Objective: Acidophilic filamentous acitnomycetes are active in the turnover of organic matter in acid litters and soils, and are a source of antifungal antibiotics and acid-stable enzymes. The aim of this study is to delineate the diversity of neutrotolerant acidophilic streptomycetes in acidic soil environment, and to investigate the resources of species.
Methods: 367 actinomycetes with cultural characteristics of streptomycetes were isolated from 14 acidic soil samples collected in Yunnan Province, China, using the method of DDC (dispersion and differential centrifugation) and a selective medium. The isolates were color grouped on the basis of their properties of aerial mycelium, substrate mycelium and diffusible pigments. 97 representative isolates were picked from the color groups for micromorphological observation and for the test of pH range for growth. Among the neutrotolerant acidophilic streptomycetes, 16 representatives were further selected and were subjected to a molecular systematic study based on almost complete 16S rRNA gene sequences and DNA-DNA relatedness.
Results: The isolates were assigned to 12 color groups, and 80% of them were neutrotolerant acidophilic streptomycetes. The 16 representative strains formed eight distinct subclades within the genus of Streptomyces, and probably represented at least eight new genotypic species of Streptomyces.
Conclusion: The neutrotolerant acidophilic streptomycetes isolated in this study were placed in eight distinct evolutionary groups, indicating the good diversity and novelty of these microorganisms in acidic soils in Yunnan Province.