蛛网和蛛体挥发物诱导的阴暗拟隙蛛（蜘蛛目：漏斗蛛科）种内选择偏好行为

化学通讯是蜘蛛类群普遍使用的种内和种间信息交流方式,极可能是蜘蛛进化过程中最初用来进行个体之间信息交流的途径。本研究利用双向选择系统,测试了阴暗拟隙蛛(Pireneitega luctuosa)对同种其他个体的蛛网和蛛体挥发物的选择行为,采用卡方检验的统计学方法、利用SPSS 19.0和Origin Pro 8等软件对所测蜘蛛的选择数据进行了分析。结果显示:①阴暗拟隙蛛雄蛛和雌蛛对来自同种异性的蛛网(P 0.001)和蛛体挥发物(P 0.05)均具有显著的趋向性,雌、雄蛛在异性蛛网或蛛体挥发物所在的选择盒表现更长时间的停留、探索、织网等行为;②雄蛛和雌蛛对幼蛛蛛体释放出来的挥发物均表现出显著的回避行为(P 0.05),倾向于远离具有幼蛛挥发物的选择盒;③幼蛛对同种幼蛛和雄蛛的蛛网(P 0.001)以及同种幼蛛的蛛体挥发物(P 0.05)均具有选择偏好性,说明幼蛛倾向于与同种个体接近。我们的研究表明,阴暗拟隙蛛雄蛛、雌蛛及幼蛛的蛛网和蛛体挥发物能诱导种内其他个体的趋向或回避行为,阴暗拟隙蛛幼蛛对同种幼蛛的选择偏好性可能是该种个体在同一地域聚集分布的主要原因。我们的研究从行为学角度证实,阴暗拟隙蛛的蛛网及体表均携带有能够标识其性别和龄期的相关信息化学物质。     

小地老虎食诱剂糖醋酒液配方筛选及发酵增效作用

【目的】为筛选和规范诱集小地老虎Agrotis ipsilon成虫的最佳糖醋酒液配方及最佳发酵时间,确定发酵液中的挥发物成分。【方法】优选以单一纯物质糖、醋、酒和水进行混配的配方A, B, C和D, 其配比分别为蔗糖(g)∶乙酸(mL)∶无水乙醇(mL)∶纯水(mL)(m/v/v/v)=3∶1∶3∶80, 3∶1∶3∶160, 3∶1∶6∶80和1∶1∶3∶80及常见配方E［白糖(g)∶白醋(mL)∶白酒(mL)∶自来水(mL)= 6∶3∶1∶10(m/v/v/v)］,分别并采用Y型嗅觉仪及GC-MS测试和分析小地老虎成虫对发酵1~15 d后的糖醋酒液的趋性及发酵液中的挥发物成分。【结果】趋性试验结果表明,糖醋酒液B配方对小地老虎诱集效果显著优于A, C, D和E配方,C配方次之。小地老虎成虫对B和C这两种配方发酵8 d发酵液的选择反应率均显著高于对未发酵及发酵5 d和7 d外的其他发酵时间发酵液的选择反应率。挥发物成分组成分析结果显示,糖醋酒液B配方发酵8 d发酵液的挥发物共有41种化合物,主要包括17种烃类化合物、8种醛类化合物、2种酮类化合物、4种醇类化合物、5种酯类化合物和5种醚类化合物。而且发酵8 d的糖醋酒液B配方与其未发酵以及发酵4 d和发酵12 d的糖醋酒液B配方之间的挥发物成分差异较大。【结论】优选并明确单一物质糖、醋、酒和水进行混配的小地老虎食诱剂配方(3∶1∶3∶160, m/v/v/v),其糖醋酒液通过发酵可以产生增效作用,最佳发酵时间为8 d。     

Induction of systemic resistance in tomato against broomrape (Phelipanche aegyptiaca)

Rhizosphere dwelling bacteria can increase plant resistance to biotic and abiotic stresses, and they promote plant growth through various mechanisms. In this study, three bioassays were conducted including the following: (a) screening for effective bacterial isolates in the suppression of broomrape, (b) evaluating induced systemic resistance against broomrape and (c) comparing the selected bacterium isolate with plant chemical inducers. Fifteen plant growth‐promoting rhizobacteria (PGPR) were examined to assess their biocontrol potential against Egyptian broomrape (Phelipanche aegyptiaca). Ten isolates significantly reduced the broomrape biomass compared to the control. The Lysinibacillus boronitolerans B124 reduced the dry weight of broomrape plants from 2.15 g in control to 0.45 g. Bacillus megaterium B6 was the best isolate in reducing the number of broomrape tubercles. In addition, the activity of three selected bacterial isolates was investigated in induced systemic resistance to broomrape by split‐root method. The Bacillus pumilus INR7 reduced the number of visible broomrape tubercles by 90%, and B. megaterium B71 and L. boronitolerans B124 were the next two in rank. Compared with the control, L. boronitolerans B124 reduced the dry weight of broomrape from 1.49 g in control to 0.39 g. In a subsequent experiment, L. boronitolerans B124 was evaluated along with some resistance‐inducing volatile compounds. Lysinibacillus boronitolerans B124 decreased the number of broomrapes by 87% on average, while the lowest dry weight of broomrape was observed in methyl jasmonate treatment. In conclusion, PGPR have considerable potential to be used in the integrated management of broomrape. It is also possible to use a mixture of rhizobacteria and defence inducers, such as biogenic volatiles as a promising approach in the management of this noxious parasitic weed.     

Development of a high throughput screening method to test flavour-forming capabilities of anaerobic micro-organisms

AIM: Development of a fast, automated and reliable screening method for screening of large collections of bacterial strains with minimal handling time. METHODS AND RESULTS: The method is based on the injection of a small headspace sample (100 microl) from culture vials (2 ml) in 96-well format directly into the mass spectrometry (MS). A special sample tray has been developed for liquid media, and anaerobically grown cultures. In principle, all volatile components can be measured, but a representative mass fragment has to be obtained in the MS. Representative masses for 3-methylbutanal, 2-methylpropanal and benzaldehyde are 58, 72 and 105, respectively. In 1 day over 1500 samples could be analysed and the coefficient of variation for the response was <5%. CONCLUSION: Screening of 72 strains belonging to the genus Lactococcus in quadruple on the production of the key-flavour compound 3-methylbutanal illustrated the effectiveness of the method. Furthermore, knowledge of the biochemistry and physiology of 3-methylbutanal formation was used to optimize the composition of the growth medium to enhance 3-methylbutanal production, and thereby improve the screening. SIGNIFICANCE AND IMPACT OF THE STUDY: A commonly used method to control flavour formation in fermented food products is the selection of bacterial strains, which are able to produce the desired flavour compounds. As large collections of strains are available for such screenings, studying biodiversity of micro-organisms on the level of metabolic routes is strongly facilitated by highly automated high throughput screening methods for measuring enzyme activities or production of metabolites. Therefore, this method will be a useful tool for selecting flavour-producing strains and for enhancing starter culture development.     

Methionine catabolism and production of volatile sulphur compounds by OEnococcus oeni

AIMS: During malolactic fermentation (MLF), the secondary metabolisms of lactic acid bacteria (LAB) contribute to the organoleptic modification of wine. To understand the contribution of MLF, we evaluated the capacity of various wine LAB to metabolize methionine. METHODS AND RESULTS: Using gas chromatography (GC) coupled either with mass spectrometry (MS) or a flame photometry detector in sulphur mode (FPD), we studied this metabolism in laboratory media and wine. In laboratory media, several LAB isolated from wine were able to metabolize methionine. They formed methanethiol, dimethyl disulphide, 3-(methylsulphanyl)propan-1-ol and 3-(methylsulphanyl)propionic acid. These are known to have powerful characteristic odours and play a role in the aromatic complexity of wine. In various red wines, after MLF only the 3-(methylsulphanyl)propionic acid concentration increased significantly, as verified with several commercial starter cultures. This compound, which is characterized by chocolate and roasted odours, could contribute to the aromatic complexity produced by MLF. CONCLUSIONS: This study shows that LAB isolated from wine, especially OEnococcus oeni strains, the major species in MLF, are able to metabolize methionine to form volatile sulphur compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study to demonstrate the capacity of wine LAB to metabolize methionine.     

Long and short term variations in suspended particulate material: the influence on light available to the phytoplankton community

The magnitude and frequency of events leading to changes in turbidity have been studied in a large (61 km²), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Mälaren, Sweden. In this paper we couple changes in suspended particulate inorganic material (SPIM) resulting from wind driven sediment resuspension, and variations in the discharge and sediment load, to spectral variations in subsurface light and estimates of photosynthetically active radiation (PAR). To accomplish this we use a semi-analytical model which predicts the spectral variations in downwelling irradiance (E _d()) and the attenuation coefficient of downwelling irradiance (K _d()), as a function of the concentrations of chlorophyll, dissolved yellow substances, and suspended inorganic and organic particulate material. Unusually high river discharge, led to large inputs of yellow substances and large in lake yellow substance concentrations (a _ys(420) 20 m^–1), causing variations in yellow substance concentration to have the greatest role in influencing temporal trends in the attenuation of PAR and variations in the depth of the euphotic zone (Z _eup). In spite of this, variations in SPIM could account for approximately 60% of the variation in Z _eup attributed to changes in yellow substances alone. Our results show that changes in suspended sediment concentration leads to both long-term and short-term changes in the attenuation of PAR, even in the presence of high concentrations of dissolved yellow substances.     

Inhibitory effect of medium-chain-length fatty acids on synthesis of polyhydroxyalkanoates from volatile fatty acids by Ralstonia eutropha

Medium-chain-length fatty acids, such as nonanoic (9:0) and octanoic (8:0) acids, are more toxic to Ralstonia eutropha than volatile fatty acids such as acetic, propionic and butyric acids. Nonanoic acid was degraded to acetic and propionic acids via -oxidation by Ralstonia eutropha for cell growth and synthesis of polyhydroxyalkanoates (PHAs). In a mixture of the fatty acids, utilization of nonanoic acid was depressed by acetic and propionic acids, and vice versa. The PHA accumulation from the volatile fatty acids was decreased from 53% (w/w) of dry cell mass to 23% due to the nonanoic acid. Similar phenomena were also observed with octanoic acid and its metabolic intermediates, acetic and butyric acids.     

Enzyme treatment to reduce solids and improve settling of sewage sludge

The effect of microbial enzymes in reducing the disposable solid content of sludge was investigated. A mixture of industrial cellulase, protease, and lipase, in equal proportion by weight, reduced total suspended solids (TSS) by 30–50% and improved settling of solids. An increase in solid reduction was observed with increasing enzyme concentration. The effect of combinations of enzyme treatments indicated that two-enzyme combinations of protease and cellulase produced better solid reduction than individual enzymes and that lipase further augmented this effect. Among the individual enzymes, protease produced a more settleable sludge as compared to cellulase and lipase. Adjustment of the pH of the enzymatically treated sludge to the acidic range (pH 2–4) further improved solid reduction, and adjustment to the alkaline range (pH 10–12) improved settleability. Journal of Industrial Microbiology & Biotechnology (2001) 26, 383–386. Received 01 November 2000/ Accepted in revised form 29 April 2001     

The consequences of volatile organic compound mediated bacterial and fungal interactions

Microbial interactions via infochemicals are fundamental to the development of spatial distribution and activity variations in ecosystems. Microorganisms produce a wide range of infochemicals, frequently secondary metabolites, most of which are soluble and many volatile. Volatile organic compounds (VOCs) have been identified in soil atmospheres and related to community structure and function. VOC profiles produced by microorganisms are consistent, relating to cultural conditions, environment and inputs, and so to population and function dynamics. VOC-mediated interactions can result in functional responses by the organisms involved that result in selective advantage to some community members. Positive, negative or neutral interactions can occur between a very wide range of soil bacteria and fungi. These effects include both stimulation and inhibition of growth, by 40 and 60%, respectively, and enzyme production. These effects are usually transient, e.g. removal of an antagonist is followed by complete recovery. Up- and down-regulation of gene expression, by mRNA and protein profiling has been demonstrated. VOCs have played an important role during the evolution of microorganisms in the context of their communities. This revised version was published online in August 2006 with corrections to the Cover Date.