Identification And Antifungal Activity Of The Cultural Microorganisms In South Atlantic Deep-sea Sediments

Fungal toxins like aflatoxin and fusariotoxins enter the food chain by pollutingcrops and animal feed which harm to people’s health. This study use Aspergillusparasiticus mutant NFRI-95and Fusarium graminearum as indicated strains,screening bacteria and actinomycetes with antifungal toxins activities isolated fro msouth Atlantic deep-sea sediments using fungal antagonism assay. Then, among175strains with high antiaflatxin activities are achieved by morphological identificationand16S rDNA sequences analysis. At last, diversity, genetic and antibacterial drugsuppression function of strains analysis is needed for all the identified strains ofactinomycetes and bacteria combining the results of previous laboratory.The study obtained288strains which included bacteria and actinomycetes. Theresults of fungal antagonism assay showed that45.9%stains which could inhibit themycelial growth and the aflatoxin production of Aspergillus parasiticus, In thesestrains, there were13strains could inhibit the growth of mycelial (the inhibitionrate was above40%) and the maxmum inhibition rate was61.9%; there were117strains could inhibit the production of Aspergillus parasiticus (the inhibition ratewas above25%) and the maxmum inhibition rate was50%. For Fusariumgraminearum, there were28strains could inhibit its mycelial growth, and thehighest inhibition rate reached96.3%; To the two kind of fungal, there were5strains could inhibit their mycelial growth, and the5strains were ZL3, ZM4, ME37,13-1T and MHE12; There were6strains could inhibit Aspergillus parasiticus’smycelial while inhibiting its production, and the6strains were ZM7, ZL3, ZE4,ZA8,01-9T and8-1E4.The classification of175strains with high fungal activities was achieved bymorphological identification and16S rDNA sequences analysis. The results showedthat7strains were Gram-positive bacilli,28strain were Gram-negative bacilli, andGram-negative cocci. According to the phylogenetic analysis,175strains wereseparated into3phyla, including proteobacteria, firmicutes and actinobacteria; Inproteobacteria has alphaproteobacteria and gammaproteobacteria. There were17genera in which Halomonas genus and Bacillus genus had the highest proportion of29%and27%. This study also obtained3strain which pairwise similarity were lowthan97%, thereso they were maybe the unidentification of novol species.To study the diversity of the culturable actinomycetes in deep sediment, and theresults showed that in actinobacteria there were30strains included6genera, and thedominant genera and species were Dietzia genus and Dietzia mari; and inproteobacteria and firmicutes, there were410strains included23genera, and the dominant genera was Halomonas. In genetic diversity analysis, the differencebetween the same samples of the same strains and different kinds of samples of thesame strains has different result need to be analied according to the sample,separation conditions et al. There was a good effection to inhibit the production ofAspergillus parasiticus in Microbacterium genus of actinobacteria. In firmicutes,bacillus was in the dominant position to inhibit the fungal toxins, and inproteobacteria, the Salinicola salarius and Halomonas alkaliantarctica were thedominant species to inhibit the production of Aspergillus parasiticus.