Thermotolerant Fungi Diversity And Molecular Phylogeny

Thermotolerant fungi are those that have a maximum growth temperature of near50℃(usually40℃and above) and a minimum growth temperature under20℃, showing the strong ability for adaptation and subsistence in high temperature. Thermotolerant fungi may perform bioconversion processes and produce industrially important metabolites. With more studies on the high temperature organisms, thermotolerant fungi have become a hot area for international research. A total of89strictly thermotolerant fungi are so far documented, while only23were recorded previously in China. Due to a variety of climatic conditions and habitat conditions, thermotolerant fungi diversity should be rich in China. Studies on thermotolerant fungi species and distribution in different climatic zones and habitats lay a foundation for the theory development and applied research of thermotolerant fungi.More than800samples were collected from Shandong,Shanxi, Hebei,Shanxi, Henan, Yunnan, Jiangxi, Hainan, Xinjiang, Neimenggu, Gansu5Guangdong, Jilin, Hunan Etc. including forest, grassland, farmland, desert, alpine meadow, wetland, wasteland from2009to2011. From these samples, based on morphological characteristics combined with rDNA-ITS sequence analysis,51species in25genera were identified. Among them,2are new species,11species are new records to China, other15first reported as thermotolerant fungi. All genera and species are fully described and illustrated morphologically. Distribution sites and habitat are also cited. Dried and living cultures of all the fungi studied have been deposited in the Herbarium of Shandong Agricultural University:Plant Pathology (HSAUP).1.Species diversity of thermotolerant fungiNew species:Taeniolella jinggangensis Y.Zhang&D.C.Li, Scutellinia subthermophila Y.Zhang&D.C.Li; New records to China:Chaetomium strumarium, Thielavia subthermophila, Hamigera avellanea, Hypoxylon fragiforme, Neosartorya fennelliae, Trichoderma ghanense, Chaetomium jodhpurense, Chaetomium luteum, Trichoderma saturnisporum, Thielavia arenaria, Chaetomium atrobrunnneum; The other38species have been known to China, include15first reported as thermotolerant fungi:Cunninghamella echinulata, Gongronella butleri, Mucor circinelloides, Chaetomium aureum, Emericella quadrilineata, Eupenicillium javanicum, Sordaria fimicola, Aspergillus ustus, Curvularia lunata, Exserohilum rostratum, Humicola fuscoatra,Scedosporium apiospermum, Penicillium funiculosum, Penicillium verruculosum, Coprinopsis cinerea. This study was aimed at investigating the species diversity and distribution of thermotolerant fungi in China to enrich the biological diversity of China and lay a useful foundation for the theory development and applied research of thermotolerant fungi.2Taxonomic criteria at species levelMorphological features are still the main basis for classification of thermotolerant fungi. Aiming to reducing the influence of environment, all species in one genus should be cultured at the same or being close to the same conditions. heat-resistant (maximum temperature, the optimum temperature, minimum temperature) is an important basis for identification of heat-resistant species and common species. Testing temperature range is5℃interval.For anamorphic thermotolerant fungi, the morphological characters of conidia, especially the shape, size, color, septum and ornamentation etc. are important characters in identification species. The characters of conidiophores and sporulation are also very useful in identification species in some genera. For the zygomycetes and ascomycetes:the morphological characteristics of the sexual state (teleomorph) should be used as the basis for species identification, such as ascocarp size, shape, color, appendages, ascus size, shape, ascospore size, shape, color, with or without germ pore and the number of germ pores. When ascomycetous taxa produce the anamorph regularly and the teleomorph only under specific cultural conditions, the name of the anamorph could be preferentially selected to introduce uniformity and correctness in name citations of thermotolerant fungi. Cultural characteristics (colony characteristics, color and growth characteristics) and sporulation phenotype can be used.as.the.necessary.and.useful.reference.3Molecular phylogeny of thermotolerant fungiBased on the morphological taxonomy, Sequencing and molecular systematics were performed on the5.8S rDNA-ITS and Mn-SOD intermediate fragment of thermotolerant fungi. The measured sequence data have been submitted to GenBank (NCBI), obtained GenBank accession numbers.5.8S rDNA-ITS sequences can be used to differentiate the thermotolerant fungi belonging to various genera and species effectively. The sequences of5.8S rDNA-ITS are more similar among different species in the same genus than among different genera. Phylogenetic tree based on5.8S rDNA-ITS sequences from the molecular level links asexual state and the sexual state, and can help determine the thermotolerant fungi problematic genera or species. Phylogenetic tree can be used to reveal the phylogenetic relationships of thermotolerant fungi and support the viewpoint of the morphology. ITS genes can make a better resolution to the differentiation between the species and even within species, suitable for thermotolerant fungus phylogenetic studies. The results of molecular systematics supported the result of morphological classification in great extent, but the different phenotypic characteristics were not recognized equally by molecular analysis. Mn-SOD amino acid sequence is highly conserved. Conserved sequences include:NHHQTYV, GGGH, QGSGW and WEHAY. The phylogenetic tree constructed on the Mn-SOD intermediate fragment can reflect the phylogenetic relationship corresponded to morphology to the most thermotolerant fungi, but to some types the phylogeny was inconsistent with morphology. Further study should be performed since it is the initial step that using the amino acid sequence of Mn-SOD for phylogenetic analysis. It may be due to the horizontal gene transfer that the distantly related strains show high homology.Studies have shown that morphological classification is still the most important to thermotolerant fungi. Molecular data are the complement of the morphological classification. In most cases, the two classification methods can achieve a unified. On the basis of morphology, combined with the molecular methods would be more scientific and more reasonable on the thermotolerant fungi classification.