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1.
The effects of freezing rate, suspending fluid and age of culture on the ability of four strains of Campylobacter pylori to survive and recover from freeze-drying were examined. Freeze-drying by standard procedures generally resulted in an overall loss in viability of between 3 and 7 log units. The exact cause of poor recovery by C. pylori was not established but strain differences were detected, with NCTC 11637 (type strain) surviving better than NCTC 11638 and NCTC 11639. Recovery of the poorest growing strain (NE 26695) was notably more erratic. The largest loss in viability occurred at the primary drying stage. Losses resulting from freezing and secondary drying were less marked and the rate of freezing had only a marginal effect on recovery. Nineteen different freeze-drying suspending fluids were investigated. Overall the best recovery results were obtained with 5% inositol-broth (or horse serum) plus 25% glucose, at pH 7.0, in which loss of viability was typically about 4 log units. Other factors, such as age of culture and number of viable bacteria in the before-dry suspension, did not have a significant effect on survival. We conclude from these results that C. pylori can survive freeze-drying, albeit in small numbers, but the degree of recovery is apparently largely strain dependent.  相似文献   
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本文记述采自新疆的皿蛛科蜘蛛一新届——颚齿蛛属Maxillodens gen.nov.及其一新种——鞭状颚齿蛛M.flageuatus sp.nov。  相似文献   
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Within island archipelagos, repeated ecological settings may lead to radiations wherein similar niches are recurrently occupied. Although it has been shown that species with common habitat requirements share particular traits, it remains relatively unexplored to what extent this may lead to the repeated evolution of almost identical phenotypes (phenocopies) and how this correlates with traits subjected to sexual selection. Exploring divergence patterns of ecological and sexual relevant traits within spiders seem promising to enhance our understanding of the relative role of natural and sexual selection. Here, we conduct a detailed morphological analysis on a large set of genital and non‐genital traits (morphometrics, colour pattern) within a radiation of the wolf spider genus Hogna Simon, 1885 on Galápagos and interpret these data, taking into account their known phylogenetic relationship. Our results show that recurrent environmental gradients have led to the parallel evolution of almost identical phenotypes, which not only proves that natural selection has driven morphological divergence, but also suggests that a similar genetic or developmental basis most likely underlies this divergence. Among‐species variation in genital traits in contrast rather reflects the phylogenetic relationships on Santa Cruz and San Cristóbal. The combination of these data indicate that speciation in this system is driven by the combined effect of ecological mechanisms and allopatric divergence in sexual traits. © 2012 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 106 , 123–136.  相似文献   
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Temporal changes in allele frequencies were studied in host-associated populations of the small ermine moth Yponomeuta padellus. At one site, populations from three host plants (Sorbus aucuparia, Amelanchier larnarckii , and Crataegus spp.) were sampled annually during a four-year-period and analysed with 20 polymorphic allozyme markers. At two other sites, allele frequencies at 5- 6 enzyme loci of Y. padellus populations from two different host plants were also tested for consistency over a 13-year-pcriod. Significant allele frequency changes occurred in the short-term analysis, whereas allele frequencies remained relatively stable through time in the long-term analyses. Furthermore, allele frequencies of Y. padellus populations from Crataegus spp. were relatively stable compared to the other host populations. The role of the agents responsible for the observed patterns is discussed.  相似文献   
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The method for specific modification of Escherichia coli RNA polymerase by a monomercuric derivative of fluorescein--fluoresceinmonomercuracetate (FMMA)--a specific reagent for SH-groups of proteins is suggested. It is shown, that in conditions of equimolar FMMA/enzyme ratio the fluorescent label interacts preferantially with a single sulfhydryl group in alpha-subunit of RNA polymerase. The mercaptide bonding formation is followed by significant alterations of all spectral parameters of FMMA, but has no effect on the kinetic parameters (KB and k2) of RNA synthesis initiation nor does it lead to inhibition of the total RNA synthesis. The modification presented may be used in structural and topological investigations of RNA polymerase functioning.  相似文献   
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A two-step procedure for the purification of 6-phosphogluconate dehydrogenase (EC 1.1.1.44; 6-PGDH) from sheep liver is described. The enzyme is directly bound to cellulose phosphate by batch extraction and eluted with a linear salt gradient. Purification is completed by affinity chromatography using NADP(+)-agarose. The result is 6-PGDH of high purity, greatly increased yield, and the highest specific activity yet achieved, with a significant reduction in the purification time.  相似文献   
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