云南酸性土壤中度嗜酸链霉菌的多样性

Diversity of neutrotolerant acidophilic streptomycetes isolated from acidic soils in Yunnan Province

摘要:

【目的】了解酸性土壤环境里中度嗜酸链霉菌的多样性, 调查其物种资源。【方法】用分散和差速离心法及选择性分离培养基从14份云南酸性土壤样品中分离到367株具有链霉菌培养特征的放线菌, 并进行了颜色分群。从各颜色类群中选取代表菌株共97株, 通过显微形态观察和pH梯度生长实验确定其中的中度嗜酸链霉菌。进一步从中筛选出16株中度嗜酸链霉菌代表菌株, 进行16S rRNA基因序列的相似性和系统发育分析, 并结合基因组DNA-DNA相关性数据。【结果】分离菌株归为12同的颜色类群, 其中80%属于中度嗜酸链霉菌, 其代表菌株在系统发育树上形成了8个距离较远且与已知种不同的进化分枝, 可能代表链霉菌属内至少8个不同的新基因种。【结论】用以上方法筛选出的中度嗜酸链霉菌可归为8个不同于已知种的进化群, 说明云南酸性土壤含有丰富多样的中度嗜酸链霉菌新物种。

Abstract:

[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.