A polyphasic taxonomic approach was used to characterise two presumably novel bacteria, designated strains CC-YHH838T and CC-YHH848T isolated from termite nest and rhizosphere of Ficus religiosa, respectively. These two nitrogen-fixing strains were observed to be Gram-staining-negative, aerobic rod, and colonies were yellowish in color. Growth of strains was observed at 20-37 °C, pH 7-8, and in the presence of 1-2% NaCl. Phylogenetic analyses based on 16S rRNA genes revealed a distinct taxonomic position attained by strain CC-YHH838T and CC-YHH848T associated with Thauera hydrothermalis (97.1% sequence identity), and formed a separate branch with Azoarcus indigens (95.4%), Aromatoleum aromaticum (96.2%), and lower sequence similarity to other species. The calculation of OrthoANI values pointed out strains CC-YHH838T and CC-YHH848T gave 78.9% and 79.8% compared to Thauera hydrothermalis, respectively. The major fatty acids (> 5%) were C16:0, C17:0 cyclo, C10:0 3-OH, C16:1ω7c/C16:1ω6c and C18:1ω7c/C18:1ω6c. The polar lipid profile comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and unidentified aminophospholipid and phospholipids; the predominant polyamines were putrescine and spermidine. The predominant respiratory system was ubiquinone (Q-8) and the DNA G + C contents were 61.4 ± 0.1 mol% and 60.2 ± 1.3 mol%, respectively. Based on the phylogenetic and polyphasic comparisons, strains CC-YHH838T and CC-YHH848T are proposed to represent two novel species within the genus Azoarcus in the family Rhodocyclaceae, for which the name Azoarcus nasutitermitis sp. nov. (type strain CC-YHH838T = BCRC 81059T = JCM 32001T) and Azoarcus rhizosphaerae sp. nov. (type strain CC-YHH848T = BCRC 81060T = JCM 32002T) were proposed.
Keywords: Azoarcus nasutitermitis; Azoarcus rhizosphaerae; Polyphasic taxonomy; Rhizosphere; Rhodocyclaceae.