A novel obligately anaerobic, non-spore-forming, rod-shaped mesophilic, halophilic bacterium staining Gram-negative, was isolated from sediments of Guaymas basin. The strain, designated Ra1766G1T, grew at 20-40 °C (optimum 30-35 °C) and at pH 6.0-8.0 (optimum pH 6.5-7.5). It required 0.5%-7.5% NaCl (optimum 2%-3%) for growth. Sulfate, thiosulfate, elemental sulfur, sulfite, fumarate, nitrate and nitrite were not used as terminal electron acceptors. Strain Ra1766G1T used cellobiose, glucose, mannose, maltose, arabinose, raffinose, galactose, ribose, saccharose, pyruvate and xylose as electron donors. The main fermentation product from glucose metabolism was acetate. The predominant cellular fatty acids were anteiso-C15:0, iso-C15:0, anteiso DMA-C15:0 and C16:0. The main polar lipids consisted of diphosphatiglycerol, phosphatidylglycerol, glycolipids and phospholipids.The G+C content of the genomic DNA was 31.2 mol%. The closest phylogenetic relatives of Ra1766G1T were Natranaerovirga pectinivoraT (92.4% similarity), Natranaerovirga hydrolytica (90.2% similarity) and Defluviitalea saccharophilaT (88.9% similarity). On the basis of phylogenetic inference and phenotypic properties, strain Ra1766G1T (= DSM 24848T = JCMT= 16313) is proposed as the type strain of a novel species of a novel genus, Vallitalea guaymasensis gen. nov., sp. nov.