Evaluation of the MicroFoss system for the analysis of Escherichia coli in water

In this study, the performance of the MicroFoss system (Foss, Spain) for the enumeration of Escherichia coli in water samples was evaluated. One hundred and eighty-five samples were analysed both by MicroFoss assay and culture isolation on Tryptone-Bile X-glucuronide agar (TBX), and the correlation coefficient obtained was 0.92. The analysis of 28 new samples using both methods showed a statistically significant relationship at the 99.5% confidence level between log colony forming units obtained by MicroFoss assay and those obtained using growth on TBX agar. Nevertheless, when the level of sample contamination was low, the variability was high. In conclusion, the MicroFoss system is a rapid and simple alternative method for the enumeration of E. coli in water although discordance between the results using these methods in samples with low counts could limit its use for the study of clean water such as potable water.     

Intralaboratory validation according to the EN ISO 16 140 Standard of the Vidas SET2 detection kit for use in official controls of staphylococcal enterotoxins in milk products

AIM: Immunological tools used to detect staphylococcal enterotoxins (SEs) in foods are numerous. The aim of this study was to evaluate, on naturally contaminated milk product samples, the performance of the Vidas SET2, in comparison to the Transia plate SET. METHODS AND RESULTS: The Vidas SET2 was compared with the Transia plate SET on supernatants of Staphylococcus aureus isolates and on naturally contaminated milk products. It is noteworthy that when using IgG rabbit treatment, both kits can be considered as equivalent to detect enterotoxins in naturally contaminated milk products. CONCLUSIONS: This study demonstrated that the Vidas SET2 performance is similar to that of Transia plate SET kit, when a rabbit IgG treatment step is used before detection step. This additional treatment significantly decreased, from 42% to 8%, the rate of positive deviations observed using the Transia plate SET detection kit. SIGNIFICANCE AND IMPACT OF THE STUDY: The Vidas SET2 was clearly found as more specific, when no preliminary rabbit IgG treatment was used, and which results in a better workflow when a large number of samples have to be analysed within a few days. Considering the results obtained, the Vidas SET2 detection kit can be used to assess the safety of milk products for SEs.     

温带草甸草原土壤N2O产生过程研究

以大量的室内模拟培养实验,以内蒙古温带草甸草原土壤为研究对象,利用AIM乙炔抑制法,模拟野外条件对原样土壤样品进行N₂O产生过程进行研究。实验结果表明:内蒙古温带草甸草原土壤N₂O产生过程以硝化作用为主。其中异养硝化作用起主导作用,自养硝化潜势和反硝化潜势在草原植物不同生长季节变化不同,总体上异养硝化潜势>自养硝化潜势>反硝化潜势。由于自养硝化作用在不同季节的发生,使得草甸草原土壤N₂O的产生潜势也高、低起伏变化。从而揭示了内蒙古温带草原土壤以异养硝化作用过程为主产生N₂O和N₂O排放通量较低的微生物学机理。     

四种提取芸芥基因组DNA方法的比较

以芸芥为材料 ,分别用CTAB法、SDS法、尿素法、NaOH法四种方法对芸芥基因组DNA进行了提取 ;并用紫外光分光光度计法、琼脂糖电泳法和RAPD分析法对所提取的DNA进行检测 ,将它们在DNA的产量、质量和耗时、耗费等方面的优缺点进行比较 ,以便在实际工作中根据不同的试验条件选取最合适的提取方法。通过四种方法的比较 ,研究认为尿素法是芸芥基因组DNA的最佳提取方法。     

响应曲面法优化马尾松中莽草酸的超声提取工艺

以马尾松松针为原料,采用超声波提取法从松针粉中提取莽草酸,通过考察料液比((VH2O∶m松针粉,mL:g)、提取时间、提取温度及超声波功率等因素对松针中总莽草酸含量的影响,并在单因素试验的基础上,选取料液比、提取时间、超声波功率3个变量,进行Box-Behnken中心组合设计优化,获得马尾松松针中莽草酸的最佳提取工艺参数为料液比1∶26,提取时间为46min,超声波功率为359 W,此条件下莽草酸的提取率为1.948%。     

发酵甜高粱计耐高浓度酒精酵母菌的选育

采用负染色计数法从非自然诱变菌株中成功地选育一株以C4植物甜高粱汁做基质发酵生产液体生物燃料（酒精）的酵母菌株,产酒率最高达12．80％（V／V）。     

An impedimetric method for rapid screening of cosmetic preservatives

An efficient impedance method was developed for rapid evaluation of cosmetic preservatives. The method used decimal reduction time or D-value to assess preservative efficacies. The D-value, which was calculated from the plot of Log CFU ml^–1 versus time by linear regression analysis, could be obtained within 48 h. Thus, the time required for the challenge test was reduced from 4–8 weeks with the standard procedures (eg US Pharmacopeia), to 2 days with the current method. A calibration curve (r=-0.95) was established by plotting the Log CFU ml^–1 versus capacitance detection time (DT) of 108 samples. With the calibration, CFU can be estimated directly from the impedance test without plating. Two commercial biocides and several other chemicals were evaluated in a shampoo by the impedance procedure againstPseudomonas aeruginosa. The D-values obtained from the impedance test were not significantly different from those produced by the conventional plate count method. The technique was found to be particularly useful when screening a large number of compounds to find novel preservatives and synergistic preservative combinations.     

Development of needle retention in Scots pine (Pinus sylvestris) in 1957–1991 in northern and southern Finland

The needle trace method was used to study retrospectively the long-term latitudinal variation in needle retention in Scots pine (Pinus sylvestris L.) in Finland. The mean annual summer needle retention (ANR) along the main stem varied from 3.4 to 6.0 needle sets during the period 1957–1991. The lowest values were observed in southern and the highest in northern Finland. The length of the growing season, expressed as the thermal sum (threshold value +5 °C), was negatively correlated with the mean ANR (r=-0.96). The geographical needle retention pattern (NRP) for the period 1957–1991 showed a clearly increasing trend from 1957 to 1969 (southern Finland) and to 1975 (northern Finland); thereafter, the NRP tended to decrease close to its minimum value recorded in 1991. The general level of the NRP was approximately 5.0 needle sets in northern Finland and 3.5–4.0 needle sets in southern Finland. The NRP, with its 6–12 year cycle for southern Finland, was clearly periodical. Differences in the NRP among the ten stands in southern Finland were small, whereas the said periodicity was missing and the differences were high among the stands in northern Finland. The results indicate that variation in the number of needle sets, viz. defoliation of pines, is a normal phenomenon. The role of net carbon assimilation as a regulator of the number of needle sets is discussed.     

The dynamics of male brooding,mating patterns,and sex roles in pipefishes and seahorses (family Syngnathidae)

Modern theory predicts that relative parental investment of the sexes in their young is a key factor responsible for sexual selection. Seahorses and pipefishes (family Syngnathidae) are extraordinary among fishes in their remarkable adaptations for paternal care and frequent occurrences of sex-role reversals (i.e., female-female competition for mates), offering exceptional opportunities to test predictions of sexual selection theory. During mating, the female transfers eggs into or onto specialized egg-brooding structures that are located on either the male's abdomen or its tail, where they are osmoregulated, aerated, and nourished by specially adapted structures. All syngnathid males exhibit this form of parental care but the brooding structures vary, ranging from the simple ventral gluing areas of some pipefishes to the completely enclosed pouches found in seahorses. We present a molecular phylogeny that indicates that the diversification of pouch types is positively correlated with the major evolutionary radiation of the group, suggesting that this extreme development and diversification of paternal care may have been an important evolutionary innovation of the Syngnathidae. Based on recent studies that show that the complexity of brooding structures reflects the degree of paternal investment in several syngnathid species, we predicted sex-role reversals to be more common among species with more complex brooding structures. In contrast to this prediction, however, both parsimony- and likelihood-based reconstructions of the evolution of sex-role reversal in pipefishes and seahorses suggest multiple shifts in sex roles in the group, independent from the degree of brood pouch development. At the same time, our data demonstrate that sex-role reversal is positively associated with polygamous mating patterns, whereas most nonreversed species mate monogamously, suggesting that selection for polygamy or monogamy in pipefishes and seahorses may strongly influence sex roles in the wild.     

金黄色葡萄球菌基因表达的DNA扣除法

[目的]金黄色葡萄球菌作为一种分布广泛的致病微生物和研究革兰氏阳性菌遗传背景的模式菌株,利用real-time RT PCR对相关毒素及调控基因进行表达定量分析,在生物、医学、食品检测等领域具有较大研究价值.[方法]对制备好的反转录(RT,含有cDNA和DNA)和非反转录(RTˉ,仅含DNA)样品进行Real-time PCR检测,根据经典(1 E)ˉ△△Ct相对定量算法并结合PCR效率公式建立一种基因表达相对定量分析的DNA扣除法,将得到的Ct值转换为各样品含量,从RT样品中扣除RTˉ样品的量,无需DNaseⅠ酶解处理就可以去除DNA的影响,RTˉ样品的检测结果还可同时作为稳定的DNA内参.[结果]采用以上方法分析金黄色葡萄球菌肠毒素A基因(sea)、16S rRNA和RNA Ⅲ的表达情况,在含有葡萄糖的NB培养基中sea的相对转录水平随着葡萄糖浓度的增大而升高,RNAⅢ的相对转录水平随葡萄糖浓度的变化而产生小幅度的波动,16S rRNA在菌体生长初期时的表达量较为稳定;与绝对定量法比较,结果差异较小(均小于15%),且差异不显著(p＞0.05).[结论]这种基于DNA扣除法的Real-time RT PCR相对定量方法可以有效的对金黄色葡萄球菌的基因表达进行分析.