Streptomyces Strains From The Soils Of The Tibetan Plateau: Isolation, Identification And Antimicrobial Activity

The Tibetan Plateau is a representative of the extreme environment, much researches ofthe soil microbes in soils of Tibetan Plateau were carried out in the distribution and thediversity of bacteria but that in Streptomyces diversity and its functional metabolism are lessstudied yet. In the view of an increasing number of multi-resistant bacteria and less possibilityto discover new antibacterial compounds, the study of Streptomyces resource in the TibetPlateau permafrost is expected to find not only new species of Streptomyces with theresistance of spectrum, but also present some important theoretical and practical values inunderstanding the distribution of Streptomyces in different regions and its resourcesdevelopment and utilization. In this study, the soil samples from Dangxiong, Wudaoliang,Beiluhe, Tongtianhe, etc. in the Tibet Plateau were took for the research material. Using themethod of separation of classical culture and the molecular biology technology, we separateand identify the Streptomyces strains growing in the soils and then the gram-positive andnegative bacteria antibacterial activity of the separated strains were examined. The mainresults obtained are as follows:The diversity Streptomyces strains present in the soil of the Tibet plateau. A total of150Streptomyces strains were isolated from the soil samples of11sampling points, and144ofthem were isolated at30℃, six strains were isolated at4℃. Of which the separatedStreptomyces strains in Dangxiong county, WudaoliangⅠregion, Beiluhe basin, Yanshipingregion, Kaixinling region, Wuli region, Amdo county, Tanggula mountain, WudaoliangⅡregion, Tongtian river and Tuotuohe basin are account for3.47%,6.94%,2.08%,2.08%,0.69%,20.83%,4.86%,1.39%,18.75%,16.67%and22.22%of the total separations,respectively. The six strains isolated at4℃are from WudaoliangⅠregion, Kaixinling region,Wuli region, WudaoliangⅡregion and Tongtian river.The16S rRNA gene sequences of the separated strains were amplified and sequenced.And the results show that the isolated strains have high homology with the Streptomycesstrain which have been registered in the resulting database and the sequence similarity werebetween99%and100%. However, the strains WDL-DM-5and TTH-DM-1had90.76%and95%similarity compared with a known Streptomyces strain, respectively. Strain WDL-DM-5and TTH-DM-1maybe a new species.Genetic diversity analysis showed that, S. avidinii, S. spororaveus, S. vinaceus, S.cirratus, S. albidochromogenes, S. flavidovirens and S. candidus are dominant andwidespread Streptomyces strains in the Tibetan Plateau soil and the proportion of sequencedstrains is11.76%,10.29%,7.35%,13.24%,10.29%,5.88%and8.82%, respectively. However, S. mirabilis and S. cellostaticus strains were only isolated in the soil of Dangxiongcounty, similarly, S. microflavus was in Beiluhe basin, S. finlayi was in Yanshiping region, S.novaecaesareae, S. anulatus and S. scabiei were in Wuli region, S. hirsutus and S. ablonigerwere in the WudaoliangⅡregion, S. tauritus was in Tongtian river, S. phaeoluteigriseus and S.griseorubiginosu were in Tuotuohe basin, S. hypolithicus and S. clavifer were in Kaixinlingregion. These results show that the species distribution of Streptomyces from the differentterritorial soils of Tibet plateau have both the similarity, and specificity particularity, and ofwhich dominant species have a large proportion.Furthermore, we detected the antibacterial activity of Streptomyces strains isolated in thisstudy. The results show that71strains have antagonistic effects on both gram-positive andnegative bacteria, which accout for47.33%of the total number of separation strains. Thenumber of the antibacterial strains resistant to Escherichia coli, Staphylococcus aureus andBacillus subtilis were55,58and67, respectively;45strains have antibacterial effects on thethree indicator bacteria species, which accounts for30%of the total bacteria. The strainsisolated form Wuli region, Amdo county, Tanggula mountain and Tongtian river have strongantibacterial activity, and the strains number with the inhibition zone D≥10mm accounts for56.25%,71.43%,100%and92.31%of total antagonistic bacteria in the same site,respectively. However, no antagonistic strain was isolated in Beiluhe and the strains from therest region samples have the weaker antibacterial activity. These results indicate that someStreptomyces grown in the soils of Tibetan Plateau have strong antimicrobial activity, whichmay be the valuable resources for potential antibiotics.