Biology subjects

Gillon, A.

Publications and source records attributed to Gillon, A..

4 recordsLinked to original sources

bioRxiv2026

A scalable screening approach reveals phylogenetic patterns of bacterial antagonism against potato pathogens

Microbial biological control agents (mBCAs) offer a promising alternative to conventional disease management, but identifying effective strains requires screening large microbial collections against many pathogens. Here, we developed a scalable screening approach to characterize the antagonistic activity of potato-associated bacteria against multiple pathogens and investigated how bacterial origin and phylogeny relate to antagonistic phenotypes. A collection of 600 bacterial strains isolated from two potato cultivars, three plant compartments using four cultivation media was screened against six major potato pathogens: the bacteria Dickeya solani and Pectobacterium carotovorum, the fungi Alternaria solani and Rhizoctonia solani, and the oomycetes Phytophthora infestans and Pythium ultimum. A scalable confrontation method was developed for non-filamentous bacteria, while complementary lower-throughput assays were used for filamentous strains. This approach enabled successful assessment of 92% of non-filamentous and 97% of filamentous strain-pathogen combinations. Isolation cultivar, plant compartment and cultivation medium had only limited effects on the proportion of antagonistic strains. In contrast, pathogen sensitivity varied markedly: P. infestans was the most susceptible pathogen, whereas D. solani and P. carotovorum were generally resistant to bacterial antagonism. Antagonistic activity clustered phylogenetically, with Bacillus and Streptomyces containing many broad-spectrum inhibitors. In addition, several taxa showed preferential activity against the oomycetes, including P. infestans-specific antagonists from the Pseudomonas genus and P. ultimum-specific antagonists from the Frigoribacterium, Curtobacterium, Pedobacter and Phyllobacterium genera. Overall, multi-pathogen screening revealed distinct generalist and specialist antagonistic profiles and identified candidate strains and taxa for further evaluation as mBCAs.

microbiology↗

bioRxiv2026

Cross-feeding enables robust coexistence between four bacterial species

AbstractMicrobial diversity is often assumed to be limited by the number of available resources, yet many communities persist well beyond that expectation. Understanding the mechanisms that enable such coexistence remains a central question in microbial ecology. Here, using a four-species bacterial consortium, we asked whether coexistence can emerge from interactions between species rather than from the external environment alone. Across 31 simple nutrient conditions, including 16 single-resource environments, all four species persisted and repeatedly reached stable coexistence. We then chose 27 additional conditions to further probe the boundaries of coexistence by varying resource concentrations, temporal dynamics, nutrient complexity and relief of auxotrophy-associated dependencies, and only observed the extinction of one species in one of these conditions. Although the community composition in each environment was largely shaped by species fitness on the supplied resources, experimental assays and consumer-resource modeling showed that the coexistence was not explained by resource supply, but rather by cross-feeding and niche partitioning of metabolic byproducts. These metabolic interactions were strong enough to sustain coexistence even for species unable to use the supplied resources directly. Furthermore, robust coexistence across environments appears to be an emergent property of microbial communities, ingrained in members metabolic byproduct profiles and niche differences. Our findings demonstrate how microbes can increase the chemical complexity of their environment sufficiently to maintain coexistence well beyond what is expected from external resource supply. SignificanceUnderstanding the drivers of microbial diversity is essential for managing natural ecosystems and designing synthetic microbiomes. This study challenges the conventional application of the competitive exclusion principle, demonstrating that a four-species consortium can coexist across 31 chemically and metabolically diverse one- and two-carbon source environments. By systematically testing and ruling out alternative stabilizing mechanisms, we show that co-existence is an emergent property of the consortium, sustained by metabolic cross-feeding and niche partitioning. Guided by computational models, we identify hallmarks of robust co-existence in simple environments, including high variance in resource affinities and growth on partner-derived metabolites. Our work demonstrates how microbes modify their environment to sustain high diversity and provides principles for designing synthetic microbiomes that persist across environments.

microbiology↗

bioRxiv2025

Microbes release lower-value metabolites at higher rates

Microbial interactions are shaped by the exchange of metabolites, ranging from intermediates in central carbon metabolism to amino acids, vitamins and fermentation by-products. While specific metabolic processes such as overflow metabolism are well documented, a general principle explaining the chemical diversity of metabolite release and the variation in individual release rates remains elusive. Here, using a combination of computational and experimental approaches on seven different microbes, we show that release rates are negatively correlated with the value of metabolites, and that this relationship explains more variability in release rates than other frequently associated factors. By measuring metabolite release from 67 E. coli mutants lacking individual transport genes, we find that transporters both cause and counteract net metabolite release. These findings suggest that metabolite release constitutes a fitness cost that microbes have evolved to reduce, while revealing the underlying transport mechanism. This unifying explanation reshapes our understanding of how microbial interactions emerge and persist.

microbiology↗

bioRxiv2025

Estrogenic Activity in Tampon Products

Tampons are widely used menstrual products with prolonged mucosal contact, raising questions about their potential role in exposing females to endocrine-disrupting chemicals (EDCs). This study evaluated estrogenic activity in tampon extracts using a cell-based estrogen receptor reporter bioassay. Synthetic and organic tampons sourced from domestic and international markets--both synthetic and organic--were tested for estrogenic bioactivity. Of the 18 brands analyzed, estrogenic activity was detected in nearly half, independent of material type. Comparative chemical analysis of one estrogenic-active brand versus one non-active brand via high-resolution mass spectrometry identified various plasticizers, surfactants, and fragrance agents, that were present in higher concentrations in the estrogenic-active brand. The list of chemicals included known EDCs, such as phthalates and alkylphenols, that may be responsible for the observed estrogenic activity. Notably, estrogenic activity varied by brand, suggesting formulation-dependent risk. Although the detected in vitro activity levels were low, the findings demonstrate that compounds capable of activating estrogen receptors can leach from tampons. These results highlight the importance of including endocrine bioactivity assays in tampon safety assessments and suggest that safer formulations are achievable. Further investigation is warranted to assess long-term health implications of cumulative low-level EDC exposure from menstrual products.

physiology↗