A novel bacterial species, Rhodocista pekingensis sp. nov., was isolated from a municipal wastewater treatment plant and characterized by polyphasic taxonomy. Cells of R. pekingensis were gram-negative, motile by a single polar flagellum, vibrioid to spiral, 0.6-0.8 microm in width and 0.8-1.5 microm in length. R-bodies were not observed. Phototrophically grown cells contained lamellar photosynthetic membranes and bacteriochlorophyll a. Cell growth was anaerobically phototrophic or aerobically chemoheterotrophic. Anaerobically grown cultures were pink-reddish. Thiamin and vitamin B12, but not biotin, were required for growth and 0.05% yeast extract stimulated growth. Acetate, lactate, pyruvate and succinate supported growth. Cysts were formed when butyrate was used as the sole carbon source. Molecular hydrogen (H2), but not sulfide or thiosulfate, was used as an electron donor. The major cellular quinone was Q-9. The DNA G + C content of cells was 68.8 mol%. The type strain of Rhodocista pekingensis is 3-pT (=AS 1.2194T=JCM 11689T).