乳酸菌与酵母菌共生机理的研究进展

早期研究者从营养角度分析乳酸菌与酵母菌的共生机制,发现混合培养过程中乳酸菌与酵母菌不仅存在互补机制,代谢产物相互之间能够产生促进或抑制作用。随着Lux S/AI-2介导的群体感应现象(QS)的发现与发展,目前研究者多从群体感应角度来探讨乳酸菌与酵母菌种间的信息交流模式。本文着重从营养及信号分子这两个角度阐述目前乳酸菌与酵母菌共生机理的研究进展。     

Endofungal bacterium controls its host by an hrp type III secretion system

Burkholderia rhizoxinica and Rhizopus microsporus form a unique symbiosis in which intracellular bacteria produce the virulence factor of the phytopathogenic fungus. Notably, the host strictly requires endobacteria to sporulate. In this study, we show that the endofungal bacteria possess a type III secretion system (T3SS), which has a crucial role in the maintenance of the alliance. Mutants defective in type III secretion show reduced intracellular survival and fail to elicit sporulation of the host. Furthermore, genes coding for T3SS components are upregulated during cocultivation of the bacterial symbiont with their host. This is the first report on a T3SS involved in bacterial–fungal symbiosis. Phylogenetic analysis revealed that the T3SS represents a prototype of a clade of yet uncharacterized T3SSs within the hrp superfamily of T3SSs from plant pathogenic microorganisms. In a control experiment, we demonstrate that under laboratory conditions, rhizoxin production was not required for establishment of the symbiotic interaction.     

Digestive capacities of leaf-cutting ants and the contribution of their fungal cultivar to the degradation of plant material

Leaf-cutting ants (tribe Attini) are a unique group of ants that cultivate a fungus that serves as a main source of their food. The fungus is grown on fresh leaves that are harvested by workers. We examine the respective contribution of ants and their symbiotic fungus in the degradation of plant material by examining the digestive capacities of seven Attini species in the genera Atta and Acromyrmex. The results show that both, the ants and their mutualistic fungi, have complementary enzymatic activities. Ants are specialized in the degradation of low molecular weight substrates (oligosaccharides and heterosides) whereas the fungus displays high polysaccharidase activity. The two genera Atta and Acromyrmex are not distinguished by a specific enzymatic activity. The seven different mutualistic associations examined display a similar enzymatic profile but have quantitative differences in substrate degradation activities. The respective contribution of ants and the fungus garden in plant degradation are discussed.     

Microbial characterization during composting of municipal solid waste

This study investigates the prevailing physico-chemical conditions and microbial community; mesophilic bacteria, yeasts and filamentous fungi, bacterial spores, Salmonella and Shigella as well as faecal indicator bacteria: total coliforms, faecal coliforms and faecal Streptococci, present in a compost of municipal solid waste. Investigations were conducted in a semi-industrial pilot plant using a moderate aeration during the composting process. Our results showed that: (i) auto-sterilization induced by relatively high temperatures (60–55°C) caused a significant change in bacterial communities. For instance, Escherichia coli and faecal Streptococci populations decreased, respectively, from 2×10⁷ to 3.1×10³ and 10⁷ to 1.5×10³ cells/g waste dry weight (WDW); yeasts and filamentous fungi decreased from 4.5×10⁶ to 2.6×10³ cells/g WDW and mesophilic bacteria were reduced from 5.8×10⁹ to 1.8×10⁷ bacteria/g WDW. On the other hand, the number of bacterial spores increased at the beginning of the composting process, but after the third week their number decreased notably; (ii) Salmonella disappeared completely from compost by the 25th day as soon as the temperature reached 60°C; and (iii) the bacterial population increased gradually during the cooling phase. While Staphylococci seemed to be the dominant bacteria during the mesophilic phase and at the beginning of the thermophilic phase, bacilli predominated during the remainder of the composting cycle. The appearance of gram-negative rods (opportunistic pathogens) during the cooling phase may represent a serious risk for the sanitary quality of the finished product intended for agronomic reuse. Compost sonication for about 3 min induced the inactivation of delicate bacteria, in particular gram-negatives. By contrast, gram-positive bacteria, especially micrococcus, spores of bacilli, and fungal propagules survived, and reached high concentrations in the compost.     

中国毁丝霉属两个新记录种

【目的】对我国西部地区土壤中嗜热毁丝霉属真菌资源进行调查。【方法】采集西部地区各省市不同环境的土壤样品,采用富集培养法,从土样中分离毁丝霉属菌株;再采用经典形态学及分子系统学方法相结合对获得的菌株进行鉴定。【结果】共从采集的样品中分离获得12株毁丝霉属菌株,其中G10菌株为异宗毁丝霉Myceliophthora heterothallica,EB6301M菌株为棉毛毁丝霉Myceliophthora vellerea,其余10株菌为嗜热毁丝霉Myceliophthora thermophila。【结论】棉毛毁丝霉和异宗毁丝霉均为我国新记录种。     

Response ofCitrus aurantium toGlomus etunicatus andG. Mosseae after soil treatment with selected fumigants

Summary In the test withGlomus mosseae and four fumigants, plant height in the SMD, NaN₃, and two highest rates of EDB was significantly less than height in the inoculated control. Vesicle formation was low but chlamydospore production suggested thatG. mosseae was least affected by EDB and DBCP. In the test withG. etunicatus and these fumigants, plant height was significantly less in the SMD treatments than in the inoculated check. Sporulation occured in all treatments; highestG. etunicatus chlamydospore numbers were in all EDB rates and the low rate of NaN₃. Significantly more vesicles formed in roots at the high DBCP rate, and significantly fewer formed in the SMD treatments and at the high rate of NaN₃ than the inoculated control. When DBCP and EDB-VAM tests were reexamined, neither EDB nor DBCP caused enhanced growth.This paper reports the results of research only. Mention of a pesticide, trade mark, proprietary product or vendor in this paper does not constitute a recommendation for use by the U.S. Department of Agriculture nor does it imply registration under FIFRA.     

The study of fungi in drinking water

The occurrence of fungi in drinking water has received increased attention in the last decades, and fungi are now generally accepted as drinking water contaminants. The knowledge about the occurrence and diversity of fungi in water has increased considerably from a low knowledge base. However, the relevance of waterborne fungi for water quality and human health is poorly understood and still conflicting. Scientific reports on effective treatment against fungi in water are also few. This article presents a review of the literature on fungal water studies, including some general results, and considerations of significance, limits, contradictions, precautions, and practical consequences.     

丝状真菌蛋白质组学研究进展

丝状真菌不仅是致病菌,而且在异源表达工业酶、化学制品以及药物活性物质中发挥着越来越重要的作用。随着人类基因组计划的实施和推进,生命科学研究已进入了功能基因组时代,特别是蛋白质组学,在蛋白质水平对丝状真菌细胞生命过程中蛋白质功能和蛋白质之间的相互作用以及特殊条件下的变化机制进行研究,对生命的复杂活动进行深入而又全面的认识也为丝状真菌工业酶制剂和重组药物的开发提供广阔的创新空间。本文综述了蛋白质组学的研究内容和方法,总结了其在丝状真菌致病菌、抗生素产生菌和纤维素酶产生菌中的应用现状。不同层次的功能基因组学分析可以从各个角度掌握生物体的代谢网络和调控机制,本文还对蛋白质组学以及功能基因组学各部分内容的整合运用进行了展望。     

Synthesis of 3β-hydroxy-androsta-5,7-dien-17-one from 3β-hydroxyandrost-5-en-17-one via microbial 7α-hydroxylation

The synthesis of 3β-hydroxy-androsta-5,7-dien-17-one from 3β-hydroxy-androst-5-en-17-one (dehydroepiandrosterone, DHEA) via microbial 7α-hydroxylation has been accomplished. At the first stage, 3β,7α-dihydroxy-androst-5-en-17-one was obtained in high yield (71.2%) using a strain of Gibberella zeae VKM F-2600, which was first applied for DHEA conversion. The further route included the substitution of 7α-hydroxyl group with chlorine followed by a dehydrochlorination stage, and required minimal purifications of the intermediate products. The steroids obtained at every step were characterized by TLC_,¹H NMR, MS, UV- and IR-spectrometry.The combination of microbial and chemical steps ensured 54.6% yield of the target 3β-hydroxy-androsta-5,7-dien-17-one from DHEA and can be applied for obtaining novel vitamin D derivatives.     

真菌通用引物Its1和Its4在丝状真菌鉴定中的价值评价

目的 对真菌通用引物Its1和Its4在丝状真菌鉴定中的价值进行评价.方法 收集中山大学附属第一医院2012年1月至2012年8月间分离的丝状真菌11株,使用真菌通用引物Its1和Its4采用PCR法扩增核糖体基因,对PCR产物进行序列测定,将测序结果与GenBank中已知标准或临床菌株DNA序列比对,确定丝状真菌的菌种;同时与传统形态学鉴定方法进行比较,从而对真菌通用引物Its1和Its4在丝状真菌鉴定中的价值进行评价.结果 从DNA提取到序列测定结束,在2个工作日内即可完成.所有菌株均测序成功,测序结果与GenBank中的序列比对,烟曲霉、杂色曲霉、橘青霉、溜曲霉可以鉴定到种;黄曲霉和米曲霉、阿姆斯特丹散囊菌和冠突散囊菌由于高度同源性无法区分鉴定到种.结论 利用真菌通用引物Its1和Its4结合PCR技术和测序技术,可快速、准确将大部分丝状真菌鉴定到种.     

新疆棉花枯萎病菌异核体及其不同表型分离子核DNA的差异

为探索丝状真菌异核体的产生机制,从新疆地区患枯萎病的棉杆中分离出棉花枯萎病菌Fusariumoxysporumf.sp.vasinfectum异核体菌株X515,并自其菌落出现的不同角变处分离出三个不同表型的分离子,X515-Ⅰ、X515-Ⅱ和X515-Ⅲ。选用200种随机引物对它们进行核DNA的RAPD分析,只在OPB-16引物对致病力强的分离子X515-Ⅰ核DNA的PCR扩增产物中出现了一条354bp的差异片段,其部分碱基序列与Fusariumoxysporumf.sp.lycopersici的短散布序列(Foxy)末端序列的相似性达88%。本研究结果提示,随着所采用引物数量的增加,可有望找出异核体及其不同分离子之间核DNA的差异,为最终阐明异核体形成的机制提供线索。     

南极乔治王岛的丝状真菌

本文报道从南极乔治王岛26个样品中分离到60株丝状真菌,其中6个样品未分离到任何真菌,经初步鉴定有8属10个种。根据本次温度实验和该地寒冷的气候,只有桔灰青霉(Penicillium aurantiogriseum Dierckx),大毛霉Mucor mucedo(L.)Fres.)和毡状金孢霉(chrysosporium pannorum(Link)Hughes)在本地能生长繁殖。其中毡状金孢霉占明显优势。     

丝状真菌基因工程研究进展

本文评述了丝状真菌基因工程的研究进展,内容涉及已被转化成功的９０余种丝状真菌种类及其所利用的选择标记,比较了几种外源ＤＮＡ进入丝状真菌受体的方法,并较为详细地评述了丝状真菌复制型与整合型转化及其转化子的有性生殖与无性生殖的遗传稳定性,最后,展望了丝状真菌基因工程在农业、工业和医药方面的应用。表明了丝状真菌基因工程具有广阔的应用前景。     

纤维二糖脱氢酶的纤维素降解中的作用研究

裂褶菌纤维二糖脱氢酶（ｃｅｌｌｏｂｉｏｓｅ ｄｅｈｙｄｒｏｇｅｎａｓｅ,ＣＤＨ）可以提高纤维素酶对纤维素的降解。以纤维二糖为电子供体,ＣＤＨ作用于羧甲基纤维可降低其溶液的粘度,作用纤维素ＣＦ１１和磷酸膨胀纤维素,分别使其悬浊液的浊度提高７％和１４．４％。ＣＤＨ与纤维二糖水解酶或切纤维素酶在降解棉花纤维素时没有表现出协同作用。但若棉花事先在纤维二糖存在下用ＣＤＨ预处理,则变得易于被水解。     

源于微生物的海鞘天然产物

海洋动物是具有生物活性海洋天然产物的重要来源。海鞘中含有丰富的微生物类群,如细菌、放线菌、真菌和蓝细菌。越来越多的直接或间接证据表明,一些从海鞘中分离的天然产物并不是海鞘本身产生的,而是由其共生微生物产生的。本文对近些年来的海鞘天然产物的微生物来源的研究方法进行综述,包括可培养细菌的分离、不可培养细菌的粗提物检测、宏基因组学、全基因组测序等直接方法,以及化合物结构比对的间接方法。通过对海鞘-微生物共生体中天然产物生物合成来源的研究,不仅可以从根本上解决动物药源的问题,而且可为研究海鞘与微生物共生关系提供有力证据。     

铅锌尾矿中耐重金属镉的丝状真菌的分离鉴定

【目的】旨在从重金属污染地分离出耐重金属镉真菌, 获得耐受重金属镉污染的高效菌株, 为重金属污染微生物修复提供菌种资源。【方法】利用稀释平板涂布法, 采用4种培养基对粤东北梅州市梅县铅锌尾矿废弃地9个样品进行分离, 并结合形态学和ITS rDNA基因序列分析, 鉴定分离到的耐镉真菌, 最后对分离到的耐镉真菌进行最小抑制浓度 (MIC) 检测。【结果】从粤东北梅州市梅县铅锌尾矿废弃地分离出72株丝状真菌, 经形态学和分子技术鉴定, 它们主要属于曲霉属(Aspergillus)、青霉属(Penicillium)、枝孢属(Cladosporium)、油瓶霉属(Lecythophora)、拟青霉属(Paecilomyces)、镰刀孢属(Fusarium)等。MIC检测发现有4株丝状真菌耐镉浓度较高, Paecilomyces lilacinus (Thom) Samson (6?20 p), Penicillium pinophilum Hedgcock (6?16 p), Penicillium rolfsii Thom (6?16 m) 和Fusarium oxysporum Schlecht. (8?11 p) 分别为200、40、25和15 mmol/L。【结论】从粤东北梅州市梅县铅锌尾矿废弃地分离到的72株丝状真菌, 不同程度耐受重金属镉, 在重金属污染的治理中有可能发挥作用。本研究为镉污染环境的微生物修复提供了重要菌株。