Biology subjects

Bachelot, B.

Publications and source records attributed to Bachelot, B..

4 recordsLinked to original sources

bioRxiv2025

Legacy of warming and microbial treatments shape root exudates and rhizosphere fungal communities of a tropical tree

O_LIPlant metabolites play a pivotal role in shaping rhizosphere microbial communities, yet how plant and microbial functions respond to environmental change remains poorly understood. We combined ecometabolomics and fungal community profiling to investigate how multiple abiotic and biotic treatments influence root exudate chemistry and fungal community assemblage in a tropical tree. C_LIO_LIGuarea guidonia seedlings were grown in sterilized soil primed with inoculum from long-term experimentally warmed or ambient plots in Puerto Rico. We manipulated soil microbes, soil moisture, and plant density and tested metabolite-fungi-plant trait associations. C_LIO_LIMetabolite diversity was significantly influenced by soil microbial legacy and moisture, while antimicrobial treatments altered metabolite composition without affecting diversity. Metabolite clusters exhibited distinct treatment-specific patterns. Fungal alpha diversity increased under low moisture, community composition shifted with antimicrobial treatments, and certain families showed strong treatment-specific responses. Although fungal diversity was not correlated with metabolite diversity, fungal community structure was significantly associated with metabolite composition. We also found global and pathway-specific correlations between fungal and metabolite distances, and weak but significant associations between metabolite/fungal composition and seedling traits. C_LIO_LIThese results underscore how environmental conditions shape belowground interactions, highlighting metabolite-fungal associations as potential early indicators of plant response to disturbance. C_LI

plant biology↗

bioRxiv2024

Experimental Warming Alters Nitrogen Cycle in a Humid Tropical Forest

O_LIHumid tropical forests typically contain high soil nitrogen (N), supporting rapid rates of primary productivity and recovery from disturbances. Nitrogen fixation is regulated by microbial communities, which can be free-living in the soil and leaf litter (asymbiotic) or in symbioses with plants. C_LIO_LITo investigate how warming affects asymbiotic and symbiotic components of the N cycle, we analyzed soil and leaf litter samples as well as annual seedling census data from an experimental warming field site in Puerto Rico. C_LIO_LI16S and nifH sequencing revealed that warming significantly altered bacterial composition. Asymbiotic N fixation rates were 55% greater in soil (0.004 nmol N2/g/hr) and 525% greater (0.217 nmol N2/g/hr) in leaf litter from warmed compared to ambient plots. This increase in fixation was associated with changes in the N-fixing bacterial community. Under warming, N fixers experienced a 4.4-fold increase in growth rate compared to non-fixers, yet competition with neighboring N fixers eventually reduced N fixer growth. Seedling growth, especially of N fixers, initially increased following hurricane disturbances before declining. C_LIO_LITogether, our findings suggest that warming increases the flux of N from the atmosphere into this tropical forest, driving changes in both microbial and tree dynamics. C_LI

ecology↗

bioRxiv2024

Tropical Forest Soil Microbiome Modulates Leaf Heat Tolerance More Strongly Under Warming than Ambient Conditions

Tropical forests are increasingly threatened by climate change. Yet, it is still unclear how tropical plants respond to increasing temperatures. Leaf heat tolerance (LHT) in tropical plants is often at its upper limit, suggesting that climate change might negatively impact tropical forests. We hypothesized that intraspecific variation in this leaf trait might be associated with changes in the soil microbiome, which might also respond to climate. Specifically, we hypothesized that warming would increase LHT through changes in the soil microbiome: this study combined an in-situ tropical warming experiment with a shade house experiment in Puerto Rico. The shade house experiment consisted of growing seedlings of Guarea guidonia, a dominant forest species, under different soil microbiome treatments (reduced arbuscular mycorrhizal fungi, reduced plant pathogens, reduced microbes, and unaltered) and soil inoculum from the field experiment. Heat tolerance was determined using chlorophyll fluorescence (FV/Fm) on individual seedlings in the field and on pooled seedlings by pot in the shade house. We sequenced soil fungal DNA to analyze the impacts of the field and shade house treatments on the soil microbiome. In the field, seedlings from ambient temperature plots showed higher FV/Fm values under high temperatures (0.648 at 46 {degrees}C and 0.067 at 52 {degrees}C) than seedlings from the warming plots (0.535 at 46 {degrees}C and 0.031 at 52 {degrees}C). In the shade house, the soil microbiome treatments, which significantly influenced the fungal community composition, significantly influenced LHT. Reduction in fungal pathogen abundance and diversity altered FV/Fm before T50 for seedlings grown with soil inoculum from the warming plots but after T50 for seedlings grown with soil inoculum from the ambient plots. Our findings emphasize that the soil microbiome might play an important role in modulating the impacts of climate change on plants. Understanding and harnessing this relationship might be vital for mitigating the effects of warming on tropical forests, emphasizing the need for further research on microbial responses to climate change.

ecology↗

bioRxiv2019

Symbiont community diversity is more constrained in holobionts that tolerate diverse stressors

Coral reefs are experiencing global declines as climate change and other stressors cause environmental conditions to exceed the physiological tolerances of host organisms and their microbial symbionts (collectively termed the holobiont). To assess the role of symbiont community composition in holobiont stress tolerance, diversity metrics and abundances of obligate dinoflagellate endosymbionts (Family: Symbiodiniaceae) were quantified from eight Acropora millepora coral colonies (hereafter called genets) that thrived under or responded poorly to various stressors. Four best performer coral genets were selected for analysis because they survived 10 days of high temperature, high pCO2, bacterial addition, or combined stressors, whereas four worst performer coral genets were analyzed because they experienced significant mortality under these stressors. At the end of the experimental period, seven of eight coral genets mainly hosted Cladocopium symbionts, but also contained Brevolium, Durusdinium, and/or Gerakladinium symbionts at lower abundances (<0.1% of the total community). After 10 days of stress, symbiont communities varied significantly among host genets, but not stress treatments, based on alpha and beta diversity metrics. A generalized joint attribute model (GJAM) also predicted that symbiont communities were primarily sensitive to host genet at regional scales. Indicator species analysis and the regional GJAM model identified significant associations among particular symbionts and host genet performance. Specifically, Cladocopium 3k contributed to the success of best performer host genets under various stressful conditions, whereas Durusdinium glynnii and Durusdinium trenchii were significantly associated with one worst performer genet. Cladocopium 3k dominance should be more broadly investigated as a potential predictor of stress resistance in Acropora millepora populations across their geographic range. Symbiodiniaceae communities exhibited higher richness and variance (beta diversity) in the worst performing genets. These findings highlight that symbiont community diversity metrics may be important indicators of resilience in hosts central to diverse disciplines, from agriculture to medicine.

ecology↗