NM48, a non-mucoid derivative of an alginate-producing strain isolated from a cystic fibrosis patient, was grown in batch culture with glycerol, glucose or succinate as carbon source, and in continuous culture ( 0.05 h) under glycerol or glucose limitation. Glycerol uptake, glycerol kinase and glycerol-3-phosphate dehydrogenase were induced by glycerol, but not by glucose or succinate. Linear uptake of [C]glycerol by washed cells ( ≤ 2 μM) was inhibited by unlabelled glycerol and glyceraldehyde, but not by cyanide or the uncoupling agent carbonyl cyanide -trifluoromethoxyphenylhydrazone (FCCP), and was accompanied by substantial intracellular accumulation of glycerol-3-phosphate and/or dihydroxyacetone phosphate but not glycerol. Prolonged growth under glycerol limitation led to substantial increases in the activities and/or concentrations of the enzymes catalysing glycerol uptake and metabolism, together with a 48000 outer-membrane protein which was also over-expressed following prolonged growth under glucose limitation. The N-terminal amino acid sequence (AEAFSPN-) and electrophoretic properties of this protein were the same as those of the previously characterized glucose porin (OprB) from , indicating that this porin is active with both glucose and glycerol. It is concluded that during growth under glycerol limitation, glycerol is transported into NM48 via OprB and a high-affinity, binding-protein-independent facilitated-diffusion system.


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