Les biofilms bactériens : leur importance en santé animale et en santé publique

Bacterial biofilms are structured communities of bacterial cells enclosed in a self-produced polymer matrix that is attached to a surface. Biofilms protect and allow bacteria to survive and thrive in hostile environments. Bacteria within biofilms can withstand host immune responses, and are much less susceptible to antibiotics and disinfectants when compared to their planktonic counterparts. The ability to form biofilms is now considered an attribute of many microorganisms. Diseases associated with biofilms require novel methods for their prevention, diagnosis and treatment; this is largely due to the properties of biofilms. Furthermore, the presence of biofilms on surfaces found at farms, slaughterhouses or food processing plants will have an impact on the efficacy of disinfection protocols. Surprisingly, biofilm formation by bacterial pathogens of veterinary or zoonotic importance has received relatively little attention. The objective of this brief Review article is to bring awareness about the importance of biofilms to animal health stakeholders.(Translated by the authors)     

Development of two types of calcium channels in cultured mammalian hippocampal neurons

Calcium influx through voltage-gated membrane channels plays a crucial role in a variety of neuronal processes, including long-term potentiation and epileptogenesis in the mammalian cortex. Recent studies indicate that calcium channels in some cell types are heterogeneous. This heterogeneity has now been shown for calcium channels in mammalian cortical neurons. When dissociated embryonic hippocampal neurons from rat were grown in culture they first had only low voltage-activated, fully inactivating somatic calcium channels. These channels were metabolically stable and conducted calcium better than barium. Appearing later in conjunction with neurite outgrowth and eventually predominating in the dendrites, were high voltage-activated, slowly inactivating calcium channels. These were metabolically labile and more selective to barium than to calcium. Both types of calcium currents were reduced by classical calcium channel antagonists, but the low voltage-activated channels were more strongly blocked by the anticonvulsant drug phenytoin. These findings demonstrate the development and coexistence of two distinct types of calcium channels in mammalian cortical neurons.     

世界粮食研究模型在黑龙江省作物产量预报中的应用

在现有研究成果的基础上，提出世界粮食研究（WOFOST）模型在黑龙江省四大作物产量预报应用中的参数分区处理方法，运用WOFOST的模拟产量和趋势产量对黑龙江省四大作物产量进行了预测分析。研究表明：该方法效果理想、可行，具有理论研究和实际应用价值，克服了只用一组参数在复杂气候区域进行作物产量模拟的局限性，拓宽了WOFOST模型在复杂气候条件下的应用领域。     

Comparative genome analysis between several tropical grasses

The availability of molecular markers allowed comparing genetic maps between distinct taxa. Among the Poaceae (grasses) family, species as divergent as rice, wheat and maize show collinearity within wide regions along the whole genome. This opens the way for the integration of knowledge across all grasses and the development of molecular tools of general interest using the simple genome of rice. Many agronomically important tropical grasses belong to two major sub-families. Comparisons between maize, sorghum and sugarcane, three members of the Andropogoneae tribe, are briefly reviewed. One example of a particular genome region is used for extending the comparison to rice and illustrating various applications of comparative genome mapping. This revised version was published online in July 2006 with corrections to the Cover Date.     

Evaluation of cassava (Manihot esculenta Crantz) germplasm collections using RAPD markers

Summary Deterioration of cotton, Gossypium hirsutum L., seed can adversely affect stands, seedling vigor, and subsequent performance of plants, but deterioration can be lessened by improved genetic resistance. This study was conducted to evaluate the relationship of physical and germination characteristics of cotton seed and to determine the inheritance of resistance to seed deterioration. Physical (weight, volume, density, and imbibition rate) and germination (germination of non-deteriorated seed and deteriorated seed) characteristics were determined for eight cotton genotypes. In addition, imbibition rate and the germination characteristics were determined for all possible F₁, including reciprocals, combinations of the eight genotypes. Variation among the parents for germination of deteriorated seed and imbibition rate were significantly, highly correlated (r=–0.97) and intrinsically related. Resistance to seed deterioration tended to increase as seed weight and volume decreased. Significant genetic effects were found for imbibition rate and germination of both non-deteriorated and deteriorated seed. However, general combining ability (GCA) accounted for only 21% of the variation in crosses sums of squares for germination of non-deteriorated seed. In contrast, GCA accounted for 90% of the variation for germination of deteriorated seed and imbibition rate. A breeding approach involving selection of early generation seed for ability to survive hot water treatment, then evaluating later generations for imbibition rate is suggested as a means to improve resistance to seed deterioration in cotton.     

Space heterogeneity,space use and short-range dispersal in Diptera: A case study

This study investigates the impact of landscape heterogeneity on community structure and population dynamics in two families of Diptera (Empididae and Chironomidae). Adult emergence is compared with aerial flow by means of emergence traps and yellow traps on a transect across four habitats (pond banks, woodland, grassland and heathland) in close proximity to each other. Empids use different space units according to their larval development, sexual behaviour and food requirements. This creates an intermingling of species and individuals originating from different habitats in the lowest part of the transect. Adult chironomids of aquatic species exhibit a preferential use of open habitats while adults with terrestrial larvae disperse largely above the four sites. Habitat fragmentation and heterogeneity lead to opposite patterns in chironomid distribution: some species disperse over the whole set of macrohabitats but others are confined to a single patch, resulting in population isolation. The impact of spatial and temporal landscape patterning is discussed with a view to community structure, life-history tactics and population dynamics.     

Theories and behavioural drivers underlying fleet dynamics models

In the domain of decision‐support tools for the management of marine fish resources, considerable attention has been paid to the development of models explaining how fish stocks change over space and time. In most models, fishing effort is assumed to be exogenous and determined by factors such as management. Increasingly, there has been a call for bio‐economic models to also account for the dynamics of fishing fleets, recognizing that fishers respond to changing environmental, institutional and economic conditions. A growing literature has sought to explicitly model the endogenous determinants of the capacity of fishing fleets, the intensity of its use and its temporal and spatial allocation across fishing opportunities. We review this literature, focusing on empirical applications of the behavioural models that have been put forward to explain and predict observed fleet dynamics. We find that although economic factors are usually included as a dominant driver in most studies, this is often based on the use of proxy variables for the key economic drivers, for which adequate data are lacking. Also, while many studies acknowledge that social and social–psychological factors play a significant role in explaining observed fishing behaviour, their inclusion in fishing fleet dynamic models is still very limited. Progress in this domain can only be achieved via the development of multidisciplinary research programmes focusing on applied quantitative analysis of the drivers of fishing fleet dynamics.     

Characterization of fungal pathogens (Diaporthe angelicae and D. eres) responsible for umbel browning and stem necrosis on carrot in France

A collection of 102 Diaporthe isolates was compiled from lesions on carrot, parsley and wild Apiaceae species in France from 2010 to 2014. Molecular typing based on ITS rDNA sequences resulted in the identification of 85 D. angelicae and 17 D. eres isolates. Based on sequences of the 3′ part of the IGS rDNA, intraspecific variability was analysed for 17 D. angelicae and 13 D. eres isolates from diverse plant species, locations in France, and plant tissues. The genetic diversity was greater for D. angelicae isolates than D. eres isolates. In vitro sensitivity of five D. angelicae and four D. eres isolates to each of nine fungicides was similar for isolates of both species, with a marked variation in fungicide sensitivity depending on the active ingredient. To assess the pathogenicity of D. angelicae and D. eres isolates on carrot, one isolate of each species was inoculated onto umbels in a controlled environment. Typical lesions were observed for both isolates. Carrot crop debris collected from a seed production field in France and placed in controlled conditions produced perithecia and ascospores typical of Diaporthe, that were further characterized molecularly as belonging to D. angelicae. Detection of Diaporthe species on seed lots from three carrot production fields in France was investigated. Both species were detected on seeds by conventional PCR assay, with a greater frequency for D. angelicae than D. eres (67% vs 33%, respectively). Overall, the results highlighted that umbel browning in carrot seed crops in France was mainly caused by D. angelicae.