Functional mgrA Influences Genetic Changes within a Staphylococcus aureus Cell Population over Time
Date
2022
Authors
Lee, J.
Carda-Diéguez, M.
Žiemytė, M.
Vreugde, S.
Cooksley, C.
Crosby, H.A.
Horswill, A.R.
Mira, A.
Zilm, P.S.
Kidd, S.P.
Editors
Galperin, M.Y.
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Journal article
Citation
Journal of Bacteriology, 2022; 204(10):e00138-22-1-e00138-22-19
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James Lee, Miguel Carda-Diéguez, Miglė Žiemytė, Sarah Vreugde, Clare Cooksley, Heidi A. Crosby, Alexander R. Horswill, Alex Mira, Peter S. Zilm, Stephen P. Kidd
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Abstract
Prolonged survival in the host-bacteria microenvironment drives the selection of alternative cell types in Staphylococcus aureus, permitting quasi-dormant sub-populations to develop. These facilitate antibiotic tolerance, long-term growth, and relapse of infection. Small Colony Variants (SCV) are an important cell type associated with persistent infection but are difficult to study in vitro due to the instability of the phenotype and reversion to the normal cell type. We have previously reported that under conditions of growth in continuous culture over a prolonged culture time, SCVs dominated a heterogenous population of cell types and these SCVs harbored a mutation in the DNA binding domain of the gene for the transcription factor, mgrA. To investigate this specific cell type further, S. aureus WCH-SK2-DmgrA itself was assessed with continuous culture. Compared to the wild type, the mgrA mutant strain required fewer generations to select for SCVs. There was an increased rate of mutagenesis within the DmgrA strain compared to the wild type, which we postulate is the mechanism explaining the increased emergence of SCV selection. The mgrA derived SCVs had impeded metabolism, altered MIC to specific antibiotics and an increased biofilm formation compared to non-SCV strain. Whole genomic sequencing detected single nucleotide polymorphisms (SNP) in phosphoglucosamine mutase glmM and tyrosine recombinase xerC. In addition, several genomic rearrangements were detected which affected genes involved in important functions such as antibiotic and toxic metal resistance and pathogenicity. Thus, we propose a direct link between mgrA and the SCV phenotype.
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© 2022 American Society for Microbiology. All Rights Reserved.