环纹矮柳(杨柳科)的后选模式指定及形态描述订正

环纹矮柳(Salix annulifera C. MarquandAiry Shaw)的模式标本材料F. K. Ward 5870包括2个完全不同的种。根据深圳法规的相应条款,在此指定F. K. Ward 5870 (K-000335077)为S. annulifera的后选模式;将F. K. Ward 5870 (K-000335083)从S. annulifera中排除,并鉴定为藏南柳(S. austrotibetica N. Chao)。此外,对环纹矮柳的形态描述进行了相应的订正。     

A taxonomic study of Salix section Cordatae subsection Luteae (Salicaceae)

Salix sectionCordatae subsectionLuteae includes 10 taxa and occurs in most of North America. The taxa are here treated as four species, one with six varieties and another with two varieties. Six new combinations are proposed underSalix eriocephala.     

Anti-pathogenic Potential of Coral Associated Bacteria Isolated from Gulf of Mannar Against Pseudomonas aeruginosa

Infections of Pseudomonas aeruginosa are of great concern because of its increasing resistance towards conventional antibiotics. Quorum sensing system of P. aeruginosa acts as a global regulator of almost all the virulence factors and majorly its biofilm formation. In the present study, quenching of QS system of P. aeruginosa has been explained with bioactives from bacteria associated with the coral Acropora digitifera. Isolated bioactives inhibited the expression of various virulence traits of P. aeruginosa like biofilm formation, and the production of extracellular enzymes like protease and elastase. This study also emphasises the potential of coral associated bacteria in producing bioactive agents with anti-pathogenic properties.     

Pathogenic fungal dynamics in a fall population of the blackmargined aphid (Monellia caryella)

A fall population of the blackmargined aphid, Monellia caryella (Fitch) (Homoptera: Aphididae), was monitored daily for mortality caused by fungi and parasitoids. Three species of Entomophthorales fungi were found. Fungal-induced mortality was found to be correlated with minimum temperature. During the period when the minimum temperature was consistently above 8°C, fungal-induced mortality was positively correlated with the sum of hours of leaf-wetness on days 5, 6, and 7 before sampling. Parasitoid wasps killed fewer hosts than fungi and were not affected by environmental factors.

---

Résumé La mortalité quotidienne provoquée par des parasitoïdes et des champignons sur une population automnale de M. caryella Fitch (Homopt. Aphididae) a été suivie à Byron (Géorgie, USA), avec enregistrement de la température, de la pluie et de l'humidité des feuilles. 3 espèces de champignons entomophthorales ont été trouvées: Neozygites sp., Entomophthora planchoniana et Erynia sp. 54% des pucerons morts étaient contaminés par Neozygites et 46% par E. planchoniana. Seuls 2 pucerons avaient été tués par Erynia sp. Les taux de mortalité quotidienne par champignons s'élevaient après les périodes pluvieuses et d'humidité des feuilles. La mortalité due au parasitisme était inférieure à la mortalité due aux champignons et ne semblait pas liée aux conditions écologiques. La discussion porte sur l'importance de la mortalité provoquée par les champignons sur la dynamique de la population de pucerons.

     

乙酰化修饰在嗜肺军团菌致病过程中的作用

乙酰化修饰是由乙酰基转移酶、去乙酰化酶介导的可逆的蛋白质翻译后修饰。其中,乙酰基转移酶将乙酰辅酶A的乙酰基团转移至底物蛋白的氨基酸残基,而乙酰基团的去除由去乙酰化酶完成。乙酰化修饰参与许多基本生物学过程的调节作用,越来越多的研究表明,蛋白质乙酰化修饰在病原菌的致病过程中具有重要作用。病原菌,如引起非典型性肺炎的嗜肺军团菌,可以通过分泌具有乙酰基转移酶活性的效应蛋白靶向宿主细胞信号通路的关键蛋白质因子,干扰宿主细胞信号通路及免疫反应。本文主要从嗜肺军团菌的致病机制、乙酰化修饰及乙酰化修饰在病原体致病过程中的调控作用进行综述,突出已知的乙酰化毒力蛋白的例子,并讨论它们如何影响与宿主的相互作用,为理解乙酰化修饰在嗜肺军团菌致病过程中的作用机制提供参考。     

A taxonomic study of Salix sections Mexicanae and Viminella subsection Sitchenses (Salicaceae) in North America

The recently recognized western North American sectionsBrewerianae, Mexicanae, andSitchenses in the genusSalix were studied in the field and herbarium. SectionsSitchenses andBrewerianae are here combined and placed under sectionViminella as a subsection. Three species and an additional variety are recognized in subsectionSitchenses and seven species are recognized in sectionMexicanae. Keys for identification and distribution maps are provided.     

Experimental Exposures of Boreal Toads (Bufo boreas) to a Pathogenic Chytrid Fungus (Batrachochytrium dendrobatidis)

One of the major causes of worldwide amphibian declines is a skin infection caused by a pathogenic chytrid fungus (Batrachochytrium dendrobatidis). This study documents the interactions between this pathogen and a susceptible amphibian host, the boreal toad (Bufo boreas). The amount of time following exposure until death is influenced by the dosage of infectious zoospores, duration of exposure, and body size of the toad. The significant relation between dosage and the number of days survived (dose-response curve) supports the hypothesis that the degree of infection must reach a particular threshold of about 10⁷–10⁸ zoosporangia before death results. Variation in air temperature between 12°C and 23°C had no significant effect on survival time. The infection can be transmitted from infected to healthy animals by contact with water containing zoospores; no physical contact between animals is required. These results are correlated with observations on the population biology of boreal toads in which mortalities associated with B. dendrobatidis have been identified.     

Presence of myelin-like structures in tanniferous vascular parenchyma cells ofSalix dasyclados Wim.

Summary In the cambial region ofSalix dasyclados plants, extensive spherical formations of myelin-like lamellar configurations were found during the transit period between winter dormancy and reactivation of growth in early spring. The lamellar structures occurred in parenchyma cells containing tannins and were associated with spherosomes. Cytomembranes in tannin-containing cells appeared with negative contrast on electron micrographs, indicating the presence of tanniferous substances in the cytoplasm.Abbreviation R_G relative growth rate (% fresh weight increase per day)     

Pathogenic potential of six isolates of entomopathogenic nematodes (Rhabditida: Steinernematidae) from Vietnam

The potential of six Steinernema isolates, isolated from different provinces in Vietnam, was evaluated in the laboratory against Galleria mellonella and Spodoptera littoralis. Steinernema sangi and S. robustispiculum TN24 had the highest penetration rate in both hosts according to a penetration rate assay. The virulence assay showed that S. sangi had a high virulence to both hosts and along with isolate TN38 it was the most mobile among the isolates tested. The migration of S. sangi in sand columns with an insect host at the bottom was significantly higher than in sand columns without insect host. This Steinernema species was the only one that penetrated a host in 24h after migrating 10cm in sand columns at 25°C. Moreover, a multiplication assay showed that S. sangi produced a high number of infective juveniles in G. mellonella. However, all Steinernema isolates tested had low multiplication rates in S. littoralis.     

Presence and behaviour of B-chromosomes in Acanthophyllum laxiusculum (Caryophyllaceae)

Two karyotypic variants were recognized in populations of Acanthophyllum laxiusculum Schiman-Czeika. Variant A had 2N = 30 and variant B showed the presence of 0 to 3 B-chromosomes in addition to 2N = 30 chromosomes. Analysis of chromosome behaviour at meiosis showed that the presence of B-chromosomes increases chiasma frequency in A-chromosomes; this effect was higher for plants with odd numbers of B-chromosomes compared with plants with even numbers of B-chromosomes. Comparisons of variants A and B, suggests that B-chromosomes have an effect pollen stainability and seed production. It seems that the presence of B-chromosomes may increase pollen stainability and seed production in variant B.     

Inhibition of <Emphasis Type="Italic">Vibrio</Emphasis> biofilm formation by a marine actinomycete strain A66

China remains by far the largest aquaculture producer in the world. However, biofilms formed by pathogenic Vibrio strains pose serious problems to marine aquaculture. To provide a strategy for biofilm prevention, control, and eradication, extracts from 88 marine actinomycetes were screened. Thirty-five inhibited the biofilm formation of Vibrio harveyi, Vibrio vulnificus, and Vibrio anguillarum at a concentration of 2.5% (v/v). Thirty-three of the actinomycete extracts dispersed the mature biofilm. Six extracts inhibited the quorum-sensing system of V. harveyi by attenuating the signal molecules N-acylated homoserine lactones’ activity. Strain A66, which was identified as Steptomyces albus, both attenuated the biofilms and inhibited their quorum-sensing system. It is suggested that strain A66 is a promising candidate to be used in future marine aquaculture.     

Regulation of CaCO(3) formation in coccolithophores

Coccolithophores impact the ocean carbon cycle principally through the generation of CO₂ during CaCO₃ production. Coccolithophore biomineralization has been examined most extensively in Pleurochrysis carterae and Emiliania huxleyi both of which produce mineralized scales—coccoliths—composed of elaborate calcite crystals attached to an underlying organic base plate. Calcification of preformed base plates is mediated by acidic polysaccharides and occurs in Golgi-derived structures known as mineralizing vesicles. In Pleurochrysis a high capacity calcium-binding polysaccharide PS2 is required for efficient nucleation of calcitic protocrystals. A galacturonomannan PS3 is required for the growth and transformation of the protocrystals into a massive double disc of calcite. The genes that regulate expression of the glycans have not yet been identified. In addition to the coccolith-bearing diploid phases, Pleurochrysis and Emiliania possess both haploid and diploid non-calcifying stages, which are self-perpetuating via binary fission. One non-calcifying Pleurochrysis phase fails to synthesis PS2 and spontaneously reverts to the mineralizing morphotype in laboratory cultures. As yet, there is little information on environmental factors that effect the expression or silencing of calcifying genes or favor the growth of calcifying over non-calcifying phases. These issues will need extensive investigation, if we are to appreciate the role of coccolithophores in the regulation of atmospheric CO₂ levels.     

Presence of sporangia of Frankia in the rhizosphere of Discaria (Rhamnaceae)

Discaria trinervis and Discaria americana are native actinorhizal plants in Argentina. Discaria seedlings growing in N-free liquid culture, inoculated with dry soils, developed Frankia colonies in the rhizosphere. The occurrence of hyphae, vesicles and sporangia characteristic of Frankia are described in these colonies. The presence of sporangia of Frankia has previously neither been reported in the genus Discaria, nor in the other genera of the tribe Colletieae inside root nodules or outside roots. The infective capacity of the colonies has been demonstrated.     

神经系统特异表达基因调控机理的研究进展

神经系统特异性基因正确的时空表达受细胞内外信号的调控,信号传导途径最终的靶位点是能结合特异转录因子的DNA序列.目前发现的决定神经系统基因特异性表达的顺式作用元件既有增强子,也有沉默子.它们可以特异性地增强基因在神经系统的表达,或特异性抑制基因在非神经系统的表达. 顺式元件要发挥这些作用,依赖于与其结合的反式因子,而这些反式因子又能与其他蛋白质或DNA序列发生互动, 通过协调作用,共同决定基因的时空表达顺序.     

Indole Affects Biofilm Formation in Bacteria

Biofilm is bacterial population adherent to each other and to surfaces or interfaces, often enclosed by a matrix. Various biomolecules contribute to the establishment of biofilms, yet the process of building a biofilm is still under active investigation. Indole is known as a metabolite of amino acid tryptophan, which, however, has recently been proved to participate in various aspects of bacterial life including virulence induction, cell cycle regulation, acid resistance, and especially, signaling biofilm formation. Moreover, indole is also proposed to be a novel signal involved in quorum sensing, a bacterial cooperation behavior sometimes concerning the biofilm formation. Here the signaling role and molecular mechanism of indole on bacterial biofilm formation are reviewed, as well discussed is its relation to bacterial living adaptivity.     

The Presence of Actinidin (Cysteine Protease) and Recombinant Plasmids Carrying the Actinidin Gene Influence the Growth of Saccharomyces Cerevisiae

Actinidin is a protease found abundantly in the fruit of Actinidia chinensis or Kiwi fruit. The overproduction of this protein in microorganisms, especially using the yeast Saccharomyces cerevisiae, would be economically valuable as it would simplify the extraction and purification of the protein. It was observed, however, that the yeast growth rate was reduced by the presence of externally supplied actinidin in the growth medium. It was also observed that actinidin present in the yeast growth medium was partially degraded. Several actinidin-encoding gene variants have been cloned in a yeast expression and secretion vector. It was observed that different actinidin gene constructions influenced the growth rate of S. cerevisiae in complete media. Recombinant plasmids carrying only the mature actinidin-encoding DNA sequences reduced yeast transformability significantly and had the least stability. The results thus suggest that the presence of a recombinant plasmid carrying a gene of a potentially toxic protein may result in a deleterious effect on the host cell.     

Pseudomonas aeruginosa quorum sensing molecule N-(3 oxododecanoyl)-l-homoserine lactone disrupts epithelial barrier integrity of Caco-2 cells

Acyl-homoserine lactone (HSL) quorum sensing molecules play an important role in regulation of virulence gene expression in Pseudomonas aeruginosa. Here, we show that 3O-C(12)-HSL can disrupt barrier integrity in human epithelial Caco-2 cells as evidenced by decreased transepithelial electrical resistance (TER), increased paracellular flux, reduction in the expression and distribution of ZO-1 and occludin, and reorganization of F-actin. P. aeruginosa 3O-C(12)-HSL activate p38 and p42/44 kinases, and inhibition of these kinases partly prevented 3O-C(12)-HSL-induced changes in TER, paracellular flux and expression of occludin and ZO-1. These findings demonstrate that P. aeruginosa 3O-C(12)-HSL can modulate tight junction integrity of Caco-2 cells.     

肠外致病性大肠杆菌致病机制及公共卫生学意义

致病性大肠杆菌包括肠致病性大肠杆菌(intestinal pathogenic Escherichia coli, IPEC)和肠外致病性大肠杆菌(extraintestinalpathogenicE.coli,ExPEC),可引起人和动物多种感染性疾病。ExPEC主要在肠道外其他组织脏器定殖并导致感染,包括尿道致病性大肠杆菌(uropathogenicE.coli, UPEC)、新生儿脑膜炎大肠杆菌(newborn meningitis E. coli, NMEC)和禽致病性大肠杆菌(avian pathogenic E. coli, APEC)。人源ExPEC (UPEC和NMEC)主要引起人尿道感染、肾盂肾炎和新生儿脑膜炎,而APEC可导致禽类的大肠杆菌病,造成家禽业的巨大经济损失。另外,乳腺致病性大肠杆菌(mammary pathogenic E. coli, MPEC)和猪源ExPEC可导致奶牛乳房炎、猪的肺炎及急性败血症等病症。研究发现,ExPEC类菌株在基因组结构上很相似,与IPEC本质区别在于致病机制不同,ExPEC具有很多相同的毒力基因和耐药基因,而且动物源ExPEC...