Publications by authors named "Philippe Constant"

The tomato brown rugose fruit virus (ToBRFV) poses a considerable threat to tomato production worldwide. Substantial experimental evidence supports the role of infected seeds as a contamination route, but the epidemiologic portrait of the virus has received less attention. This study reports the first survey of ToBRFV prevalence in commercial greenhouses.

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Objective: Evaluate the effects of five disinfection methods on bacterial concentrations in hospital sink drains, focusing on three opportunistic pathogens (OPs): Serratia marcescens, Pseudomonas aeruginosa and Stenotrophomonas maltophilia.

Design: Over two years, three sampling campaigns were conducted in a neonatal intensive care unit (NICU). Samples from 19 sink drains were taken at three time points: before, during, and after disinfection.

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Trees can play different roles in the regulation of fluxes of methane (CH), a greenhouse gas with a warming potential 83 times greater than that of carbon dioxide. Forest soils have the greatest potential for methane uptake compared to other land uses. In addition to their influence on soil CH fluxes, trees can act directly as a source or sink of CH, by transporting CH produced in the soil and harbouring the key microorganisms involved in CH production and consumption (methanogens and methanotrophs).

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Article Synopsis
  • - The study explores high-throughput short sequence typing (HiSST) methods to evaluate genetic similarities in bacterial isolates, particularly focusing on opportunistic pathogens and their links to environmental DNA profiling.
  • - Two HiSST schemes were developed using four specific genetic loci for each pathogen, allowing for precise differentiation without the need for traditional culturing methods.
  • - The effectiveness of these HiSST schemes was validated through in silico tests, comparisons with reference cultures, and practical application on environmental samples, enhancing the potential for improved epidemiological studies.
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High-affinity H2-oxidizing bacteria (HA-HOB) thriving in soil are responsible for the most important sink of atmospheric H2. Their activity increases with soil organic carbon content, but the incidence of different carbohydrate fractions on the process has received little attention. Here we tested the hypothesis that carbon amendments impact HA-HOB activity and diversity differentially depending on their recalcitrance and their concentration.

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Compelling evidence suggests a contribution of the sink environment to the transmission of opportunistic pathogens from the hospital environment to patients in neonatal intensive care units (NICU). In this study, the distribution of the opportunistic pathogen Serratia marcescens in the sink environment and newborns in a NICU was investigated. More than 500 sink drain and faucet samples were collected over the course of five sampling campaigns undertaken over 3 years.

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Microorganisms are informative biological integrators of past and present environmental abiotic and biotic conditions. At the same time, they are directly involved in ecosystem processes. Unfortunately, the complexity of microbial communities has so far resulted in most studies being descriptive.

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Previous studies have shown that it is possible to accurately predict wheat grain quality and yields using microbial indicators. However, it is uncertain what the best timing for sampling is. For optimal usefulness of this modeling approach, microbial indicators from samples taken early in the season should have the best predictive power.

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The integration of winter cover crop (WCC) in culture rotations promotes multiple ecosystem services, but concomitant microbial diversity and functioning responses in soil have received less attention. A field trial was established to test the hypothesis that enhanced crop diversity with the integration of WCC in a conventional maize-soy rotation promotes microbial diversity and the biological sink of H in soil, while reducing NO emissions to the atmosphere. Vicia villosa (hairy vetch), Avena sativa (oat), and Raphanus sativus (Daikon radish) were cultivated alone or in combinations and flux measurements were performed throughout two subsequent growing seasons.

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Crops yield and quality are difficult to predict using soil physico-chemical parameters. Because of their key roles in nutrient cycles, we hypothesized that there is an untapped predictive potential in the soil microbial communities. To test our hypothesis, we sampled soils across 80 wheat fields of the province of Quebec at the beginning of the growing season in May-June.

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Molecular typing methods are used to characterize the relatedness between bacterial isolates involved in infections. These approaches rely mostly on discrete loci or whole-genome sequencing (WGS) analyses of pure cultures. On the other hand, their application to environmental DNA profiling to evaluate epidemiological relatedness among patients and environments has received less attention.

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The saprophyte Pseudomonas aeruginosa is a versatile opportunistic pathogen causing infections in immunocompromised individuals. To facilitate its adaptation to a large variety of niches, this bacterium exploits population density-dependent gene regulation systems called quorum sensing (QS). In P.

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The microbiome composition of living organisms is closely linked to essential functions determining the fitness of the host for thriving and adapting to a particular ecosystem. Although multiple factors, including the developmental stage, the diet, and host-microbe coevolution have been reported to drive compositional changes in the microbiome structures, very few attempts have been made to disentangle their various contributions in a global approach. Here, we focus on the emerald ash borer (EAB), an herbivorous pest and a real threat to North American ash tree species, to explore the responses of the adult EAB gut microbiome to ash leaf properties, and to identify potential predictors of EAB microbial variations.

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The gut microbial communities of beetles play crucial roles in their adaptive capacities. Environmental factors such as temperature or nutrition naturally affect the insect microbiome, but a shift in local conditions like the population density on a host tree could also lead to changes in the microbiota. The emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an exotic wood borer that causes environmental and economic damage to ash trees in North America.

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Aedes aegypti develop in aquatic habitats in which mosquito larvae are exposed to physicochemical elements and microorganisms that may influence their life cycle and their ability to transmit arboviruses. Little is known about the natural bacterial communities associated with A. aegypti or their relation to the biotic and abiotic characteristics of their aquatic habitats.

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Plant root activities shape microbial community functioning in the soil, making the rhizosphere the epicenter of soil biogeochemical processes. With this opinion article, we argue to rethink the rhizosphere boundaries: as gases can diffuse several centimeters away from the roots into the soil, the portion of soil influenced by root activities is larger than the strictly root-adhering soil. Indeed, gases are key drivers of biogeochemical processes due to their roles as energy sources or communication molecules, which has the potential to modify microbial community structure and functioning.

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Shiga toxin-producing Escherichia coli O157:H7, one of the most severe human foodborne pathogens, can withstand several stresses, including some levels of γ-irradiation. In this study, the response of E. coli O157:H7 to a sensitization irradiation dose of 0.

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Trace gas uptake by microorganisms controls the oxidative capacity of the troposphere, but little is known about how this important function is affected by changes in soil microbial diversity. This article bridges that knowledge gap by examining the response of the microbial community-level physiological profiles (CLPPs), carbon dioxide (CO) production, and molecular hydrogen (H) and carbon monoxide (CO) oxidation activities to manipulation of microbial diversity in soil microcosms. Microbial diversity was manipulated by mixing nonsterile and sterile soil with and without the addition of antibiotics.

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Deciphering the rules defining microbial community assemblage is envisioned as a promising strategy to improve predictions of pathogens colonization and proliferation in food. Despite the increasing number of studies reporting microbial co-occurrence patterns, only a few attempts have been made to challenge them in experimental or theoretical frameworks. Here, we tested the hypothesis that observed variations in co-occurrence patterns can be explained by taxonomy, relative abundance, and physiological traits of microbial species.

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The atmosphere of the early Earth is hypothesized to have been rich in reducing gases such as hydrogen (H). H has been proposed as the first electron donor leading to ATP synthesis due to its ubiquity throughout the biosphere as well as its ability to easily diffuse through microbial cells and its low activation energy requirement. Even today, hydrogenase enzymes enabling the production and oxidation of H are found in thousands of genomes spanning the three domains of life across aquatic, terrestrial, and even host-associated ecosystems.

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Background: The biofilm of a methanol-fed, fluidized denitrification system treating a marine effluent is composed of multi-species microorganisms, among which NL23 and JAM1 are the principal bacteria involved in the denitrifying activities. Strain NL23 can carry complete nitrate (NO[Formula: see text]) reduction to N, whereas strain JAM1 can perform 3 out of the 4 reduction steps. A small proportion of other denitrifiers exists in the biofilm, suggesting the potential plasticity of the biofilm in adapting to environmental changes.

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Background: strain JAM1 is a methylotrophic, marine bacterium that was isolated from a denitrification reactor treating a closed-circuit seawater aquarium. It can sustain growth under anoxic conditions by reducing nitrate ([Formula: see text]) to nitrite ([Formula: see text]). These physiological traits are attributed to gene clusters that encode two dissimilatory nitrate reductases (Nar).

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While high-affinity H-oxidizing bacteria (HA-HOB) serve as the main sink of atmospheric H, the ecology of this specialist functional group is rather unknown due to its recent discovery. The main purpose of our study is to provide the first extensive survey of HA-HOB in farmland, larch, and poplar soils exposed to 0.5 and 10,000 ppmv H.

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The enrichment of H-oxidizing bacteria (HOB) by H generated by nitrogen-fixing nodules has been shown to have a fertilization effect on several different crops. The benefit of HOB is attributed to their production of plant growth-promoting factors, yet their interactions with other members of soil microbial communities have received little attention. Here we report that the energy potential of H, when supplied to soil, alters ecological niche partitioning of bacteria and fungi, with multifaceted consequences for both generalist and specialist microbial functions.

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Soil microbial communities are continuously exposed to H2 diffusing into the soil from the atmosphere. N2-fixing nodules represent a peculiar microniche in soil where H2 can reach concentrations up to 20,000 fold higher than in the global atmosphere (0.530 ppmv).

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