GENES ENCODING OSMOREGULATORY PROLINE GLYCINE BETAINE TRANSPORTERS AND THE PROLINE CATABOLIC SYSTEM ARE PRESENT AND EXPRESSED IN DIVERSE CLINICAL ESCHERICHIA-COLI ISOLATES/

Sixty-three clinical isolates identified as Escherichia coli, 30 from the human urinary tract and 33 derived from other human origins, were screened for proline/glycine betaine transporters similar to those tha t support proline catabolism and proline- or glycine betaine-based osm oregulation in E. coli K-12. Both molecular (DNA- and protein-based) a nalyses and physiological tests were performed. All tests were calibra ted with E. coli K-12 derivatives from which genetic loci putP (encodi ng a proline transporter required for proline catabolism), proP, and ( or) proU (loci encoding osmoregulatory proline/glycine betaine transpo rters) had been deleted. All clinical isolates showed both enhanced se nsitivity to the toxic proline analogue azetidine-2-carboxylate on med ia of high osmolality and growth stimulation by glycine betaine in an artificial urine preparation of high osmolality. DNA sequences similar to the putP, proP, and proU loci of E. coli K-12 were detected by DNA amplification and (or) hybridization and protein specifically reactiv e with antibodies raised against the ProX protein of E. coli K-12 (a P roU constituent) was detected by western blotting in over 95% of the i solates. Two anomalous isolates were reclassified as non-E. coli on th e basis of the API 20E series of tests. A protein immunochemically cro ss-reactive with the ProP protein of E. coli K-12 was also expressed b y the clinical isolates. Since all three transporters were ubiquitous, no particular correlation between clinical origin and PutP, ProP, or ProU activity was observed. These data suggest that the transporters e ncoded in loci purP, proP, and proU perform housekeeping functions ess ential for the survival of E. coli cells in diverse habitats.