Studies On Screening Of Marine Actinomycetes With Anti-MRSA Activity And The Active Compounds Produced By Strain AM105

Methicillin-resistant Staphylococcus aureus (MRSA) which is resistant to most antibiotics is increasing rapidly and has become the "super-bacteria" in the clinic due to absense of effective drugs, which badly endangers the health of human. It is essential to find novel drugs for us. Marine environment is being exploited for new drugs with unique structure and excellent bioactivity. Marine microorganisms with biodiversities on species, genotypes and ecological functions have become the resource treasury of natural drugs, thereby they have turned to the hotspot of new drug research in the world.In this study, research was carried out on following aspects: isolation of marine actinomycete, screening and identification of anti-MRSA strains, optimizing fermentation condition and medium, separation and purification of active compounds and structure identification of the active compound AM105-â…¡ and so on.Employing several culture media and inhibitors, marine actinomycetes were isolated from mangrove sediment by the method of dilution. The results showed that Gause No.1 medium containing 0.005% K₂Cr₃O₇ was the best one for marine actinomycete isolation. Utilizing the aforesaid medium, a total of 395 actinomycetes isolates were separated from 75 marine samples, which were collected from near-shore of Hainan Island, Zhangjiang and Beihai. 43 active actinomycetes isolates were obtained by the method of Kirby Bauer. From them 3 strains with prominent anti-MRSA bioactivity and genetic stabilization were selected, named A115, A209 and AM105.By studying the morphology, cultural characteristics, physiological and biochemical properties, 16S rDNA and phylogenetic tree, A115 was proposed as Streptomyces albogriseolus var. marine, A209 as Streptomyces aureofaciens and AM105 was closely related to Micromonospora floridensis DSM43907 and Micromonospora matsumotoense DSM44100. Strain AM105 exhibited levels of DNA-DNA relatedness of 73.5% and 53.6% to M. floridensis DSM43907 and M. matsumotoense DSM44100 respectively. On the basis of DNA-DNA relatedness and the character of producing Rifamycin, strain AM105 is proposed the name as Micromonospora floridensis subsp. rifamycetica. Strain AM105 is the first discovery of M. floridensis that produces Rifamycin. The GenBank accession number for the 16S rDNA gene sequence of strain AM 105 is AY561829.The best optimal liquid fermentation condition and medium component was...