Evidence of the Cost of the Production of Microcystins by Microcystis aeruginosa under Differing Light and Nitrate Environmental Conditions

The cyanobacterium Microcystis aeruginosa is known to proliferate in freshwater ecosystems and to produce microcystins. It is now well established that much of the variability of bloom toxicity is due to differences in the relative proportions of microcystin-producing and non-microcystin-producing cells in cyanobacterial populations. In an attempt to elucidate changes in their relative proportions during cyanobacterial blooms, we compared the fitness of the microcystin-producing M. aeruginosa PCC 7806 strain (WT) to that of its non-microcystin-producing mutant (MT). We investigated the effects of two light intensities and of limiting and non-limiting nitrate concentrations on the growth of these strains in monoculture and co-culture experiments. We also monitored various physiological parameters, and microcystin production by the WT strain. In monoculture experiments, no significant difference was found between the growth rates or physiological characteristics of the two strains during the exponential growth phase. In contrast, the MT strain was found to dominate the WT strain in co-culture experiments under favorable growth conditions. Moreover, we also found an increase in the growth rate of the MT strain and in the cellular MC content of the WT strain. Our findings suggest that differences in the fitness of these two strains under optimum growth conditions were attributable to the cost to microcystin-producing cells of producing microcystins, and to the putative existence of cooperation processes involving direct interactions between these strains

The identification of a new genotype of avian paramyxoviruses type I in West-Africa provides new outcomes for phylogeny reconstruction

International audienc

Final Report of the ModSysC2020 Working Group - Data, Models and Theories for Complex Systems: new challenges and opportunities

Final Report of the ModSysC2020 Working Group at University Montpellier 2At University Montpellier 2, the modeling and simulation of complex systems has been identified as a major scientific challenge and one of the priority axes in interdisciplinary research, with major potential impact on training, economy and society. Many research groups and laboratories in Montpellier are already working in that direction, but typically in isolation within their own scientific discipline. Several local actions have been initiated in order to structure the scientific community with interdisciplinary projects, but with little coordination among the actions. The goal of the ModSysC2020 (modeling and simulation of complex systems in 2020) working group was to analyze the local situation (forces and weaknesses, current projects), identify the critical research directions and propose concrete actions in terms of research projects, equipment facilities, human resources and training to be encouraged. To guide this perspective, we decomposed the scientific challenge into four main themes, for which there is strong background in Montpellier: (1) modeling and simulation of complex systems; (2) algorithms and computing; (3) scientific data management; (4) production, storage and archiving of data from the observation of the natural and biological media. In this report, for each theme, we introduce the context and motivations, analyze the situation in Montpellier, identify research directions and propose specific actions in terms of interdisciplinary research projects and training. We also provide an analysis of the socio-economical aspects of modeling and simulation through use cases in various domains such as life science and healthcare, environmental science and energy. Finally, we discuss the importance of revisiting students training in fundamental domains such as modeling, computer programming and database which are typically taught too late, in specialized masters

ProAKAP4 Semen Concentrations as a Valuable Marker Protein of Post-Thawed Semen Quality and Bull Fertility : a Retrospective Study

Functional sperm quality markers to predict bull fertility have been actively investigated. Among them, proAKAP4, which is the precursor of AKAP4, the main structural protein in the fibrous sheath of spermatozoa; appears to be promising, especially since spermatozoa lacking AKAP4 expression were shown to be immotile, abnormal, and infertile. In this study, the objective was to evaluate proAKAP4 concentration values with the classic sperm motility descriptors and fertility outcomes (NRR at 90 days) in post-thawed conditions of 10 bulls' semen. ProAKAP4 expression was confirmed by Western blotting and proAKAP4 concentrations were determined by ELISA. Variations in proAKAP4 concentrations were observed independently of the motility sperm descriptors measured using computer-assisted semen analysis (CASA). A ProAKAP4 concentration of 38.67 ± 8.55 ng/10 million spermatozoa was obtained as a statistical mean of all samples. Threshold values of proAKAP4 were then determined between 19.96 to 96.95 ng/10 million spermatozoa. ProAKAP4 concentrations were positively correlated with progressive motility and the linearity coefficient. The sperm showing the lowest progressive motility were the samples exhibiting proAKAP4 concentrations below 20 ng/10 million spermatozoa. Furthermore, proAKAP4 concentrations were significantly higher in bulls with a higher NRR in the field. Our results demonstrate a correlation between the semen concentration of proAKAP4 and NRR-90d (p = 0.05) in post-thawed bull semen, highlighting the potential of proAKAP4 as a predictive marker of bull fertility

Analyse μ-structurale du fil électrode en soudage MIG-MAG : Cas des mélanges Ar-CO2 et Ar-O2

L’étude réalisée porte sur l’influence de la nature et de la proportion de gaz actif dans le gaz de protection sur le comportement du soudage MIG-MAG en polarité inverse. Une analyse de la colonne d’arc par spectroscopie optique d’émission et imagerie rapide équipée d’un filtre interférentiel, complétée par une étude physico-chimique de l’extrémité du fil électrode par sonde de Castaing, MEB-EDX et DRX. Cela permet de formuler des hypothèses quant aux mécanismes mis en jeu concernant les phénomènes observés en régime spray sous Ar, Ar-CO2 et Ar-O2

Identification of a new reovirus causing tendinitis in broilers in France

Clinical cases of tendinitis have appear sporadically and then more regularly in broilers flocks among different regions in France since 2010. These tendinitis have been identified as a consequence of Reovirus infection despite the vaccination of breeders stock with vaccines containing different strains of Reovirus previously described in the field ; additionnally an horizontal transmission, especially at the time of hatch, has been observed. Virological studies conducted in two laboratories lead to the identification of a new type of Reovirus non described in Europe until now. In addition to genetic differences between this new virus and the vaccine strains used on the field, cross seroneutralisation tests have shown antigenic differences which could explain the inefficacy of the vaccines used in the field. In order to prevent the multiplication of theses viruses it seems usefull to update the composition of vaccines for a better protection of breeders and their progenyDes cas cliniques de tendinite sont apparus sporadiquement, puis plus régulièrement, dans des élevages de poulets de chair dans différentes régions de France depuis 2010. Ces tendinites ont été identifiées comme dues à une réovirose en dépit de la vaccination des poules parentales avec des vaccins contenant différentes valences de réovirus précédemment décrits comme présents sur le terrain ; en outre une transmission horizontale notamment lors de l’éclosion a été observée. Les études virologiques conduites dans deux laboratoires aboutissent à l’identification d’un nouveau réovirus jusqu’à présent non décrit en Europe. Outre des différences au plan génétique entre ce nouveau virus et les souches vaccinales utilisées sur le terrain, des tests de séroneutralisation croisée ont montré des différences antigéniques, ce qui peut expliquer l’inefficacité des vaccins observée sur le terrain. Pour prévenir la multiplication de ces virus il apparait donc utile de réactualiser la composition des vaccins de manière à protéger les poules reproductrices et leur descendanc