ISOLATION AND CLONING OF A AZOSPIRILLUM-LIPOFERUM LOCUS THAT COMPLEMENTS ESCHERICHIA-COLI PROU MUTANT

Glycine betaine relieved sodium chloride-mediated inhibition of growth in Azospirillum lipoferum ATCC 29708. S-35-methionine labelling of pr oteins after salinity up-shock revealed strong induction of a 30 kDa p rotein which cross-reacted with the anti-glycine betaine binding prote in antibody from Escherichia coil. This suggested that A. lipoferum ha d a salinity-induced ProU-like high-affinity glycine betaine transport system. A genomic library of A. lipoferum ATCC 29708 was screened for the pro U-like gene by complementation of a Pro U mutant of E. coli. Four recombinant cosmids, capable of restoring growth of the proU muta nt on plates containing 600 mM NaCl and 1 mM glycine betaine were sele cted. Selected recombinant cosmids hybridized with a proU gene probe f rom E. coli. Complementation of E. coli ProU mutant with the A. lipofe rum genomic DNA was evident by the ability of proU mutant (containing selected recombinant cosmids) to grow on minimal medium supplemented w ith 600 mM NaCl and 1 mM glycine betaine. (C) 1998 Published by Elsevi er Science B.V.