Raineya orbicola gen. nov., sp. nov. a slightly thermophilic bacterium of the phylum Bacteroidetes and the description of Raineyaceae fam. nov

Abstract

An isolate, designated SPSPC-11^T, with an optimum growth temperature of about 50 °C and an optimum pH for growth between 7.5 and 8.0, was recovered from a hot spring in central Portugal. Based on phylogenetic analysis of its 16S rRNA sequence, the new organism is most closely related to the species of the genus Thermonema but with a pairwise sequence similarity of <85 %. The isolate was orange-pigmented, formed non-motile long filaments and rod-shaped cells that stain Gram-negative. The organism was strictly aerobic, oxidase-positive and catalase-positive. The major fatty acids were iso-C15:0, iso-C15 : 0 2-OH and iso-C17 : 0 3-OH. The major polar lipids were one aminophospholipid, two aminolipids and three unidentified lipids. Menaquinone 7 was the major respiratory quinone. The DNA G+C content of strain SPSPC-11^T was 37.6 mol% (draft genome sequence). The high quality draft genome sequence corroborated many of the phenotypic characteristics of strain SPSPC-11^T. Based on genotypic, phylogenetic, physiological and biochemical characterization we describe a new species of a novel genus represented by strain SPSPC-11^T (=CECT 9012^T=LMG 29233^T) for which we propose the name Raineya orbicola gen. nov., sp. nov. We also describe the family Raineyaceae to accommodate this new genus and species.

Keywords: Bacteroidetes; Raineya gen. nov.; Raineya orbicola sp. nov; Raineyaceae fam. nov.; new taxa.

Fig. 1.

Electron microscopy by SEM and TEM of exponential phase cells of strain SPSPC-11^T. (a) Filamentous cells from a young culture (2–5 h) observed by SEM. (b) Filamentous cells from a young culture (2–5 h) observed by TEM. (c) A septum is indicated by an arrow. (d) High magnification showing the Gram-negative type of cell wall.

Fig. 2.

Phylogenetic position of strain SPSPC-11^T within the radiation of representatives of the families of the phyla Bacteroidetes and ‘Rhodothermaeota’. The phylogenetic dendrogram was generated using the neighbour-joining method [38] in mega 6.0 [39]. Bootstrap values, expressed as percentages of 1000 replications, are given at branching points. Bar, 2 inferred nucleotide substitutions per 100 nucleotides.

Fig. 3.

Phylogenetic position of strain SPSPC-11^T within the radiation of representatives of environmental clone sequences to belong to the Raineya lineage. The source of the environmental clone sequences is shown in Table S2. The phylogenetic dendrogram was generated using the neighbour-joinging method [38] in mega 6.0 [39]. Bootstrap values, expressed as percentages of 1000 replications, are given at branching points. Bar, 2 inferred nucleotide substitutions per 100 nucleotides.