The “bessbug” beetle not only eats its own poop, known as frass, but also uses the material to line the walls of its log-based galleries and to build protective chambers around its young. UC Berkeley scientists have discovered that the frass contains antibiotic and antifungal chemicals produced by actinomycete bacteria, helping to protect the insect from pathogens.
Credit: UC Berkeley photo by Rita de Cassia Pessotti
Exactly what potential resources there are in nature can only be guessed at - which is why conservation is so important, not just for the sake of biodiversity on 'spaceship' Earth, but to conserve stuff that could be essential to our long-term survival. Who would have guessed, for example, that the excrement of a beetle would contain potentially powerful antibiotics and fungicides, but that's exactly what a team of researchers from the University of California at Berkeley have discovered.
The horned passalus beetle, Odontotaenius disjunctus, commonly known as the bessbug or betsy beetle, not only eats its excrement, but it also lines the walls of the tunnels in wood where it lays its eggs with it. It turns out that the excrement is
O. disjunctus beetles (A) inhabit and feed on decomposing logs.
They build galleries that are filled with frass (B, white arrows are pointing to the frass), which is a central material in this system. This material is also used to build pupal chambers (C). We sampled 22 galleries across 11 states (E) and isolated actinomycetes from all samples. This actinomycete collection showed a high rate of antimicrobial activity against B. subtilis and/or C. albicans (D). Each gallery is represented on the map by a circle with the gallery code next to it. CT: Connecticut; DC: District of Columbia; VA: Virginia; KY: Kentucky; TN: Tennessee; GA: Georgia; FL: Florida; AL: Alabama; MS: Mississippi; LA: Louisiana; TX: Texas.
The team's research is published open access in the eLife:
AbstractActinomycetes have been engaged in arms races with other organisms for millions of years so it is not really surprising that they would have evolved these defensive substances, but to discover them in beetle excrement illustrates how precious Earth's natural resources can prove to be for us, so it is imperative that we conserve as much of it as possible or we could be losing something we're not even aware we have. We are in arms races ourselves with several harmful pathogens and in imminent danger danger of losing some of them. Actinomycetes have been doing this for millions of years and will have evolved antibiotics for which their potential pathogens have not yet evolved counter measures.
Some insects form symbioses in which actinomycetes provide defense against pathogens by making antimicrobials. The range of chemical strategies employed across these associations, and how these strategies relate to insect lifestyle, remains underexplored. We assessed subsocial passalid beetles of the species Odontotaenius disjunctus, and their frass (fecal material), which is an important food resource within their galleries, as a model insect/actinomycete system. Through chemical and phylogenetic analyses, we found that O. disjunctus frass collected across eastern North America harbored multiple lineages of Streptomyces and diverse antimicrobials. Metabolites detected in frass displayed synergistic and antagonistic inhibition of a fungal entomopathogen, Metarhizium anisopliae, and multiple streptomycete isolates inhibited this pathogen when co-cultivated directly in frass. These findings support a model in which the lifestyle of O. disjunctus accommodates multiple Streptomyces lineages in their frass, resulting in a rich repertoire of antimicrobials that likely insulates their galleries against pathogenic invasion.
Pessotti, Rita de Cassia; Hansen, Bridget L; Reaso, Jewel N; Ceja-Navarro, Javier A; El-Hifnawi, Laila; Brodie, Eoin L; Traxler, Matthew F
Multiple lineages of Streptomyces produce antimicrobials within passalid beetle galleries across eastern North America
eLife 2021;10:e65091 DOI: 10.7554/eLife.65091
Copyright: © 2021 The authors. Published by eLife
Open access
Reprinted under a Creative Commons CC0 1.0 Universal Public Domain Dedication (CC0 1.0)
Thanks Rosa Rubicondior for highlighting our work! :)
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