Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Analysis of the effect of acid stress in Lactococcus lactis MG1363

ABSTRACT: To understand the system response to pH changes in the environment, the expression of genes during the pH shift was investigated. Pre-adaptation effects were examined by comparing the effects seen with cells pre-grown in pH 5.1 or pH 6.5 to those occuring after a sudden pH change (pre-grown in pH 6.5, and suspended in buffer of pH 5.1). mRNA of L. lactis MG1363 cells grown at pH 6.5 and suspended in 50 mM KPi buffer, pH 5.1 and of those grown at pH 5.1 and suspended in 50 mM KPi buffer, pH 5.1 were compared. Control experiment was performed with mRNA of cells grown at pH 6.5 and suspended in buffer of pH 6.5 compared to that of cells grown in pH 5.1 and suspended in buffer of 5.1.

ORGANISM(S): Lactococcus lactis subsp. cremoris MG1363

SUBMITTER: Ana Solopova

PROVIDER: E-GEOD-47012 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Every cyanobacterial species contains gene encoding site-2-protease (S2P) homolog. The studied prokaryotic S2P homologs play essential roles in regulating stress response through intramembrane proteolysis of membrane-bound anti-sigma factors. Here, gene of Slr0643, one of four S2P homologs in Synechocystis sp. PCC 6803, was insertionally disrupted to explore its physiological role. Only a partially segregated mutant was obtained, indicating its indispensability for growth. The partially disrupted mutant could not grow at pH 6.5, while wild type acclimated to pH 6.5 quickly. The slr0643 gene expression was transiently induced after pH transfer from 7.5 to 6.5. Both evidences demonstrated the pivotal role of fully functional Slr0643 in acid acclimation. DNA microarray and quantitative RT-PCR analyses decoded genes involved in early acid acclimation and revealed differentially expressed genes due to slr0643 disruption at both pH conditions. Early acid acclimation to pH 6.5 included upregulation of sigH, hik16 and hik35, and downregulation of pcrR and sigG; as well as downregulation of porins and upregulation of inorganic carbon and nitrogen transporters. Defective photosynthesis and excess expression of NADH dehydrogenase, together with over upregulation of carbon transporter and repression of nitrogen transporter and metabolism gene contributed to the acid lethality of mutant at pH 6.5. Most interestingly, analysis of microarray data revealed the close relationship between slr0643 disruption and expression of sigH operon. Therefore it was implied that Slr0643/Sll0857/SigH might acts through S2P/anti-Sigma factor/Sigma factor mechanism to play a role in acid acclimation. M-bM-^@M-^C Loop design was used to compare differential expression of wild type and mutant at pH 7.5 and pH 6.5 respectively, including dye-swape. Biological variation was sampled by extracting RNA from three independent experiments and pooling them together before hybridizations. Two or four replicate chips for each comparison and two replicate printings per chip represent technical repeats.

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Analysis of the effect of acid stress in Lactococcus lactis MG1363

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