Characteristics of Naþ-dependent respiratory chain in Vibrio anguillarum, a ¢sh pathogen, in comparison with other marine

The activity of membrane-bound NADH oxidase of Vibrio anguillarum M93 (serotype J-O-1), which causes vibriosis in freshwater area was activated by Naþ in the same manner as other marine Vibrios. However, in addition to Naþ, Kþ was also found to positively enhance the NADH oxidase activity of strain M93. This tendency has not been recognized in other marine Vibrios. Furthermore, the Naþ-dependent NADH oxidase of strain M93 required less Naþ (0.1 M) for its maximum activity than those of other Vibrios such as Vibrio alginolyticus and ‘Vibrio angustum ’ S14, which were in the range of 0.4 M NaCl, similar as seawater. Destruction of Hþ motive force by a proton conductor carbonylcyanide m-chlorophenylhydrazone (CCCP) revealed high dependency of V. anguillarum on the primary Hþ pump. Even at pH 8.5, V. anguillarum strains other than serotype O-4 could not grow well with the addition of CCCP. In contrast, marine-type Vibrios such as V. alginolyticus and V. angustum S14 can grow well at pH 8.5 even with the addition of CCCP. The lower requirement for Naþ in V. anguillarum probably reflects the salinity of their original habitats