Actinobacterial Communities of Chosen Extreme Habitats in China

ABSTRACT Actinobacteria living in frozen soils which potentially could be producers of valuable and biologically active metabolites, remain still largely unexplored. Therefore, the diversity of culturable actinobacteria in the six frozen soil samples collected from the high-latitude and the high-altitude regions in China was investigated by using the culture-dependent method and 16S rRNA gene analysis. A total of 184 culturable actinobacterial isolates (morphotypes) were obtained. The abundance of culturable actinobacteria was 6.20 × 103–3.49 × 105 colony forming units (CFU) per gram of soil (dry weight). The actinobacteria isolated from the high-latitude region in China belong to five genera: Streptacidiphilus, Kitasatospora, Streptomyces, Arthrobacter, and Rhodococcus. The strains belonging to Arthrobacter were dominant, the 19 strains were closely related to Arthrobacter globiformis in terms of evolutionary distance. The actinobacterial isolates from the high-altitude region, from 2, 813 m to 4, 775 m in elevation, in China could be grouped into six genera (Arthrobacter, Microbacterium, Streptomyces, Rhodococcus, Nocardia, and Nocardiopsis), with dominant Streptomyces and Arthrobacter strains. The 4 strains were closely related to Rhodococcus fascians and one strain was closely with Microbacterium hydrocarbonoxydans in terms of evolutionary distance. Three genera of Arthrobacter, Streptomyces, and Rhodococcus were found in both areas. Our research provides new insight into the characteristics of the distribution of actinobacteria associated with frozen soils, which help us gain a better understanding of the potential of the cryogenic environments – the potential source of actinobacterial antibiotics.