GROWTH REQUIREMENTS OF HYPERTHERMOPHILIC SULFUR-DEPENDENT HETEROTROPHIC ARCHAEA ISOLATED FROM A SHALLOW SUBMARINE GEOTHERMAL SYSTEM WITH REFERENCE TO THEIR ESSENTIAL AMINO-ACIDS

Three hyperthermophilic sulfur-dependent heterotrophs were isolated fr om a shallow submarine hydrothermal system at an inlet of Kodakara-jim a island, Kagoshima, Japan. The isolates grew at 60 to 97 degrees C, w ith the optimum temperatures at 85 to 90 degrees C. Sensitivity to rif ampin and the existence of ether lipids indicated that the isolates ar e hyperthermophilic archaea. Partial sequencing of the genes coding fo r 16S rRNA showed that the three isolates are closely related to the g enus Thermococcus. They grew on proteinaceous mixtures, such as yeast extract, Casamino Acids, and purified proteins (e.g., casein and gelat in), but not on carbohydrates or organic acids as sole carbon and ener gy sources. Nine amino acids were essential for growth of isolate KS-1 (Thr, Leu, Ile, Val, Met, Phe, His, Tyr, and Arg). Isolate KS-2 requi red Lys in addition to the nine amino acids, and KS-8 required Lys ins tead of Tyr. In comparative studies, it was shown that Thermococcus ce ler DSM 2476 required 10 amino acids (Thr, Leu, Ile, Val, Met, Phe, Ty r, Trp, Lys, and Arg) while Pyrococcus furiosus DSM 3638 required only Ile and Val. The hyperthermophilic fermentative eubacterium Thermotog a neapolitana DSM 4359 did not require any amino acids for growth.