Identification of a GntR family regulator BusRTha and its regulatory mechanism in the glycine betaine ABC transport system of Tetragenococcus halophilus

Glycine betaine is one of the most effective compatible solutes of the halophilic lactic acid bacterium Tetragenococcus halophilus, the transportation of which is essential for its survival under salinity stress condition. In the current study, we attempted to define a glycine betaine ABC transporter system of T. halophilus, busATha, which plays an important role in adapting to salinity condition. The expression of busATha enhanced the growth of the recombinant strain under high salinity. BusRTha, a transcription regulator that represses the expression of busATha, was characterized, and the repression was abrogated under high salinity. The binding of the regulator was demonstrated through electrophoretic mobility shift assays, and the binding sites were characterized as 5′-AAA(T/G)TGAC(C/A)(G/A)T(C/A)C-3′. This is the first studied transcription regulator of T. halophilus, and our findings provide insights into the molecular mechanism of halophilic life and tools for further application of halophiles as chassis in industrial biotechnology.