NUMERICAL TAXONOMIC STUDY OF THERMOPHILIC BACILLUS ISOLATED FROM 3 GEOGRAPHICALLY SEPARATED DEEP-SEA HYDROTHERMAL VENTS

A numerical taxonomic study has been carried out with 80 strains, newl y isolated, from three geographically separated deep-sea hydrothermal vents (Mid-Atlantic Ridge, Guaymas Basin and Lau Basin) and eleven the rmophilic reference strains representing 11 Bacillus species. The deep -sea isolates were all halotolerant spore forming rods and grew aerobi cally above 65 degrees C. Results from unweighted average linkage clus ter analysis of a Similarity matrix derived from the simple matching c oefficient, showed formation of nine major phena, which were defined a t the 83% similarity level or above. Seven phena were composed exclusi vely of strains isolated from the same site (4 from Mid-Atlantic Ridge , 1 from Guaymas Basin and 2 from Lau Basin). The majority of the Lau Basin isolates clustered with 6 of the reference strains in one phenon , while isolates from Mid-Atlantic Ridge and Guaymas Basin were found separated from this phenon at the 69% similarity level. The other refe rence strains showed less than 69% similarity with the deep-sea isolat es.