Open AccessSalt Stress-Induced Changes in the Transcriptome, Compatible Solutes, and Membrane Lipids in the Facultatively Phototrophic Bacterium Rhodobacter sphaeroides
Author(s) -
Minoru Tsuzuki,
Oleg V. Moskvin,
Masayuki Kuribayashi,
Katsuaki Sato,
Susana B. Retamal,
Mitsuru Abo,
Jill H. Zeilstra-Ryalls,
Mark Gomelsky
Publication year - 2011
Publication title -
applied and environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.552
H-Index - 324
eISSN - 1070-6291
pISSN - 0099-2240
DOI - 10.1128/aem.05463-11
Subject(s) - betaine , rhodobacter sphaeroides , osmoprotectant , operon , biochemistry , ectoine , trehalose , biology , transcriptome , phospholipid , osmotic shock , proline , sigma factor , gene , chemistry , gene expression , promoter , membrane , escherichia coli , photosynthesis , amino acid
Responses to NaCl stress were investigated in phototrophically grownAlphaproteobacterium Rhodobacter sphaeroides by transcriptome profiling, mutational analysis, and measurements of compatible solutes and membrane phospholipids. After exposure to salt stress, genes encoding two putative glycine betaine uptake systems,proVWX andbetS , were highly upregulated. Mutational analysis revealed that BetS, not ProVWX, was the primary transporter of this compatible solute. Upon the addition of salt, exogenous glycine betaine was taken up rapidly, and maximal intracellular levels were reached within minutes. In contrast, synthesis of another important compatible solute inR. sphaeroides , trehalose, increased slowly following salt stress, reaching maximal levels only after several hours. This accumulation pattern was consistent with the more gradual increase in salt-induced transcription of the trehalose biosynthesis operonotsBA . Several genes encoding putative transcription factors were highly induced by salt stress. Multiple copies of one of these factors,crpO (RSP1275), whose product is a member of the cyclic AMP receptor protein/fumarate and nitrate reduction regulator (CRP/FNR) family, improved NaCl tolerance. WhencrpO was provided in multicopy, expression of genes for synthesis or transport of compatible solutes was unaltered, but the membrane phospholipid composition became biased toward that found in salt-stressed cells. Collectively, this study characterized transcriptional responses to salt stress, correlated changes in transcription with compatible solute accumulation rates, identified the main glycine betaine transporter and trehalose synthase, characterized salt-induced changes in phospholipid composition, and uncovered a transcription factor associated with changes in phospholipids. These findings set the stage for deciphering the salt stress-responsive regulatory network inR. sphaeroides .