scholarly journals Pore Size Dependence on Growth Temperature Is a Common Characteristic of the Major Outer Membrane Protein OprF in Psychrotrophic and Mesophilic Pseudomonas Species

2004 ◽  
Vol 70 (11) ◽  
pp. 6665-6669 ◽  
Author(s):  
Thomas Jaouen ◽  
Emmanuelle D� ◽  
Sylvie Chevalier ◽  
Nicole Orange
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Lipid Bilayers ◽  
Growth Temperature ◽  
Outer Membrane Proteins ◽  
Ecological Niches ◽  
Rich Cluster ◽  
Channel Size ◽  
Outer Membrane Permeability ◽  
Psychrotrophic Strain

ABSTRACT Pseudomonas species adapt well to hostile environments, which are often subjected to rapid variations. In these bacteria, the outer membrane plays an important role in the sensing of environmental conditions such as temperature. In previous studies, it has been shown that in the psychrotrophic strain P. fluorescens MF0, the major porin OprF changes its channel size according to the growth conditions and could affect outer membrane permeability. Studies of the channel-forming properties of OprFs from P. putida 01G3 and P. aeruginosa PAO1 in planar lipid bilayers generated similar results. The presence of a cysteine- or proline-rich cluster in the central linker region is not essential for channel size modulations. These findings suggest that OprF could adopt two alternative conformations in the outer membrane and that folding is thermoregulated. In contrast, no difference according to growth temperature was observed for structurally different outer membrane proteins, such as OprE3 from the Pseudomonas OprD family of specific porins. Our results are consistent with the fact that the decrease in channel size observed at low growth temperature is a particular feature of the OprF porin in various psychrotrophic and mesophilic Pseudomonas species isolated from diverse ecological niches. The ability to reduce outer membrane permeability at low growth temperature could provide these bacteria with adaptive advantages.

scholarly journals Outer Membrane Permeability of Cyanobacterium Synechocystis sp. Strain PCC 6803: Studies of Passive Diffusion of Small Organic Nutrients Reveal the Absence of Classical Porins and Intrinsically Low Permeability

2017 ◽  
Vol 199 (19) ◽  
Author(s):  
Hikaru Kowata ◽  
Saeko Tochigi ◽  
Hideyuki Takahashi ◽  
Seiji Kojima
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Outer Membrane Proteins ◽  
Inorganic Ions ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Content Type ◽  
Organic Nutrients ◽  
Outer Membrane Permeability ◽  
Pcc 6803

ABSTRACT The outer membrane of heterotrophic Gram-negative bacteria plays the role of a selective permeability barrier that prevents the influx of toxic compounds while allowing the nonspecific passage of small hydrophilic nutrients through porin channels. Compared with heterotrophic Gram-negative bacteria, the outer membrane properties of cyanobacteria, which are Gram-negative photoautotrophs, are not clearly understood. In this study, using small carbohydrates, amino acids, and inorganic ions as permeation probes, we determined the outer membrane permeability of Synechocystis sp. strain PCC 6803 in intact cells and in proteoliposomes reconstituted with outer membrane proteins. The permeability of this cyanobacterium was >20-fold lower than that of Escherichia coli. The predominant outer membrane proteins Slr1841, Slr1908, and Slr0042 were not permeable to organic nutrients and allowed only the passage of inorganic ions. Only the less abundant outer membrane protein Slr1270, a homolog of the E. coli export channel TolC, was permeable to organic solutes. The activity of Slr1270 as a channel was verified in a recombinant Slr1270-producing E. coli outer membrane. The lack of putative porins and the low outer membrane permeability appear to suit the cyanobacterial autotrophic lifestyle; the highly impermeable outer membrane would be advantageous to cellular survival by protecting the cell from toxic compounds, especially when the cellular physiology is not dependent on the uptake of organic nutrients. IMPORTANCE Because the outer membrane of Gram-negative bacteria affects the flux rates for various substances into and out of the cell, its permeability is closely associated with cellular physiology. The outer membrane properties of cyanobacteria, which are photoautotrophic Gram-negative bacteria, are not clearly understood. Here, we examined the outer membrane of Synechocystis sp. strain PCC 6803. We revealed that it is relatively permeable to inorganic ions but is markedly less permeable to organic nutrients, with >20-fold lower permeability than the outer membrane of Escherichia coli. Such permeability appears to fit the cyanobacterial lifestyle, in which the diffusion pathway for inorganic solutes may suffice to sustain the autotrophic physiology, illustrating a link between outer membrane permeability and the cellular lifestyle.

scholarly journals Omp35, a New Enterobacter aerogenes Porin Involved in Selective Susceptibility to Cephalosporins

2004 ◽  
Vol 48 (6) ◽  
pp. 2153-2158 ◽  
Author(s):  
Charléric Bornet ◽  
Nathalie Saint ◽  
Lilia Fetnaci ◽  
Myrielle Dupont ◽  
Anne Davin-Régli ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Antibiotic Susceptibility ◽  
Enterobacter Aerogenes ◽  
Artificial Membranes ◽  
Specific Location ◽  
Outer Membrane Permeability ◽  
Constriction Region ◽  
High Conductance

ABSTRACT In Enterobacter aerogenes, β-lactam resistance often involves a decrease in outer membrane permeability induced by modifications of porin synthesis. In ATCC 15038 strain, we observed a different pattern of porin production associated with a variable antibiotic susceptibility. We purified Omp35, which is expressed under conditions of low osmolality and analyzed its pore-forming properties in artificial membranes. This porin was found to be an OmpF-like protein with high conductance values. It showed a noticeably higher conductance compared to Omp36 and a specific location of WNYT residues in the L3 loop. The importance of the constriction region in the porin function suggests that this organization is involved in the level of susceptibility to negative large cephalosporins such as ceftriaxone by bacteria producing the Omp35 porin subfamily.

scholarly journals Sporadic Emergence of Klebsiella pneumoniae Strains Resistant to Cefepime and Cefpirome in Greek Hospitals

1998 ◽  
Vol 36 (1) ◽  
pp. 266-268 ◽  
Author(s):  
L. S. Tzouvelekis ◽  
E. Tzelepi ◽  
E. Prinarakis ◽  
M. Gazouli ◽  
A. Katrahoura ◽  
...  
Keyword(s):  
Klebsiella Pneumoniae ◽  
Membrane Permeability ◽  
Outer Membrane ◽  
Outer Membrane Permeability ◽  
Greek Hospitals ◽  
Hydrolysis Of

The sporadic emergence of Klebsiella pneumoniae strains resistant to cefepime and cefpirome was observed in Greek hospitals during 1996. Examination of six epidemiologically distinct strains and clones selected in vitro provided indications that resistance is due to the cooperation of decreased outer membrane permeability and hydrolysis of the cephalosporins by SHV-5 β-lactamase, which was produced in large amounts.

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