Possible role of a taurine transporter in the deep-sea mussel Bathymodiolus septemdierum in adaptation to hydrothermal vents

Various invertebrates inhabiting hydrothermal vents possess sulfur-oxidizing bacteria in their tissues; however, the mechanisms by which toxic sulfides are delivered to these endosymbionts remain unknown. Recently, detoxification of sulfides using thiotaurine, a sulfur-containing amino acid, has been suggested. In this study, we propose the involvement of a taurine transporter in sulfide detoxification in the deep-sea mussel Bathymodiolus septemdierum by demonstrating: (i) the abundance of its mRNA in the gill; (ii) its activity under a wide range of salinities; (iii) its low Michaelis constant value in taurine transportation; and (iv) its affinity for thiotaurine and the thiotaurine precursor, hypotaurine.