Fig. 7.

A simplified model of P. aeruginosa QS regulation under anaerobic conditions. During anaerobic growth, production of three major QS signal molecules, PAI-1, PAI-2, and PQS, is highly suppressed, rendering P. aeruginosa incapable of QS. Gene names are shown in italic, while protein names are shown in roman inside gray squares. Downregulated gene transcripts and proteins are shown in squares with dashed lines. Anaerobiosis-induced suppression of lasB transcription (shown in the center) is mediated by inactivation of PAI-1- (top), PAI-2- (left), and PQS-mediated (right) QS. Abbreviations and symbols: SAM, S-adenosylmethionine; ACP, acyl carrier protein; MTA, 5′-methylthioadenosine; HHQ, 2-heptyl-4-quinolone; ANT, anthranilate; arrow, activation or production; arrow with circle and slash, suppressed contribution. The lack of oxygen is denoted by a cross. Dashed arrows indicate suppressed association of QS signals with their cognate regulator proteins.