Diversity and Systematics of Yeasts




Дата канвертавання26.04.2016
Памер22.78 Kb.

Diversity and Systematics of Yeasts


Part I. Introduction

Research area: 1) culture collection of yeasts from various sources, focusing on the yeasts with economic and medical importance; 2) diversity and ecology of yeasts, currently focusing on the basidiomycetous yeasts in the phylosphere; and 3) molecular taxonomy and phylogeny of yeasts on the basis of molecular karyotyping and sequence analysis of various genes.

Group leader: Feng-Yan Bai, Research Professor. Ph.D., 1996, Graduate School of Chinese Academy of Sciences; M.Sc., 1987, Graduate School of Chinese Academy of Sciences; B.Sc., 1984, Zhongshan University.

Staff: Qi-Ming Wang, Ph.D., Research Associate; Jian-Hua Jia, Senior Engineer.


Graduate students: Jian-Hua Zhao (M.Sc., 2002), Hui-Zhong Lu (M.Sc., 2004), Qi-Ming Wang (Ph.D., 2004), Zuo-Wei Wu (Ph.D. candidate), Juan Li (Ph.D. candidate), Shi-An Wang (Ph.D. candidate).

Part II. Background and Significance

Yeasts are fungi with vegetative states that predominantly reproduce by budding or fission, resulting in growth that is comprised mainly of single cells. At present, approximately 700 yeast species classified in more that 90 genera are recognized. Relatively few natural habitats have been thoroughly investigated for yeasts, and therefore we can assume that many more species await discovery.

"The importance of yeasts is underscored by our often daily consumption of bread as well as fermented beverages. Recent advances in biotechnology have increased reliance on yeasts for pharmaceuticals and for bulk biochemicals such as citric acid. Furthermore, clinically important yeasts are commonplace, especially with increasing numbers of immune-suppressed patients, and biologists are continuing to discover the importance of yeasts in the ecosystem. All of these areas of science and technology have a common need, the rapid and accurate identification of yeasts." (from The Yeasts, a Taxonomic Study, 4th edn., 1998).

The research group for yeast taxonomy in the Institute of Microbiology, Chinese Academy of Sciences was established in the early 1970s. It is the only one group remained in China that focuses on taxonomic research of yeasts.



Part III. Major Achievements (2001-2005)

1) Culture collection of yeasts.

More than 4,000 yeast strains were isolated from various natural substrata collected form different regions of China. Approximately 140 type or authentic reference yeast strains were obtained from international culture collection authorities including the Centraalbureau voor Schimmelcultures (CBS), The Netherlands, and the Japan Collection of Microorganisms (JCM), The Institute of Physical and Chemical Research, Japan.

2) Species diversity and molecular phylogeny of basidiomycetous yeasts.

From the ballistoconidium-forming and related basidiomycetous yeast strains isolated from plant material collected in representative regions of China, more than 90 species belonging to 14 genera have been identified based on phenotypic and molecular characterization. Approximately one third of them were new to science. The high frequency of new species discovery indicates that species diversity of the basidiomycetous yeasts in nature is very high and that a considerable number of new taxa remain to be found.

The phylogenetic relationships of the new basidiomycetous yeast species from China and the described ones were revealed from 18S rDNA, ITS region and 26S rDNA D1/D2 domain sequence analyses. Several new and distinct clades in different lineages of basidiomycetous yeasts have been recognized by adding new species to the existing phylogenetic trees, which are significant to reclassify the basidiomycetous yeast species into more homogeneous groups.

The intra-specific conservation and inter-specific variation of the ITS and 26S rDNA D1/D2 domain sequences in basidiomycetous yeasts were addressed based on sequencing of a large scale of strains from different sources. The data indicated that the sequences of both ITS and D1/D2 regions of the strains within the same species are quite conservative, with no more than 3 nucleotides divergences in each region. However, the inter-specific variations of them within different lineages are quite different. The strains with the same or similar ITS sequences may have quite different D1/D2 data, or vice versa.



3) rRNA gene sequence comparison of yeasts by SSCP.

Single-Stranded Conformational Polymorphism (SSCP) technique was employed to compare ITS and D1/D2 sequence differences among yeast strains with similar morphological and physiological characters. The SSCP method established in our laboratory could distinguish yeast strains with as less as one base difference in the ITS or D1/D2 region, resulting in the examination of species and genetic diversity among a large number of yeast strains more rapidly and effectively.



4) Intragenomic heterogeneity of rRNA gene sequences in yeasts.

A considerable number of yeast strains with intragenomic rRNA gene sequence heterogeneities have been found in our laboratory; different types of ITS repeats within individual genomes may differ dramatically. Four different ITS types, which differed from each other by 3% nucleotides in ITS 1, were identified in the genome of a strain of Kazachstania solicola (CBS 6904). Four types of ITS sequences were found in the genome of a strain of Pichia membranifaciens (CBS 215), which differed from each other by more than 40 (~ 10%) nucleotides. The sequences of ITS Types I and II of CBS 215 are identical with those of the type strains of P. membranifaciens and P. derossii, respectively. ITS Types III and IV of CBS 215 appeared to be formed by recombination of types I and II.


Part IV. Future Research Plan


1) Diversity and molecular phylogeny of basidiomycetous yeasts.

Previous study indicates that species diversity of the ballistoconidium- forming and related basidiomycetous yeasts is very high in nature and much more new taxa remain to be discovered. The genera of basidiomycetous yeasts are currently defined mainly based on phenotypic criteria. The majority of genera are heterogeneity as demonstrated by rRNA gene sequence analyses. Relationships among lineages and clades of these yeasts should become clearer as novel species are added to the phylogenetic trees, which is certainly helpful to make the demarcation of genera more homogenous and reliable.



2) Species and genetic diversity of human pathogenic yeasts in China.

Many yeasts are highly successful opportunistic pathogens, especially the species in the genus Candida. Candidiasis has become one of the commonest causes of life-threatening systematic infections. The disease is most frequent in immunocompromised hosts. However, invasive candidiasis in critically ill, non- immunocompromised patients is of increasing importance. The list of pathogenic yeast species has been substantially increasing. Studies on species and genetic diversity of pathogenic yeasts are essential for epidemiology of these important pathogens.



3) Intragenomic heterogeneity of rRNA gene sequences in yeasts.

Intragenomic rRNA gene sequence polymorphisms have been reported in bacteria and some eukaryotic organisms including filamentous fungi, but have not been reported in yeasts. We will study the phenomena in yeasts further in the following aspects: the commonness and distribution of yeast strains with intra-genome rRNA gene sequence polymorphisms; the origin and evolutionary significance of the phenomena.



Publications (2001-2005)

International journal papers

  1. Bai F-Y, Takashima M, Hamamoto M & Nakase T. 2001. Sporobolomyces yunnanensis sp. nov., a Q-10(H2)-containing yeast species with a close phylogenetic relationship to Erythrobasidium hasegawianum. Int. J. Syst. Evol. Microbiol. 51: 231-235.

  2. Bai F-Y, Takashima M & Nakase T. 2001. Description of Bullera kunmingensis sp. nov., and clarification of the taxonomic status of Bullera sinensis and its synonyms based on molecular phylogenetic analysis. FEMS Yeast Res. 1: 103-109.

  3. Bai F-Y, Takashima M & Nakase T. 2001. Phylogenetic analysis of strains originally assigned to Bullera variabilis: descriptions of Bullera pseudohuiaensis sp. nov., Bullera komagatae sp. nov. and Bullera pseudoschimicola sp. nov. Int. J. Syst. Evol. Microbiol. 51: 2177-2187.

  4. Bai F-Y, Takashima M, Jia J-H & Nakase T. 2002. Dioszegia zsoltii sp. nov., a new ballistoconidium-forming yeast species with two varieties. J. Gen. Appl. Microbiol. 48: 17-23.

  5. Bai F-Y, Zhao J-H, Takashima M, Jia J-H, Boekhout T & Nakase T. 2002. Reclassification of the Sporobolomyces roseus and Sporidiobolus pararoseus complexes, with the description of Sporobolomyces phaffii sp. nov. Int. J. Syst. Evol. Microbiol. 52: 2309-2314.

  6. Zhao J-H, Bai F-Y, Guo L-D & Jia J-H. 2002. Rhodotorula pinicola sp. nov., a basidiomycetous yeast species isolated from xylem of pine twigs. FEMS Yeast Res. 2: 159-163.

  7. Bai F-Y, Takashima M, Zhao J-H, Jia J-H & Nakase T. 2003. Bullera anomala sp. nov. and Bullera pseudovariabilis sp. nov., two new ballistoconidium-forming yeast species from Yunnan, China. Antonie van Leeuwenhoek 83: 257-263.

  8. Wang Q-M, Bai F-Y, Zhao J-H & Jia J-H. 2003. Bensingtonia changbaiensis sp. nov. and Bensingtonia sorbi sp. nov., novel ballistoconidium-forming yeast species isolated from plant leaves. Int. J. Syst. Evol. Microbiol. 53: 2085-2089.

  9. Wang Q-M, Bai F-Y, Zhao J-H & Jia J-H. 2003. Dioszegia changbaiensis sp. nov., a basidiomycetous yeast species isolated from northeast China. J. Gen. Appl. Microbiol. 49(5): 295-299.

  10. Zhao J-H, Bai F-Y, Wang Q-M & Jia J-H. 2003. Sporobolomyces bannaensis, a new ballistoconidium-forming yeast species in the Sporidiobolus lineage. Int. J. Syst. Evol. Microbiol. 53: 2091-2093.

  11. Fungsin B, Takashima M, Bai F-Y, Artjariyasripong S & Nakase T. 2003. Bullera panici sp. nov. and Bullera siamensis sp. nov., two new yeasts in the Bullera variabilis cluster isolated in Thailand. Mircobiol. Cult. Coll. 19: 23-32.

  12. Wang Q-M & Bai F-Y. 2004. Four new yeast species of the genus Sporobolomyces from plant leaves. FEMS Yeast Res. 4: 579-586.

  13. Lu H-Zh, Jia J-H, Wang Q-M & Bai F-Y. 2004. Candida asparagi sp. nov., Candida diospyri sp. nov. and Candida qinlingensis sp. nov., novel anamorphic ascomycetous yeast species. Int. J. Syst. Evol. Microbiol. 54: 1409-1414.

  14. Wang Q-M, Bai F-Y, Lu H-Zh, Jia J-H & Takashima M. 2004. Bullera cylindrica, Bullera hubeiensis and Bullera nakasei, ballistoconidium-forming yeast species isolated from plant leaves. Int. J. Syst. Evol. Microbiol. 54: 1877-1882.

  15. Lu H-Zh, Cai Y, Wu Z-W, Jia J-H & Bai F-Y. 2004. Kazachstania aerobia sp. nov., an ascomycetous yeast species from aerobically deteriorating corn silage. Int. J. Syst. Evol. Microbiol. 54: 2431-2435.

  16. Bai F-Y, Cai Y, Wang Q-M & Ohkubo H. 2004. Rhodotorula oryzae sp. nov., a novel basidiomycetous yeast species isolated from paddy rice. Antonie van Leeuwenhoek 86: 295-299.

  17. Wu Z-W & Bai F-Y. 2005. Kazachstania aquatica sp. nov. and Kazachstania solicola sp. nov., new ascomycetous yeast species. Int. J. Syst. Evol. Microbiol. 55 (in press).

  18. Wu Z-W & Bai F-Y. 2005. ITS sequence and electrophoretic karyotype comparisons of Candida ethanolica with Pichia deserticola and Candida odintsovae with Pichia rabaulensis. J. Gen. Appl. Microbiol. 51(5) (in press).

  19. Wang Q-M, Jia J-H & Bai F-Y. Pseudozyma hubeiensis sp. nov. and Pseudozyma shanxiensis sp. nov., novel ustilaginomycetous anamorphic yeast species from plant leaves. Int. J. Syst. Evol. Microbiol. (submitted, manuscript ID: IJSEM 63827).

  20. Wu Z-W, Robert V & Bai F-Y. Reclassification of Pichia membranifaciens based on rRNA gene sequencing and electrophoretic karyotyping, with the proposal of Candida californica comb. nov. FEMS Yeast Res. (submitted, manuscript ID: FEMSYR-05-06-0108).

Domestic journal papers

  1. Bai F-Y, Liang H-Y & Jia J-H. 2001. Differentiation between the two phenotypically similar yeast species Candida maltosa and Candida tropicalis by electrophoretic karyotyping. Mycosystema 20: 37-43.

  2. Bai F-Y & Jia J-H. 2001. Comparative molecular karyotype analysis of four Candida species and their teleomorphs. Mycosystema 20: 471-474 (in Chinese with English abstract).

  3. Yang R-Y, Li D-W, Zhao J-H, Ao J-H, Wang W-L & Bai F-Y. 2001. 26S rDNA D1/D2 domain sequence analysis of the pathogenic strain of the first case disseminated trichosporonosis in China. Natl. Med. J. China 81: 472-475 (in Chinese with English abstract).

  4. Bai F-Y, Jia J-H & Liang H-Y. 2002. Molecular taxonomic study on the problematic Candida strains based on 26s rdna d1/d2 domain sequence comparison. Mycosystema 21: 27-32 (in Chinese with English abstract).

  5. Zhao J-H, Jia J-H, & Bai F-Y. 2002. Taxonomic status of three Trichosporon species described in China as revealed by 26s rdna d1/d2 domain sequence comparison. Mycosystema 21: 533-537 (in Chinese with English abstract).

  6. Zhao J-H, Jia J-H & Bai F-Y. 2004. Phylogenetic position of Kluyveromyces hubeiensis as revealed from rDNA sequence analysis. Mycosystema 23: 28-32 .

  7. Lu H-Zh, Wang Q-M, Jia J-H & Bai F-Y. 2004. Species diversity of ascomycetous yeasts in Qinling area of Shaanxi Province. Mycosystema 23: 183-187 (in Chinese with English abstract).

  8. Li X-L, Zhu J-X, Lin Y-Z, Gao S-Q & Bai F-Y, 2004. Kerion caused by Geotrichum: first case report in China. Chin. J. Dermatol. 37: 446-448 (in Chinese with English abstract).

  9. Wu Z-W & Bai F-Y. 2005. ITS sequence and electrophoretic karyotype comparisons of the ascomycetous yeast species with identical or similar LSU rRNA gene D1/D2 domain sequences. Mycosystema 24:193-198.







База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка