1
|
Modelling of ionized and non-ionized carbon nanotubes used as selective nano-platforms for water desalination. APPLIED NANOSCIENCE 2022. [DOI: 10.1007/s13204-021-02327-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
2
|
Cell-Free Expression of Unnatural Amino Acid Incorporated Aquaporin SS9 with Improved Separation Performance in Biomimetic Membranes. BIOMED RESEARCH INTERNATIONAL 2018; 2018:3560894. [PMID: 30363687 PMCID: PMC6181008 DOI: 10.1155/2018/3560894] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Revised: 07/29/2018] [Accepted: 09/06/2018] [Indexed: 11/17/2022]
Abstract
Aquaporins (AQPs) are widely applied in biomimetic membranes for water recycling and desalination. In this study, a novel aquaporin was isolated from Photobacterium profundum SS9 (AQP SS9), which showed high water permeability and potential for practical water purification applications. To improve the stability of the AQP SS9 embedded biomimetic membranes, a modified AQP SS9 was obtained by incorporation of an unnatural amino acid (p-propargyloxyphenylalanine, pPpa) (P-AQP SS9) in vitro using a mutated Methanocaldococcus jannaschii tyrosyl-tRNA synthetase (TyrRS) and the cell-free expression system. The modified AQP SS9 can covalently link with phospholipids and hence significantly improve the stability of biomimetic membranes. The concentration of Mg2+ and fusion expression with signal peptides were evaluated to enhance the expression level of P-AQP SS9, resulting in a highest yield of 49 mg/L. The modified AQP SS9 was then reconstituted into DOPC liposomes and analyzed by a stopped-flow spectrophotometer. The obtained water permeability coefficient (Pf) of 7.46×10−4 m/s was 5.7 times higher than that of proteoliposomes with the wild-type AQP SS9 (Pf=1.31×10−4 m/s) and 12.1 times higher than that of the DOPC liposomes (Pf=6.15×10−5m/s). This study demonstrates the development of a cell-free system for the expression of membrane proteins with much higher stability and the potential application of the modified aquaporins for water filtration.
Collapse
|
3
|
Bio-Inspired Aquaporinz Containing Double-Skinned Forward Osmosis Membrane Synthesized through Layer-by-Layer Assembly. MEMBRANES 2015; 5:369-84. [PMID: 26266426 PMCID: PMC4584286 DOI: 10.3390/membranes5030369] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Accepted: 08/03/2015] [Indexed: 11/17/2022]
Abstract
We demonstrated a novel AquaporinZ (AqpZ)-incorporated double-skinned forward osmosis (FO) membrane by layer-by-layer (LbL) assembly strategy. Positively charged poly(ethyleneimine) (PEI) and negatively charged poly(sodium 4-styrenesulfonate) (PSS) were alternately deposited on both the top and bottom surfaces of a hydrolyzed polyacrylonitrile (H-PAN) substrate. Subsequently, an AqpZ-embedded 1,2-dioleloyl-sn-glycero-3-phosphocholine (DOPC)/1,2-dioleoyl-3-trimethylammonium- propane (chloride salt) (DOTAP) supported lipid bilayer (SLB) was formed on PSS-terminated (T-PSS) membrane via vesicle rupture method. The morphology and structure of the biomimetic membranes were characterized by in situ atomic force microscopy (AFM), scanning electron microscope (SEM), Fourier transform infrared spectrometer using the attenuated total reflection technique (ATR-FTIR), and contact angle. Moreover, the FO performance of the resultant membrane was measured by using 2 M MgCl2 solution as draw solution and deionized (DI) water as feed solution, respectively. The membrane with a protein-to-lipid weight ratio (P/L) of 1/50 exhibits 13.2 L/m2h water flux and 3.2 g/m2h reversed flux by using FO mode, as well as 15.6 L/m2h water flux and 3.4 L/m2h reversed flux for PRO mode (the draw solution is placed against the active layer). It was also shown that the SLB layer of the double-skinned FO membrane can increase the surface hydrophilicity and reduce the surface roughness, which leads to an improved anti-fouling performance against humic acid foulant. The current work introduced a new method of fabricating high performance biomimetic FO membrane by combining AqpZ and a double-skinned structure based on LbL assembly.
Collapse
|
4
|
Xie W, Wei Jun Low J, Armugam A, Jeyaseelan K, Wah Tong Y. Regulation of Aquaporin Z osmotic permeability in ABA tri-block copolymer. AIMS BIOPHYSICS 2015. [DOI: 10.3934/biophy.2015.3.381] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
|
5
|
Beebo A, Mathai JC, Schoefs B, Spetea C. Assessment of the requirement for aquaporins in the thylakoid membrane of plant chloroplasts to sustain photosynthetic water oxidation. FEBS Lett 2013; 587:2083-9. [PMID: 23732702 DOI: 10.1016/j.febslet.2013.05.046] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 04/30/2013] [Accepted: 05/16/2013] [Indexed: 11/18/2022]
Abstract
Oxygenic photosynthetic organisms use sunlight energy to oxidize water to molecular oxygen. This process is mediated by the photosystem II complex at the lumenal side of the thylakoid membrane. Most research efforts have been dedicated to understanding the mechanism behind the unique water oxidation reactions, whereas the delivery pathways for water molecules into the thylakoid lumen have not yet been studied. The most common mechanisms for water transport are simple diffusion and diffusion facilitated by specialized channel proteins named aquaporins. Calculations using published data for plant chloroplasts indicate that aquaporins are not necessary to sustain water supply into the thylakoid lumen at steady state photosynthetic rates. Yet, arguments for their presence in the plant thylakoid membrane and beneficial action are presented.
Collapse
Affiliation(s)
- Azeez Beebo
- Department of Biological and Environmental Sciences, University of Gothenburg, Box 461, 405 30 Gothenburg, Sweden
| | | | | | | |
Collapse
|
6
|
Hernández-Castro R, Rodríguez MC, Seoane A, García Lobo JM. The aquaporin gene aqpX of Brucella abortus is induced in hyperosmotic conditions. MICROBIOLOGY-SGM 2004; 149:3185-3192. [PMID: 14600230 DOI: 10.1099/mic.0.26678-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
An aquaporin gene (aqpX) was previously detected in the pathogenic bacterium Brucella abortus. Earlier studies showed that AqpX mediated rapid and large water fluxes in both directions in response to sudden osmotic up- or downshifts. Here, to study the role and the expression of the aqpX gene in B. abortus, an aqpX null mutant was constructed using an aqpX : : lacZ gene fusion. This mutant showed no significant difference in growth rate compared to the wild-type strain when grown in rich and minimal media, demonstrating that disruption of the aqpX gene was not lethal for B. abortus. The role of the B. abortus AqpX water channel was investigated by exposing the cells to hypo- and hyperosmolar conditions. While in hyperosmolar environments the growth rate of the knockout mutant was not affected, in hypo-osmolar conditions this mutant showed reduced viability after 50 h of growth. beta-Galactosidase assays and RT-PCR revealed that aqpX gene expression and the amount of aqpX mRNA were markedly increased in hyperosmolar conditions. Moreover, B. abortus aqpX expression levels were enhanced during the mid-exponential phase of growth. These results indicated that the expression of aqpX was regulated during the growth curve and induced in hyperosmolar conditions. This report is believed to be the first example of the induction of a bacterial aquaporin in hypertonic conditions.
Collapse
Affiliation(s)
- Rigoberto Hernández-Castro
- Departamento de Microbiología e Inmunología, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Coyoacan 04510, Mexico DF, Mexico
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain
| | - María Cruz Rodríguez
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain
| | - Asunción Seoane
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain
| | - Juan María García Lobo
- Departamento de Biología Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad Asociada al Centro de Investigaciones Biológicas (CSIC), Cardenal Herrera Oria s/n, 39011 Santander, Spain
| |
Collapse
|
7
|
Hohmann S. Osmotic adaptation in yeast--control of the yeast osmolyte system. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 215:149-87. [PMID: 11952227 DOI: 10.1016/s0074-7696(02)15008-x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The yeast Saccharomyces cerevisiae (baker's yeast or budding yeast) is an excellent eukaryotic model system for cellular biology with a well-explored, completely sequenced genome. Yeast cells possess robust systems for osmotic adaptation. Central to the response to high osmolarity is the HOG pathway, one of the best-explored MAP kinase pathways. This pathway controls via different transcription factors the expression of more than 150 genes. In addition, osmotic responses are also controlled by protein kinase A via a general stress response pathway and by presently unknown signaling systems. The HOG pathway partially controls expression of genes encoding enzymes in glycerol production. Glycerol is the main yeast osmolyte, and its production is essential for growth in a high osmolarity medium. Upon hypo-osmotic shock, yeast cells transiently stimulate another MAP kinase pathway, the so-called PKC pathway, which appears to orchestrate the assembly of the cell surface and the cell wall. In addition, yeast cells show signs of a regulated volume decrease by rapidly exporting glycerol through Fps1p. This unusual MIP channel is gated by osmotic changes and thereby plays a key role in controlling the intracellular osmolyte content. Yeast cells also possess two aquaporins, Aqy1p and Aqy2p. The production of both proteins is strictly regulated, suggesting that these water channels play very specific roles in yeast physiology. Aqy1p appears to be developmentally regulated. Given the strong yeast research community and the excellent tools of genetics and functional genomics available, we expect yeast to be the best-explored cellular organism for several years ahead, and osmotic responses are a focus of interest for numerous yeast researchers.
Collapse
Affiliation(s)
- Stefan Hohmann
- Department of Cell and Molecular Biology, Göteborg University, Sweden
| |
Collapse
|
8
|
Rodrı Guez MAC, Froger A, Rolland JP, Thomas D, Agüero J, Delamarche C, Garcı A-Lobo JM. A functional water channel protein in the pathogenic bacterium Brucella abortus. MICROBIOLOGY (READING, ENGLAND) 2000; 146 Pt 12:3251-3257. [PMID: 11101683 DOI: 10.1099/00221287-146-12-3251] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The gene for a new bacterial aquaporin, AqpX, was cloned from the pathogenic Gram-negative bacterium Brucella abortus. The gene was mapped on the large chromosome of B. abortus. It is flanked by one upstream and two downstream copies of the Brucella repeated sequence Bru-RS. Prediction from the nucleotide sequence indicated that the protein is a member of the MIP family, which comprises channels for water and/or solute transport. Expression in Xenopus oocytes and cryoelectron microscopy of Escherichia coli cells transformed with the aqpX gene confirmed that the protein is an efficient water channel. Glycerol uptake experiments in E. coli also showed that the protein is not able to transport glycerol.
Collapse
Affiliation(s)
- Marı A C Rodrı Guez
- Departamento de Biologı́a Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad asociada al Centro de Investigaciones Biológicas, CSIC, Cardenal Herrera Oria s/n, 39011 Santander, Spain1
| | - Alexandrine Froger
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex, Bretagne, France2
| | - Jean-Paul Rolland
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex, Bretagne, France2
| | - Daniel Thomas
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex, Bretagne, France2
| | - Jesús Agüero
- Departamento de Biologı́a Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad asociada al Centro de Investigaciones Biológicas, CSIC, Cardenal Herrera Oria s/n, 39011 Santander, Spain1
| | - Christian Delamarche
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes cedex, Bretagne, France2
| | - Juan M Garcı A-Lobo
- Departamento de Biologı́a Molecular, Facultad de Medicina, Universidad de Cantabria, Unidad asociada al Centro de Investigaciones Biológicas, CSIC, Cardenal Herrera Oria s/n, 39011 Santander, Spain1
| |
Collapse
|
9
|
Delamarche C, Thomas D, Rolland JP, Froger A, Gouranton J, Svelto M, Agre P, Calamita G. Visualization of AqpZ-mediated water permeability in Escherichia coli by cryoelectron microscopy. J Bacteriol 1999; 181:4193-7. [PMID: 10400575 PMCID: PMC93919 DOI: 10.1128/jb.181.14.4193-4197.1999] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Transport of water across the plasma membrane is a fundamental process occurring in all living organisms. In bacteria, osmotic movement of water across the cytoplasmic membrane is needed to maintain cellular turgor; however, the molecular mechanisms of this process are poorly defined. Involvement of aquaporin water channels in bacterial water permeability was suggested by the recent discovery of the aquaporin gene, aqpZ, in Escherichia coli. By employing cryoelectron microscopy to compare E. coli cells containing (AqpZ+) and lacking (AqpZ-) aquaporin, we show that the AqpZ water channel rapidly mediates large water fluxes in response to sudden changes in extracellular osmolarity. These findings (i) demonstrate for the first time functional expression of a prokaryotic water channel, (ii) evidence the bidirectional water channel feature of AqpZ, (iii) document a role for AqpZ in bacterial osmoregulation, and (iv) define a suitable model for studying the physiology of prokaryotic water transport.
Collapse
Affiliation(s)
- C Delamarche
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex, France
| | | | | | | | | | | | | | | |
Collapse
|
10
|
Abstract
Bacteria can survive dramatic osmotic shifts. Osmoregulatory responses mitigate the passive adjustments in cell structure and the growth inhibition that may ensue. The levels of certain cytoplasmic solutes rise and fall in response to increases and decreases, respectively, in extracellular osmolality. Certain organic compounds are favored over ions as osmoregulatory solutes, although K+ fluxes are intrinsic to the osmoregulatory response for at least some organisms. Osmosensors must undergo transitions between "off" and "on" conformations in response to changes in extracellular water activity (direct osmosensing) or resulting changes in cell structure (indirect osmosensing). Those located in the cytoplasmic membranes and nucleoids of bacteria are positioned for indirect osmosensing. Cytoplasmic membrane-based osmosensors may detect changes in the periplasmic and/or cytoplasmic solvent by experiencing changes in preferential interactions with particular solvent constituents, cosolvent-induced hydration changes, and/or macromolecular crowding. Alternatively, the membrane may act as an antenna and osmosensors may detect changes in membrane structure. Cosolvents may modulate intrinsic biomembrane strain and/or topologically closed membrane systems may experience changes in mechanical strain in response to imposed osmotic shifts. The osmosensory mechanisms controlling membrane-based K+ transporters, transcriptional regulators, osmoprotectant transporters, and mechanosensitive channels intrinsic to the cytoplasmic membrane of Escherichia coli are under intensive investigation. The osmoprotectant transporter ProP and channel MscL act as osmosensors after purification and reconstitution in proteoliposomes. Evidence that sensor kinase KdpD receives multiple sensory inputs is consistent with the effects of K+ fluxes on nucleoid structure, cellular energetics, cytoplasmic ionic strength, and ion composition as well as on cytoplasmic osmolality. Thus, osmoregulatory responses accommodate and exploit the effects of individual cosolvents on cell structure and function as well as the collective contribution of cosolvents to intracellular osmolality.
Collapse
Affiliation(s)
- J M Wood
- Department of Microbiology and Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Guelph, Guelph, Ontario, Canada N1G
| |
Collapse
|
11
|
Bonhivers M, Carbrey JM, Gould SJ, Agre P. Aquaporins in Saccharomyces. Genetic and functional distinctions between laboratory and wild-type strains. J Biol Chem 1998; 273:27565-72. [PMID: 9765289 DOI: 10.1074/jbc.273.42.27565] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Aquaporin water channel proteins mediate the transport of water across cell membranes in numerous species. The Saccharomyces genome data base contains an open reading frame (here designated AQY1) that encodes a protein with strong homology to aquaporins. AQY1 from laboratory and wild-type strains of Saccharomyces were expressed in Xenopus oocytes to determine the coefficients of osmotic water permeability (Pf). Oocytes injected with wild-type AQY1 cRNAs exhibit high Pf values, whereas oocytes injected with AQY1 cRNAs from laboratory strains exhibit low Pf values and have reduced levels of Aqy1p due to two amino acid substitutions. When the AQY1 gene was deleted from a wild-type yeast and cells were cultured in vitro with cycled hypo-osmolar or hyper-osmolar stresses, the AQY1 null yeast showed significantly improved viability when compared with the parental wild-type strain. We conclude that Saccharomyces cerevisiae contains at least one aquaporin gene, but it is not functional in laboratory strains due to apparent negative selection pressures resulting from in vitro methods.
Collapse
Affiliation(s)
- M Bonhivers
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | | | |
Collapse
|
12
|
Abstract
This map is an update of the edition 9 map by Berlyn et al. (M. K. B. Berlyn, K. B. Low, and K. E. Rudd, p. 1715-1902, in F. C. Neidhardt et al., ed., Escherichia coli and Salmonella: cellular and molecular biology, 2nd ed., vol. 2, 1996). It uses coordinates established by the completed sequence, expressed as 100 minutes for the entire circular map, and adds new genes discovered and established since 1996 and eliminates those shown to correspond to other known genes. The latter are included as synonyms. An alphabetical list of genes showing map location, synonyms, the protein or RNA product of the gene, phenotypes of mutants, and reference citations is provided. In addition to genes known to correspond to gene sequences, other genes, often older, that are described by phenotype and older mapping techniques and that have not been correlated with sequences are included.
Collapse
Affiliation(s)
- M K Berlyn
- Department of Biology and School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06520-8104, USA.
| |
Collapse
|
13
|
Froger A, Tallur B, Thomas D, Delamarche C. Prediction of functional residues in water channels and related proteins. Protein Sci 1998; 7:1458-68. [PMID: 9655351 PMCID: PMC2144022 DOI: 10.1002/pro.5560070623] [Citation(s) in RCA: 188] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
In this paper, we present an updated classification of the ubiquitous MIP (Major Intrinsic Protein) family proteins, including 153 fully or partially sequenced members available in public databases. Presently, about 30 of these proteins have been functionally characterized, exhibiting essentially two distinct types of channel properties: (1) specific water transport by the aquaporins, and (2) small neutral solutes transport, such as glycerol by the glycerol facilitators. Sequence alignments were used to predict amino acids and motifs discriminant in channel specificity. The protein sequences were also analyzed using statistical tools (comparisons of means and correspondence analysis). Five key positions were clearly identified where the residues are specific for each functional subgroup and exhibit high dissimilar physico-chemical properties. Moreover, we have found that the putative channels for small neutral solutes clearly differ from the aquaporins by the amino acid content and the length of predicted loop regions, suggesting a substrate filter function for these loops. From these results, we propose a signature pattern for water transport.
Collapse
Affiliation(s)
- A Froger
- UPRES-A CNRS 6026, Biologie Cellulaire et Reproduction, Equipe Canaux et Récepteurs Membranaires, Université de Rennes1 bâtiment 13, France
| | | | | | | |
Collapse
|
14
|
Calamita G, Kempf B, Bonhivers M, Bishai WR, Bremer E, Agre P. Regulation of the Escherichia coli water channel gene aqpZ. Proc Natl Acad Sci U S A 1998; 95:3627-31. [PMID: 9520416 PMCID: PMC19886 DOI: 10.1073/pnas.95.7.3627] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/1997] [Accepted: 01/29/1998] [Indexed: 02/06/2023] Open
Abstract
Osmotic movement of water across bacterial cell membranes is postulated to be a homeostatic mechanism for maintaining cell turgor. The molecular water transporter remained elusive until discovery of the Escherichia coli water channel, AqpZ, however the regulation of the aqpZ gene expression and physiological function of the AqpZ protein are unknown. Northern analysis revealed a transcript of 0.7 kb, confirming the monocistronic nature of aqpZ. Regulatory studies performed with an aqpZ::lacZ low copy plasmid demonstrate enhanced expression during mid-logarithmic growth, and expression of the gene is dependent upon the extracellular osmolality, which increased in hypoosmotic environments but strongly reduced in hyperosmolar NaCl or KCl. While disruption of the chromosomal aqpZ is not lethal for E. coli, the colonies of the aqpZ knockout mutant are smaller than those of the parental wild-type strain. When cocultured with parental wild-type E. coli, the aqpZ knockout mutant exhibits markedly reduced colony formation when grown at 39 degrees C. Similarly, the aqpZ knockout mutant also exhibits greatly reduced colony formation when grown at low osmolality, but this phenotype is reversed by overexpression of AqpZ protein. These results implicate AqpZ as a participant in the adaptive response of E. coli to hypoosmotic environments and indicate a requirement for AqpZ by rapidly growing cells.
Collapse
Affiliation(s)
- G Calamita
- Dipartimento di Fisiologia Generale ed Ambientale, University of Bari, via Amendola, 165/A, 70126 Bari, Italy.
| | | | | | | | | | | |
Collapse
|