840–51. http://dx.doi.org/10.1039/c7mt00112f.
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Terwilliger, Austen, Michelle C. Swick, Kathryn J. Pflughoeft, Andrei Pomerantsev, C. Rick Lyons, Theresa M. Koehler e Anthony Maresso. "Bacillus anthracis Overcomes an Amino Acid Auxotrophy by Cleaving Host Serum Proteins". Journal of Bacteriology 197, n. 14 (11 maggio 2015): 2400–2411. http://dx.doi.org/10.1128/jb.00073-15.
Testo completoAbstract (sommario):
ABSTRACTBacteria sustain an infection by acquiring nutrients from the host to support replication. The host sequesters these nutrients as a growth-restricting strategy, a concept termed “nutritional immunity.” Historically, the study of nutritional immunity has centered on iron uptake because many bacteria target hemoglobin, an abundant circulating protein, as an iron source. Left unresolved are the mechanisms that bacteria use to attain other nutrients from host sources, including amino acids. We employed a novel medium designed to mimic the chemical composition of human serum, and we show here thatBacillus anthracis, the causative agent of anthrax disease, proteolyzes human hemoglobin to liberate essential amino acids which enhance its growth. This property can be traced to the actions of InhA1, a secreted metalloprotease, and extends to at least three other serum proteins, including serum albumin. The results suggest that we must also consider proteolysis of key host proteins to be a way for bacterial pathogens to attain essential nutrients, and we provide an experimental framework to determine the host and bacterial factors involved in this process.IMPORTANCEThe mechanisms by which bacterial pathogens acquire nutrients during infection are poorly understood. Here we used a novel defined medium that approximates the chemical composition of human blood serum, blood serum mimic (BSM), to better model the nutritional environment that pathogens encounter during bacteremia. Removing essential amino acids from BSM revealed that two of the most abundant proteins in blood—hemoglobin and serum albumin—can satiate the amino acid requirement forBacillus anthracis, the causative agent of anthrax. We further demonstrate that hemoglobin is proteolyzed by the secreted protease InhA1. These studies highlight that common blood proteins can be a nutrient source for bacteria. They also challenge the historical view that hemoglobin is solely an iron source for bacterial pathogens.