[Micirobial diversity and screening of antitumor activity of actinomycete strains from saline and alkaline environments in the Qinghai Province, P. R. China].

Soil and sediment samples were collected from saline and alkaline soils or lakes in the Qinghai Province, northwestern China. 145 actinomycete strains were isolated using Glucose-Peptone-Yeast extract agar (GPY) and ISP medium 2 agar supplemented with 1.0 - 3.0 mol/L NaCl at pH 7.5 - 10. The antitumor activities in vitro of the fermentation broth extracts from the 145 test strains were detected in 6 human tumor cell lines (gastric cancer GXF251L, lung cancer LXFL529L, mammary cancer MAXF401NL, melanoma cancer MEXF462NL, renal cancer RXF486L and uterus cancer UXF1138L). Out of 145 test strains, 26 strains were positive in antitumor activities (17.9%), among them 19 strains belong to the genus Nocardiopsis, 7 strains belong to the genus Streptomyces. Then 8 antitumor-positive strains were submitted for 16S rRNA gene amplification and phylogenetic analysis after a comparison of antitumor activities, morphological, physiological characteristics and whole cell amino acids analysis. The results suggested that strain YIM 80139 is a member of a known Streptomyces species S. griseus, while strain YIM 80038 may represent a potential new Streptomyce species, and that the other 6 strains may represent 4 potential new species of the genus Nocardiopsis. The results presented above showed that actinomycetes isolated from saline and alkaline samples are important resources for bioactive compounds, and the abundant microbial diversity in the saline and alkaline environments in the Qinghai Province, Northwestern China is attractive for further investigation.