Figure 1.

Staphylococcus aureus encodes a fourth biologically relevant l-lactate utilization enzyme. (A) Known metabolic end products of S. aureus glucose catabolism. (B) Levels of extracellular D-lactate (light blue squares) and l-lactate (dark blue squares) following exposure to exogenous NO· (red circles). Cells were grown in chemically defined medium to an OD₆₆₀ = 0.15 (black circles) at such time a combination of NO·-donors (10 mM NOC-12 and 1 mM DEA/NO) was added. The resulting NO· burst peaked at 1.5 h at ∼1 mM. (C) Δddh mutants (LEFT) no longer excrete D-lactate anaerobically (inset) and specifically lack the ability to grow on D-lactate as a primary carbon source. In contrast, while Δldh1Δldh2 mutants (RIGHT) do not produce measurable l-lactate anaerobically (inset), the double mutant is still able to utilize l-lactate as a primary carbon source. Residual growth on medium components was subtracted from depicted growth curves (see Materials and Methods).