Chitosanases from Family 46 of Glycoside Hydrolases: From Proteins to Phenotypes

Chitosanases, enzymes that catalyze the endo-hydrolysis of glycolytic links in chitosan, are the subject of numerous studies as biotechnological tools to generate low molecular weight chitosan (LMWC) or chitosan oligosaccharides (CHOS) from native, high molecular weight chitosan. Glycoside hydrolases belonging to family GH46 are among the best-studied chitosanases, with four crystallography-derived structures available and more than forty enzymes studied at the biochemical level. They were also subjected to numerous site-directed mutagenesis studies, unraveling the molecular mechanisms of hydrolysis. This review is focused on the taxonomic distribution of GH46 proteins, their multi-modular character, the structure-function relationships and their biological functions in the host organisms.     

Levels of domestication in fish: implications for the sustainable future of aquaculture

The agricultural world today is dominated by a few domesticated mammal species, that is, animals modified from their wild ancestors through selective breeding in captivity for traits beneficial to human usages. As a result, a clear dichotomy exists between wild (from hunting) and domesticated mammals (produced in farms) used for human consumption. Similar to agriculture, aquaculture is often viewed as the only solution that can provide more fish products given that harvesting wild stocks have reached an upper limit. Aquaculture is considerably younger than agriculture relying on natural sources to farm numerous species. To better describe the diverse strategies for fish production, we propose a new classification comprising five levels of ‘domestication’ with 1 being the least to 5 being the most domesticated. Our classification places 70% of the 250 farmed finfish species recorded in the 2009 FAO database into levels 1, 2 and 3 representing a transitory form of fish production dependent on the availability of the wild resource. In contrast, only a few species, or more accurately populations, can be considered truly domesticated, similar to cattle or sheep. Based on this classification, two scenarios for the future of aquaculture are discussed: either the industry focuses on few truly domesticated species, similar to the path taken by agriculture, but avoiding its negative impacts or aquaculture proceeds with inter‐specific diversification by focusing primarily on the domestication of native species.     

Elective Caesarean Operation in the Bitch Using Aglepristone Before the Pre-Partum Decline in Peripheral Progesterone Concentration

The aim of this study was to investigate caesarean operation (CO) undertaken before the pre-partum decrease of progesterone but following administration of a progesterone receptor antagonist and to evaluate the innocuity of this procedure for the dam and pups. Thirty seven bitches of 15 different breeds, received an injection of 15 mg/kg aglepristone 59 or 60 days after the estimated day of ovulation, determined by progesterone quantitative assays, and caesarean section (CS) was performed between 20 and 24 h after administration. Progesterone remained above 6 nmol/l at the time of CS (mean = 15.75, SD = 3.84). No post-operative clinical complications were reported in any of the bitches. All bitches were able to nurse and feed their puppies in the first 24 h following surgery. No pups showed any signs of prematurity and 5 out of 188 pups (2.6) died in the first 2 weeks after delivery. This small study demonstrates that a CS may be safely and successfully performed an average of 2 days before the expected date of parturition following the administration of aglepristone, without any harmful consequence for the dam and her neonates.     

Development of two microsatellite multiplex PCR systems for high throughput genotyping in Populus euphratica

Eighteen microsatellite primer pairs previously developed at Oak Ridge National Laboratory for Populus tremuloides Michx. and Populus trichocarpa Torr. & Gray were screened for amplification in Euphrates poplar, Populus euphratica Oliv. Thirteen loci were found to express polymorphisms ranging from two to 17 alleles. The eight most variable loci were selected to set up and optimize two multiplex polymerase chain reaction (PCR) assays. Three populations containing altogether 436 trees were used to characterize the selected loci and ascertain their applicability for parentage analysis and genotyping studies. Through cross-checking of clonal identity against sex of the genotyped trees we estimated the maximum error rate for merging genotypes to be less than 0.045. Foundation project: This study was supported by the Deutsche Forschungsgemeinschaft DFG (grant number SCHN 1080/1-1)     

两种微卫星多样PCR系统应用于胡杨高效生产基因型

对已在橡树岭国家实验室建立起来的美洲山杨(Populus tremuloides Michx.)和毛果杨(Populus trichocarpa Torr.＆ Gray)18个微卫星引物进行筛选,用于胡杨相关基因的扩增.发现有13个基因位点可以表达基因多态性,范围是2～17个等位基因.选择了8个最易变的基因位点,来构建和优化2种多样PCR法.用来自3个种群的436株树木表征选择的位点,确定他们在亲缘关系分析、基因型研究的适用性.通过克隆基因型鉴定树木性别的交叉检验,我们估计并入基因型最大误差率小于O.045.     

Antibacterial activity in microalgae cultures

Five cultures of microalgae (Chlorella minutissima, Tetraselmis chui, Nannochloropsis sp., Arthrospira platensis and Isochrysis sp.) with no culturable bacteria were tested for their ability to inhibit the growth of six Vibrio bacterial strains (V. parahaemolyticus, V. anguillarum, V. splendidus, V. scophthalmi, V. alginolyticus and V. lentus). The influence of light on the antibacterial activity of the microalgae was investigated. All microalgae cultures inhibited the growth of bacteria compared with the control treatments (P < 0.05), and their antibacterial activity was not influenced by the presence or absence of light. In the control groups, the numbers of bacteria increased exponentially during the experimental period in the absence of microalgae cells demonstrating that the bacterial cells were able to utilize the growth medium of microalgae cultures. The present results may explain the low levels or absence of Vibrio strains in microalgae cultures, and the positive effect of addition of microalgae in rearing of fish larvae, and implicate the production of antibacterial compounds by microalgae cells.     

PESO: a modelling framework to help improve management strategies for epidemics – application to sharka

The optimization of management strategies for plant diseases is a difficult task because of the complexity and variability of epidemic dynamics. Thanks to their ability to numerically simulate many scenarios, models can be used to estimate epidemiological parameters, assess the effectiveness of different management strategies and optimize them. This article presents the PESO (parameter estimation–simulation–optimization) modelling framework to help improve plant disease management strategies. This framework is based on (i) the characterization of the epidemic dynamics to estimate key epidemiological parameters, (ii) the use of spatially explicit models to simulate epidemic dynamics and disease management, and (iii) the use of numerical optimization methods to identify better management strategies. This approach is generic and can be applied to many diseases. The work presented here focuses on sharka (caused by Plum pox virus), which has a worldwide impact on the Prunus industry, and is associated with huge disease management costs in many countries, especially in France.     

Patient characteristics influencing the variability of distributed parameter‐based models in DCE‐CT kinetic analysis

Kinetic parameter variability may be sensitive to kinetic model choice, kinetic model implementation or patient‐specific effects. The purpose of this study was to assess their impact on the variability of dynamic contrast‐enhanced computed tomography (DCE‐CT) kinetic parameters. A total of 11 canine patients with sinonasal tumours received high signal‐to‐noise ratio, test‐double retest DCE‐CT scans. The variability for three distributed parameter (DP)‐based models was assessed by analysis of variance. Mixed‐effects modelling evaluated patient‐specific effects. Inter‐model variability (CV_inter) was comparable to or lower than intra‐model variability (CV_intra) for blood flow (CV_inter:[4–28%], CV_intra:[28–31%]), fractional vascular volume (CV_inter:[3–17%], CV_intra:[16–19%]) and permeability‐surface area product (CV_inter:[5–12%], CV_intra:[14–15%]). The kinetic models were significantly (P<0.05) impacted by patient characteristics for patient size, area underneath the curve of the artery and of the tumour. In conclusion, DP‐based models demonstrated good agreement with similar differences between models and scans. However, high variability in the kinetic parameters and their sensitivity to patient size may limit certain quantitative applications.     

Removal of Phenolic Compounds from Aqueous Solutions Using Sludge-Based Activated Carbons Prepared by Conventional Heating and Microwave-Assisted Pyrolysis

Sludge-derived activated carbons (ACs) were prepared by conventional heating and microwave pyrolysis. The ACs were characterized using several analytical and functional techniques and used for removal of six phenolic compounds from aqueous solutions. The adsorbents exhibited similar features and possessed hydrophobic surfaces. The ACs were assigned mesoporous materials, with specific surface areas of up to 641 and 540 m² g^?1 for CAC-500 and MAC-980, respectively. The preliminary results indicated that phenol removal onto the ACs increased in the order: m-cresol?<?phenol?<?o-cresol?<?2-chrorophenol?<?2-nitrophenol?<?hydroquinone. Hydroquinone exhibited the highest adsorption capacity and was chosen to continue the remaining part of the experimental work—kinetic and isothermal studies. The adsorption kinetic and isotherm data were well described by the Avrami fractionary order and Redlich–Peterson models, respectively. The maximum amounts (Q _max) of hydroquinone adsorbed at 25 °C were too high, reaching 1218.3 and 1202.1 mg g^?1 for CAC-500 and MAC-980, respectively. The mechanism of adsorption was proposed in this work, and it was suggested that donor–acceptor complex and π–π interactions play major roles in the adsorption process. The adsorbents were also tested on simulated effluents. The two ACs displayed good efficiency for the treatment of industrial simulated effluents.     

Determinants of fenhexamid effectiveness against grey mould on grapevine: Respective role of spray timing,fungicide resistance and plant defences

Botrytis bunch rot of grapes is mainly controlled by applying fungicides at three crop growth stages: the end of flowering (BBCH 68), bunch closure (BBCH 77) and the beginning of veraison (BBCH 81). The hydroxyanilide derivative fenhexamid is among the most effective fungicides registered to control Botrytis cinerea. Its effectiveness was examined in relation to spray timing, fungicide resistance and defense responses of grapevine. Overall, the earlier fenhexamid was applied, the more effective it was at controlling B. cinerea. Frequencies of B. cinerea strains which were resistant to fungicides were evaluated at harvest. The frequencies of resistant phenotypes were similar among treatments and years with the exception of a class of multidrug resistant strain (MDR 2) whose frequency appeared to increase after fenhexamid applications. If current spray programs including fenhexamid appear to control bunch rot at the current MDR frequency, a propagation of MDR 2 strains might lead to a decline in disease control. Finally, defense responses were studied in grapevine flowers/berries following fenhexamid application. None of the defense processes tested was induced in flowers/berries at stages 68 and 77. Only an increase in chitinase activity was observed in treated-berries at stage 81, suggesting that fenhexamid effectiveness was not related to a stimulation of defense responses.