Nocardiopsis protaetiae sp. nov., a novel actinobacterium isolated from the frass of Protaetia brevitarsis larvae.

Four actinobacterial strains, designated NEAU-PBA1^T, NEAU-PB14, NEAU-PB65 and NEAU-PB77, were isolated from the frass of Protaetia brevitarsis collected from Harbin, Heilongjiang Province, China. These strains were Gram-stain positive, aerobic and produced branched substrate mycelium and aerial hyphae, without producing diffusible pigments in the tested media. Upon maturity, spore chains formed on the aerial hyphae, while the mycelium fragmented with age. The genome sizes of these four strains ranged from 7.41 to 7.49 Mbp, with the genomic DNA G+C content varying from 71.8% to 72.9%. Phylogenetic analysis based on 16S rRNA gene sequences indicated that these four strains belonged to the genus Nocardiopsis and exhibited high sequence similarity with Nocardiopsis changdeensis Mg02^T. The average nucleotide identity and digital DNA-DNA hybridization values between these four isolates exceeded the threshold for species delineation, while the values between the four isolates and their close relatives were below the threshold. The predominant menaquinones in strain NEAU-PBA1^T are MK-10 (H₄, H₆, H₈) and MK-10, while the phospholipids included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, phosphoglycolipid, phosphatidylcholine, one phospholipid and one lipid. The major cellular fatty acids comprised anteiso-C_15:0, iso-C_16:0, anteiso-C_17: 0 and C_18:1  ω9c. Based on polyphasic taxonomic analysis, strains NEAU-PBA1^T, NEAU-PB14, NEAU-PB65 and NEAU-PB77 were identified as a novel species within the genus Nocardiopsis, and the name Nocardiopsis protaetiae sp. nov. was proposed. The type strain is NEAU-PBA1^T (=MCCC 1K08877^T=JCM 37021^T).