Diversity of culturable actinobacteria from soils collected in Ali, Naqu and Haixi Districts on the Qinghai-Tibet Plateau

Abstract:

[Objective] This study is aimed at studying the diversity of culturable actinobacteria in soils of the north Qinghai-Tibet Plateau and comparing the effect of different selective isolation media on the isolation of actinobacteria.[Methods] We used 9 isolation media to isolate actinobacteria from 14 soil samples collected from Ali, Naqu and Haixi districts on the Qinghai-Tibet Plateau. We added the fermentation broth of Micrococcus luteus to the medium to help the isolation. The isolates were identified based on the 16S rRNA gene sequences, and diversity of actinobacterial isolates were analyzed at different taxonomic levels.[Results] We isolated a total of 255 dereplicated strains, belonging to 8 orders, 14 families and 23 genera of the phylum Actinobacteria. The isolates were delineated into 94 OTUs, which corresponded to 94 putative species. Among them, at least 25 putative species were new, spanning 13 genera; and 108 strains, which contained 28 putative species, belonged to the genus Streptomyces, the most dominant genus of culturable actinobacteria from the soils. Addition of the Micrococcus luteus fermentation broth obviously increased the number and diversity of actinobacterial isolates. Diluted glucose-yeast extract-malt extract medium was suitable for the isolation of Streptomyces, and starch-glycerol-proline medium, sodium propionate-casein medium, etc. were suitable for the isolation of rare actinobacteria.[Conclusion] Soils of the north Qinghai-Tibet Plateau contain a high diversity of culturable actinobacteria and a number of novel actinobacterial species. Addition of the Micrococcus lutea fermentation broth into the isolation medium can effectively improve the isolation efficiency for actinobacteria.