The Screening Of Active Actinomycetes Strains Producting Type Ii Polyketide

Polyketide is microbiology secondary metabolites, which has good antibacterial actitity, it has been widely developed and applicated. Now, there are more than 10,000 kinds of polyketide synthase have been found, most of the antibiotics, immunosuppressive and antineoplastic agents, biological-pesticides are polyketide. Polyketide is closely related to human production and life. Actinomycetes is the main productor of polyketide, 70 percent of natural polyketide come from actinomycetes, so that, people isolate and culture strains from nature to get the activeactinomycetes strain, optimizate the fermentation conditions to regain the bio-active secondary metabolites. However, this traditional method isolate compounds with a high rate of repetition to known compounds, therefore, the new molecular method of targeted screening are taking place and favored by people.As we known, polyketide biosynthetic pathway is formed in the continuous decarbox- ylation condensation of simple carboxylic acids, such as acetic acid, propionic acid. Many cloned PKS gene cluster show that the KS gene is conserved. Accordingly, this experiment designs type II KS gene degenerate primers to amplify KS gene fragments from actinomycete DNA. In this paper, 38 strains were screened from 58 unknown actinomycetes strains. Cloned and sequenced to obtain 38 nucleotide sequences, BLAST, 35 sequences are type II KS gene. The phylogenetic analysis showed that the KS gene of strain HVG60, T12-218, GT1H, T1, MY09, MY01 are significantly different from the known KS gene, and independent branch of the phylogenetic tree. The antifungal testing of the 6 strains showed that strain GT1H and HVG60 had a better antifungal activity. 16S rDNA classify and identify that GT1H was Streptomyces.rishiriensis, HVG60 was Streptomyces.olivochromogenes. S. rishiriensis produ- ces bio-active substances coumermycin A1, it does not have anti-fungal activity, but strain GT1H hasanti-fungal activity, there are something difference between the two strains. S.olivochromogenes has no report of active metabolites. Therefore, strain GT1H and HVG60 may produce a new type of metabolic compounds, they have in-depth study of value, can be used as an alternative strain to further development and application.This study screened two strains that had new-polyketide producting activity from 58 unknown actinomycetes, established a rapid and efficient screening system. It provides apre-requisite for the polyketide screening, contributes to the development and utilization of natural microbiology resources.