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Identification of an osmo‐dependent and an osmo‐independent choline transporter in A cinetobacter baylyi : implications in osmostress protection and metabolic adaptation
Author(s) -
Sand Miriam,
Stahl Julia,
Waclawska Izabela,
Ziegler Christine,
Averhoff Beate
Publication year - 2014
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.12188
Subject(s) - betaine , biology , glycine , choline , transporter , osmotic concentration , biochemistry , function (biology) , flux (metallurgy) , gene , microbiology and biotechnology , amino acid , chemistry , organic chemistry
Summary Members of the genus A cinetobacter are well known for their metabolic versatility that allows them to adapt to different ecological niches. In previous studies, we have demonstrated that A cinetobacter baylyi ADP 1 can cope with high salinities by uptake and accumulation of the well‐known compatible solute glycine betaine. Here, we demonstrate that addition of choline restores growth at high salinities. We further show that choline was actively taken up by the cells and converted to glycine betaine. Uptake of choline was induced by high salinity and the presence of choline in the growth medium. At high salinities, glycine betaine was accumulated in the cells whereas in the absence of osmotic stress it was exported. Inspection of the genome sequence followed by mutant studies led to the identification of two genes encoding secondary transporters ( BetT 1 and BetT 2) of the betaine‐choline‐carnitine transporter ( BCCT ) family. The BetT 1 transporter lacks an extended C ‐terminal domain usually found in osmoregulated choline BCCT s. BetT 1 was found to facilitate osmolarity‐independent choline transport most likely by a uniport mechanism. We propose that BetT 1 does not primarily function in osmoadaptation but might play a role in metabolic adaptation to choline‐rich environments.