Absence of cell wall chitin in Saccharomyces cerevisiae leads to resistance to Kluyveromyces lactis killer toxin

Kluyveromyces lactis killer toxin causes sensitive strains of a variety of yeasts to arrest at the G1 stage of the cell cycle, and to lose viability. We describe here the isolation and characterization of a class of recessive mutations in Saccharomyces cerevisiae that leads to toxin resistance and a temperature-sensitive phenotype. These mutant cells arrest growth at 37°C with a characteristic phenotype of elongated buds. Cloning of the gene complementing these defects revealed it to be CAL1, coding for chitin synthase 3 activity. Calcofluor staining of the mutant cells indicated that chitin is absent both at 23°C and 37°C. Given that the CAL1 activity is responsible for the synthesis of most of chitin in yeast cells, and that in its absence the cells are viable but resistant to the killer toxin, our results strongly suggest that chitin might represent the receptor for this killer toxin.     

Identification of the antibiotic phomalactone from the entomopathogenic fungusHirsutella thompsonii var.synnematosa

Dichloromethane extracts of culture broth from three strains of the entomopathogenic fungusHirsutella thompsonii var.synnematosa were toxic to two species of tephritid fruit fly and inhibited conidial germination in vitro in several other entomopathogenic fungi includingBeauveria bassiana, Tolypocladium spp., andMetarhizium anisopliae. A major metabolite, toxic to apple maggot,Rhagoletis pomonella, and inhibitory to conidial germination inB. bassiana, was isolated and identified as the antibiotic (+)-phomalactone, 6-(1-propenyl)-5,-6-dihydro-5-hydroxypyran-2-one. This is the first biologically active compound of low molecular weight isolated from the genusHirsutella.Mention of a commercial or proprietary product does not constitute an endorsement by the USDA.     

贵州茯茶散茶发花条件优化及微生物多样性分析

贵州是我国茶树品种资源最丰富的省份之一,茶园面积大,但经济产值低,夏秋茶浪费严重,品种结构单一。该研究以贵州省安顺市黑毛茶为供试原材料,人工接种茯砖茶“金花”发酵剂,优化散茯茶发花工艺条件,并开展了理化指标变化及真菌多样性研究。通过单因素试验及正交优化试验分析不同因素对黑毛茶散茶发花的影响。结果表明,其最佳发花条件为：含水量30%、温度24 ℃、发酵时间9 d及接种量1:100（m/m）。在此发花条件下,成品散茯茶冠突曲霉孢子数为3×108 CFU/mL,水分、总灰分、茶多酚、游离氨基酸、水浸出物含量分别为3.0%、6.8%、12.0%、2.4%、42.6%。经过上述优化后,茶汤色明亮,金花茂盛,香气纯正,滋味醇和。通过高通量测序技术分析不同发酵时间下散茯茶的真菌多样性。结果表明,发酵3 d后,曲霉属（Aspergillus）相对丰度达到98.8%。该研究优化了贵州散茶发花的工艺条件,对提高茯砖茶品质具有重要意义,为其他茶叶散茶发花工艺提供参考。     

蛋白质定量质谱技术及其在食品加工用酵母中的应用

蛋白质是所有生命体生命活动的重要参与者,对蛋白质的精确定性定量研究有助于加深对生命规律的认识。食品加工用酵母作为一类在基础研究、食品酿造和工业发酵等领域广泛应用的真核微生物,其蛋白质组的研究持续引起了许多科研工作者的兴趣,其研究结果可促使其在食品加工中得到更加广泛的应用。基于酵母中不同蛋白质之间存在理化性质各异、浓度差异悬殊等特点,质谱法已发展成为目前最有效的酵母蛋白质组鉴定技术手段之一。本文总结了近5年来液相色谱-质谱联用技术在酵母蛋白质组学研究中的进展,探讨了“自下而上”法酵母蛋白质定量技术,重点分析了酵母蛋白质组提取、鉴定及分析技术方面的最新成果,总结了酵母蛋白质组定量技术在食品加工用酵母研究中的应用前景。     

酱香型白酒第四轮次酒酿造过程中真菌多样性分析

该研究应用Illumina MiSeq高通量测序技术解析酱香型白酒第四轮次酒酿造过程中真菌多样性,并阐明其优势真菌群落结构及其随酿造工艺动态变化。结果表明,在酒曲中主要优势菌有曲霉属（Aspergillus）、嗜热子囊菌属（Thermoascus）;堆积发酵酒醅中主要优势菌有拟青霉属（Paecilomyces）、念珠菌属（Candida）;窖内发酵酒醅中主要优势菌有嗜热子囊菌属（Thermoascus）、嗜热真菌属（Thermomyces）;窖泥中主要优势菌有假霉样真菌属（Pseudallescheria）、镰刀菌属（Fusarium）。同一酒厂和不同酒厂新老车间酒曲、堆积发酵、窖内发酵、窖泥之间真菌组成相似度较高,但其优势菌群丰度差异显著。发酵车间使用年限及窖龄影响着酿酒微生物多样性;使用时间长的车间和窖池其环境微生物种群结构更稳定,优势菌群更突出。     

光敏化作用对曲霉孢子失活的影响

通过曲霉孢子与光敏剂的孵育、光照、平板菌落计数、计算孢子失活率实验,结合荧光显微镜观察孢子产生的荧光,探讨光敏化作用对曲霉孢子的影响。结果表明,孵育时间对孢子失活率影响不大,光敏剂浓度>100μg/mL且光照时间为60min时孢子失活率能达到80%以上,并且黑曲霉孢子对光敏化作用比黄曲霉孢子更敏感,无光照时2种曲霉孢子对此方法都不敏感。因此,光敏化作用对2种曲霉孢子有明显的抑制作用。     

烤烟有益真菌菌株的筛选与鉴定

为比较不同真菌对烟叶品质的影响,用分离到的27株真菌菌株处理烟叶,通过烟叶化学成分和评吸结果的比较得出:SZ14和YZ2 2个菌株处理烟叶后,烟叶化学成分较协调,烟叶评吸得分明显高于对照;CZ3、CZ12、CZ19、CZ22、CZ61、CZ62和SZ5 7个菌株处理烟叶后,烟叶化学成分较协调,评吸得分高于对照;其它18个菌株对烟叶品质影响不明显。对得分较高的2个菌株进行分子鉴定表明,YZ2为木霉属长梗木霉(Trichoderma longibrachiatum),SZ14为曲霉属(Aspergillussp)。