A New Lineage of Halophilic, Wall-less, Contractile Bacteria from a Brine-filled Deep of the Red Sea

Centro de Neurociências e Biologia Celular, Department of Zoology, University of Coimbra, 3004-517 Coimbra, Portugal; Department of Biological Sciences, Louisiana State University, Baton Rouge, La 70803, USA; Department Biology I, Ludwig-Maximilians-Universität München, D-80638 Munich, Germany; Research Center Ocean Margins, University of Bremen, D-28334 Bremen, Germany; Department of Biochemistry, University of Coimbra, 3001-401 Coimbra, Portugal; Kommunale Berufsfachschule für biologisch-technische Assistenten, D-94315 Straubing, Germany

^* To whom correspondence should be addressed. Email: milton{at}ci.uc.pt.

	Abstract

A novel strictly anaerobic bacterium designated strain SSD-17B^T, was isolated from the hypersaline brine-sediment interface of the Shaban Deep, Red Sea. Cells were pleomorphic but usually consisted of a central coccoid body with one or two "tentacle-like" protrusions. These protrusions actively alternated between a straight, relaxed form, and a contracted corkscrew-like one. A peptidoglycan layer was not detected by electron microscopy. The organism forms "fried-egg"-like colonies on MM-X medium. The organism is strictly anaerobic, halophilic, has an optimum temperature for growth of about 30 to 37°C and an optimum pH of about 7. Nitrate and nitrite are reduced; lactate is a fermentation product. The fatty acid profile is dominated by straight saturated and unsaturated chain compounds. Menaquinone 4 (MK-4) is the major respiratory quinone. Phylogenetic analysis demonstrated that strain SSD-17B^T represents a novel and distinct lineage within the radiation of the domain Bacteria. The branching position of strain SSD-17B^T was equidistant to the taxa considered to be representative lineages of the phyla "Firmicutes" and "Tenericutes" (with its sole class Mollicutes). The phenotypic and phylogenetic data clearly show the distinctiveness of this unusual bacterium and we, therefore, propose that strain SSD-17B^T (=DSM 18853 =JCM 14575) represents a new genus and a new species for which we recommend the name Haloplasma contractile gen. nov., sp. nov. We are also of the opinion that the organism represents a new order level taxon for which we propose the name Haloplasmatales.