Halobaculum halophilum sp. nov. and Halobaculum salinum sp. nov., isolated from salt lake and saline soil

Two halophilic archaeal strains, Gai3-2^T and NJ-3-1^T, were isolated from salt lake and saline soil samples, respectively, collected in PR China. The 16S rRNA gene sequences of the two strains were 97.5% similar to each other. Strains Gai3-2^T and NJ-3-1^T had the highest sequence similarities to 'Halobonum tyrrellense' G22 (96.7 and 97.8%, respectively), and displayed similarities of 91.5-93.5% and 92.3-94.7%, respectively, to Halobaculum members. Phylogenetic analysis revealed that the two strains formed different branches and clustered tightly with 'H. tyrrellense' G22 and Halobaculum members. The average nucleotide identity (ANI), in silico DNA-DNA hybridization (isDDH) and amino acid identity (AAI) values between the two strains were 83.1, 26.9 and 77.9%, respectively, much lower than the threshold values proposed as a species boundary. These values between the two strains and 'H. tyrrellense' G22 (ANI 77.9-78.2%, isDDH 22.5-22.6% and AAI 68.8-69.3%) and Halobaculum members (ANI 77.53-77.63%, isDDH 21.8-22.3% and AAI 68.4-69.4%) were almost identical, and much lower than the recommended threshold values for species delimitation. These results suggested that strains Gai3-2^T and NJ-3-1^T represent two novel species of Halobaculum. Based on phenotypic, chemotaxonomic and phylogenetic properties, strains Gai3-2^T (=CGMCC 1.16080^T=JCM 33550^T) and NJ-3-1^T (=CGMCC 1.16040^T=JCM 33552^T) represent two novel species of the genus Halobaculum, for which the name Halobaculum halophilum sp. nov. and Halobaculum salinum sp. nov. are proposed.