Contribution of chemical changes in membrane lipids to the osmoadaptation of the halophilic bacterium Chromohalobacter salexigens

 
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Contribution of chemical changes in membrane lipids to the osmoadaptation of the halophilic bacterium Chromohalobacter salexigens (EN)

Vargas, C. (EN)

Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας (EL)
Vargas, C. (EN)

The long-term response of the broad-salt growing halophile Chromohalobacter salexigens DSM 3043(T) to salt stress has been investigated with respect to adaptive changes in membrane lipid composition. This study included the wildtype and three salt-sensitive, ectoine-deficient strains: CHR62 (ectA::Tn1732, unable to grow above 0.75M NaCl), CHR63 (eetC::Tn1732, unable to grow above 1.5 M NaCl), and CHR64, which was able to grow in minimal medium M63 up to 2.5 M NaCl, but its growth was slower than the wild-type strain at salinities above 1.5 M NaCl. This mutant accumulated ectoine and hydroxyectoine as major compatible solutes, but also the ectoine precursor, N-gamma-acetyldiaminobutyric acid, and was found to be affected in the ectoine synthase gene ectC. The main phospholipids of the wild-type strain were phosphatidylethanolamine, phosphatidylglycerol (PG), and cardiolipin (CL). Major fatty acids were detected as 16:0, 18:1, and 16:1, including significant amounts of cyc-19:0, and cyc-17:0. CL and cyclopropane fatty acids (CFA) levels were elevated when the wild-type strain was grown at high salinity (2.5 M NaCl). Membranes of the most salt-sensitive trains CHR62 and CHR63, but not of the less salt-sensitive strain CHR64, contained lower levels of CL. The proportion of cyc-19:0 in CHR64 was three-fold (at 2.0 M NaCl) and 2.5-fold (at 2.5 M NaCl) lower than that of the wild type, suggesting that this mutant has a limited capacity to incorporate CFA into phospholipids at high salt. The addition of 1 mM ectoine to cultures of the wild-type strain increased the ratio PG/ CL from 1.8 to 3.3 at 0.75 M NaCl, and from 1 to 6.5 at 2.5 M NaCl, and led to a slight decrease in CFA content. Addition of 1 mM ectoine to the mutants restored the steady-state levels of CL and CFA found in the wild-type strain supplemented with ectoine. These findings suggest that exogenous ectoine might attenuate the osmostress response involving changes in membrane lipids. (c) 2005 Elsevier GmbH. All rights reserved. (EN)

osmoadaptation (EN)

Πανεπιστήμιο Ιωαννίνων (EL)
University of Ioannina (EN)

Systematic and Applied Microbiology (EN)

2005

<Go to ISI>://000231799700001

Elsevier (EN)



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