Thermomonas hydrothermalis sp nov., a new slightly thermophilic γ-proteobacterium isolated from a hot spring in Central Portugal

Several non-pigmented bacterial isolates, with an optimum growth temperature of about 50 degreesC, were recovered from the hot spring at Sao Gemil in Central Portugal. Phylogenetic analyses of the 16S rRNA gene sequence of strain SGM-6(T) indicated that this organism represents a new species of the gamma-subclass of the Proteobacteria that is closely related to the newly described slightly thermophilic species Thermomonas haemolytica. The major fatty acids of strains SGM-6(T) and SGM-7 are C15:0 iso, C16:0 iso, C11:0 iso and C11:0 iso 3OH. Ubiquinone 8 is the major respiratory quinone. The new isolates are strictly organotrophic and aerobic. Strain SGM-6(T) only assimilated D-glucose, D-maltose, D-cellobiose, D-furanose, L-glutamate, L-glutamine, L-lysine, L-proline, L-ornithine, acetate, L-glutamic acid and pyruvate of sixty-five carbon sources tested. Strain SGM-7 also assimilates L-serine, but does not assimilate L-ornithine. On the basis of the phylogenetic analyses, physiological and biochemical characteristics, we propose that strains SGM-6(T) and SGM-7 represent a new species most closely related to Thermomonas haemolytica for which we propose the name Thermomonas hydrothermalis.