In the
dental caries pathogen Streptococcus mutans,
phosphotransacetylase (Pta) catalyzes the conversion of
acetyl coenzyme A (
acetyl-CoA) to
acetyl phosphate (AcP), which can be converted to
acetate by
acetate kinase (Ack), with the concomitant generation of
ATP. A ΔackA mutant displayed enhanced accumulation of AcP under aerobic conditions, whereas little or no AcP was observed in the Δpta or Δpta ΔackA mutant. The Δpta and Δpta ΔackA mutants also had diminished
ATP pools compared to the size of the
ATP pool for the parental or ΔackA strain. Surprisingly, when exposed to oxidative stress, the Δpta ΔackA strain appeared to regain the capacity to produce AcP, with a concurrent increase in the size of the
ATP pool compared to that for the parental strain. The ΔackA and Δpta ΔackA mutants exhibited enhanced (
p)ppGpp accumulation, whereas the strain lacking Pta produced less (
p)ppGpp than the wild-type strain. The ΔackA and Δpta ΔackA mutants displayed global changes in gene expression, as assessed by microarrays. All strains lacking Pta, which had defects in AcP production under aerobic conditions, were impaired in their abilities to form biofilms when
glucose was the growth
carbohydrate. Collectively, these data demonstrate the complex regulation of the Pta-Ack pathway and critical roles for these
enzymes in processes that appear to be essential for the persistence and pathogenesis of S. mutans.