Biology subjects

Poirier, V.

Publications and source records attributed to Poirier, V..

5 recordsLinked to original sources

bioRxiv2026

Microbial community composition, but not diversity, influence microbial necromass mineralization

Soil harbours a wide diversity of microbes responsible for essential functions, such as depolymerizing the C and N in organic matter through the production of exoenzymes. Some of these exoenzymes are universal, whereas others are specific to certain microbes. We hypothesized that higher microbial alpha diversity is associated with greater depolymerization capacity, specifically for protein and cellulose depolymerization, which will result in more N being mineralized. We therefore diluted two soil microbial communities, one from a forest soil and one from an agricultural soil, to create a diversity gradient. After nine weeks, we transferred these communities to a synthetic soil in which microbial necromass was the only nitrogen source. Before the transfer and two weeks after, we quantified protease, deaminase and {beta}-glucosidase potential activity, characterized the bacterial and fungal communities, and measured the quantity of nitrogen mineralized. The dilution had very little effect on the processes measured, with no clear trend. For identical alpha diversity values, some communities had high process rates, while other not. It appeared that these communities varied widely, a side effect of the dilution approach, and that this variation was significantly linked to process rates. This shows that community composition (beta diversity) is more strongly related to enzymatic potential and mineralization than species richness (alpha diversity) following necromass addition. In conclusion, the relationship between diversity and depolymerization of microbial necromass is not simply a matter of a linear decrease along with diversity but is rather linked to how reduced diversity results in more stochastic microbial communities. Highlights- Community composition (beta diversity) influence more microbial necromass depolymerization than species richness - Abundance of specific microbes explained ammonification and nitrification processes - Mineralization rates is different between crop and forest soil

microbiology↗

bioRxiv2026

Urbanization drives dietary specialization in insectivorous bird communities: insights from a multi-prey cafeteria experiment monitored by innovative cameras

1. Urbanization is widely associated with functional homogenization of ecological communities, including declines in insectivorous bird species and concomitant restructuring of arthropod assemblages. While these changes are often assumed to alter ecosystem functioning through trophic interactions, it remains unclear whether bird insectivory in cities can be inferred from community composition alone, or whether it also depends on which species actively forage, on natural prey availability and on the arthropod guilds exploited. 2. We hypothesized that urbanization (i) restructures both insectivorous bird communities and arthropod prey assemblages, thereby (ii) increasing divergence between trait-based potential and realized insectivory, while (iii) prey use is shaped by natural prey availability and active prey selection. 3. We used 25 plots distributed along a controlled urbanization gradient in Montreal, Canada. We combined acoustic monitoring of insectivorous bird communities, arthropod surveys, and camera-monitored cafeteria-like experiments deployed on 73 trees to quantify trait-based potential insectivory, realized insectivory through direct foraging interactions, natural prey availability and prey selection among three arthropod guilds (lepidopteran larvae, spiders and ants). 4. Urbanization reduced bird functional diversity while also decreasing the availability of high-quality prey, particularly lepidopteran larvae and spiders. Realized insectivory was consistently decoupled from community-based expectations, with actively foraging assemblages systematically less insect-specialized than predicted by broader community compositions (potential insectivory). This mismatch was non-random and only weakly related to urban and vegetation gradients. Prey use was largely independent of natural prey availability and instead reflected consistent preferences for larval prey over other guilds, with some indication that the functional composition of bird foraging assemblages further shaped which prey were exploited. 5. Our results show that realized trophic interactions emerge through successive ecological filters rather than directly from community composition: environmental conditions restructure bird communities and prey availability, subsequent foraging filters determine which species actively participate, and prey selection governs which guilds are consumed. Predicting ecosystem functioning in cities therefore requires considering not only biodiversity patterns but also the ecological processes linking community composition to realized trophic interactions.

ecology↗

bioRxiv2025

Previous legume identity influences wheat protein content through organic matter depolymerization

In crop rotation systems, plant-soil feedback (PSF) effects can modulate nutrient cycling in soil, like organic carbon (C) and nitrogen (N) cycling. Organic nitrogen is present in plant and microbial necromass, and it must be depolymerized by microbes to become available for crops. Since plant identity can modulate microbial diversity and community composition, we thought that previous crop identity and its residue management would also change the microbial functional capacity, and thereby impact soil N availability, and the quality and yield of the following crop. To test this, two legumes (Vicia faba L., i.e. faba bean, and Pisum sativum L., i.e., yellow pea) were grown in two fields (Cloutier, and Palmarolle) in Abitibi-Temiscamingue, Quebec, Canada (n=3 for each field). At the end of the growing season, we harvested peas and faba beans in both fields. During the following growing season, spring wheat (Triticum aestivum L.) was sown and received, or not granulated chicken manure as an organic fertilizer. We determined the diversity and composition of the microbial communities and their enzymatic depolymerization capacity in the soil and the rhizosphere each growing season. During wheat growth, previous legumes shaped bacterial (p-value = 0.006) and fungal (p-value = 0.001) communities without modulating the enzymatic activity of wheat-associated rhizosphere microbes. However, faba bean as a previous crop increased soil ammonium and wheat grain protein content at harvest as compared to peas at Cloutier. Altogether, our results show that faba beans can enhance wheat N nutrition, without a concomitant increase in potential protein or cellulose depolymerization, suggesting more mineralization due to increases in fungal: bacterial ratio or in the availability of substrates. Understanding plant-soil feedback in crop rotation systems is crucial to improve our practices and sustainably meet crops nutritional needs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=122 SRC="FIGDIR/small/694934v2_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@129f684org.highwire.dtl.DTLVardef@1f78d20org.highwire.dtl.DTLVardef@152466dorg.highwire.dtl.DTLVardef@8da2e2_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIPrevious crop identity distinctively shaped wheat rhizosphere microbial communities C_LIO_LIPrevious legume did not altered the enzymatic activity of wheat-associated rhizosphere microbes, but increased soil ammonium C_LIO_LIWheat grain protein content was higher following faba bean than peas C_LI

microbiology↗

bioRxiv2025

Use of ANCHOR viruses to validate radiative, physical and chemical decontamination systems in operational conditions.

ANCHOR tagged viruses provide a high-performance platform for the rapid evaluation of disinfection methods across chemical, radiative, and physical modalities. This study highlights the robustness of Vaccinia virus (VACV) and human Adenovirus type 5 (hAdV5) as environmental persistence models, demonstrating their suitability for testing disinfection protocols. ANCHOR imaging capability allows real-time visualization of disinfection efficacy, enabling rapid calibration and cost-effective validation of new disinfection systems. This technology provides essential support for the development and optimization of disinfection solutions in public areas up to the improvement of safety protocols in high-containment laboratories. The increasing number of BSL-4 laboratories worldwide underscores the critical needs for efficient and reliable decontamination systems and methods to test them in operational conditions to ensure biohazard safety. HighlightsO_LIANCHOR-tagged viruses provide a rapid and cost-effective platform for evaluating disinfection methods across chemical, physical, and radiative modalities. C_LIO_LIHuman Adenovirus type 5 (hAdV5) and Vaccinia virus (VACV) serve as robust environmental persistence models for testing viral decontamination protocols. C_LIO_LIThe use of ANCHOR viruses enables rapid real-time visualization of disinfection efficacy, improving safety validation in high-containment laboratories and public health applications. C_LI

microbiology↗

bioRxiv2017

Global Proteomic Analyses of Macrophage Response to Mycobacterium tuberculosis Infection

Alveolar macrophages serve as the first line of defence against microbial infection, yet provide a unique niche for the growth of Mycobacterium tuberculosis. To better understand the evasive nature of the tubercle bacilli and its molecular manifest on the macrophage response to infection, we conducted a global quantitative proteomic profile of infected macrophages. By examining four independent controlled infection experiments, we detected 42,007 peptides resulting in the characterization of 4,868 distinct proteins. Of these, we identified 845 macrophage proteins whose expression is modulated upon infection in all replicates. We showed that the macrophages response to M. tuberculosis infection includes simultaneous and concerted upregulation of selected proteins. Using a number of statistical methods, we identified 27 proteins whose expression levels are significantly regulated outside of a 90% confidence interval about the mean. These host proteins represent the macrophage transcriptional, translational, and innate immune response to infection as well as its signaling capacity. The contribution of PtpA, an M. tuberculosis secreted virulence factor, modulated the expression levels of 11 host macrophage proteins, as categorized by RNA metabolism, translation, and cellular respiration.

microbiology↗