The Genus Sulfurospirillum

Abstract

The only organohalide-respiring Epsilonproteobacteria (e-proteobacteria) described so far are found in the genus Sulfurospirillum . This genus consists of versatile, often microaerophilic bacteria, growing with many different growth substrates. Only a few of these organisms use halogenated compounds, mainly chlorinated ethenes, as electron acceptors. Organohalide respiration was extensively studied in Sulfurospirillum multivorans, but seems to be similar in other reductively dehalogenating Sulfurospirilla like Sulfurospirillum halorespirans. While most Sulfurospirillum species are unable to utilize organohalides as electron acceptors, many of them grow with other toxic substrates such as arsenate or selenate. Other typical electron acceptors are nitrate and sulfur compounds. Electron donors used are pyruvate, hydrogen and formate. The anaerobic respiratory chains of Sulfurospirillum spp. involve most likely menaquinones and cytochromes for most electron donor/acceptor combinations. The growth substrate range which includes many toxic compounds enables many Sulfurospirillum species to thrive in polluted habitats, which is reflected by the presence of these bacteria in many contaminated sites. The genomes of Sulfurospirillum spp. are small to average in size (about 2.5–3 Mbp) and the genes necessary for organohalide respiration, if present, are clustered in one area, including corrinoid biosynthesis genes responsible for production of the unique norpseudovitamin B12. The gene inventory in this area differs from that of other organohalide-respiring bacterial classes in that a putative quinol dehydrogenase and other accessory proteins are encoded. This points to a respiratory chain differing from other organohalide-respiring bacteria.