1887

Abstract

WR101 was identified as a mutant of WSM419 that contained a minitransposon-induced transcriptional fusion activated at least 20-fold at pH 5.7. The expression of this fusion in moderately acid conditions was dependent on the calcium concentration; increasing the calcium concentration to enhance cell growth and survival in acid conditions decreased the expression of the fusion. A gene region containing the fusion was sequenced, revealing five genes: , , , and . The reporter in WR101 was fused to , which encodes a putative transmembrane protein also found in other such as , and . As LpiA has partial sequence similarity to the lysyl-phosphatidylglycerol (LPG) synthetase FmtC/MprF from , membrane lipid compositions of strains were analysed. Cells cultured under neutral or acidic growth conditions did not induce any detectable LPG and therefore this lipid cannot be a major constituent of membranes. Expression studies in localized the acid-activated promoter within a 372 bp region upstream of the start codon. The acid-activated transcription of required the fused sensor–regulator product of the gene, because expression of was severely reduced in an mutant. strain 1021 does not contain and acid-activated expression of the fusion did not occur in this species. Although acid-activated transcription was not required for cell growth, its expression was crucial in enhancing the viability of cells subsequently exposed to lethal acid (pH 4.5) conditions.

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2006-10-01
2020-01-20
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