A microbiological survey of Montserrat Island hydrothermal biotopes

In March 1996, a survey of hydrothermal sites on the island of Montserrat w as carried out. Six sites (Galway's Soufriere, Gages Upper and Lower Soufri eres, Hot Water Pond, Hot River, and Tar River Soufriere) were mapped and s ampled for chemical, ATP, and microbial analyses. The hydrothermal Soufrier e sites on the slopes of the active Chances Peak volcano exhibited temperat ures up to almost 100 degreesC and were generally either mildly acidic at p H 5-7 or strongly acidic at pH 1.5-3, but with some hot streams and pools o f low redox potential at pH 7-8. Hot Water Pond sites, comprising a series of heated pools near the western shoreline of the island, were neutral and saline, consistent with subsurface heating of entrained seawater. Biologica l activity shown by ATP analyses was greatest in near-neutral pH samples an d generally decreased as acidity increased. A variety of heterotrophic and chemolithotrophic thermophilic organisms were isolated or observed in enric hment cultures. Most of the bacteria that were obtained in pure culture wer e familiar acidophiles and neutrophiles, but novel, iron-oxidizing species of Sulfobacillus were revealed. These species included the first mesophilic iron-oxidizing Sulfobacillus strains to be isolated and a strain with a hi gher maximum growth temperature (65 degreesC) than the previously described moderately thermophilic Sulfobacillus species.