Conjugal transfer of streptococcal plasmids to strains of Bacillus sphaericus

Abstract The streptococcal plasmids pIP501, pDC10535 and pSM15346 coding for MLS resistance have been successfully transferred to Bacillus sphaericus strains 1593, 2297, 2362 and local strains after mating on filter. The transfer occurred at high frequency and was demonstrated electrophoretically. Conjugation in liquid media also took place but at lower frequency. The conjugation process was studied by electron microscopy. A kind of a bridge of electron-dense material between the mating cells has been observed. The addition of trypsin did not change significantly the transfer frequency in our experimental conditions.     

大肠埃希菌对化疗药物顺铂体外敏感性的探讨

目的通过体外细菌敏感性试验研究细胞周期非特异性化疗药物顺铂（Cisplatin,DDP）对条件性致病菌———大肠埃希菌的抑菌活性。方法分别用滤纸片法和96孔板法对顺铂的抑菌活性进行研究。其中,滤纸片法是以庆大霉素作为阳性对照,以生理盐水作为阴性对照,用直尺测不同浓度顺铂抑菌圈直径大小;96孔板法是用酶标仪测定吸光值,然后计算抑菌率。根据不同浓度大肠埃希菌的抑菌率曲线,利用origin 75拟合标准曲线做图并计算出能使50%大肠埃希菌死亡所需的顺铂使用剂量（IC50）。结果滤纸片法检测结果发现,5、2.5、1.25、0.625、0.313和0.156 mg/mL的顺铂对大肠埃希菌的抑菌圈大小分别为14、121、19、.678、.33和0 mm,而阳性对照6 670 IU/mL庆大霉素的抑菌圈大小为18 mm。96孔板法检测结果发现,顺铂对大肠埃希菌的抑制率均随用药剂量的增加而增大,呈＂S＂型曲线。用药后6、24、48和72 h时顺铂的IC50值分别为30.29、42.56、80.24和98.69μg/mL。结论顺铂对大肠埃希菌有抑制生长的作用;其抑菌作用随顺铂用药作用时间的延长而减弱。     

Utilization of carbohydrates content of paper tube residuals for ethanol production

Paper tube residual was utilized as a raw material for ethanol production. The effects of two pretreatment methods namely dilute acid steam explosion (DASE) and concentrate phosphoric acid (CPA) on enzymatic hydrolysis and SSF were studied. Cellulose, lignin, glue (PVA), and xylan were the main components of paper tube accounting for 52%, 20%, 9% and 7% of dry matter, respectively. Presence of PVA delayed the growth of yeast cells but showed no effect on ultimate yield of ethanol. Higher cellulase concentration as well as pretreatments increased hydrolysis rate and ultimate yield of ethanol. Enzymatic hydrolysis of native paper tube for 72 h resulted in 49% of theoretical glucose conversion while pretreatments by DASE and CPA increased this value to 67% and 93%, respectively. The best result of SSF process was from the CPA-pretreated paper tubes with an ethanol yield of 0.42 g/g after 48 h. Under optimal condition, 308 ml ethanol per kg paper tube could be produced.     

Primary simple assays of cellulose-degrading fungi

Some 25 fungi, including at least 14 basidiomycetes, one ascomycete, and five anamorphic fungi were evaluated for their cellulose-degrading abilities in Difco potato dextrose broth or Difco malt extract broth cultures with cellulosic substrates (e.g., filter paper) in plastic Petri dishes. Among them, Peniophora sp. 06-13 and Phlebia sp. 99-335 reduced the dry weights of the whole cultures with these substrates more than the dry weights of the respective original substrates after 30 days of culture, showing definite cellulose degradation. In the cultures with more than 10 test fungi including Pycnoporus coccineus 84-117, such weight losses did not occur. This assay technique for the primary screening for cellulose degrading fungi is simple, inexpensive, reproducible and accurate.     

Detection of filarial infection usingWuchereria bancrofti microfilariae culture antigen and filter paper blood samples in enzyme linked immunosorbent assay

Blood collected on filter paper by finger-prick gave results comparable to intravenous serum samples when analysed by enzyme-linked immunosorbent assay (ELISA). All the 100 microfilaraemia, 5 out of 100 endemic normals and none of the 10 nonendemic normal filter paper blood samples showed the presence of filarial antibody when tested by this method,using culture antigen and anti-immunoglubulins, class G, M and A — penicillinase conjugate. When the same samples were screened for the presence of IgM antibody, 91 out of 100 microfilaraemia, 13 out of 100 endemic normal and none of the 10 nonendemic normal samples showed a positive reaction. Enzyme linked immunosorbent assay, using culture antigen and filter paper blood samples, appears to work in large field studies for detection of filarial infection.     

Plant characteristics are poor predictors of microsite colonization during the first two years of primary succession

Questions: Do plant characteristics predict microsite colonization in severe habitats dominated by abiotic factors? Specifically, does colonization of microsites differ among shrubs, forbs and grasses or between wind‐ and water‐dispersed plants, non‐native and native plants, or N‐fixing and non‐N‐fixing plants? Location: Kowhai River floodplain, Kaikoura, South Island, New Zealand. Methods: Five microsite characteristics were measured for > 1000 individuals representing 27 colonizing plant species on a two‐year old surface of a primary succession on a New Zealand floodplain. The microsite characteristics included surface contour (convex, concave, or flat), the position of the plant (e.g., upstream, downstream) relative to the closest rock with > 20 cm maximum dimension, the distance to that same rock, the depth of the base of the stem below the surface of a plane resting on the adjacent microrelief, and soil particle size (gravel, pebbles or sand). Results: All plants preferred concave microsites near large rocks relative to systematically placed null points. We found no clear preferences for microhabitats by dispersal mode, native vs. non‐native status, or plants with or without nitrogen‐fixing symbionts, but grasses preferentially colonized fine soil particles. Highly variable responses among species contributed to these results. Better predictability of microsite preference was obtained for individual species than forplants grouped by characteristics. Conclusions Our results suggest that in severe habitats with strong abiotic filters and low microsite availability, such as found in early primary succession, coarse categories of species characteristics are poor predictors of colonization success.     

Detection and quantification of tau aggregation using a membrane filter assay

Aggregation of the microtubule-associated protein tau contributes to the formation of neurofibrillary lesions in Alzheimer's disease and is a useful marker of disease progression. Although filter trap assays have been employed to assess the extent of tau aggregation in cells and tissues as well as in vitro, their performance relative to other assay modalities has not been reported. To clarify this issue, the ability of the filter trap approach to quantify aggregation of purified recombinant full-length tau protein in vitro was examined as a function of membrane chemistry in a 96-well format. Results showed that nitrocellulose yielded the greatest assay sensitivity relative to polyvinylidene fluoride or cellulose acetate at equal membrane porosity. However, all combinations of filter chemistries, porosities, and monoclonal detection antibodies yielded nonlinear correlations between signal intensity and analyte concentration. When corrected for nonlinearity, the filter trap assay determined a value for the critical monomer concentration for tau aggregation that was statistically identical to determinations made by electron microscopy assay. The data suggest conditions under which filter trap assays can be used to estimate tau aggregation kinetics.     

缙云山四川大头茶树木年轮生长动态与气候因子关系的研究

应用相关分析、逐步回归、数字滤波以及功率谱方法对四川缙云山四川大头茶年轮生长动态进行了分析研究,通过数学模型滤除树木本身生长的遗传因素及定年后,建立了缙云山青龙寨和香炉峰的树木年轮年表。结果表明,四川大头茶年轮中保存的信息量较大,两地点年轮年表与其生长环境重庆地区的年降水量相关密切,可以用该年表表征重庆地区的降水情况。气象因子与四川大头茶年轮宽度间的统计数学模型为:Y=-2.19+0.00747J₁+0.00612J₂+0.00140J₃+0.00384J₄+0.00371J₅+0.0731T₁+0.0564T₅,年轮的功率谱密度值随波数的分布不均匀,由年轮宽度变异的功率谱周期分析揭示了树木生长环境2、11～12、22年左右的降水波动周期。树木年轮表的建立与分析,是研究森林生态系统动态及环境历史变迁的重要途径.     

Development of a filter assay for measuring homogalacturonan: alpha-(1,4)-Galacturonosyltransferase activity

Alpha-(1,4)-galacturonosyltransferases (GalATs) catalyze the addition of (1,4)-linked alpha-D-galacturonosyl residues onto the nonreducing end of homogalacturonan chains. The nucleotide-sugar donor for the enzymatic reaction is uridine diphospho-D-galactopyranosyluronic acid (UDP-D-GalpA). Many GalAT activity assays are based on the incorporation of D-[(14)C]GalpA from UDP-D-[(14)C]GalpA onto exogenously added homogalacturonan acceptors. Reactions based on this method can be time-consuming because multiple labor-intensive centrifugations and washes with organic solvents are required to remove the unincorporated UDP-D-[(14)C]GalpA from the (14)C-labeled products. Here we report the development of an alternative GalAT filter assay based on the ability of homogalacturonan to bind to cetylpyridinium chloride (CPC). GalAT assay reaction products made using radish (Raphanus sativus) microsomal membranes or solubilized proteins from tobacco (Nicotiana tabacum L. cv. Samsun) and Arabidopsis thaliana (cv. Columbia) were spotted onto Whatman 3MM paper treated with 2.5% (w/v) CPC. Unincorporated UDP-D-[(14)C]GalpA was selectively removed from the filters by washing with 150-250 mM NaCl. The versatility of this assay is demonstrated by using it to identify GalAT activity in fractions obtained during the partial purification of tobacco GalAT by SP Sepharose cation exchange chromatography and by detecting the GalAT-catalyzed incorporation of D-[(14)C]GalpA onto endogenous acceptors from Arabidopsis membranes.