Anaerobic survival of Pseudomonas aeruginosa by pyruvate fermentation

Recently, we identified a pyruvate fermentation pathway in Pseudomonas aeruginosa sustaining anaerobic survival in the absence of alternative anaerobic respiratory and fermentative energy generation systems (M. Eschbach, K. Schreiber, K. Trunk, J. Buer, D. Jahn and M. Schobert, J. Bacteriol. 186:4596-4604, 2004). Anaerobic long-term survival of P. 5 aeruginosa might be essential for survival in deeper layers of a biofilm and the persistent infection of anaerobic mucus plaques in the cystic fibrosis lung. Proteome analysis of P. aeruginosa cells during a seven-day period of pyruvate fermentation revealed the induced synthesis of three enzymes involved in arginine fermentation, ArcA, ArcB, ArcC and the outer-membrane protein OprL. Moreover, formation of two proteins of unknown function 10 PA3309 and PA4352 increased by factors of 72and 22-fold, respectively. Both belong to the group of universal stress proteins (Usp). Long-term survival of a PA3309 knock-out mutant by pyruvate fermentation was found drastically reduced. The oxygen-sensing regulator Anr controls expression of the PPA3309-lacZ reporter gene fusion after a shift to anaerobic conditions and further pyruvate fermentation. PA3309 expression was also found induced 15 during the anaerobic and aerobic stationary phase. This aerobic stationary phase induction is independent of the regulatory proteins Anr, RpoS, RelA, GacA, RhlR and LasR indicating a currently unknown mechanism of stationary phase dependent gene activation. PA3309 promoter activity was detected in the deeper layers of a P. aeruginosa biofilm using a PPA3309gfp fusion and confocal laser scanning microscopy. This is the first description of an Anr20 dependent, anaerobically induced and functional Usp-like protein in bacteria.