Demequina globuliformis sp. nov., Demequina oxidasica sp. nov. and Demequina aurantiaca sp. nov., actinobacteria isolated from marine environments, and proposal of Demequinaceae fam. nov.

Abstract

Three Gram-stain-positive actinobacterial strains, designated YM24-125T, YM05-1041T and YM12-102T, were isolated from marine environments. Phylogenetic analysis based on 16S rRNA gene sequences indicated that they belonged to the suborder Micrococcineae and were most closely related to members of the genus Demequina with 95.0–98.4 % sequence similarities. Cells of strains YM05-1041T and YM12-102T were rod-shaped, similar to members of the genus Demequina, while cells of strain YM24-125T were cocci to short ovoid rods. All strains grew in the absence of NaCl, but tolerated up to 15 % NaCl. The major menaquinone was demethylmenaquinone DMK-9 (H4) and the major polar lipids were phosphatidylinositol, diphosphatidylglycerol and phosphatidyglycerol. All strains contained straight-chain, iso-branched and anteiso-branched saturated fatty acids. The DNA G+C contents were 65.3–67.3 mol%. The peptidoglycans of strains YM05-1041T and YM12-102T were the A4β type with ornithine while that of strain YM24-125T contained ornithine and lysine as diamino acids. Phylogenetic analyses and differences in physiological and biochemical characteristics indicated that these three isolates represent novel species within the genus Demequina, for which the names Demequina globuliformis sp. nov. (with YM24-125T  = NBRC 106266T  = KCTC 19747T  = MBIC 08349T as the type strain), Demequina oxidasica sp. nov. (with YM05-1041T  = NBRC 106264T  = KCTC 19746T  = MBIC 08346T as the type strain) and Demequina aurantiaca sp. nov. (with YM12-102T  = NBRC 106265T  = KCTC 19745T  = MBIC 08347T as the type strain) are proposed. Based on differences in the quinone system, the presence of demethylmenaquinone DMK-9(H4) and the pattern of 16S rRNA signatures, the three novel strains and current members of the genus Demequina represent a unique family within the suborder Micrococcineae. Therefore, the family Demequinaceae fam. nov. is also proposed.