Aeromicrobium endophyticum sp. nov., an endophytic actinobacterium isolated from reed (Phragmites australis)

Abstract

A Gram-staining-positive, motile and short-rod-shaped actinobacterium designated 9W16Y-2^T was isolated from surface-sterilized leaves of reed (Phragmites australis) collected from Taklamakan Desert in Xinjiang Uygur Autonomous Region, China. Colonies were pale greenish yellow, circular, smooth, and convex. The 16S rRNA gene sequence of strain 9W16Y-2^T exhibited highest sequence similarities with Aeromicrobium camelliae CGMCC 1.12942^T (99.0%) and Aeromicrobium erythreum NRRL B-3381^T (97.2%). Phylogenetic analyses based on 16S rRNA gene sequences and single-copy phylogenetic marker genes (pMGs) showed that strain 9W16Y-2^T belonged to the genus Aeromicrobium and formed a monophyletic clade with Aeromicrobium camelliae CGMCC 1.12942^T. Furthermore, average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) clearly separated strain 9W16Y-2^T from the other species of the genus Aeromicrobium with values below the thresholds for species delineation. The G+C content of the genomic DNA is 68.9 mol%. The diagnostic diamino acid of the cell-wall peptidoglycan was LL-diaminopimelic acid. The predominant menaquinone was MK-9(H₄). The major fatty acids (> 10% of the total fatty acids) were C_18:0 10-methyl (TBSA) (28.2%), C_16:0 (21.0%), C_16:0 2-OH (20.8%) and C_18:1ω9c (12.8%). The polar lipid profile comprised diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylinositol, an unidentified aminophospholipid and an unidentified lipid. Based on the phylogenic, phenotypic and chemotaxonomic features, strain 9W16Y-2^T represents a novel species of the genus Aeromicrobium, for which the name Aeromicrobium endophyticum sp. nov. is proposed. The type strain is 9W16Y-2^T (= CGMCC 1.13876^T = JCM 33141^T).

Keywords: Aeromicrobium endophyticum; endophytic actinobacterium; genome comparison; single-copy phylogenetic marker genes.