Biology subjects

Francoeur, C. B.

Publications and source records attributed to Francoeur, C. B..

3 recordsLinked to original sources

bioRxiv2026

Myrmecocystus honeypot ants have species specific resident gut microbiome

Myrmecocystus honeypot ants rely on specialized workers, repletes, to store dissolved carbohydrates in their crops long term. The repletes store this liquid, which does not spoil in their crops, for many months at a time. When resources are scarce, repletes redistribute the stored nutrients to their colony members via trophallaxis. While we suspect that the gut microbiome of honeypot ants may aid in spoilage prevention, before we can investigate this, we must first characterize it. Here, we used 16S rRNA gene sequencing to determine the microbial community composition across six Myrmecocystus honeypot ant species, sampling multiple colonies, castes, and organs. We found that microbiome community composition was strongly shaped by species, with variation between colonies in M. arenarius, M. depilis, and M. mexicanus. Organ level differences were observed in the crop and midgut in M. mexicanus. Caste differences were observed in M. flaviceps and M. mexicanus. Replete crops of M. mexicanus and M. depilis were enriched in Fructilactobacillus, other lactic acid bacteria, and acetic acid bacteria, whereas halophiles were more prominent in the gut of species such as M. flaviceps and M. wheeleri. In this study we demonstrate that Myrmecocystus ants host species-specific gut microbiomes and identify an association between lactic acid bacteria, acetic acid bacteria, and halophiles within replete crops. While much work remains in understanding the roles of the microbes in the symbiosis with their host ants, the dominance of these particular taxonomic groups suggests an association with a high sugar environment and a potential microbial role in preventing spoilage of the crop contents.

microbiology↗

bioRxiv2021

Burkholderia from fungus gardens of fungus-growing ants produce antifungals that inhibit the specialized parasite Escovopsis

Within animal associated microbiomes, the functional roles of specific microbial taxa are often uncharacterized. Here, we use the fungus-growing ant system, a model for microbial symbiosis, to determine the potential defensive roles of key bacterial taxa present in the ants fungus gardens. Fungus gardens serve as an external digestive system for the ants, with mutualistic fungi in the genus Leucoagaricus spp. converting plant substrate into energy for the ants. The fungus garden is host to specialized parasitic fungi in the genus Escovopsis. Here, we examine the potential role of Burkholderia spp. that occur within ant fungus gardens in inhibiting Escovopsis. We isolated members of the bacterial genera Burkholderia spp. and Paraburkholderia spp. from 50% of the 52 colonies sampled, indicating that the family Burkholderiaceae are common fungus garden inhabitants of a diverse range of fungus-growing ant genera. Using antimicrobial inhibition bioassays, we found that 28 out of 32 isolates inhibited at least one Escovopsis strain with a zone of inhibition greater than 1 cm. Genomic assessment of Burkholderiaceae isolates indicated that isolates with strong inhibition all belonged to the genus Burkholderia and contained biosynthetic gene clusters that encoded the production of two antifungals: burkholdine1213 and pyrrolnitrin. Organic extracts of cultured isolates confirmed these compounds as responsible for antifungal activity that inhibit Escovopsis but, at low concentrations, not Leucoagaricus spp. Overall, these new findings, combined with previous evidence, suggest that members of the fungus garden microbiome play an important role in maintaining the health and function of the fungus-farming ant colony. IMPORTANCEMany organisms partner with microbes to defend themselves against parasites and pathogens. Fungus-growing ants must protect Leucoagaricus spp., the fungal mutualist that provides sustenance for the ants, from a specialized fungal parasite, Escovopsis spp. The ants take multiple approaches, including weeding their fungus gardens to remove Escovopsis spores, as well as harboring Pseudonocardia that produce antifungals that inhibit Escovopsis. In addition, a genus of bacteria commonly found in fungus gardens, Burkholderia spp., is known to produce secondary metabolites that inhibit Escovopsis spp. In this study, we isolated Burkholderia spp. from fungus-growing ants, assessed the isolates ability to inhibit Escovopsis spp., and identified two compounds responsible for inhibition. Our findings suggest that Burkholderia spp. are often found in fungus gardens, adding another possible mechanism within the fungus-growing ant system to suppress the growth of the specialized parasite Escovopsis.

microbiology↗

bioRxiv2019

Bacteria contribute to plant secondary compound degradation in a generalist herbivore system

Herbivores must overcome a variety of plant defenses, including coping with plant secondary compounds (PSCs). To help detoxify these defensive chemicals, several insect herbivores are known to harbor gut microbiota with the metabolic capacity to degrade PSCs. Leaf-cutter ants are generalist herbivores, obtaining sustenance from specialized fungus gardens that act as external digestive systems, degrading the diverse collection of plants foraged by the ants. There is in vitro evidence that certain PSCs harm Leucoagaricus gongylophorus, the fungal cultivar of leaf-cutter ants, suggesting a role for the Proteobacteria-dominant bacterial community present within fungus gardens. Here, we investigate the ability of symbiotic bacteria present within fungus gardens of leaf-cutter ants to degrade PSCs. We cultured fungus garden bacteria, sequenced the genomes of 42 isolates, and identified genes involved in PSC degradation, including genes encoding cytochrome p450s and genes in geraniol, cumate, cinnamate, and -pinene/limonene degradation pathways. Using metatranscriptomic analysis, we show that some of these degradation genes are expressed in situ. Most of the bacterial isolates grew unhindered in the presence of PSCs and, using GC-MS, we determined that isolates from the genera Bacillus, Burkholderia, Enterobacter, Klebsiella, and Pseudomonas degrade -pinene, {beta}-caryophyllene, or linalool. Using a headspace sampler, we show that sub-colonies of fungus gardens reduced -pinene and linalool over a 36-hour period, while L. gongylophorus strains alone only reduced linalool. Overall, our results reveal that the bacterial community in fungus gardens play a pivotal role in alleviating the effect of PSCs on the leaf-cutter ant system. ImportanceLeaf-cutter ants are dominant neotropical herbivores capable of deriving energy from a wide range of plant substrates. The success of leaf-cutter ants is largely due to their external gut composed of key microbial symbionts, specifically, the fungal mutualist L. gongylophorus and a consistent bacterial community. Both symbionts are known to have critical roles in extracting energy from plant material, yet comparatively little is known about their role in the detoxification of plant secondary compounds. Here, we assess if the bacterial community associated with leaf-cutter ant fungus gardens can degrade harmful plant chemicals. We identify plant secondary compound detoxification in leaf-cutter ant gardens as a process that depends on the degradative potential of both the bacterial community and L. gongylophorus. Our findings suggest the fungus garden and its associated microbial community influences the generalist foraging abilities of the ants, underscoring the importance of microbial symbionts in plant substrate suitability for herbivores.

ecology↗