[Study on diversity of actinomycetes under salt and alkaline environments].

Actinomycetes have been attached a great attention owing to these microorganisms product various natural compounds and have special mechanism of adapting extreme environments. But the research work on actinomycetes under extreme environments is few. Soil and sediment samples were collected from saline and alkaline soil and lakes in Xinjiang, Qinghai Province, P. R. China and Egypt. Diversity and some biological characteristics of Actinomycete were studied by using cultivation and DGGE methods. Results showed that large amount of unknown microorganisms exist in the salt lake Chaka, isolated strains account for only a small portion of species diversity. Designing new strategies for isolation of as yet uncultured microorganisms from natural extreme environments is the key step to exploit microbial resources. The 87% of alkalophilic or alkalinetolerant actinomycete strains were able to grow at pH 6.0 - 12.0. 14 strains grow well at pH 8.5 - 11.5, but not at pH 7.0. 34 halotolerant actinomycete cab grow in 15% - 20% NaCl. Based on the study of the halophilic and halotolerant actinomycetes isolated from the saline and the alkaline soils collected from Xinjiang and Qinghai Province, China, we can conclude that the relationship of actinomycetes (especially halophilic actinomycetes strains) to positive ions such as Na+, K+ and Mg2+ is very complex, and there were sodiumphilic, kaliumphilic, magnesiumphilic, and calciumphilici actinomycete strains. One new family, eight new genera and more than 30 new species of halophilic and alkalophilic actinomycetes were fund. Many strains with PKS genes were selected. We believe based on the research results that there is a very high density of new or unknown actinomycete resources in these areas in China and Egypt.