The two-component regulatory system CenK–CenR regulates expression of a previously uncharacterized protein required for salinity and oxidative stress tolerance in Sinorhizobium meliloti
Genes of unknown function constitute a considerable fraction of most bacterial genomes. In a Tn5-based search for stress response genes in the nitrogen-fixing facultative endosymbiont Sinorhizobium ( Ensifer ) meliloti , we identified a previously uncharacterized gene required for growth on solid me...
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Veröffentlicht in: | Frontiers in microbiology 2022-09, Vol.13, p.1020932-1020932 |
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Zusammenfassung: | Genes of unknown function constitute a considerable fraction of most bacterial genomes. In a Tn5-based search for stress response genes in the nitrogen-fixing facultative endosymbiont
Sinorhizobium
(
Ensifer
)
meliloti
, we identified a previously uncharacterized gene required for growth on solid media with increased NaCl concentrations. The encoded protein carries a predicted thioredoxin fold and deletion of the gene also results in increased sensitivity to hydrogen peroxide and cumene hydroperoxide. We have designated the gene
srlA
(stress resistance locus A) based on these phenotypes. A deletion mutant yields phenotypic revertants on high salt medium and genome sequencing revealed that all revertants carry a mutation in genes homologous to either
cenK
or
cenR
.
srlA
promoter activity is abolished in these revertant host backgrounds and in a strain carrying a deletion in
cenK
. We also observed that the
srlA
promoter is autoregulated, displaying low activity in a wildtype (wt) host background and high activity in the
srl
deletion mutant background. The
srlA
promoter includes a conserved inverted repeat directly upstream of the predicted −35 subsequence. A mutational analysis demonstrated that the site is required for the high promoter activity in the
srlA
deletion background. Electromobility shift assays using purified wildtype CenR response regulator and a D55E phosphomimetic derivative suggest this protein acts as a likely Class II activator by binding promoter DNA. These results document the first identified CenK–CenR regulon member in
S. meliloti
and demonstrate this two-component regulatory system and gene
srlA
influences cellular growth and persistence under certain stress-inducing conditions. |
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ISSN: | 1664-302X 1664-302X |
DOI: | 10.3389/fmicb.2022.1020932 |