Thèses sur le sujet « Bactéries flagellées »
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Duchesne, Ismael. « La motilité des bactéries flagellées en milieu anisotrope ». Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34999.
Texte intégralBacteria play an essential role in nature. We can simply think of their impact on human health to convince ourselves. To be able to play their role in the environment, bacteria often need to reach specific locations. The most common bacterial locomotion system is the flagellar motor. To propel themselves, the flagellated bacteria possess one (or few) rotary motor anchored in their membrane. This motor transfers its rotation to a long helical filament located outside the bacterium thanks to a universal joint called the hook. This motor was the first biological rotary motor discovered. Furthermore, several studies have shown the importance of the flagellar motor during bacterial infections. Thus, it has been the subject of intensive studies for several decades. Most of these studies, however, have been conducted in simple media that represent only a small fraction of natural biological environment. Indeed, bacteria often move in anisotropic media, where the physical properties depend on the direction. For example, mucus found throughout the human body, synovial fluid that lubricates our joints, skin and biofilms are all media that can be anisotropic and where bacteria proliferate. This thesis by article presents our study of the motility of flagellar bacteria in anisotropic media. Since natural biological media are difficult to manipulate in the laboratory, a synthetic medium was first chosen to mimic the properties of natural anisotropic media. Two types of anisotropic media were tested, the liquid crystals (LCs) 5CB and DSCG. Only the LC DSCG has been used since bacteria cannot penetrate the LC 5CB. To create the DSCG LC, molecules of disodium cromoglycate (DSCG) are dissolved in a water-based solvent. At low concentration, the medium is isotropic, and at high concentration the medium becomes anisotropic (a LC). First, the speed and the orientation of the body of the bacteria were recorded while changing the concentration of the DSCG LC to bring the solution from the isotropic phase to the anisotropic phase. These measurements first confirmed that, in an anisotropic environment, the bacteria move in a straight line and reverse their movement rather than performing a random walk as in isotropic media. Observation of bacterial behavior also demonstrated the presence of a pretransition zone in isotropic solutions of DSCG. At these concentrations of DSCG, the molecules begin to organize into rods. This organization explains why bacteria become sticky (via the depletion force), and why the viscosity increases in the pretransition zone. To understand how bacteria can reverse their motion in anisotropic media, the filaments have also been studied. These observations have shown that during the change of direction of the bacteria, the hook is no longer a universal joint and momentarily locks, thus changing the orientation of the filament. This reorientation of the filament does not only reverse the movement of the bacteria in the LC, but it also triggers the reorientation of the filament in other media as in porous media. This observation, supplemented by results from literature, suggests that the blocked hook is a universal phenomenon occurring in all environments. Finally, light-guided dark field microscopy and a microrheological technique will be exposed. These techniques were used during the characterization of the pretransition zone. Throughout this work, it will also be highlighted how our multidisciplinary approach has been beneficial.
Chalmeau, Jérôme. « Contribution from nanotechnologies to the study and assembly of the flagellar nano-motor of bacteria ». Toulouse, INSA, 2009. http://eprint.insa-toulouse.fr/archive/00000343/.
Texte intégralThe bacteria flagellar nanomotor is a nature marvel due to its structure and importance for bacteria. It allows the rotation at high frequency ( 300 Hz) of a long external filament. This filament plays a role comparable to a submarine helix and propels its host in the liquid environment. Despite its size, 45 nm at the largest diameter, this nano-bio-machine is composed of thousands of proteins. These proteins work together in order to generate the flagellar rotation and allow bacteria to swim freely in a liquid environment. Despite its importance for bacteria’s life, its precise mechanism remains unclear today. This motor was discovered more than 3o years ago and a large number of experimental data and hypotheses about its structure and mechanism have been accumulated. The overall assembly, the crystal structure of some constitutive proteins, and the role played by each component permit to draw a possible architecture of the motor. Others experiments has also highlighted some crucial aspects of this machine, through mechanical measurement of the torque developed by the motor, in order to define the torque/speed relationship. However, the nanoscale description of the motor remains limited and many interpretations are still questionable. In this work, I have developed two ambitious parallel and complementary ways to elucidate some open questions: the in vitro re-assembly in a control maner of an essential part of the motor, and a large scale study of the interactions between identified motor’s proteins crucial for the motor rotation. These approaches have been supported by the use of new tools, which had never been used before for studying this nano-motor: the Atomic Force Microscope (AFM), for visualizing in a close native environment part of the motor reassembled, and the Quartz Micro Balance for the interactions study. New experimental datas have been obtained and permitted to propose a new hypothesis of the mechanism of the Bacteria Flagellar Nano-Motor
Lemaire, Laurine. « Étude des propriétés physico-chimiques de la membrane plasmique comme facteurs modulant l'interaction de molécules et des structures protéiques exogènes ». Electronic Thesis or Diss., Compiègne, 2022. http://www.theses.fr/2022COMP2713.
Texte intégralThe plasma membrane was often described as a structure delimiting and protecting the cell from its external environment. However, his role is much more complex and multifunctional. The membrane is an exchange platform at the cellular external and internal environments. Many cellular functions are closely related to it, such as migration, transport of molecules, some pathways of metabolic signaling, or the contact with micro-organisms. This thesis focuses on the study of some cellular processes occurring at the membrane interface using a system that can mimic the lipid bilayer properties. This membrane models that allow a precise control of the in vitro conditions, represent a good alternative to the often inconclusive studies on whole cells. Liposomes allow focusing on a particular function or constituent. In this thesis, the use of the biomimetic model was declined for the study of several processes. The mechanisms of adhesion of flagellated bacteria to lipid bilayers were studied as a function of the physical properties of the lipid bilayers. This information is of paramount importance in the context of antibiotic resistance, giving more information for the potential development of alternative therapies. The liposome model was also used for forming proteoliposomes to study of a transmembrane protein, MRP4 (multidrug resistance associated protein). The study of this protein is an issue in multi-drug treatments. Indeed, this protein is widely involved in drug interactions. Finally, the liposome model was used to characterize the interaction with lipid bilayers of molecules with high therapeutic potential: polyphenols. All of this work was done in collaboration with the team of the Prof Patrick Trouillas (INSERM U1248 team, Limoges University Hospital) working on the development of biomimetic cell models in silico
Arnold, Françoise. « Étude de la flagelline de Clostridium tyrobutyricum ATCC 25755 : analyse biochimique et séquencage de la partie codante du gène ». Brest, 1997. http://www.theses.fr/1997BRES2042.
Texte intégralHoury, Ali. « Rôle des flagelles et de la mobilité dans la formation de biofilms par Bacillus cereus ». Paris 11, 2009. http://www.theses.fr/2009PA112369.
Texte intégralBacillus cereus is an opportunistic pathogen frequently associated with food poisoning and involved in rare but severe local or systemic infections. Contamination of food industry products by B. Cereus can result in economical injuries and might raise safety concerns. The capacity of B. Cereus to form biofilm on different surfaces increases its persistence in the food industry equipments. Here, we have determined the dynamics of biofilm formation by B. Cereus and the roles played by flagella and flagellar motility in B. Ce reus biofilm formation in different growth conditions. We have shown that, in static cultures runned in glass tubes or in microtiter plates, flagellar motility is required for biofilm formation. Motility was necessary for the bacteria to have access to the air-liquid interface where the biofilm develops. Flagellar motility was also involved in the recruitment of planktonic bacteria by the biofilm and promoted biofilm expansion on the colonized surface. We found that B. Cereus is able to form immersed biofilms in continuous flow conditions in flowcells. However, in these growth conditions, flagellar motility was not required for biofilm formation. Observation of biofilms by confocal microscopy have shown the presence of a subpopulation of bacteria able to move through the different biofilm. The speed of these mobile bacteria could reach values up to approximately 16 μm/s. This speed decreased when the biofilm became older and mature, probably as a consequence of an increase in the exopolysaccharide matrix density. Finally, we demonstrated that flagellar mobility was involved in the bacterium pathogenicity in an isect model. In this model, larvae of the wax moth Galleria mellonela was infected by the oral route. Motility, but not the simple presence of flagella, promoted adhesion of bacteria on epithelial HeLa cells
Karayanni, Héra. « Rôle des nanoflagellés hétérotrophes et des ciliés dans la régulation du pico- et nanoplancton photosynthétique et des bactéries en Atlantique NE et le recyclage de la matière organique ». Aix-Marseille 2, 2004. http://www.theses.fr/2004AIX22063.
Texte intégralTruchon, Dany. « Nouveaux marqueurs pour l'observation du moteur flagellaire bactérien ». Thesis, Université Laval, 2011. http://www.theses.ulaval.ca/2011/28827/28827.pdf.
Texte intégralOry, Pascaline. « Interactions entre les virus, les flagellés et les bactéries au sein du réseau microbien planctonique du bassin de Marennes-Oléron ». Thesis, La Rochelle, 2010. http://www.theses.fr/2010LAROS294.
Texte intégralPlanktonic microbial compartments are important in the trophic and biogeochemical functioning of marine ecosystems. This assessment brought us to place these objectives: characterization of virus, bacteria and flagellate compartments and their interactions in Marennes-Oléron Bay (France). Two different approaches have been followed: 1) In situ annual surveys were performed in 2006 and 2007 in order to characterize microbial compartments dynamics and to place them within the bay functioning, compared to Arcachon Bay. The succession of trophic models implied the importance of the microbial food web in both bays. In Marennes Oléron Bay, spatially homogeneous, large inter annual and inter seasonal variations are observed considering the strength of the common link between virioplankton and bacterioplankton. These variations are related to the occurrence of an occasional interaction of phytoplankton. 2) In vitro experiments allow to focus on the processes controlling the dynamics of viruses, flagellates and bacteria and their interactions. The impacts of viral bacteriolysis and flagellate bacterivory are assessed considering environmental variability factors: trophic models, predation pressure and influence of benthic contribution. The bacterial community composition is always influenced by viral lysis and bacterivory due to the sensitivity of bacterial groups. However, bacterial cellular production evolves differently with a stimulation by flagellates during herbivorous food web while bacterivory induces daily production loss of 16% during multivorous food web. Finally, the resuspension of benthic organic components during tide phase tends to increase the microbial loop activity
Soutourina, Olga. « Contrôle de l'expression des gènes dans le processus de motilité chez les bactéries à Gram-négatif ». Versailles-St Quentin en Yvelines, 2001. http://www.theses.fr/2001VERS011V.
Texte intégralGauthier, Mathieu. « Développement d'un système in vitro pour l'étude du moteur flagellaire bactérien d'Escherichia coli ». Doctoral thesis, Université Laval, 2011. http://hdl.handle.net/20.500.11794/23107.
Texte intégralPersonnic, Sébastien. « Dynamique des communautés microbiennes et impacts des virus sur les bactéries auto- et hétérotrophes en milieu lacustre ». Chambéry, 2007. http://www.theses.fr/2007CHAMS023.
Texte intégralA pluri-annual study was conducted, from July 2002 to December 2006, in the three peri-alpine lakes : Annecy, Bourget and Geneva. It allowed us to observe spatial and temporal variations for the abundances of viruses, auto- and heterotrophic bacteria, flagellates, ciliates and small-pigmented eukaryotes between 0 and 50 m depth. We could observe that (I) the dynamics of these micro organisms was relatively well reproducible from one year to the other (II) abiotic parameters (e. G. Temperature) and water column layers (i. E. Epi- vs. Hypolimnion) were significantly involved in the variability of microorganism abundance (III) some differences were observed according to the trophic status of lakes (the mesotrophic Geneva and Bourget vs. The oligotrophic lake Annecy), (IV) at a pluri-annual scale, the variation of abundance of grazers and viruses explained only a low fraction of bacterial abundance variability. A second approach (based on a modified dilution method) was used to quantify simultaneously the impact of viruses and flagellated predators (< 10 µm) as mortality agents of heterotrophic bacteria and picocyanobacteria. Lysis and predation pressure exerted on heterotrophic bacteria was undetectable in winter, whereas in summer they could be responsible for up to 71 % of the heterotrophic bacterial mortality in Lake Geneva. Also, in autumn, lysis and predation reached 42 and 18 % in Lake Geneva and Bourget, respectively. At the same period, viruses could explain 9,8 % and 7,6 % of the picocyanobacterial mortality in the two mesotrophic lakes, suggesting that they could play a key role in fall bloom termination. In contrast, for the oligotrophic Lake Annecy, viruses and predators did not seem to impact strongly and thus control bacterial community abundance. All together, the results obtained during this PhD work allowed us to verify and specify the variability and potential importance of viruses and predators to regulate the procaryotic abundance in large peri-alpine lakes. This work also highlighted the necessity to go further in the knowledge of the different viral life strategies and determine which factors are involved in the control of these strategies
Mazet, Muriel. « Culture in vitro et caractérisation d'enzymes hydrogénosomales chez Histomonas meleagridis, protozoaire flagellé parasite de gallinacés ». Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2007. http://tel.archives-ouvertes.fr/tel-00718217.
Texte intégralHisatugo, Karina Ferreira. « Avaliação do consumo de bactérias pelo zooplâncton em um reservatório eutrófico raso (Reservatório do Monjolinho São Carlos SP) ». Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/2055.
Texte intégralUniversidade Federal de Minas Gerais
Bacteria, found in terrestrial and aquatic environments, besides their important role in organic matter decomposition and nutrient cycling, are a food source for organisms of the higher trophic levels in the food chain, such as protozooplanktonic and metazooplanktonic organisms. This study aimed to evaluate the relative importance of protozooplanktonic (ciliates and heterotrophic nanoflagellates) and metazooplanktonic organisms (rotifers, cladocerans and copepods) as bacterial consumers throughout a year, which included a rainy and a dry season, in a eutrophic environment (Monjolinho reservoir-SP) by quantifying their ingestion rates. For this purpose, grazing experiments were carried out bimonthly during one year at the sub-surface of a central station of the reservoir using fluorescently labeled bacteria (FLB) dyed with DTAF. In each survey, besides the experiments, limnological (pH, dissolved oxygen, temperature, conductivity, water transparency and nutrients) and biological (chlorophyll-a and phaeophytin concentrations, bacterioplankton, protozooplankton and metazooplankton density) water parameters were also sampled. The heterotrophic nanoflagellates (HNF) showed higher population ingestion rates than the ciliates in dry and rainy seasons, and the HNF smaller than 5μm were the main consumers of bacteria. Among the metazooplanktonic organisms, the rotifers dominated the bacterial ingestion, and the organisms belonging to the genus Filinia and Keratella and to the families Testudinellidae and Brachionidae were the main bacterial consumers. Besides ingesting bacteria, however, protozoa and rotifers population also seemed to be controlled by cladocerans and copepods predation, which, in turn, seemed to be regulated by predation of larger organisms, such as small vertebrates. Thus, the predation control (top-down) occured both on bacterial communities and protozooplanktonic and metazooplanktnic communities and bacteria were regulated both by direct and indirect predation of zooplanktonic population. The resources control (bottom-up) semmed to be higher during the dry season, while in the rainy season bacterial communities were more controlled by predation. The greatest impact on bacterial communities was caused by HNF and ciliates during the rainy season and by HNF and rotifers during the dry one.
As bacterias, encontradas em ambientes terrestres e aquaticos, alem de possuirem importante papel na decomposicao da materia organica e na ciclagem de nutrientes, sao fonte de alimento para organismos de niveis troficos superiores, tais como protozoarios e organismos do metazooplancton. O presente trabalho avaliou a importancia relativa de organismos protozooplanctonicos e metazooplanctonicos (rotiferos, cladoceros e copepodes) como consumidores de bacterias em um ambiente eutrofico (Reservatorio do Monjolinho-SP) pela quantificacao das taxas de consumo durante o periodo de um ano, que englobou uma estacao seca e uma chuvosa. Para isso, na superficie de um ponto central no reservatorio, foram realizados experimentos de bacterivoria (grazing) bimestralmente durante um ano, utilizando bacterias marcadas fluorescentemente (FLB) com o corante DTAF. Nos dias dos experimentos foram tambem analisados parametros limnologicos (pH, oxigenio dissolvido, temperatura, condutividade, transparencia da agua, e nutrientes) e biologicos (concentracoes de clorofila-a e feofitina, densidade do bacterioplancton, protozooplancton e metazooplancton). Os nanoflagleados heterotroficos (NFH), quando comparados aos ciliados, apresentaram maiores taxas populacionais de ingestao de bacterias tanto no periodo seco quanto no chuvoso, sendo os NFH menores que 5 μm os maiores consumidores de bacterias. Dentre os organismos metazooplanctonicos, os rotiferos dominaram o consumo de bacterias, sendo os representantes dos generos Filinia e Keratella e das familias Testudinellidae e Brachionidae os maiores consumidores de bacteria. Os dados obtidos indicaram que, alem de predadores de bacterias, as populacoes de protozoarios e rotiferos pareceram ser reguladas pela predacao de cladoceros e copepodes, os quais, por sua vez, parecem sofrer pressao de predacao por organismos maiores, como provavelmente pequenos vertebrados. Assim, o controle por predacao (top-down) ocorreu tanto sobre as comunidades bacterianas quanto sobre as protozooplanctonicas e metazooplanctonicas, sendo as comunidades bacterianas reguladas tanto pela predacao direta quanto indireta das populacoes zooplanctonicas. O controle por disponibilidade de recursos (bottom-up) pareceu ter maior influencia no reservatorio no periodo seco, enquanto no periodo chuvoso, as comunidades bacterianas pareceram mais controladas por predacao, sendo que maiores impactos sobre as comunidades bacterianas foram causados pelos NFH e ciliados no periodo chuvoso, e pelos NFH e rotiferos no periodo seco.
Heo, Minyoung. « Dynamique fonctionnelle du moteur flagellaire bactérien entraîné par des stators marqués par des protéines fluorescentes et par des stators étrangers modifiés par évolution ». Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT080/document.
Texte intégralThe bacterial flagellar motor (BFM) is the macromolecular complex which allows bacteria to swim in liquid media. Located at the base of the flagellum, anchored in the cell membrane, this remarkably small (~45nm) yet powerful rotary motor rotates each flagellum of the cell switching between counterclockwise (CCW) and clockwise (CW) direction. The motor rotation is generated at the interface between the two key components of the motor: the stator protein complexes (each composed of 4 MotA and 2 MotB proteins) and the C- ring protein complex at the base of the rotor. The stator complexes are structurally and functionally discernible modules of the motor, and their dynamical association and dissociation around the rotor controls the generation of torque.The first project of this study aims to investigate how the FP tag on the stator protein modifies the torque generation and switching of the motor. This is particularly important because the fluorescent protein tag lies at the interface between stator and rotor, where torque and switching are produced. Three different FPs (eGFP, YPet, Dendra2) were fused to MotB. Interestingly, despite the high similarity of their structures, our analysis revealed that the three fusion stators generate different torque. Furthermore, in the presence of fusion stators, the motor showed significantly impaired switching abilities. When switching direction of the rotation, the absolute value of the speed of WT motors does not change, whereas this symmetry of speed upon switching is not observed in the fusion stator motors, and switching can be accompanied with a significant (~30%) decrease in absolute speed. Both the impaired torque generation and the switching ability were improved by introducing a rigid linker between the stator and the FP tag. Taken together, this study provides a further insight into the dynamics of the stator and rotor interaction at its interface.When the cells carrying the fluorescently labeled stators were observed in a custom made TIRF-fluorescence microscope with single molecule capability, the fluorescence signals were detected as concentrated clusters in the membrane as expected for these membrane proteins around the motors, together with a population of stators diffusing in the membrane. Fluorescent clusters were visible at the center of rotating cells tethered to the glass slide by a single flagellum, confirming that the fluorescent tags can be visualized in functioning motors.In a second project developed in Bertus Beaumont lab at TU Delft, taking BFM as an experimental evolutionary model system, its modularity and evolvability have been explored to learn the molecular details of the evolution of molecular machines. The stators of E.coli have been exchanged by a set of 21 homologue foreign stators. The experiments revealed that the stator proteins can be exchanged between distant bacteria species, and some of the non-compatible stators can be positively modified by evolution to become functional. Those evolved strains accumulated beneficial mutations in their foreign motA and motB genes, especially on their functional domains. Identical mutations in different stators were common, indicating that evolution is repeatable. The functional investigation at the single motor level revealed that those beneficial mutations improved the torque generation and/or the switching ability of the motor. The detailed genotype and phenotype investigations of the evolutionary modified BFM may bring an insight into how molecular machines such as BFM have evolved as well as the functional effects of the beneficial mutations that facilitate functional integration
Picard, Virginie. « Structure et dynamique du potamoplancton de la Loire moyenne (France) en période de basses eaux ». Clermont-Ferrand 2, 2003. http://www.theses.fr/2003CLF21424.
Texte intégralArantxa, Camus Etchecopar. « Mécanismes moléculaires impliqués dans la formation de biofilm à l’interface eau-composés organiques hydrophobes ». Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3032/document.
Texte intégralHydrophobic organic compounds (HOC), a large family of naturally-produced or anthropogenic molecules including lipids and hydrocarbons, represent a significant part of organic matter in marine ecosystems. Because of their low solubility in water, bacteria that degrade those compounds require the establishment of specific cell functions to increase their biodisponibility. Biofilm formation in water-HOC interface is one of these adaptations. The model of bacteria used in our laboratory, Marinobacter hydrocarbonoclasticus SP17, is able to form a biofilm on a wide range of HOC, such as alkanes, fatty alcohols and triglycerides, in order to use them as a carbon and energy source. The main purpose of my work was to broaden the knowledge of how bacteria adhere to and from biofilms on HOC, through the functional characterization of 10 candidate genes highlighted during proteomic and transcriptomic studies. Genetic tools and a gene-specific functional characterization have been developed in order to carry out this project. Functional study conducted on MARHY2686 revealed its involvement in the formation of biofilm on alkanes. Co-expression of MARHY2686 and the adjacent genes MARHY2687 and MARHY2685 durnig transcriptomic analysis together with their phylogenetic distribution and synteny conservation suggest that these three genes are involved in the same biological process. According to the high peptide sequence identity between MARHY2686 and AdeT, a periplasmic protein of a tripartite efflux pump system of Acinetobacter baumanii, MARHY2686 in combination with MARHY2687 and MARHY2685 could be the components of such a system. Other phenotypic observations would consider the involvement of MARHY2686 either in the assimilation of HOC or in the accumulation of intracellular lipid reserves. M. hydrocarbonoclasticus SP17 uses type IV pili during biofilm formation on HOC. These appendages are involved in the adhesion of this strain to and in a detachment process from HOC. Type IV pili could either act directly to allow bacteria to detach from the surface to which it is adhered, or indirectly through the action of bacteriophages. The presence of twitching motility on HOC has also been suggested. Finally, the role of the type VI secretion system (T6SS), a well-known protein system which allows interactions between bacteria and host cells, during the formation of a mono-species biofilm on HOC where no other microorganism than M. hydrocarbonoclasticus SP17 is present, has been studied
Malandrin, Laurence. « Les protéines de surface de pseudomonas syringae (sensu lato) : description, variabilité et application taxonomique ». Angers, 1995. http://www.theses.fr/1995ANGE0015.
Texte intégralChalmeau, Jerôme. « Contributions des nanotechnologies à l'étude et à l'assemblage du Nano-Moteur flagellaire des bacteries ». Phd thesis, INSA de Toulouse, 2009. http://tel.archives-ouvertes.fr/tel-00468919.
Texte intégralMichaud, Caroline. « Dynamique des symbioses mutualistes hôtes-microbiotes : mode et efficacité de transmission des symbiotes dans les populations du termite xylophage Reticulitermes grassei ». Thesis, Tours, 2019. http://www.theses.fr/2019TOUR4027.
Texte intégralMany animals including humans live in symbiotic interaction with gut microorganisms contributing to essential functions (nutrition, immunity). The ‘vertical’ way of transmission of symbionts (i.e., from parents to offspring) must stabilise these symbioses, notably by strengthening partner fidelity. However, the efficiency of vertical transmission has rarely been studied, especially in the case where hosts harbour a complex microbial community (or ‘microbiota’) composed by many microbial taxa interacting between them and with the host.The objective of this work was to study the mode and efficiency of transmission of gut microorganisms (protists and bacteria) helping the wood-feeding termite Reticulitermes grassei to digest ingested wood (lignocellulose fibres). Our results revealed contrasted situations between microorganisms. While protists are efficiently vertically transmitted, the majority of bacterial taxa is not only vertically transmitted but seems to be acquired by the environment