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51.
Hajar Ben Moussa Jacques Pédron Nicole Hugouvieux-Cotte-Pattat Marie-Anne Barny 《Environmental microbiology》2023,25(11):2465-2480
Historically, research on Soft Rot Pectobacteriacea (SRP) has focused on economically important crops and ornamentals and knowledge of these bacteria outside the plant context remains poorly investigated. Recently, two closely related species Pectobacterium aquaticum and Pectobacterium quasiaquaticum were isolated from water and have not been isolated from any plant yet. To identify the distinctive characteristics of these two species, we performed a comparative genomic analysis of 80 genomes representing 19 Pectobacterium species and performed an evolutionary reconstruction. Both water species underwent a reduction in genome size associated with a high pseudogene content. A high gene loss was predicted at the emergence of both species. Among the 199 gene families missing from both P. aquaticum and P. quasiaquaticum genomes but present in at least 80% of other Pectobacterium genomes, COG analysis identified many genes involved in nutrient transport systems. In addition, many type II secreted proteins were also missing in both species. Phenotypic analysis revealed that both species had reduced pectinolytic activity, a biofilm formation defect, were highly motile and had reduced virulence on several plants. These genomic and phenotypic data suggest that the ecological niche of P. aquaticum and P. quasiaquaticum may differ from that of other Pectobacterium species. 相似文献
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53.
Moussa Douno Emmanuel Asampong NFaly Magassouba Elisabeth Fichet-Calvet Marí Sez Almudena 《PLoS neglected tropical diseases》2021,15(3)
As a consequence of the Ebola outbreak, human–animal contact has gained importance for zoonotic transmission surveillance. In Faranah (Upper Guinea), daily life is intertwined with rodents, such as the Natal multimammate mouse, Mastomys natalensis; a reservoir for Lassa virus (LASV). However, this contact is rarely perceived as a health risk by residents, although Lassa fever (LF) is known to be endemic to this region. Conversely, these observations remain a great concern for global health agendas. Drawing on ethnographic research involving interviews, focus group discussions, participant observations, and informal discussions over four months, we first identified factors that motivated children to hunt and consume rodents in Faranah villages, and thereafter, explored the knowledge of LF infection in children and their parents. Furthermore, we studied two dimensions of human-rodent encounters: 1) space-time of interaction and 2) factors that allowed the interaction to occur and their materiality. This approach allowed us to contextualize child-rodent contacts beyond domestic limits in the fallow fields, swamps, and at other times for this practice. A close look at these encounters provided information on rodent trapping, killing, and manipulation of cooking techniques and the risk these activities posed for the primary transmission of LASV. This research facilitated the understanding of children’s exposure to M. natalensis during hunting sessions and the importance of rodent hunting, which is a part of their boyish identity in rural areas. Determination of when, where, why, and how children, rodents, and environments interacted allowed us to understand the exposures and risks important for human and animal surveillance programs in the Lassa-endemic region. 相似文献
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55.
Rock art provides new evidence on the biogeography of kudu (Tragelaphus imberbis), wild dromedary,aurochs (Bos primigenius) and African wild ass (Equus africanus) in the early and middle Holocene of north‐western Arabia 下载免费PDF全文
56.
Jiafang Xu Moussa Camara Jinxiang Liu Lin Peng Rui Zhang Tingji Ding 《Molecular simulation》2017,43(8):575-589
Over the last two decades, the swelling properties of montmorillonite (MMT) have been studied in many experimental and simulation works, but less attention has been given to MMT containing a mixture of monovalent/monovalent and monovalent/bivalent cations in the interlayer spaces. We carried out a molecular dynamics simulation of the swelling patterns of Na-, Mg-, Na/Cs-, Na/Mg-MMT in an isobaric isothermal ensemble (NPT) at T = 300 K and p = 1 atm. The simulation reproduced a swelling pattern of Na-, Mg-, Na/Cs-, Na/Mg-MMT and the swelling curves obtained showed the difference between the hydration mechanisms of the type of MMT used in this study. We also found out that the differences in size and hydration energy of Na, Cs and Na, Mg ions have strong implications on the structure of interlayer water. This has led to the difference in the swelling curves of the simulated Na-, Mg-, Na/Cs- and Na/Mg-MMT. For Na/Cs-MMT, the hydration energy of Na cations increased compared to that in Na-MMT, the hydration energy of Cs cations decreased in Na/Cs-MMT compared to that in Cs-MMT and also for Na/Mg-MMT, the hydration energy of Na cations increased compared to that in Na-MMT and that of Mg cations decreased in comparison with that in Mg-MMT. The diffusion coefficient of Cs cations obtained in this simulation was higher than that of Mg and Na cations in Cs-, Mg- and Na-MMT, respectively. Cesium cations have been seen to have a low hydration energy compared to Na and Mg cations and can be used as a good inhibitor of Na-MMT swelling process. 相似文献
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58.
Marwen Moussa Vincent Espinasse Jean-Marie Perrier-Cornet Patrick Gervais 《Applied microbiology and biotechnology》2009,85(1):165-174
We investigated the influence of cell hydration on the ability of Saccharomyces cerevisiae CBS 1171 to withstand extreme hydrostatic pressure in order to determine the mechanisms involved in cell resistance. Hydration
conditions were modified in two different ways. We first modulated the chemical potential of water by adding glycerol in cell
suspensions. Another procedure consisted in dehydrating cells aerobically and immersing them in perfluorooctane, an innocuous
hydrophobic liquid used as a pressure-transmitting medium, prior to pressure treatments. This original method made it possible
to transmit isostatic pressure to yeast powders without changing the initial water activity (a
w) level at which cells had been equilibrated. The a
w ranged between 0.11 and 0.99. Pressure treatments were applied at levels of up to 600 MPa for 10 min, 24 h, and 6 days. The
dehydration of cells was found to strongly limit, or even prevent, cell inactivation under pressure. Notably, cells suspended
in a water–glycerol mixture with a
w levels of 0.71 or below were completely protected against all pressure treatments. Moreover, cells dehydrated aerobically
survived for 6 days at 600 MPa even when a
w levels were relatively high (up to 0.94). We highlighted the crucial role of water content in determining cellular damage
under pressure. When water is available in a sufficient amount, high pressure induces membrane permeabilization, causing uncontrolled
mass transfers that could lead to death during a prolonged holding under pressure. Possible mechanisms of membrane permeabilization
are discussed. 相似文献
59.
The perturbation of the racemic equilibrium of luminescent D3 terbium(III) complexes with chelidamic acid (CDA), a hydroxylated derivative of 2,6-pyridine-dicarboxylic acid (DPA), by added chiral biomolecules such as L-amino acids has been studied using circularly polarized luminescence and 13C NMR spectroscopy. It is shown in this work that the chiral-induced equilibrium shift of [Tb(CDA)3](6-) by L-amino acids (i.e. L-proline or L-arginine) was largely influenced by the hydrogen-bonding networks formed between the ligand interface of racemic [Tb(CDA)3](6-) and these added chiral agents. The capping of potential hydrogen-bonding sites by acetylation in L-proline led to a approximately 100-fold drop in the induced optical activity of the [Tb(CDA)3](6-):N-acetyl-L-proline system. This result suggested that the hydrogen-bonding networks serve as the basis for further noncovalent discriminatory interactions between racemic [Tb(CDA)3](6-) and added L-amino acids. 相似文献
60.
Quantification of Key Genes Steering the Microbial Nitrogen Cycle in the Rhizosphere of Sorghum Cultivars in Tropical Agroecosystems 总被引:2,自引:0,他引:2
Brigitte Hai Ndeye Hélène Diallo Saidou Sall Felix Haesler Kristina Schauss Moussa Bonzi Komi Assigbetse Jean-Luc Chotte Jean Charles Munch Michael Schloter 《Applied and environmental microbiology》2009,75(15):4993-5000
The effect of agricultural management practices on geochemical cycles in moderate ecosystems is by far better understood than in semiarid regions, where fertilizer availability and climatic conditions are less favorable. We studied the impact of different fertilizer regimens in an agricultural long-term observatory in Burkina Faso at three different plant development stages (early leaf development, flowering, and senescence) of sorghum cultivars. Using real-time PCR, we investigated functional microbial communities involved in key processes of the nitrogen cycle (nitrogen fixation, ammonia oxidation, and denitrification) in the rhizosphere. The results indicate that fertilizer treatments and plant development stages combined with environmental factors affected the abundance of the targeted functional genes in the rhizosphere. While nitrogen-fixing populations dominated the investigated communities when organic fertilizers (manure and straw) were applied, their numbers were comparatively reduced in urea-treated plots. In contrast, ammonia-oxidizing bacteria (AOB) increased not only in absolute numbers but also in relation to the other bacterial groups investigated in the urea-amended plots. Ammonia-oxidizing archaea exhibited higher numbers compared to AOB independent of fertilizer application. Similarly, denitrifiers were also more abundant in the urea-treated plots. Our data imply as well that, more than in moderate regions, water availability might shape microbial communities in the rhizosphere, since low gene abundance data were obtained for all tested genes at the flowering stage, when water availability was very limited.Land degradation is one of the most serious threats to food production on the African continent. Soil erosion, nutrient depletion, low organic matter content, and unfavorable pH values are some of the reasons for a deficient soil fertility (30), mainly in Central African countries. Combined with high variability and irregular distribution of rainfall, these factors contribute to negative nutrient balances. For example, 4.4 million tons of nitrogen (N) are lost per year in African soils, but only 0.8 million tons are reapplied by fertilization (12, 34). Since nitrogen is a key nutrient determining the productivity of agroecosystems (7, 11, 43), it is of central importance to optimize the nitrogen balance in these countries, mainly by steering the genetic resources of soil microbes in a way that losses of applied nitrogen are minimized and biological nitrogen fixation is increased. The aim should be to obtain a highly efficient nitrogen turnover, with leaching of nitrate and losses of gaseous products such as nitrous oxide (N2O) or dinitrogen (N2) as low as possible.Despite the importance of this issue, not much data are available on microbial community structure and function related to the nitrogen cycle in agroecosystems of Central Africa, and scenarios from moderate climatic regions cannot simply be transferred to tropical agroecosystems. Furthermore, the few studies published thus far only investigated effects of agricultural management on a single process of the nitrogen turnover (18, 20, 32) and ignore the fact that nitrogen turnover is a network of closely interlinked processes.Therefore, we sought to investigate the effects of different fertilizer regimens on multiple transformation processes within the nitrogen cycle in agroecosystems from semiarid areas in Central Africa. We investigated nitrogen dynamics on a full-cycle approach, including the most important steps in well-aerated agricultural soils (nitrification, denitrification, and nitrogen fixation). We hypothesized that each fertilizer regimen results in typical abundance pattern of the functional populations. While in moderate agroecosystems the plant (respectively, the plant development stage and the plant performance) plays an important role in shaping microbial community structure and function in the rhizosphere, we further postulated that nitrogen turnover and the corresponding populations are also influenced by the availability of water in semiarid soils. To test these hypotheses on a molecular basis, we quantified bacterial genes encoding the nitrogenase reductase (nifH), ammonia monooxygenase (amoA), and nitrite reductase (nirK and nirS), as well as archaeal amoA genes, by real-time PCR and linked the data to soil properties and grain yield. 相似文献