The Doubtful Status of the Species Zymomonas anaerobia and Z. mobilis

S ummary . During the course of an investigation of Zymomonas spp. in the brewing industry, a strain was isolated from different habitats and identified as Z. mobilis. It is the first occasion on which this species has been isolated from British beers. Closer examination of one isolate showed that it was different from the stock strain of Z. mobilis , both in vitamin requirements and serology. Strains of Z. anaerobia were also isolated and it was possible to induce these bacteria to metabolize sucrose. Since the ability to utilize this sugar is one of the major differences between Z. mobilis and Z. anaerobia , and in view of the closeness of the G + C ratios, the whole question of whether 2 species of Zymomonas are justified is thrown into doubt.