Two new nitrogen-fixing bacteria from the rhizosphere of mangrove trees: Their isolation, identification and in vitro interaction with rhizosphere Staphylococcus sp

Two new diazotrophic bacteria, Listonella anguillarum and Vibrio campbellii, and one nonnitrogen-fixing bacterium, Staphylococcus sp., were isolated from the rhizosphere of mangrove trees. Strains of these newly-defined diazotrophs are known as pathogenic bacteria in fish and shellfish. During the purification of diazotrophic species from the entire rhizosphere population, N2 -fixation of the bacterial mixtures decreased. When grown in vitro in mixed cultures, the nonfixing bacterium Staphylococcus sp. increased the nitrogen-fixing capacity of L. anguillarum by 17% over the pure culture; the nitrogen-fixing capacity per bacterial cell increased 22%. This interaction was not due to a change in O2 concentration. Staphylococcus sp. decreased the nitrogen-fixing capacity of V. campbellii by 15%.