Anoxygenic phototrophic purple sulfur bacterium. Cells are gram-negative rods averaging 1.6 × 2.6 μm. Color of phototrophically grown cells, brownish-red. In vivo absorption maxima at 805 and 858 nm with a shoulder at 890 nm; no absorption maxima above 900 nm. Cells contain bacteriochlorophyll a and carotenoids of the spirilloxanthin series; rhodopin is the dominant carotenoid. Intracytoplasmic membranes are of the vesicular type. Grows photoautotrophically on sulfide plus CO2 and incorporates acetate and pyruvate during photoheterotrophic growth. Thiosulfate but not H2 stimulates growth above that achieved on sulfide/acetate/CO2 alone. Ammonia and glutamine serve as N sources but nitrate is not assimilated and nitrogen fixation does not occur. Unable to grow in darkness by respiration. No growth factors required. Growth temperature optimum, 44–45 °C. Weak growth at 50 °C; minimum growth temperature (after prolonged incubation), 27 °C. Optimum pH, 7. Phylogeny, a member of the family Chromatiaceae (Gammaproteobacteria) and genus Allochromatium, with its closest relative by 16S rRNA gene sequence comparison Allochromatium warmingii. Genomic GC content, 64.8%. Genbank accession information: 16S rRNA gene sequence accessioned as AF384209 and genome sequence accessioned as AP024563 (chromosome) and AP024564 (plasmid).

Type strain, Allochromatium tepidum NZT (= JCM 33379T = DSM 26924T) isolated from a Chlorobaculum tepidum-dominated microbial mat from “Travel Lodge Stream”, Rotorua, New Zealand.