Genomic insights into the genus Halalkalibacter and proposal of two novel Halalkalibacter species, Halalkalibacter haasae sp. nov., and Halalkalibacter salibacillus sp. nov

Background The present study aimed to investigate the genomic insights into the genus Halalkalibacter and evaluate the taxonomic positions of haloalkaliphilic strains HAAS-P013 T and HAAS-P014 T , isolated from saline-alkali soil using a polyphasic approach. Results Strains HAAS-P013 T and HAAS-P014 T were Gram-positive, aerobic, motile, and rod-shaped. Phylogenetic and 16S rRNA gene sequence analyses assigned both strains to the genus Halalkalibacter . Strain HAAS-P013 T grew at 12-45 °C (optimum at 32 °C), pH 6.0–11.0 (optimum at pH 10.0) and demonstrates tolerance to NaCl concentration up to 15% (w/v), while strain HAAS-P014 T grew at 12–45 °C (optimum at 37 °C), pH 7.0–11.0 (optimum at pH 10.0) and could tolerate NaCl up to 20% (w/v). Both strains consist of meso- 2,6-diaminopimelic acid, MK-6 and MK-7 as menaquinones, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, unidentified lipid as polar lipids, and anteiso-C 15:0 and C 16:0 as dominant fatty acids. Strain HAAS-P013 T contained two unidentified phospholipids in addition to the above polar lipids, whereas strain HAAS-P014 T contained one unidentified phospholipid. The genomic analysis of strains HAAS-P013ᵀ and HAAS-P014ᵀ showed the presence of multiple genes potentially involved in osmotic and alkaline stress responses. The average nucleotide identity/digital DNA-DNA hybridization values among strains HAAS-P013 T , HAAS-P014 T , and other Halalkalibacter species were below the threshold values (95-96/70%) for species delineation. Conclusions Based on the above results, the strains HAAS-P013 T and HAAS-P014 T represent two novel species of the genus Halalkalibacter , for which the names Halalkalibacter haasae sp. nov., and Halalkalibacter salibacillus sp. nov., are proposed. The type strains are HAAS-P013 T ( = KCTC 43869 T = GDMCC 1.6158 T ) and HAAS-P014 T ( = KCTC 43870 T = GDMCC 1.6094 T ).