Profundirhabdus halotolerans gen. nov., sp. nov., an haloalkaliphilic actinobacterium isolated from seawater of the Mariana Trench

A Gram- stain- positive, strictly aerobic, rod- shaped actinobacterium, designated strain ZYF776(T), was isolated from seawater of the Mariana Trench collected at a depth of 4000 m. Results of 16S rRNA gene sequence analysis indicated that strain ZYF776(T) was a member of the class Nitriliruptoria and closely related to Nitriliruptor alkaliphilus DSM 45188(T) (member of the order Nitriliruptorales, 94.94 % sequence similarity) and Egicoccus halophilus KCTC 33612(T) (member of the order Egicoccales, 94.46 %). Strain ZYF776(T) was catalase- positive and oxidase- negative. Growth occurred at 16-37 C-degrees (optimum, 28 C-degrees), in the presence of 0-13 % NaCl (w/v; optimum, 4 %) and at pH 7.0-10.0 (optimum, pH 8.0). Cell - wall hydrolysates of strain ZYF776(T) contained meso- diaminopimelic (peptidoglycan type A1 gamma), with ribose, rhamnose and a smaller amount of xylose as the cell - wall sugars. The major menaquinone was MK - 10. The predominant fatty acids (>10 %) were C-16:0, C-17:1 omega 8c and summed feature 3 (C-16:1 omega 7c and/or C-16:1 omega 6c). The polar lipid profile mainly contained diphosphatidylglycerol, phosphatidylglycerol and phosphoglycolipid. The genomic DNA G+C content of strain ZYF776(T) was 68.7mol%. The genome of strain ZYF776T was about 5.61 Mbp in size, which was larger than those of the reference strains N. alkaliphilus DSM45188(T) (5.56 Mbp) and E. halophilus KCTC 33612(T) (3.98 Mbp). The average nucleotide identity and digital DNA-DNA hybridization values between ZYF776(T) and the related strains N. alkaliphilus DSM 45188(T) and E. halophilus KCTC 33612(T) were 76.7 and 20.3 % and 75.8 and 20.0 %, respectively. Based on the polyphasic evidence, a novel genus and species with the name Profundirhabdus halotolerans gen. nov., sp. nov. is proposed. The type strain is ZYF776(T) (=JCM 33008T=MCCC 1K03555(T)).