Geosporobacter subterraneus gen. nov., sp. nov., a spore-forming bacterium isolated from a deep subsurface aquifer

Abstract

A novel, strictly anaerobic, chemo-organotrophic bacterium, designated strain VNs68T, was isolated from a well that collected water from a deep aquifer at a depth of 800 m in the Paris Basin, France. Cells were thin, non-motile, Gram-positive rods forming terminal endospores (3.0–5.0×0.5 μm). Strain VNs68T grew at temperatures between 30 and 55 °C (optimum 42 °C) and at pH 5.6–8.4 (optimum pH 7.3). It did not require salt for growth but tolerated up to 40 g NaCl l−1. Strain VNs68T was an obligate heterotroph fermenting carbohydrates such as glucose, xylose, fructose, ribose and cellobiose. Casamino acids and amino acids (arginine, serine, lysine, alanine, aspartate, asparagine, isoleucine, histidine) were also fermented. The main fermentation products from glucose were acetate with H2 and CO2. Sulfate, sulfite, thiosulfate, elemental sulfur, nitrate and nitrite were not used as electron acceptors. The G+C content of the genomic DNA was 42.2 mol%. Phylogenetic analysis of the 16S rRNA gene sequence indicated that strain VNs68T was affiliated to cluster XI, order Clostridiales, domain Bacteria. On the basis of 16S rRNA gene sequence comparisons and physiological characteristics, strain VNs68T is considered to represent a novel species of a new genus, for which the name Geosporobacter subterraneus gen. nov., sp. nov. is proposed. The type strain of Geosporobacter subterraneus is VNs68T (=DSM 17957T =JCM 14037T).