产紫青霉EL-02的分离鉴定及其絮凝活性

摘要：【目的】分离鉴定有絮凝活性真菌,同时对其絮凝活性进行初步研究。【方法】采用梯度稀释、平板划线、18S rDNA检测等方法分离鉴定絮凝活性菌株。通过高速离心、超声破碎、乙醇沉淀、定性试验等方法确定絮凝活性物质性质。【结果】从渤海湾海岸土壤样品中分离筛选出一株有较高絮凝活性的真菌,经鉴定为产紫青霉（Penicillium purpurogenum）,命名为产紫青霉EL-02（P. purpurogenum EL-02）。超声破碎试验证实其絮凝活性主要存在于发酵上清液。根据絮凝活性曲线,确定4 d为积累絮     

Genetic selection for protein solubility enabled by the folding quality control feature of the twin-arginine translocation pathway

One of the most vexing problems facing structural genomics efforts and the biotechnology enterprise in general is the inability to efficiently produce functional proteins due to poor folding and insolubility. Additionally, protein misfolding and aggregation has been linked to a number of human diseases, such as Alzheimer's. Thus, a robust cellular assay that allows for direct monitoring, manipulation, and improvement of protein folding could have a profound impact. We report the development and characterization of a genetic selection for protein folding and solubility in living bacterial cells. The basis for this assay is the observation that protein transport through the bacterial twin-arginine translocation (Tat) pathway depends on correct folding of the protein prior to transport. In this system, a test protein is expressed as a tripartite fusion between an N-terminal Tat signal peptide and a C-terminal TEM1 beta-lactamase reporter protein. We demonstrate that survival of Escherichia coli cells on selective medium expressing a Tat-targeted test protein/beta-lactamase fusion correlates with the solubility of the test protein. Using this assay, we isolated solubility-enhanced variants of the Alzheimer's Abeta42 peptide from a large combinatorial library of Abeta42 sequences, thereby confirming that our assay is a highly effective selection tool for soluble proteins. By allowing the bacterial Tat pathway to exert folding quality control on expressed target protein sequences, we have generated a powerful tool for monitoring protein folding and solubility in living cells, for molecular engineering of solubility-enhanced proteins or for the isolation of factors and/or cellular conditions that stabilize aggregation-prone proteins.     

Intrinsic reproductive isolation between Trinidadian populations of the guppy, Poecilia reticulata

Although Trinidadian populations of the guppy, Poecilia reticulata, show considerable adaptive genetic differentiation, they have been assumed to show little or no reproductive isolation. We tested this assumption by crossing Caroni (Tacarigua River) and Oropuche (Oropuche R.) drainage populations from Trinidad's Northern Range, and by examining multiple aspects of reproductive compatibility in the F1, F2 and BC1 generations. In open-aquarium experiments, F1 males performed fewer numbers of mating behaviours relative to parental population controls. This is the first documentation of hybrid behavioural sterility within a species, and it suggests that such sterility may feasibly be involved in causing speciation. The crosses also uncovered hybrid breakdown for embryo viability, brood size and sperm counts. In contrast, no reductions in female fertility were detected, indicating that guppies obey Haldane's rule for sterility. Intrinsic isolation currently presents a much stronger obstacle to gene flow than behavioural isolation, and our results indicate that Trinidadian populations constitute a useful model for investigating incipient speciation.     

Social effects on fruit fly courtship song

Courtship behavior in Drosophila has often been described as a classic innate behavioral repertoire, but more recently extensive plasticity has been described. In particular, prior exposure to acoustic signals of con‐ or heterspecific males can change courtship traits in both sexes that are liable to be important in reproductive isolation. However, it is unknown whether male courtship song itself is socially plastic. We examined courtship song plasticity of two species in the Drosophila melanogaster subgroup. Sexual isolation between the species is influenced by two male song traits, the interpulse interval (IPI) and sinesong frequency (SSF). Neither of these showed plasticity when males had prior experience of con‐ and heterospecific social partners. However, males of both species produced longer bursts of song during courtship when they were exposed to social partners (either con‐ or heterospecific) than when they were reared in isolation. D. melanogaster carrying mutations affecting short‐ or medium‐term memory showed a similar response to the social environment, not supporting a role for learning. Our results demonstrate that the amount of song a male produces during courtship is plastic depending on the social environment, which might reflect the advantage of being able to respond to variation in intrasexual competition, but that song structure itself is relatively inflexible, perhaps due to strong selection against hybridization.     

Gymnotus capanema, a new species of electric knife fish (Gymnotiformes, Gymnotidae) from eastern Amazonia, with comments on an unusual karyotype

Gymnotus capanema n. sp. is described on the basis of cytogenetic, morphometric, meristic and osteological data from nine specimens (one male and eight females) from the municipality of Capanema, Pará, in the eastern Amazon of Brazil. Later, three additional specimens were found in museums and regarded as nontypes (not cytogenetically analysed). Gymnotus capanema, which occurs in sympatry with Gymnotus cf. carapo cytotype 2n = 42 (30m/sm + 12st/a) exhibits a novel karyotype for the genus, with 2n = 34 (20m/sm + 14st/a). Gymnotus capanema can be unambiguously diagnosed from all congeners on the basis of a combination of characters from external anatomy, pigmentation and osteology. The constitutive heterochromatin, rich in adenine-thymine (A-T) base pairs [4',6 diamidino-2-phenylindole dihydrochloride (DAPI) positive], occurs in the centromeric region of all of the chromosomes, and in the pericentromeric and the entire short arm of some chromosomes. The nucleolar organizing region (NOR), stained by silver nitrate, chromomycin A(3) (CMA(3)) and 18S ribosomal (r)DNA fluorescence in situ hybridization (FISH), occurs in the short arm of pair 15. FISH, with telomeric probes did not show interstitial telomeric sequences (ITS), despite the reduced 2n in comparison to the karyotypes of other species of Gymnotus. The karyotype of G. capanema, with a reduced 2n, is strikingly different from all other previously studied congeners.     

Cuticular hydrocarbon profiles as a taxonomic tool: advantages,limitations and technical aspects

Cuticular hydrocarbons (CHCs) are expressed on an insect's cuticle and are one of the major factors allowing insects to identify members of their own species, colony and gender. As a result of their species‐specificity, CHCs are increasingly used to delimit species in addition to more conventional methods, such as morphology or genetic markers, and so play an important role in chemotaxonomy. Species vary in the type of CHCs that they produce, as well as in the relative quantities of shared compounds. This review summarizes not only how taxonomists may differentiate between species based on CHC profiles, but also the incentive for using CHC composition as taxonomic tool. Benefits regarding the identification of cryptic species and early signs of reproductive isolation are then discussed, giving examples from studies of taxonomy, behaviour and biosynthesis. For taxonomic characters to reliably indicate species boundaries, their limitations need to be known. Potential problems caused by environmental effects, intra‐species variation in profiles and other technical issues are highlighted, and suggestions are made regarding their avoidance. It remains a challenge to determine the variation beyond which two species can be called independent; a problem shared by most methods of delimitation. Recently, there has been a shift towards using a combination of different taxonomic tools, both molecular and non‐molecular, to test observed species differences.     

一株嗜酸硫氧化菌的分离

从江西德兴分离得到一株嗜酸硫氧化杆菌DX-2,采用双层固体培养基进行分离纯化,对分离菌株进行了形态、生理生化特性研究及16SrRNA序列分析.该菌株为革兰氏阴性细菌,短杆状,菌体大小（0.4～0.5）μm×（1～2）μm,化能自养,可利用硫磺和硫代硫酸盐为能源生长,不能利用亚铁进行生长.以16SrRNA序列同源性为基础构建了相关种属在内的系统发育树,结果表明,DX-2与喜温硫杆菌（Acidithiobacillus caldus）处于同一进化树分支中,相似性达99%以上.考察了不同重金属离子对DX-2的生长的影响.     

Experimental interspecific hybridization in Daphnia

Hybridization is a common phenomenon in Daphnia (Cladocera; Anomopoda); interspecific hybrids have been found between several species and hybrids are found in many European lakes. Although much information on the morphology, ecology and genetics of hybrids is available, little is known about the level of reproductive isolation among species or about the relative fitness of hybrids and parental species. In order to facilitate studies on differentiation and speciation processes and comparative experimental studies on hybrids and recombinant genotypes, we present the first successful laboratory crossing experiments of two different Daphnia species, D. galeata and D. cucullata. Males and sexual females from two D. galeata and two D. cucullata clones were reciprocally crossed, juveniles hatched from resting eggs and reared until maturity. Hatching and juvenile survival rates of hybrids were relatively low (12.1% and 24%, respectively). D. galeata and D. cucullata clones vary in their level of successful interspecific matings and in the number of subsequent offspring. In general, hybrid crosses between D. cucullata females and D. galeata males were more successful than reciprocal crosses.