Screening On Rare Actinomycetes Produced Pesticidal Metabolites

In oder to screen some rare actinomycete strains produced pesticidal metabolites, 42 samples were collected from Anhui, Zhejiang, Shandong, Shaanxi, Sichuan et al 5 provinces of China.578 actinomycete strains were isolated by means of hight selective methods and their pestcidal activity have been tested. And 4 pestcide-active strains were identified by the way of traditional method and molecular techniques.The main results are as fellow:(1)578 strains were isolated from 42 samples, they were subordinate to Streptomyces, Micromonospora, Actinomadra, Nocardia, Streptosporangium, Actinoplanes, Microbiospora and Microbiospora. The results showed that when use the improved HVA agar as the isolation medium, dilute the sample 100 times and use 20mg·L-1 Potassium Dichromate plus 20mg·L-1 Nalidixic Acid plus 10mg·L-1 Kanamycin as inhibitor, the isolation effect was the best.(2)All the fermentation of the 578 strains were tested against the plant pathogenic fungi, such as Bipolaris sorokiniana ,Exserohilum turcicum, Alternaria longipes, and pathogenic bacteria, such as Bacillus subtilis, Escherichia coli, Staphylococcus aureus. Eight of them have been proven antibiotic, they were labeled as NWAFU032, NWAFU075, NWAFU223, NWAFU227, NWAFU238, NWAFU309, NWAFU313 and NWAFU526, respectively.By means of mycelium growth rate, the fermentations of NWAFU 223 and NWAFU 238 showed the best inhibitive action, both EC50 less than 10 mL·L^-1. Spore germination tests showed that the fermentation of NWAFU526 exhibited the strongest antibiotic activity against Bipolaris sorokiniana, Exserohilum turcicum, Alternaria longipes, the EC50 were 14.01 mL·L^-1, 14.56 mL·L^-1and 17.36 mL·L^-1, respectively. Cup-plate tests against Bacillus subtilis, Escherichia coli, Staphylococcus aureus indicated that the inhibitive diameters of the fermentations of strain NWAFU 223 were all more than 30mm. Pot tests on Blumeria graminis exhibited that the protective efficacy of fermentations of the 5 strains were 71.29%～82.35%, therapeutic efficacy were 58.53%～70.80%. No strain were found have insectidal or herbicidal activity in the test.(3)Four pestcide-active strains were identified by way of traditional method and molecular techniques. The phylogenetic tree, based on 16SrDNA sequences, indicated that strains NWAFU227, NWAFU238, NWAFU309 subordinate to Streptomyces and NWAFU313 subordinate to Micromonospora. The 16S rDNA sequence similarities of all the 4 strains to their type strain were 98%. Base on the morphological, cultural, physiologica and biochemical characteristics test, proposed the strain NWAFU238, NWAFU309 and NWAFU313 as novel species, strain NWAFU227 as a close or the similar species of Streptomyces sp. US80.