Diversity,Antimicrobial And Extracellular Enzyme Activity Of Culturable Freshwater Fungi In Chenghai Lake

Freshwater fungi includes any species which, for the whole or part of their life cycle, rely on freshwater.they are a polyphyletic group of true fungi and are quite diverse.As a virtually untapped natural resource, freshwater fungi has a great potential and has become another important source of bioactive metabolites.The content of the research was to isolate and identify freshwater fungi from Chenghai lake-a plateau freshwater lake in Yunnan province, to test their antimicrobial activity and extracellular enzyme activity,and to carry out Phylogenetic analysis on the effcient antimicrobial activity fungi.the research aims to explore freshwater fungal community composition,diversity and ecological distribution in Chenghai lake,enrich freshwater fungi resource in our country and lay the foundation for speeding up the use of freshwater fungi in Production of new drugs and enzyme concoctions.The results were as follows:Totally,we isolated524freshwater fungi and identified them as3classes,5orders,8families,50genera.The dominant genera were Penicillium(13.93%), Cladosporium (11.83%) and Aspergillus(9.54%).Fungal species and amount in lake water and sediment differed.the sediment had40fungal genera-larger than the number in lake water(34genera).The dominant group in lakewater was different from sediment.The dominant groups in lakewater were Cladosporium and Phoma, While the dominant groups in sediment were Penicillium and Aspergillus.18genera distributed both in the water and sediment and32genera (10genera in lakewater and22genera in sediment) distributed Only in water or sediment.Fungal diversity, evenness and similarity analysis in lakewater and sediment showed:the sediment had higher diversity but lower evenness, Shannon-Wiener index and Simpson index of which was2.9107,0.9185, and2.6429,0.9027respectively;while the Pielou index was0.7692,0.7931.Similarity coefficient revealed that fungal similarity between lakewater and sediment was quite low, the Jaccard index and Sorenson index between them was0.3654,0.5352.With fourteen species of pathogens,We selected473freshwater fungi and conducted the inhibitory activity screening by scrip testing, then identified the active strains. Results showed that290strains, accounting for61.31%of all strains, had inhibitory activity to one indictor or more.they belonged to44genera,and the dominant genera were Penicillium(12.76%), Aspergillus (11.72%) and Cladosporium (11.03%).Among the active strains, most were moderate antimocrobial activity (antibiotic circle diameter10mm<d<15mm) strains(208,71.72%).Freshwater fungi had the largest strains against Trichoderma sp.(200,42.27%),the second largest were the ones against Candida albicans(195,40.95%), The minimum strains were against Phytophthora sp.(73,15.43%).We selected290antimicrobial activity strains to explored amylase, lipase and cellulase activity with transparent circle method. Result displayed that138freshwater fungi produced at least one kind of extracellular enzyme(47.59%). Among the enzyme-production strains, most were moderate activity(transparent circle diameter10mm<d<15mm) strains(90,29.71%). The extracellular enzyme activity strains belonged to33genera,the domitant genera were Cladosporium(21%),Penicillium(11%) and Aspergillus(10%).Among138enzyme-production freshwater fungi, most were the ones that produced cellulase(97,33.45%),the follow were the ones which produced proteinase(82,28.28%);the rest strains were the ones that produced amylase and lipase(55,18.97%and13,4.48%).Secondary screening of290antimicrobial activity fungi showed that41efficient activity strains were obtained.20strains were choosed to carry out the Large fermentation antimicrobial experiment and phylogenetic analysis of rDNA-ITS.Results revealed20strains had stable antimicrobial activity (d≥15mm) and a wide antimicrobial spectrum. by morphological characteristics and phylogenetic analysis, they were classified as2phyla:Ascomycota and Zygomycota.Most strains belonged to Ascomycota and were major groups of effective efficient activity strains (19,95%).16ascomycetes belonged to3genera7species, dominant groups were Penicillium and Alternaria and the rest were of pending status.only1strain belonged to Zygomycete,Mucorales,Mucoraceae,Rhizopus oryzae.