THE EFFECT OF NUTRIENT LIMITATION ON GLYCEROL UPTAKE AND METABOLISM IN CONTINUOUS CULTURES OF PSEUDOMONAS-AERUGINOSA

Pseudomonas aeruginosa NM48, a non-mucoid derivative of an alginate-pr oducing strain isolated from a cystic fibrosis patient, was grown in b atch culture with glycerol, glucose or succinate as carbon source, and in continuous culture (D 0.05 h(-1)) under glycerol or glucose limita tion. Glycerol uptake. glycerol kinase and glycerol-3-phosphate dehydr ogenase were induced by glycerol, but not by glucose or succinate. Lin ear uptake of [C-14]glycerol by washed cells (K-m less than or equal t o 2 mu M) was inhibited by unlabelled glycerol and glyceraldehyde, but not by cyanide or the uncoupling agent carbonyl cyanide p-trifluorome thoxyphenylhydrazone (FCCP), and was accompanied by substantial intrac ellular accumulation of glycerol-3-phosphate and/or dihydroxyacetone p hosphate but not glycerol. Prolonged growth under glycerol limitation led to substantial increases in the activities and/or concentrations o f the enzymes catalysing glycerol uptake and metabolism, together with a 48 000 M(r) outer-membrane protein which was also overexpressed fol lowing prolonged growth under glucose limitation. The N-terminal amino acid sequence (AEAFSPN-) and electrophoretic properties of this prote in were the same as those of the previously characterized glucose pori n (OprB) from P. aeruginosa, indicating that this porin is active with both glucose and glycerol. It is concluded that during growth under g lycerol limitation. glycerol is transported into P. aeruginosa NM48 vi a OprB and a high-affinity, binding-protein-independent facilitated-di ffusion system.