MICROBIAL CHARACTERIZATION OF THERMOPHILIC ARCHAEA ISOLATED FROM THE GUAYMAS BASIN HYDROTHERMAL VENT

Extremely thermophilic bacteria were isolated from sediments collected at the Guaymas Basin hydrothermal vent located in the Gulf of California. One isolate (FC89) is a hydrogenotrophic methanogen with an optimal growth temperature of 85-degrees-C; this isolate appears to be closely related to the previously described Methanococcus jannaschii. Thermophilic isolates TY and TYS are heterotrophic, sulfur-reducing archaea that differ from other thermophilic heterotrophic strains in physiological and molecular properties. Both heterotrophic isolates fermented carbohydrates and proteinaceous substrates; acetate was the primary product of carbohydrate fermentation, whereas acetate and a mix of organic acids were primary products of proteinaceous substrate fermentation. A detailed microbiological characterization of the isolates and a profile of fermentable substrates and fermentation products are described.