A xylan-degrading thermophilic and obligate anaerobe Xylanivirga thermophila gen. nov., sp. nov., isolated from an anammox dominant wastewater treatment plant, and proposal of Xylanivirgaceae fam. nov.

In our search for novel anaerobes with potential carbohydrate polymers degrading activity, we have isolated a xylan-degrading bacterial strain SYSU GA17129 ^T from an anammox bacteria dominant wastewater treatment plant. Phylogenetic analysis of the 16S rRNA gene sequence indicated the strain SYSU GA17129 ^T belong to the order Clostridiales and shared highest sequence identity with Caldicoprobacter faecalis DSM 20678 ^T (89.9%). The strain was thermophilic, obligately anaerobic, non-motile and rod shaped. Optimum growth of the strain was observed at 45 °C, pH 8.0 and in the presence of 0.5% NaCl (w/v). The chemotaxonomic features of the strain SYSU GA17129 ^T comprised of C _14:0 FAME, iso-C _15:0 FAME and C _16:0 FAME as the major fatty acids (>10%), diphosphatidylglycerol, phosphatidylinositol mannoside, an unidentified phospholipid, three unidentified polar lipids and two unidentified glycolipids as its polar lipids, and meso-diaminopimelic acid (meso-DAP) as the diamino acid in peptidoglycan. The G + C content of the genomic DNA was 35.9%. The strain could be distinguished from other defined families within the order Clostridiales by the differences in phenotypic and physiological characteristics, distinct phylogenetic lineage in 16S rRNA gene- and genome-based phylogenies and low genomic relatedness index. Based on these distinguishing properties, strain SYSU GA17129 ^T is proposed to represent a new species of a new genus Xylanivirga thermophila gen. nov., sp. nov., within a new family Xylanivirgaceae fam. nov. The type species of the new taxon is SYSU GA17129 ^T (=KCTC 15754 ^T  = CGMCC 1.5282 ^T ). This strain is characterized within the order Clostridiales, class Clostridia of the phylum Firmicutes.
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