IADR Abstract Archives
The Staphylococcus aureus Small Colony Variants: occasional and unusual inhabitants of the mouth and their link disease.
Objectives: To undertsand the strain specific and universal cellular and molecualr changes in S. aureus when grown under controlled growth-rate, nutrient limitation and for a prolonged time period.
Methods: We have established a continuous culture systems to grow the bacteria at steady state for 60 days. We have analysed the bacteria taken at every day for colony phenotypes, antibiotic tolerance and growth characteristics. Furthermore, at various timepoints we used membrane proteomics, transcriptomics and genomics to determine the changes in the cells, the changes to the surface proteins, the whole genome gene expression and genetic events. We have used different strains of S. aureus to determine universal and strains specific traits.
Results: There was a repeatable and strain-consistent change over time to the non-pigmented, low growth rate cell type: the Small Colony Variant (SCV). This was connected by an extracellular matrix that was not polysaccharide but protein and extracellualr DNA. There was a distinctive profile of gene expression, including the up-regulation of the giant surface protein (1 MDa) Ebh and the cell's lantibiotic. There was down-regulation of a range of immune mediators and toxins (capsule, pigment, leukocidins). There were genetic events including single nucleotide polymorphisms (SNP) in the regulatory systems RsbU and MgrA. We have used USA300 and clinical strains and largely noticed the same events. Also, using a strain that had the ebh knock-out, still established SCV but did not have the extracellular matrix.
Conclusions: Providing time and with a low growth rate, allows for the diversity of cell types within a bacterial population to emerge. For S. aureus, a bacterial species that can periodically exist with the the mouth at a low growth rate, these alternaitve cell types include a distinctive SCV. These have an altered cellular and molecular profile, altering its colonisation and pahtogenesis.
Methods: We have established a continuous culture systems to grow the bacteria at steady state for 60 days. We have analysed the bacteria taken at every day for colony phenotypes, antibiotic tolerance and growth characteristics. Furthermore, at various timepoints we used membrane proteomics, transcriptomics and genomics to determine the changes in the cells, the changes to the surface proteins, the whole genome gene expression and genetic events. We have used different strains of S. aureus to determine universal and strains specific traits.
Results: There was a repeatable and strain-consistent change over time to the non-pigmented, low growth rate cell type: the Small Colony Variant (SCV). This was connected by an extracellular matrix that was not polysaccharide but protein and extracellualr DNA. There was a distinctive profile of gene expression, including the up-regulation of the giant surface protein (1 MDa) Ebh and the cell's lantibiotic. There was down-regulation of a range of immune mediators and toxins (capsule, pigment, leukocidins). There were genetic events including single nucleotide polymorphisms (SNP) in the regulatory systems RsbU and MgrA. We have used USA300 and clinical strains and largely noticed the same events. Also, using a strain that had the ebh knock-out, still established SCV but did not have the extracellular matrix.
Conclusions: Providing time and with a low growth rate, allows for the diversity of cell types within a bacterial population to emerge. For S. aureus, a bacterial species that can periodically exist with the the mouth at a low growth rate, these alternaitve cell types include a distinctive SCV. These have an altered cellular and molecular profile, altering its colonisation and pahtogenesis.