Diversity Analysis and Biocontrol Potential of Cultivatable Terrestrial Bacterial Streptomyces in Southern China

Streptomyces are filamentous bacteria that are extensively present in soil, play an important role in carbon cycling, and produce a large number of highly valuable secondary metabolites. In this study, total number of 411 isolates of Streptomyces were collected from ecologically similar habitats from 13 provinces in Southern China. They were clustered into 96 operational taxonomic units including eight potentially new species based on their 16S rDNA sequences. Phylogenetic analysis disclosed that the isolates with similar geographical distributions clustered together. Beta diversity of Streptomyces showed it manifests in a latitudinal diversity gradient (R-2 = 0.3828, p = 0.0113). The beta diversity did not change significantly with geographic distance, and this could be due to the large longitudinal and relatively smaller latitudinal sampling range, as the phylogenetic clustering of regions with higher annual average temperature was analyzed with the nearest taxon index (R = -0.23, p = 0.045). Result of the Streptomyces biogeography evaluation shows the diversity of the genus is controlled by many of the same processes. Bioassay results disclosed that there were 27 isolates strongly antagonistic to plant pathogenic fungi and 71 isolates with strong nematocidal activity against pine wood nematode. Our results provide significant insights into the diversity and biocontrol potential of cultivatable Streptomyces in Southern China.