Study On Marine Halophilic And Halotolerant Fungi And Their Secondary Metabolites

Halophilic microorganism is a kind of extremophiles which exists on the hypersaline habitats. For the environment with a high salt concentration, the halophilic and halotolerant microorganism have evolved unique metabolic mechanisms that are responsive to salt concentration, and may produce novel metabolites which posses various bioactivity.In this study, the halophilic and halotolerant fungi were isolated from samples which were collected from the intertidal zone and inshore area around south of Fujian. The salt tolerance and the antimicrobial activity of those fungi were investigated, and then the effect of salt concentration in a culture medium on fungal growth and the production of antimicrobial metabolites were studied, and also two strains which were isolated from mangroves were selected to study their secondary metabolites.390 strains of halophilic and halotolerant fungi were isolated from 29 samples. In the investigation of the salt tolerance and the antimicrobial activity, more than 85% of strains could grow in PDA with 15% NaCl, also we found that 63.3% of strains have antagonism against one of more indicators, such as Escherichia coli, Bacillus subtilis, Staphlococcus aureus, Candida albicans, Aspergillus niger. The active halophilic and halotolerant fungi were identified as 9 genera, most of which belong to Penicillium sp. and Aspergillus sp. .The result also showed that the growth and antimicrobial activity of halophilic and halotolerant fungi could be affected by the salinity in a culture medium. Most of the isolated grown more abundantly and the production of antimicrobial materials reduced as the salt concentration increased, however the antimicrobial activity of some strains was improved as the salt concentration increased. Detection of the affected metabolites in different salinity in a culture medium by HPLC, compound H1 produced by strain Ty01b-8 had come to attention, for the compound H1 could be evident improved as the salt concentration increased. After isolation and purification, compound H1 was identified as chrysogine. It was the first report that the secondary metabolite which was improved as the salt concentration increased had been isolated and identified.In the study of the secondary metabolites of strain hy02a-3 and strain HSGb-14f which were isolated from mangroves, 7 compounds (B1, B5, K1, K2, K3, K6 and k7) were isolated. 6 of them except B1 were identified, and B5 was identified as 4-(2-benzyl-2,3-dihydroxy-3-methylbutoxy)-2,3-dihydroxy-2,3-dimethl-4-oxobutanoic acid, a new compound which had not been reported. In the latter investigation of antimicrobial and antitumor activities, compound K3 showed antifungal activity against Candida albicans with MIC of 50μg/mL.Our study indicated that halophilic and halotolerant fungi included numbers of potent fungi with antimicrobial activity, and they might become reliable resources for novel metabolites with bioactivity.