This study first described the composition and characteristics of culturable endophytic bacteria isolated from wild alpine-subnival plant species growing under extreme environmental conditions (i.e., on the border of a glacier with frequently fluctuating and freezing temperatures, strong wind, and high ultraviolet radiation). Using a cultivation-dependent approach and 16S rRNA gene amplification techniques, 93 bacterial isolates showing different phenotypic properties were obtained from 20 different subnival plant species, of which gram-positive bacteria (61.5%), psychrotolerant bacteria (67.3%), and pigmented isolates (70.9%) accounted for a large proportion. All these characteristics of endophytes were closely related to the survival environment of their host plants and were in good agreement with microbes occurring in other cold environments. Phylogenetic analysis indicated that the endophytic isolates consisted of five phylogenetic groups comprising α-proteobacteria, γ-proteobacteria, the high G+C content gram-positive bacteria, the low G+C content gram-positive bacteria, and Flavobacterium-Bacteroides-Cytophaga. The largest generic diversity was found in the HGC group, while Clavibacter, Agreia, Rhodococcus, Sphingomonas, and Pseudomonas were the most prevalent genera. Of all isolates, 46.4% showed a high sequence similarity (98-100%) to strains discovered from other cold environments such as glaciers, tundra, and polar seas. Furthermore, 36.4% of the isolates produced Indole-3-acetic acid and 76.3% were able to solubilize mineral phosphate, which revealed that endophytic bacteria with multiple physiological functions were abundant and widespread in subnival plants. These results are essential for understanding the ecological roles of endophytes and as a foundation for further studying the interactions with plants and environment.
Two rod-shaped and Gram-stain-positive bacteria (strains C64T and C62) were isolated in 2020 from faeces of greater white-fronted geese (Anser albifrons) from Poyang Lake, PR China. Their optimal growth conditions were at 37 °C, pH 7.0 and with 0.5 % (w/v) NaCl. The two isolates showed a highest 16S rRNA gene sequence similarity to Bowdeniella nasicola DSM 19116T (92.1 %). Phylogenetic/phylogenomic analyses indicated that strains C64T and C62 clustered independently in the vicinity of the genera Varibaculum , Winkia and Mobiluncus within the family Actinomycetaceae , but could not be classified clearly as members of any of these known genera. The average amino acid identity values between our isolates and available genomes of members of the family Actinomycetaceae were around the genus threshold value (45–65 %). The major cellular fatty acids of the strains were C18 : 1ω9c and C16 : 0. The predominant polar lipids were phosphatidylinositol, phosphatidylglycerol, phosphatidylcholine, diacylglycerol, triacylglycerol and cardiolipin. The amino acid composition of peptidoglycan contained alanine, glutamic acid and glycine. The major respiratory menaquinones were MK-8(H4) and MK-9(H4). The whole cell sugars included galactose, arabinose and glucose. On the basis of the results of the 16S rRNA gene sequences comparison, whole-genome phylogenomic analysis, phenotypic and chemotaxonomic characteristics, we propose that strains C64T and C62 represent a novel species belonging to a novel genus within the family Actinomycetaceae , for which the name Nanchangia anserum gen. nov., sp. nov. is proposed. The type strain is Nanchangia anserum C64T (=CGMCC 1.18410T=GDMCC 1.1969T=KCTC 49511T=KACC 22143T).
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