Characteristics of Na +-dependent respiratory chain in Vibrio anguillarum, a fish pathogen, in comparison with other marine Vibrios

The activity of membrane-bound NADH oxidase of Vibrio anguillarum M93 (serotype J-O-1), which causes vibriosis in freshwater area was activated by Na + in the same manner as other marine Vibrios. However, in addition to Na +, K + 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 Na +-dependent NADH oxidase of strain M93 required less Na + (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 H + motive force by a proton conductor carbonylcyanide m-chlorophenylhydrazone (CCCP) revealed high dependency of V. anguillarum on the primary H + 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 Na + in V. anguillarum probably reflects the salinity of their original habitats.