Effects of RelA on Key Virulence Properties of Planktonic and Biofilm Populations ofStreptococcus mutans

• DOI: 10.1128/iai.72.3.1431-1440.2004
• Publication Date: 2004-02-21T04:42:58Z
• Authors: José A. C. Lemos; Thomas A. Brown; Robert A. Burne
• Keywords: Stringent response

Streptococcus mutans is a biofilm-forming bacterium that adapted to tolerate rapid and dramatic fluctuations in nutrient availability, carbohydrate source, pH its natural environment, the human oral cavity. Dissecting pathways used form stable biofilms environmental stress central understanding virulence of this organism. Here, we investigated role S. relA gene, which codes for guanosine tetraphosphate pentaphosphate [(p)ppGpp] synthetase/hydrolase, biofilm formation acid tolerance. Two mutants was insertionally inactivated or replaced by an antibiotic resistance determinant were constructed. Under normal growth conditions, grew slower than wild-type strain, although final yields similar. The mutants, still able accumulate (p)ppGpp after induction stringent response, showed significant reductions on microtiter plates hydroxylapatite disks. There no difference sensitivities killing parent strains grown planktonic cultures. However, when cells biofilms, became more resistant could lower through glycolysis faster greater extent strain. Differences not correlated with increases F-ATPase activity, bacterial sugar:phosphotransferase activity elevated mutants. Expression luxS gene increased as much fivefold suggesting link between AI-2 quorum sensing response.