Bacteria associated with leaf-cutter ants drive natural antibiotic resistance in soil bacteria

Abstract

Actinobacteria that live mutualistically with leaf-cutter ants secrete antibiotics that may induce antibiotic resistance in nearby soil bacteria. We tested for the first time whether soil bacteria near and inside Atta cephalotes nests in Costa Rica show higher levels of antibiotic resistance than bacteria collected farther away. We collected soil samples 0 m to 50 m away from ant nests and grew bacteria from them on agar with paper discs treated with antibiotics of common veterinary use. As a proxy for antibiotic resistance, we measured the distance from the edge of each disc to the closest bacterial colonies. In general, resistance to oxytetracycline increased with proximity to leaf-cutter ant nests. Antibiotic resistance to oxytetracycline was also higher in samples collected inside the nest than in samples from the nest mound; not all antibiotics demonstrated the same trend. A preliminary exploratory morphological analysis suggests bacterial communities between 0 m and 50 m from ant nests were similar in diversity and abundance, indicating the pattern of antibiotic resistance described above may not be caused by differences in community composition. We conclude that actinobacteria living mutualistically with A. cephalotes drive natural antibiotic resistance to tetracycline in proximal bacterial communities.

Antifungal metabolites, their novel sources, and targets to combat drug resistance

“…Table 1 lists the novel natural antifungal compounds that have been isolated from actinomycetes since 2011. Several recent research on natural product discovery has concentrated on the examination of insect-microbe symbioses and especially, interactions between insects and actinobacteria because bacterial symbionts need small molecules to communicate with the host or take part in host defence (Chouvenc et al, 2018;Simon et al, 2022). The associations between endosymbiotic bacteria with arthropods can vary from facultative to obligate mutualisms; these bacteria can assist with nutrient uptake, promote resistance to plant secondary metabolite, and chemical pollutant and pesticide detoxification (Zhao et al, 2022), while some symbionts exude antifungals to inhibit the proliferation of the arthropods' fungal antagonists (Kett et al, 2021).…”