| 146 wild yeast isolates were separated from 45 soil samples(or grape) collected from Dunhuang, Yumen, Jiayuguan, Zhangye, Wuwei, Baiyin, Lanzhou, Dingxi, Gannan, Longnan, Tianshui, Pingliang and Qingyang in Gansu province from July to September in 2005, 2006 (now these strains were conserved in Molecular Biology Lab, College of Food and Biological Engineering, Shangdong Institute of Light Industry). The taxonomic work of wild yeast strains were determined according to the results of morphology, physiology and molecular identification by recent yeast taxonomic system. In order to prove up firstly the diversity of wild yeasts in Gansu province, to analyze the genetic diversity between strains, to evaluate resistance of some wild strains including growth viability under high temperatures, high osmotic pressure, high concentration of glucose and alcohol, so as to use for industry strain improving. There were 4 main results:Firstly, 84 strains were chosen from 146 wild yeast isolates according to colony characters, sequenced for 26S rDNA D1/D2 domain. The rate of homologous similarity in 75 strains sequenced is more than 99% compared with type strain sequence in GenBank nucleic acid sequence data, i.e. base pair discrepancy rate is 1% below, which was the normal range of same species. The analysis of all the aligned sequences, by MegAlign program in DNA Star software, produced a phylogenetic tree according to Clustal W arithmetic. The relative relationship showed the same as BLAST in GenBank.Secondly, part of physiology tests from 29 strains were done, found that a few physiologic characters for some strains are different from the standard description of type species by 26S rDNA D1/D2 domain sequence analysis. ITS domain sequence analysis, including ITS1, 5.8S and ITS2, showed that there are more variations in ITS1 domain, the rate of similarity of most strains sequence tested is below 99%, but it's suitable to compare and analyze the genetic relationship between strains from same species by ITS1, e.g. Galactomyces geotrichum.Thirdly, 84 wild strains were classified as 32 species included in 15 genera, in which10 species are Chinese new records, including Williopsis californica, Cryptococcus aerius, Candida pseudolambic, Candida fermentat, Hanseniaspora occidentalis, Pichia pijperi, Hanseniaspora guilliermondii, Pichia galeiformis, Zygoascus hellenicus var. hellenicus, Trichosporon coremiiforme.In addition, there is one suspected new specie, colony color is dark brown, texture is wet, near with Cryptococcus in relative relationship, more experiments need to determine taxnomic degree in the future.Fourthly, the resistance of 29 wild strains was evaluated. Strain 38A (determined as Candida tropicalis)can grow in media at high osmotic pressure (Glucose 60%, NaCl 14%), at high temperature(45℃), in high alcohol(14%). Glucose fermentation experiment indicated that its fermentive period is short in primary, and alcoholicity is 8.5(V/V),with potential application prospect. |
