海洋共附生微生物天然产物生物合成基因研究进展

对海洋无脊椎动物天然产物的研究表明,很多种活性物质的真正生产者是与其共生或附生的未培养微生物.克隆这些未培养微生物中特定活性物质的生物合成基因,不仅为活性物质的来源提供遗传学证据,也使通过异源表达相关生物合成基因来大量获取目标化合物成为可能.本文综述了来源于海绵、海鞘、苔藓虫、深海管状蠕虫和深海沉积物中共附生微生物天然产物生物合成基因簇的研究进展.     

凝结芽胞杆菌TBC 169株对肠道致病菌的抑菌作用

目的 研究凝结芽胞杆菌TBC 169株对大肠埃希菌、痢疾志贺菌、伤寒沙门菌、普通变形杆菌、铜绿假单胞菌和金黄色葡萄球菌的抑制作用。方法 先将大肠埃希菌、痢疾杆菌等6种菌分别进行单独培养,测定不同培养时间内的pH和活菌数,然后将凝结芽胞杆菌TBC 169株分别和致病菌进行混合培养,再测pH和活菌数,并与单独培养时的测定情况进行比较。结果 凝结芽胞杆菌TBC 169株对大肠埃希菌、痢疾志贺菌、伤寒沙门菌等6种菌均有明显的抑制作用,尤其是对伤寒沙门菌和铜绿假单胞菌的抑制作用更强。结论 凝结芽胞杆菌TBC 169株对肠道致病菌有显著的抑制作用。     

分子生态学技术及其在环境微生物研究中的应用

分子生态学作为一门新兴的学科已经成为国内外科学家关注和研究的热点。目前的分子生态学技术主要有核酸杂交分析技术、特异性PCR扩增技术、DNA序列分析、基因芯片技术等。这些技术在环境微生物研究中的应用主要包括对微生物多样性的研究、种群结构和动力学的研究、代谢活性的研究以及在全球气候变化中对微生物影响的研究。最后,对环境微生物的分子生态学研究进行了展望。     

金龟子绿僵菌中性海藻糖酶基因的克隆及其表达特性分析

根据中性海藻糖酶NTL基因的同源序列设计引物,PCR扩增出杀蝗专一菌株———金龟子绿僵菌CQMa102NTL基因片段,利用5′_RACE和3′_RACE扩增出NTLcDNA的5′和3′端序列,经拼接得到CQMa102NTL基因cDNA全长。根据其全长cDNA序列,设计引物PCR扩增出CQMa102NTL的完整基因。为了解该基因的上游调控信息,采用PanhandlePolymeraseChainReactionAmplification方法扩增其上游序列。序列分析表明,CQMa102NTL全长DNA3484bp,cDNA全长2385bp,编码737个氨基酸的蛋白,推测蛋白分子量为83.1kD;含有3个内含子,包含一个依赖于cAMP的磷酸化作用位点(RRGS)和一个钙附着位点(DTDGNMQITIED);上游序列含有一个压力反应元件(CCCCT);与金龟子绿僵菌广谱性菌株ME1NTL的核苷酸序列和氨基酸序列分别具有93%和99%同源性,由此确定该序列为金龟子绿僵菌中性海藻糖酶基因序列。Southern杂交表明,NTL基因在CQMa102基因组中为单拷贝。Northern杂交表明,NTL基因转录出约2.5kb的mRNA单带,在液体培养条件下,对数生长前期表达水平最高,对数生长后期降到最低,进入稳定生长期后表达水平又有所提高。金龟子绿僵菌CQMa102中性海藻糖酶基因DNA全长和cDNA全长登录GenBank,登录号分别为:AY557613,AY557612。     

Phytohormones and Antibiotics Produced by Bacillus subtilis and their Effects on Seed Pathogenic Fungi and on Soybean Root Development

Summary Bacteria belonging to the genus Bacillus were isolated from soil samples of Paraná State, Brazil, with the aim of evaluating their potential biological control of soybean seed pathogens. Strain PRBS-1 was selected, showing similar effectiveness to that of the strain AP-3, used as a reference due to its known antibiotic potential. The sequencing of the ribosomal 16S rRNA gene confirmed that both strains belong to the species B. subtilis, although showing high genetic diversity in relation to this species. Both strains inhibited five soybean seed pathogenic fungi in vitro, Rhizoctonia solani, Colletotrichum truncatum, Sclerotinia sclerotiorum, Macrophomina phaseolina and Phomopsis sp. Furthermore, the metabolites of AP-3 increased production of root hairs, while the metabolites of PRBS-1 stimulated outgrowth of lateral roots in soybean. The antibiotic effect of both strains seemed to be related to compounds of the iturin group, while the root growth promotion by PRBS-1 was at least partially related to the production of indoleacetic acid. The results have shown the potential of using selected strains of B. subtilis in the biological control of seed pathogens, as well as in promoting soybean growth.     

水杨酸对苦瓜叶片白粉病抗性及抗氧化酶活性的影响

以‘碧绿3号’苦瓜幼苗为材料,采用100、500和1000μmol.L-1的水杨酸(SA)溶液预处理后进行白粉菌的诱导接种,研究了SA处理对苦瓜叶片光合色素含量和4个抗氧化酶活性的影响。结果显示:各浓度SA处理苦瓜植株的病情指数均显著低于对照(蒸馏水处理),并随SA处理浓度增加而逐渐下降;各SA处理苦瓜叶片的光合色素含量均高于其对照,且随SA处理浓度升高而逐渐增加;苦瓜叶片APX、CAT和GR活性随SA处理浓度增加而升高,但GPX活性反而下降,各处理CAT和GR活性增幅均高于病情指数增幅,1000μmol.L-1SA处理的APX活性增幅也高于病情指数增幅。研究发现,SA处理可以提高苦瓜感染白粉病植株叶片的光合色素含量及其抗氧化酶活性,显著降低其病情指数,增强其白粉病抗性,且以1000μmol.L-1SA处理效果最好。     

Bacterial endophytes: recent developments and applications.

Endophytic bacteria have been found in virtually every plant studied, where they colonize the internal tissues of their host plant and can form a range of different relationships including symbiotic, mutualistic, commensalistic and trophobiotic. Most endophytes appear to originate from the rhizosphere or phyllosphere; however, some may be transmitted through the seed. Endophytic bacteria can promote plant growth and yield and can act as biocontrol agents. Endophytes can also be beneficial to their host by producing a range of natural products that could be harnessed for potential use in medicine, agriculture or industry. In addition, it has been shown that they have the potential to remove soil contaminants by enhancing phytoremediation and may play a role in soil fertility through phosphate solubilization and nitrogen fixation. There is increasing interest in developing the potential biotechnological applications of endophytes for improving phytoremediation and the sustainable production of nonfood crops for biomass and biofuel production.     

Improvement in the quality of a fermented seaweed beverage using an antiyeast starter of <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> DW3 and partial sterilization

The quality of a fermented beverage (FSB) produced from seaweed (Gracilaria fisheri) was investigated after four different fermentation processes. 1, a normal fermentation as control (N-N); 2, batch with addition of an inoculum of an antiyeast starter culture, Lactobacillus plantarum DW3 (N-S); 3, a partial sterilization of the seaweed with 0.5% potassium metabisulfite (KMS) (P-N); and 4, a partial sterilization followed by an inoculum as for 2 (P-S). At the end of fermentation (60 days) and after storage for 3 months, all treatment sets passed the microbiological quality guidelines, as no bacterial indicators (total coliforms and Escherichia coli) or foodborne pathogens (Salmonella sp. Clostridium perfringens and Staphylococcus aureus) were detected. All treatments improved the availability of elements (Cu, Zn, and Fe) in the seaweed beverage and they were all below the recommended safety levels. Toxic compounds such as methanol, and the elements As and Pb were below either the detection or safety limits. The starter culture controlled yeast contamination and had inhibitory effects against foodborne pathogenic bacteria (Vibrio parahaemolyticus PSSCMI 0064 > Bacillus cereus ATCC 11778 > Salmonella typhi PSSCMI 0034 ∼ Staphylococcus aureus PSSCMI 0004 ∼ E. coli PSSCMI 0001). The inoculation set without pretreatment by KMS (N-S) was the treatment that produced the best FSB based on its antibacterial activity, reduction of contaminated yeasts, remaining probiotic LAB and organoleptic properties.     

Gut microbiomes of mobile predators vary with landscape context and species identity

Landscape context affects predator–prey interactions and predator diet composition, yet little is known about landscape effects on insect gut microbiomes, a determinant of physiology and condition. Here, we combine laboratory and field experiments to examine the effects of landscape context on the gut bacterial community and body condition of predatory insects. Under laboratory conditions, we found that prey diversity increased bacterial richness in insect guts. In the field, we studied the performance and gut microbiota of six predatory insect species along a landscape complexity gradient in two local habitat types (soybean fields vs. prairie). Insects from soy fields had richer gut bacteria and lower fat content than those from prairies, suggesting better feeding conditions in prairies. Species origin mediated landscape context effects, suggesting differences in foraging of exotic and native predators on a landscape scale. Overall, our study highlights complex interactions among gut microbiota, predator identity, and landscape context.