Interestingly, pyruvate is secreted by P. aeruginosa PA14 in the
late stationary phase under aerobic/microaerobic growth conditions
(Price-Whelan et al., 2007). This suggests the followingmodel:
Cells in a biofilm or in an environment with steep oxygen gradients
secrete pyruvate in the presence of oxygen. Pyruvate diffuses
into the anoxic layers of the biofilm and supports anaerobic survival
via pyruvate fermentation (Price-Whelan et al., 2007). Genes
encoding enzymes for pyruvate fermentation are induced during
anaerobic growth on CF sputum, but the role of this fermentation
during persistent infections remains to be elucidated. Pyruvate fermentation
is activated by the global oxygen-sensing Anr regulator,
which activates transcription of the ackA-pta operon (Fig. 2). These
genes encode the enzymes acetate kinase and phosphotransacetylase.
Both enzymes are required for ATP-generating formation of
acetate (Eschbach et al., 2004). In addition to Anr, the DNA-bending
integration host factor (IHF) is needed for transcription of the ackApta
operon