Halorussus halophilus sp. nov., A Novel Halophilic Archaeon Isolated from a Marine Solar Saltern.

The halophilic archaeal strain ZS-3T (= CGMCC 1.12866T = JCM 30239T) was isolated from a sediment sample of Zhoushan marine solar saltern, P. R. China. Phylogenetic analyses based on 16S rRNA, rpoB' genes and the concatenation of 738 protein sequences reveal that strain ZS-3T was related to members of the genus Halorussus. The OrthoANI and in silico DDH values between strain ZS-3T and the current Halorussus members are much lower than the threshold values proposed as the species boundary (ANI 95-96% and in silico DDH 70%), suggesting that strain ZS-3T represents a novel species of Halorussus (Halorussus halophilus sp. nov.). Diverse phenotypic characteristics differentiate strain ZS-3T from current Halorussus members. Since the strain expressed diverse hydrolyzing enzyme activity, its complete genome was sequenced. The genome of strain ZS-3T was found to be 4,450,731 bp with total GC content of 61.51%, and comprises one chromosome and three plasmids. A total of 4694 protein coding genes, 43 tRNA genes and 6 rRNA genes were predicted. A CRISPR-Cas system was also detected. The genome encodes sixteen putative glycoside hydrolases, nine extracellular proteases, seventeen aminopeptidases, seven carboxypeptidases, one esterase and one nitrite reductase. The exploration of the hydrolase genes may expand our understanding of adapted mechanism of halophilic archaea surviving optimally in hypersaline environments where containing organic matter. Meanwhile, various hydrolyzing enzymes may extend this microorganism for further applications in salt-based fermentation.