A Primary Study On Bio-activity Of Actinomycetes Isolated From Mangrove Sediments

Mangrove are unique woody plant communities growing in intertidal zones of tropical and subtropical coast, which possess importantly economic and ecological value. Microbe is an important part in mangrove ecosystem, expecially Actinomycetes which are famous for their abilities to produce all kinds of compounds with bioactivities.In this study we collected mangrove sediments from Zhangjiang estuary, Fujian of China and actionmycetes were isolated. B. subtilis, S. aureus, E. coli, C. albicans, R. solani are used to test the their ability of anti-bacterial. BEL7402, A549, HL60 are used to test their ability of anti-tumorcell. The results showed that 42.3% of the isolates possessed anti-bacterial activity while 37.4% have anti-tumorcell activity.16s rDNA sequences of 163 isolates and diversity were analyzed. They belong to genus Streptomyces(89%), Micromonospora(6.1%), Sacharomonospora(0.6%), Actinomadura (3.7%) and Nocardiopsis(0.6%). In addition, The isolates MGR035, MGR082, MGR105 were suggested as three novel Streptomyces. spp. with the highest 16S rDNA similarity less than 97% to Streptomyces carpacticus, Streptomyces glauciniger and Streptomyces cacaoi subsp, cacaoi.Molecular screening was done to detect the existence of PKS (polyketide synthesis) and NRPS(nonribosomal peptide synthetases) genes of the isolates using primers designed to amplify their conserved region. The detection results were used to realize their potential of producing compound with activities. Diversity of the amplification fragments was also investigated. 77 isolates including 5 genus were analyzed. The detection results of PKS and NRPS gene showed that genus Streptomyces are abundant resources to produce polyketide and nonribosomal peptide: 36.4% of 66 Streptomyces strains have typeâ… PKS gene while 59.1% have typeâ…¡PKS gene and 51.5% have NRPS gene. PKS and NRPS gene are also detected in other genus including Micromonospors and rare actinomycetes.Analysis of the relationship between antagonistic activities and the detection results of secondary metabolites biosynthetic genes showed that they were not directly correlative. Strains with no activity also have PKS and NRPS gene. Isolates with high 16S rDNA similarity have different antagonistic activities and PKS/NRPS genes. And PKS genes of some isolates that belong to rare actinomycetes have distinct evolution relationship between strains that belong to Streptomyces which suggest they have potential ability to produce novel compounds. The resluts showed that all the isolates not only have genus diversity but also complex gene diversity that related to secondary metabolites biosynthsis. MGR157 and MGR010 which have PKS and NRPS gene but have no antibacte-rial activities were studied as parent strain to elicit the bacterial abilities using Ribos-ome Engneering method. Streptomycin and Gentamycin resistant mutants of MGR-157 were obtained while Rifamycin resistant mutant of MGR010 were obtained. Ant-agonistic activity test showed some mutants gained anti-bacterial abilities and they have typical morphological difference with original strains. It proved that Ribosome Engneering is an efficient method to fully elicit the bacterial abilities and improve the efficiency of utilization of actinomycetes in mangrove sediments.