Nocardioides epinepheli sp. nov., an Epsilon-Poly-l-lysine-Producing Actinobacterium Isolated from the Fish Intestine

A Gram-stain-positive, irregular short rod, non-motile, non-acid-fast, non-spore-forming, aerobic actinomycete strain, designated GXZ039^T, was isolated from the fish gut of grouper from the Beibu Gulf, Guangxi, China. Growth conditions of the strain ranged from pH 6.0 to 10.0 (optimum pH 7.5), 4-40 ℃ (optimum 30 ℃), and 0-10% NaCl (w/v) (optimum 3.5%). Chemotaxonomic characteristics showed that the major menaquinone of strain GXZ039^T was MK-8 (H₄). The main cellular fatty acids were iso-C_16:0 (39.2%), C_17:1ω6c (11.6%), and anteiso-C_15:0 (10.9%). The type of the cell wall peptidoglycan was LL-diaminopimelic acid, and the polar lipids of the strain consisted of phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), one uncharacterized lipid (L), and two unknown phospholipids (PL1-2). Whole-cell sugars were xylose, arabinose, glucose, and galactose. The DNA G + C content of the strain was 71.1%. Sequence comparison of 16S rRNA genes represented that strain GXZ039^T belonged to the genus Nocardioides and its closest relatives were Nocardioides plantarum NCIMB 12834 ^T (98.0%), Nocardioides dongxiaopingii S-1144 ^T (97.5%), Nocardioides litoris 002-2 ^T (97.5%), and Nocardioides rubriscoriae Sco-A25^T (97.4%). The average nucleotide identity (ANI) values of strain GXZ039^T with its closest relative strains were 77.1-85.1%, while the digital DNA-DNA hybridization (dDDH) values were 21.6-27.7%. On the basis of physiological, chemotaxonomic, and phylogenetic data, strain GXZ039^T is considered to represent a novel species of the genus Nocardioides and propose the name Nocardioides epinepheli sp. nov. to accommodate it. The type strain is GXZ039^T (= MCCC 1K09118^T = KCTC 59248 ^T).