一步法扩增克隆IBDV上海超强毒VP2-4-3基因

分离、纯化了鸡传染性法氏囊病病毒超强毒 (vvIBDV) 上海株SH95的病毒核酸dsRNA,应用随机引物将RNA反转录成cDNA,以此为模板一步扩增出A片段前体融合蛋白基因即VP2-4-3基因,将其克隆入pGEM-T载体,并进行序列分析,其与超强毒株HK46的核苷酸序列的同源性达98%,整个基因有5个氨基酸差异,同源性达99.51%(1007/1012).     

中国近海牡蛎系统分类研究的现状和对策

探讨了中国近海沿岸牡蛎分类的诸多疑难和热点问题,回顾了国内外包括贝类等动物的分子系统发生学研究的主要进展,分析了中国近海牡蛎系统分类目前存在的问题,重点阐述了利用分子标记等手段解决形态相似种的鉴定和种系发生关系等问题的巨大潜力,报道了利用分子标记进行牡蛎分类研究所取得的最新进展。预期经典分类学和分子系统发生学研究的交叉综合,将大力推动中国近海牡蛎的系统分类和系统发生研究的发展。     

大豆蚜嗅觉在选择寄主植物中的作用

大豆蚜 Aphis hlycines 有翅和无翅孤雌生殖蚜为其寄主植物大豆叶和鼠李叶气味所引诱,而非寄主植物棉花叶和黄瓜叶气味处于中性,丝瓜叶和南瓜叶气味具有明显的排斥作用。非寄主植物气味可以遮蔽寄主植物气味的引诱作用。大豆蚜触角感受器对植物气味具有嗅觉生理反应,对一些化合物的最小感觉阈值达10-5至10-6体积比浓度,表明大豆蚜触角上存在识别植物气味的嗅觉受体细胞。由此证明,嗅觉在大豆蚜选择寄主植物过程中起重要作用。     

Effect of Tooth Removal on Recaptures of Raccoons

Abstract: Researchers have extensively used mark—recapture techniques to obtain information on demographic parameters of wildlife populations. However, researchers have recognized that a number of factors can influence capture probabilities of wildlife species, which in turn can bias mark—recapture estimates of demographic parameters. Tooth extraction, which is a commonly used technique in studies of mesopredator species to obtain precise age estimates and to monitor the use of vaccine baits, is an aspect of animal handling that clearly might affect the recapture probability of individuals. However, the effect that tooth removal has on the individual recapture probabilities of wildlife species is unknown. During 2005, we trapped and marked 91 raccoons (Procyon lotor) in northern Indiana, USA, as part of a mark—recapture study designed specifically to determine if tooth extractions have an effect on recapture probabilities of individuals. We performed tooth extractions on 50% of the raccoons at the time of capture, and we attempted to balance tooth extractions with respect to sex and age of raccoons. We used logistic regression to model the effects of sex, age, and tooth removal on recapture probabilities, and we used Mann—Whitney U-tests to examine the effect of tooth removal on the number of times we recaptured individuals. The probability of recapture differed between sexes but did not differ as a function of tooth removal or among age classes. In addition, we failed to detect any difference in the mean number of times that we recaptured raccoons between the tooth removed and non—tooth-removed groups. Our results suggest that managers can use tooth extractions as an effective management tool without biasing population estimates or compromising other management objectives.     

Markov invariants and the isotropy subgroup of a quartet tree

The purpose of this article is to show how the isotropy subgroup of leaf permutations on binary trees can be used to systematically identify tree-informative invariants relevant to models of phylogenetic evolution. In the quartet case, we give an explicit construction of the full set of representations and describe their properties. We apply these results directly to Markov invariants, thereby extending previous theoretical results by systematically identifying linear combinations that vanish for a given quartet. We also note that the theory is fully generalizable to arbitrary trees and is equally applicable to the related case of phylogenetic invariants. All results follow from elementary consideration of the representation theory of finite groups.     

The first world swimming championships of roseobacters—Phylogenomic insights into an exceptional motility phenotype

Many marine Alphaproteobacteria of the Roseobacter group show a characteristic swim-or-stick lifestyle, for which motility is a crucial trait. Three phylogenetically distinct flagellar gene clusters (FGCs) have been identified in Rhodobacteraceae that have been named fla1, fla2 and fla3 according to their relative abundance. In addition to the flagellar-dependent swimming and swarming motility, pilus-dependent twitching mediates bacterial locomotion. Furthermore, filament independent modes of motility, namely gliding and sliding, have been described for various microorganisms. However, no mode of motility other than swimming has so far been described for roseobacters. In the present study, we investigated motility, distribution of flagellar systems and the phylogeny of 120 genome-sequenced Rhodobacteraceae. The phylogenetically broad taxon sampling that included 114 type strains revealed the presence of at least ten distinct clades that were statistically well supported. The investigation of the actual physiological capacity for swimming motility on soft agar plates showed that only about half of the 120 tested strains were motile under the tested conditions. Seven strains developed a conspicuous dendritic motility phenotype that was reminiscent of the swarming motility in Pseudomonas aeruginosa. The observed dendritic motility in two strains (i.e. Sulfitobacter pseudonitzschiae DSM 26842 and Roseovarius pacificus DSM 29589) was particularly surprising because they did not harbor any genes of the FGC. Accordingly, it was concluded that this form of dendritic motility was independent of a flagellum. A comparative genomics approach allowed a remarkable number of pilus-related candidate genes to be identified for this novel type of motility in Rhodobacteraceae.     

Phosphatidylcholine and cholesterol interactions in model membranes

Various phosphatidylcholines differing either in the stereochemistry around their chiral center or in the position of a cis double bond along the acyl chains were synthesized in order to study critical contact regions in the phospholipid molecule with adjacent cholesterol in model membranes. Microviscosities calculated from fluorescence depolarization of diphenylhexatriene and chain order from spin label studies were measured to monitor physical membrane properties. The enhancing effect of cholesterol on the microviscosity of membranes containing phosphatidylcholines with comparable acyl chain length was largest when the two acyl chains were saturated and smallest when both were unsaturated. Membranes prepared from phosphatidylcholines having a single cis double bond at different positions along the sn-2 acyl chain showed roughly the same changes of microviscosity or chain order upon incorporation of cholesterol. No discrimination was evident in the interaction between cholesterol and enantiomeric phosphatidylcholines or between the enantiomeric phosphatidylcholine molecules themselves. We conclude that the rigidifying effect of cholesterol in membranes does not depend on specific sites of interaction and that with respect to physical membrane properties phosphatidylcholine behaves as an achiral molecule.     

Evidence for plasmid-associated crystal toxin production in Bacillus thuringiensis subsp. israelensis

Three crystalliferous (Cry⁺) strains of Bacillus thuringiensis subsp. israelensis (serotype 14) that produce parasporal protein crystals toxic to dipteran larvae and several acrystalliferous (Cry^?) mutants, either induced or spontaneously derived from a single Cry⁺ parent, were examined for the presence of covalently closed circular (CCC) DNA in attempts to correlate toxin production with the presence of a specific plasmid. The plasmid profiles of both Cry⁺ and Cry^? variants were analyzed by both a cleared lysate- and a modified Eckhardt lysateelectrophoresis technique. All of the Cry^? mutants derived from the Cry⁺ parental strain had lost a 4.0- to 4.4-megadalton (Mdal) plasmid. Bioassay data confirmed loss of toxin production by the Cry^? variants. All three Cry⁺ strains, including the parent of the Cry^? strains, contained CCC plasmids DNAs of the following approximate molecular weights: 4.0 to 4.4, 5.2 to 6.0, and 11.4 to 13.0 Mdal. One Cry⁺ strain contained an additional CCC plasmid of 6.7 to 7.2 Mdal. The plasmid patterns for several Cry^? derivatives differed in other respects from the pattern for their parent strain. The various Cry⁺ and Cry^? strains could be distinguished either by phenotypical differences in antibiotic sensitivity, crystal production, and toxicity, or by differences in their plasmid profiles.