Porphyrobacter cryptus sp. nov., a novel slightly thermophilic, aerobic, bacteriochlorophyll a-containing species

Two strains of a novel aerobic, bacteriochlorophyll a-containing species of the alpha-4 subclass of the Proteobacteria were isolated from the hot spring at Alcafache in central Portugal. 16S rRNA gene sequence-based phylogenetic analyses showed the two novel isolates to be phylogenetically related to members of the genera Erythrobacter, Erythromicrobium and Porphyrobacter. The strains produce reddish-orange-pigmented colonies, have an optimum growth temperature of about 50 degrees C and could be distinguished from the species Porphyrobacter tepidarius, which also has a high growth temperature, primarily on the basis of the fatty acid composition. The novel species does not grow anaerobically in the presence or absence of a light source. The strains of the novel species utilize several single carbon sources for growth, most of which are also used by P. tepidarius. The species status of strains ALC-2T and ALC-3 was confirmed by low reassociation values of the DNA with species of the genera Erythrobacter, Erythromicrobium and Porphyrobacter. Phenotypic characteristics and 16S rRNA gene sequence analyses also show that strains ALC-2T (=DSM 12079T =ATCC BAA-386T) and ALC-3 (=DSM 12080) represent a novel species, for which the name Porphyrobacter cryptus sp. nov. is proposed.