Cellular Envelopes and Tolerance to Acid pH in Mesorhizobium loti

Correa, Olga Susana; Rivas, Emilio; Barneix, Atilio J.

doi:10.1007/pl00006812

Cited by 26 publications

(12 citation statements)

References 34 publications

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“…This can partly be achieved by avoiding the diffusion of protons from the medium into the cell, so changes in envelope composition (phospholipid, fatty acid, and protein composition) may be an adaptation to survive at low pH, as suggested for M. loti (Correa et al 1999). In the present study, several genes coding for outer membrane and other cell envelope proteins, namely, ABC transporters, were reported as overexpressed, thus probably contributing to maintenance of the cell internal pH.…”

Section: Cog Categorysupporting

confidence: 52%

“…Studies on rhizobia acid stress response have been conducted in Ensifer medicae , Ensifer meliloti (de Lucena et al 2010;Hellweg et al 2009), Rhizobium tropici (Graham et al 1994) and M. loti (Correa and Barneix 1997;Correa et al 1999). Overall, these studies suggest that act (for acid tolerance) and exo (exopolysaccharide I biosynthesis) genes are commonly involved in acid response.…”

Section: Introductionmentioning

confidence: 99%

“…In rhizobia, acid tolerance mechanisms seem to involve regulation of cytoplasmic pH, proton exclusion and/or extrusion (Graham et al 1994) and exopolysaccharide (EPS) production (Correa et al 1999). The quantity of EPS produced by rhizobia isolates from Cicer, Phaseolus, Leucaena and Melilotus species is positively correlated with acid tolerance, and it is postulated that EPS could modify the rhizobia microenvironment and so decrease the stresses induced by an acid soil (Cunningham and Munns 1984).…”

Section: Introductionmentioning

confidence: 99%

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Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Laranjo

Alexandre

Oliveira

2014

Appl Microbiol Biotechnol

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Rhizobia are legume bacterial symbionts that fix nitrogen in the root nodules of plants. The aim of the present study was to investigate the global transcriptional response of rhizobia upon an acidic shock. Changes in the transcriptome of cells of Mesorhizobium loti strain MAFF303099 upon an acidic shock at pH 3 for 30 min were analysed. From a total of 7,231 protein-coding genes, 433 were found to be differentially expressed upon acidic shock, of which 322 were overexpressed. Although most of the overexpressed genes encode hypothetical proteins, the two most represented Cluster of Orthologous Group (COG) categories are 'defence mechanisms' and 'transcription'. Differentially expressed genes are dispersed throughout the chromosome, with the exception of the symbiosis island, where most genes remain unchanged. A significant number of transcriptional regulators and ABC transporter genes are overexpressed. No overexpression of genes typically associated to acid tolerance in rhizobia, such as act and exo genes, was detected. Overall, this study suggests a transcriptional response to acidic shock of M. loti distinct from other rhizobia. Additional studies are in course to explore the role of some of the highly overexpressed genes and to further elucidate the molecular bases of acid stress response.

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Section: Cog Categorysupporting

confidence: 52%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Laranjo

Alexandre

Oliveira

2014

Appl Microbiol Biotechnol

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“…These variations are accompanied by a higher membrane microviscosity (Ló pez et al, 2001(Ló pez et al, , 2002. Similar variations in the CL content have also been described in protoplasts of B. subtilis due to a polyethylene glycol stress (Sánchez- Rivas & Bohin, 1983), in Rhodobacter sphaeroides (Catucci et al, 2004) and in Mesorhizobium loti grown under acidic stress (Correa et al, 1999), thus suggesting that an increased CL content might be a general cellular response due to membrane adjustments.…”

Section: Introductionmentioning

confidence: 60%

Role of anionic phospholipids in the adaptation of Bacillus subtilis to high salinity

et al. 2006

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The importance of the content of anionic phospholipids [cardiolipin (CL) and phosphatidylglycerol (PG)] in the osmotic adaptation and in the membrane structure of Bacillus subtilis cultures was investigated. Insertion mutations in the three putative cardiolipin synthase genes (ywiE, ywnE and ywjE) were obtained. Only the ywnE mutation resulted in a complete deficiency in cardiolipin and thus corresponds to a true clsA gene. The osmotolerance of a clsA mutant was impaired: although at NaCl concentrations lower than 1?2 M the growth curves were similar to those of its wild-type control, at 1?5 M NaCl (LBN medium) the lag period increased and the maximal optical density reached was lower. The membrane of the clsA mutant strain showed an increased PG content, at both exponential and stationary phase, but no trace of CL in either LB or LBN medium. As well as the deficiency in CL synthesis, the clsA mutant showed other differences in lipid and fatty acids content compared to the wild-type, suggesting a cross-regulation in membrane lipid pathways, crucial for the maintenance of membrane functionality and integrity. The biophysical characteristics of membranes and large unilamellar vesicles from the wild-type and clsA mutant strains were studied by Laurdan's steady-state fluorescence spectroscopy. At physiological temperature, the clsA mutant showed a decreased lateral lipid packing in the protein-free vesicles and isolated membranes compared with the wild-type strain. Interestingly, the lateral lipid packing of the membranes of both the wild-type and clsA mutant strains increased when they were grown in LBN. In a conditional IPTG-controlled pgsA mutant, unable to synthesize PG and CL in the absence of IPTG, the osmoresistance of the cultures correlated with their content of anionic phospholipids. The transcriptional activity of the clsA and pgsA genes was similar and increased twofold upon entry to stationary phase or under osmotic upshift. Overall, these results support the involvement of the anionic phospholipids in the growth of B. subtilis in media containing elevated NaCl concentrations.

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“…Typically, CFA synthase studies have involved analysis of total fatty acids by gas chromatography coupled to mass spectrometry (GC/MS) or fatty acid analysis of lipid classes isolated using thin-layer chromatography (TLC) (Correa et al, 1999;Grogan & Cronan, 1997). However, intact lipids can be analysed directly by the infusion of crude extracts without the need for chromatography, using a combination of tandem mass spectrometric techniques (ESI/MS/MS); this approach is known as 'shotgun lipidomics' (Han & Gross, 2003, 2005a.…”

Section: Introductionmentioning

confidence: 99%

Cyclopropane fatty acyl synthase in Sinorhizobium meliloti

et al. 2009

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Cyclopropane fatty acyl synthases (CFA synthases) are enzymes that catalyse the addition of a methylene group across cis double bonds of monounsaturated fatty acyl chains in lipids. We have investigated the function of two putative genes, cfa1 and cfa2, proposed to code for CFA synthases in Sinorhizobium meliloti. Total fatty acid composition and fatty acid distributions within lipid classes for wild-type and cfa1 and cfa2 mutant strains grown under P i starvation and in acidic culture conditions were obtained by GC/MS and by infusion ESI/MS/MS, respectively. For wildtype cells and the cfa1 mutant, total cyclopropane fatty acids (CFAs) increased by 10 % and 15 % under P i starvation and acidic conditions, respectively; whereas in the cfa2 mutant, CFAs were less than 0.1 % of wild-type under both growth conditions. Reporter gene fusion experiments revealed that cfa1 and cfa2 were expressed at similar levels in free-living cells. Thus under the conditions we examined, cfa2 was required for the cyclopropanation of lipids in S. meliloti whereas the role of cfa1 remains to be determined. Analysis of intact lipids revealed that cyclopropanation occurred on cis-11-octadecenoic acid located in either the sn-1 or the sn-2 position in phospholipids and that cyclopropanation in the sn-2 position occurred to a greater extent in phosphatidylcholines and sulfoquinovosyldiacylglycerols under acidic conditions than under P i starvation. The cfa2 gene was also required for cyclopropanation of non-phosphoruscontaining lipids. Principal components analysis revealed no differences in the cyclopropanation of four lipid classes. We concluded that cyclopropanation occurred independently of the polar head group. Neither cfa1 nor cfa2 was required for symbiotic nitrogen fixation.

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Cellular Envelopes and Tolerance to Acid pH in Mesorhizobium loti

Cited by 26 publications

References 34 publications

Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Genes commonly involved in acid tolerance are not overexpressed in the plant microsymbiont Mesorhizobium loti MAFF303099 upon acidic shock

Role of anionic phospholipids in the adaptation of Bacillus subtilis to high salinity

Cyclopropane fatty acyl synthase in Sinorhizobium meliloti

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