Biology subjects

Brochet, S.

Publications and source records attributed to Brochet, S..

3 recordsLinked to original sources

bioRxiv2026

Species boundaries structure competitive interactions among honeybee gut bacteria

Bacterial species often harbor extensive strain-level diversity, raising the question of whether strains, rather than species, are the relevant ecological units. We quantified pairwise interactions among 12 strains from four prevalent Lactobacillus species of the honeybee gut microbiota using gnotobiotic bees. Microbiota-depleted bees were colonized with individual strains and all 66 pairwise combinations, with strain abundances measured by colony counts and strain-resolved amplicon sequencing. Negative interactions predominated, with most significant interactions involving mutual inhibition. Within-species interactions were stronger and more asymmetric than between-species interactions, producing less even community compositions. Across repeated cycles of colonization in microbiota-depleted bees, three of four within-species pairs lost one strain, whereas all four between-species pairs persisted. These results indicate that closely related strains experience greater niche overlap and stronger competition than strains from different species, supporting bacterial species as ecologically differentiated units while highlighting the importance of strain-specific traits in shaping community assembly and stability.

microbiology↗

bioRxiv2021

Niche partitioning facilitates coexistence of closely related gut bacteria

Ecological processes underlying bacterial coexistence in the gut are not well understood. Here, we disentangled the effect of the host and the diet on the coexistence of four closely related Lactobacillus species colonizing the honey bee gut. We serially passaged the four species through gnotobiotic bees and in liquid cultures in the presence of either pollen (bee diet) or simple sugars. Although the four species engaged in negative interactions, they were able to stably coexist, both in vivo and in vitro. However, coexistence was only possible in the presence of pollen, and not in simple sugars, independent of the environment. Using metatranscriptomics and metabolomics, we found that the four species utilize different pollen-derived carbohydrate substrates indicating resource partitioning as the basis of coexistence. Our results show that despite longstanding host association, gut bacterial interactions can be recapitulated in vitro providing insights about bacterial coexistence when combined with in vivo experiments.

microbiology↗

bioRxiv2018

Genomic changes underlying host specialization in the bee gut symbiont Lactobacillus Firm5

Bacteria that engage in longstanding associations with particular hosts are expected to evolve host-specific adaptations that limit their capacity to thrive in other environments. Consistent with this, many gut symbionts seem to have a limited host range, based on community profiling and phylogenomics. However, few studies have experimentally investigated host specialization of gut symbionts and underlying mechanisms have largely remained elusive. Here, we studied host specialization of a dominant gut symbiont of social bees, Lactobacillus Firm5. We show that Firm5 strains isolated from honey bees and bumble bees separate into deep-branching phylogenetic lineages. Despite their divergent evolution, colonization experiments show that bumble bee strains are capable of colonizing the honey bee gut. However, they were less successful than honey bee strains, and competition with honey bee strains completely abolished their colonization, whereas honey bee strains were able to coexist. This suggests that both host selection and interbacterial competition play important roles for host specialization. Using comparative genomics of 27 Firm5 isolates, we identified candidate genomic changes underlying host specialization. We found that honey bee strains harbored a larger and more diverse gene pool of carbohydrate-related functions than bumble bee strains. As dietary-derived carbohydrates are the main energy source for strains of the Firm5 phylotype, the metabolic flexibility of honey bee strains may give these bacteria a competitive advantage over bumble bee strains in colonizing the gut niche and hence contribute to host specialization.

microbiology↗