Diversity And Secondary Metabolites Biosynthetic Gene Screening Of Actinomycetes In Taiwan Strait Marine Sediments

Objective: To investigate the diversity of actinomycetes isolated fromTaiwan strait marine sediments and to isolate new actinomycetes for discoveringcompounds of pharmaceutical importance. Methods: Six selective media were usedto isolate actinomycetes from15sediment samples. Actinobacterial diversity in thesesediments was investigated by phylogenetic analysis based on16S rRNA genesequences. To detect potential producer strains of enediyne antibiotics andhalometabolites, PCR based screening strategy was used to investigate134marineactinomycetes including95representative isolates and39previous isolates. Results:A total of497strains of actinomycetes were isolated and95representative isolateswere selected on the basis of their morphologies on different media.16S rRNA genesequences phylogenetic analysis showed that these strains belonged to seven familiesincluding eleven genera. Phylogenetic analyses also grouped many of the strains intoclades distinct from all known genera within Micromonosporaceae, indicating thatthey may be new genera.41.8%of the134strains were identified containingenediyne polyketide synthase (PKSE) gene fragment. To our knowledge it is the firstreport that Jishengella, Saccharomonospora and Micrococcus contained PKSE gene.They are potential producer strains of enediyne antibiotics and provide newactinomycetes for discovering enediyne family compouds.16reduced flavin adeninedinucleotide (FADH2)-dependent halogenase gene-positive strains were identifiedafter the PCR screening of the above134strains, the occurrence of the halogenasegene in these marine-origin actinomycetes was11.9%. A phylogenetic analysis of theamino acid sequences of the newly identified halogenases displayed high similarity(53.0%-83.0%) with unkown halogenase gene sequences rather than known ones.These halogenase sequences clustered into a couple of distinct clades in thephylogenetic tree. It showed that these halogenase gene positive isolates may have thepotential of producing novel halometabolites. Conclusion: The above results confirmthat marine sediments are rich source of rare actinomycetes and the actinomycetesfrom marine environment have the potential of producing new enediyne antibioticsand halometabolites.