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Uncoupling of choline‐ O ‐sulphate utilization from osmoprotection in Pseudomonas putida
Author(s) -
Galvão Teca Calcagno,
De Lorenzo Víctor,
Cánovas David
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05488.x
Subject(s) - pseudomonas putida , betaine , biology , biochemistry , mutant , glycine , choline , gene , amino acid
Summary The genomic context of the recognized bet genes for choline‐ O ‐sulphate (C O S) utilization in Pseudomonas putida KT2440 is such that betC (choline sulphatase) lies adjacent to an ATP‐binding cassette transporter and a LysR type regulator, but well away from betBA , encoding enzymes for transformation of choline into glycine betaine. The consequences of such genetic layout of the functions for C O S metabolism have been examined with a suite of genetic and biochemical approaches. An early clue of the utilities of the bet ‐encoded products was exposed by the phenotypes of a betC deletion. This mutant still accumulated intact C O S but failed to use this compound as carbon or nitrogen source . Furthermore, betC expression was downregulated at high salt concentrations, showing that the principal role of this gene lied in C O S metabolism, not in osmoprotection. In contrast, the betBA genes were required for choline transformation into the highly effective compatible solute glycine betaine (and the concomitant endurance to high salt) and also for its utilization as carbon or nitrogen source. Thus, unlike in the cases of Bacillus subtilis and Sinorhizobium meliloti , betC is unrelated to osmoprotection in Pseudomonas putida while the betBA genes are required for both betaine synthesis and tolerance to high osmotic pressure.