Halococcus agarilyticus sp. nov., an agar-degrading haloarchaeon isolated from commercial salt.

Abstract

Two agar-degrading halophilic archaeal strains, 62 E(T) and 197 A, were isolated from commercial salt samples. Cells were non-motile cocci, approximately 1.2-2.0 µm in diameter and stained Gram-negative. Colonies were pink-pigmented. Strain 62 E(T) was able to grow with 24-30% (w/v) NaCl (optimum, 27%), at pH 6.5-8.5 (optimum, pH 7.5) and at 22-47 °C (optimum, 42 °C). The 16S rRNA gene sequences of strains 62 E(T) and 197 A were identical, and the level of DNA-DNA relatedness between them was 90 and 90% (reciprocally). The closest relative was Halococcus saccharolyticus JCM 8878(T) with 99.7% similarity in 16S rRNA orthologous gene sequences, followed by Halococcus salifodinae JCM 9578(T) (99.6%), while similarities with other species of the genus Halococcus were equal to or lower than 95.1%. The rpoB' gene tree strongly supported that the two strains were members of the genus Halococcus . Mean DNA-DNA relatedness between strain 62 E(T) and H. saccharolyticus JCM 8878(T) and H. salifodinae JCM 9578(T) was 46 and 44%, respectively. The major polar lipids were archaeol derivatives of phosphatidylglycerol, phosphatidylglycerol phosphate methyl ester, derived from both C20C20 and C20C25 archaeol, and sulfated diglycosyl archaeol-1. Several unidentified glycolipids were present. Based on the phenotypic and phylogenetic analyses, the isolates are considered to represent a novel species of the genus Halococcus , for which the name Halococcus agarilyticus sp. nov. is proposed. The type strain is 62 E(T) ( = JCM 19592(T) =KCTC 4143(T)).