PRELIMINARY DESCRIPTION AND NUTRITIONAL CHARACTERIZATION OF A CHEMOORGANOTROPHIC ARCHAEOBACTERIUM GROWING AT TEMPERATURES OF UP TO 110-DEGREES-C ISOLATED FROM A SUBMARINE HYDROTHERMAL VENT ENVIRONMENT

An extremely thermophilic coccoid bacterium, designated strain ES4, was isolated from a flange (a newly described geological structure associated with massive sulphide mounds) at the Juan de Fuca Ridge hydrothermal vent system. The organism is a salt-requiring obligately anaerobic chemoorganotroph which reduces elemental sulphur but can grow very poorly in the absence of sulphur. Organic substrates utilized include yeast extract, peptone and amino acid hydrolysate as well as individual amino acids, the peptide Leu-Ser and starch. When growing on a defined medium, ES4 requires a supplement of vitamins and 20 amino acids at trace concentrations. Growth is most rapid in the temperature range 90-99-degrees-C, with a maximum growth temperature of about 110-degrees-C. In the optimal temperature range for growth, ES4 has a doubling time of about 1 h and can reach densities of 10(9) cells ml-1. Insensitivity to the antibiotics vancomycin, streptomycin and chloramphenicol, and the presence of di- and tetra-ether phytanyl lipids, indicate that ES4 is an archaeobacterium.