Phylogenetic Diversity Of Fungi Associated With Sea Anemone Palythoa Haddoni And Secondary Metabolites From A Sea Anemone-derived Fungus Trichoderma Sp.

Because of the particularity, the medicinal values, huge potential developmentand utilization in the development of marine drugs, the related research of marinemicroorganisms has been paid close attention in recent years. Searching the medicinalmicroorganisms is the first step of obtaining the lead compounds of marine drugs.Fungus, as an important composition of marine microorganisms, has become avaluable resource for drug discovery. Sea anemones, marine invertebrates, had beenreported that many compounds were dicovered from them with huge medicinal value.Investigation on diversity of culturable fungi mainly focused on sponges and corals oncoral reef systems, and a large number of active secondary metabolites have beenidentified, yet little attention had been paid to the fungal communities associated withsea anemones.In this study, we study phylogenetic diversity of the fungi which were isolatedfrom the sea anemone Palythoa haddoni collected from the South China Sea.Fourty-nine independent isolates had been identified using internal transcribed spacer(ITS) sequence analyses, as well as morphological traits. According the analysis offungal ITS-rDNA,34strains were selected for phylogenetic analysis. The resultsindicated that at least18genera (Alternaria, Cladosporium, Cochliobolus,Coprinellus, Exserohilum, Fusarium, Leptosphaerulina, Massarina,Microsphaeropsis, Myrothecium, Nigrospora, Penicillium, Pestalotiopsis, Phomopsis,Stachybotrys, Stagonospora, Teratosphaeria and Trichoderma) within8taxonomicorders (Agaricales，Capnodiales, Diaporthales, Eurotiales, Hypocreales, Pleosporales,Trichosphaeriales and Xylariales) of2phyla (7orders of the phylum Ascomycota and1order of the phylum Basidiomycota) were achieved from the sea anemone Palythoahaddoni. Particularly,15genera were isolated from sea anemone for the first time. This is the first report of4genera of Coprinellus, Leptosphaerulina, Stagonosporaand Teratosphaeria discovered from marine environment, and no secondarymetabolites has been reported about these four genera. Twenty nine strains (59.2%) ofthe identified fungi displayed different levels of antibacterial activity against testpathogenic bacteria with their fermentation broth and/or mycelia. Fungi whichshowed antibacterial activity could be classified within Capnodiales and Pleosporales.Five fungal isolates, Cladosporium (TA26-2and TA26-6), Nigrospora (TA26-9andTA26-58), and Fusarium (TA26-56) displayed strong (+++) antibacterial activitytoward all the test bacteria. It seemed that all the identified fungi belonging to thegenus of Alternaria, Cochliobolus, and Exserohilum, have no activities for S. albus. Incontract, all the identified fungi in genera of Nigrospora have special inhibitiontowards S. albus.In this study, one strain Trichoderma sp.(TA26-28) isolated from sea anemonePalythoa haddoni was select for fermentation. Seventeen compounds were isolatedfrom the EtOAc extract of the fungal fermentation broth. The structures of secondarymetabolites were respectively determined as lactone (1), anthraquinones (2-4),xanthone (5), indole alkaloids (6), cerebrosides C (7-9), steroidal saponins (10),steroids (11-17). Among them, compounds5and9were reported frommarine-derived fungus for the first time. It was noteworthy that5showed pronouncedantibacterial activity against all the tested bacteria with the MIC values of rangingfrom0.78to6.25μM, which were nearly equivalent with the positive controlciprofloxacin. In addition, cerebrosides7and8showed selective antibacterial activityagainst Gram-negative bacteria, while9displayed no activity. The results suggestedthat the C18-sphingosine with9-methyl gro up may play an important role inantibacterial activity. Among them,2and5exhibited strong lethality to brine shrimpArtemia salina with the LC50values of14.26and8.69μg/mL, respectively.This is the first report of phylogenetic diversity of sea anemone-associated fungi,building the phylogenetic trees. Under the guidance of the antibacetrial activity model,the activited strains were obtained from the sea anemone Palythoa haddoni. It notonly contributes to expand the pool of drug source strains, but also play a guidingsignificance for finding the lead compounds of marine drugs from the marine-derived fungi and marine antibiotic medicinal research from the marine environment.