THERMUS-SCOTODUCTUS, SP-NOV, A PIGMENT-PRODUCING THERMOPHILIC BACTERIUM FROM HOT TAP WATER IN ICELAND AND INCLUDING THERMUS SP X-1

Thermophilic, aerobic heterotrophic bacteria, producing a water solubl e dark brown melanin-like pigment, were isolated from a hot water pipe line in a small town in southern Iceland. The bacteria stained Gram-ne gative, are short rods, 1.5 mum long and 0.5 mum in diameter. The cell s vare usually single or in pairs. A very dense peptidoglycan layer wa s seen as well as cytoplasmic membrane and an outer membrane. The bact eria are nonmotile and do not form spores. They could grow at 42-73-de grees-C with optimum growth temperature of 65-degrees-C and optimum pH at 7.5. The bacteria were oxidase and catalase positive, sensitive to the antibiotics penicillin, erythromycin, tetracyclin, chloramphenico l and streptomycin but resistant to polymyxin B and rifampicin. The GC was about 64.5%. The isolates were compared to other known aerobic, h eterotrophic bacteria and turned out to resemble to colourless Thermus strain X-1, which was also found to produce the brown pigment. The DN A:DNA similarity between the new isolates and Thermus X-1 was about 83 %, whereas the similarity with Thermus aquaticus was about 46%. The ne w isolates together with strain X-1 are therefore considered to repres ent a new species, Thermus scotoductus.