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An XRE-superfamily transcriptional regulator XrpA controls low pH tolerance of Serratia marcescens

ABSTRACT: The acid tolerance of industrial strains is a significant challenge in the fermentation process. The bacterium Serratia marcescens is part of the Enterobacteriaceae family of eubacteria, which is a potential industrial microorganism. However, the molecular mechanism behind S. marcescens acid resistance is not properly understood. In this study, we screened for novel regulators that respond to acidic conditions by a Tn5G transposon insertion mutagenesis of S. marcescens and found mutations in a gene encoding for the HTH_XRE super-family regulatory protein member, here named xrpA. Using transcriptomics and further experiments, we showed that the xrpA disruption conferred pleiotropic phenotype changes, including highly decreased biomass, altered cell shape, H+-ATPase activity, and deficiency of cell membrane permeability and integrity, compared with those of the parent (JNB5-1) strain at low pH. These data revealed that the molecular mechanism by which xrpA affects acid resistance of S. marcescens is through positive regulation of cell membrane permeability, integrity, and H+-ATPase activity to maintain intracellular homeostasis at low pH. Finally, we constructed an acidic resistant strain JNB5-1/pSX1314 by overexpression of xrpA in S. marcescens and found that its ability to produce prodigiosin by fermentation increased by 21.74% compared with that of parent strain at pH4.0. These results indicated that xrpA regulates tolerance to low pH by transcriptional regulation of acid stress response genes to maintain cell membrane function in S. marcescens.

ORGANISM(S): Serratia marcescens WW4

PROVIDER: GSE137185 | GEO | 2019/09/15

REPOSITORIES: GEO

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Project description:The yeast protein kinases Sat4/Hal4 and Hal5 are required for the plasma membrane stability of the K+ transporter Trk1 and some amino acid and glucose permeases. The transcriptomic analysis presented here indicates alterations in the general control of both nitrogen and carbon metabolism. Accordingly, we observed reduced uptake of methionine and leucine in the hal4 hal5 mutant. This decrease correlates with activation of the Gcn2-Gcn4 pathway, as measured by expression of the lacZ gene under the control of the Gcn4 promoter. However, with the exception of methionine biosynthetic genes, few amino acid biosynthetic genes are induced in the hal4 hal5 mutant, whereas several genes involved in amino acid catabolism are repressed. Concerning glucose metabolism, we found that this mutant exhibits derepression of respiratory genes in the presence of glucose, leading to an increased activity of mitochondrial enzymes, as measured by SDH activity. In addition, the reduced glucose consumption in the hal4 hal5 mutant correlates with a more acidic intracellular pH and with low activity of the plasma membrane H+-ATPase. As a compensatory mechanism for the low glycolytic rate, the hal4 hal5 mutant overexpresses the HXT4 high affinity glucose transporter and the hexokinase genes. These results indicate that the hal4 hal5 mutant presents defects in the general control of nitrogen and carbon metabolism, which correlate with reduced transport of amino acids and glucose, respectively. A more acidic intracellular pH may contribute to some defects of this mutant. Four biological replicates were used to assess diferentially expression between wild type yeast strain and the hal4hal5 mutant strain for three sample sets: 1) cells grown in YPD pH 4.5 and BY4741 genetic background, 2) cells grown in YPD pH 4.5 and W303 genetic background, 3) cells grown in YPD pH 6.0 and W303 genetic background. Differentially expressed genes were identified using one-class significant analysis of microarrays (SAM; Tusher et al, 2004)

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An XRE-superfamily transcriptional regulator XrpA controls low pH tolerance of Serratia marcescens

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