1887

Abstract

The MarR-like transcriptional regulator and two ABC transporters encoded by the operon in the dental caries pathogen have important regulatory roles related to oxidative stress tolerance, genetic competence and (p)ppGpp metabolism. A unique feature of the operon, when compared to other bacteria, is the presence of two peptides, designated Pep1 and Pep2, encoded in alternative reading frames at the 3′ end of . Here, we show that the operon, including Pep1 and 2, is essential for to survive and maintain viability at elevated temperatures. No major changes in the levels of the heat shock proteins DnaK or GroEL that could account for the thermosensitivity of mutants were observed. By introducing a single amino acid substitution into the gene that deletes an internally encoded peptide, XrpA, we found that XrpA is a contributing factor to the thermosensitive phenotype of a Δ strain. Overexpression of XrpA on a plasmid also caused a significant growth defect at 42 °C. Interestingly, loss of the gene for the RelA/SpoT homologue (RSH) enzyme, , restored growth of the Δ strain at 42 °C. During heat stress and when a stringent response was induced, levels of (p)ppGpp were elevated in the Δ strain. Deletion of in the Δ strain lowered the basal levels of (p)ppGpp to those observed in wild-type . Thus, (p)ppGpp pools are dysregulated in Δ, which likely leads to aberrant control of transcriptional/translational processes and the thermosensitive phenotype. In summary, the genes and peptides encoded in the operon are critical for thermotolerance, and in some strains these phenotypes are related to altered (p)ppGpp metabolism and increased production of the XrpA peptide.

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/content/journal/micro/10.1099/mic.0.000887
2020-01-10
2020-01-24
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