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 165 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.

Automated summary

Two halophilic archaeal strains, Gai3-2(T) and NJ-3-1(T), isolated from salt lake and saline soil samples in PR China, represent novel species of Halobaculum genus. The 16S rRNA gene sequences of these strains showed high similarity but lower than recommended threshold for species delimitation.