Editor’s Choice 56:5 – diverse communities of dung beetles and soil microbiota promote food safety

Associate Editor, Bret Elderd explains the importance of insects and microbes in decreasing risks to humans from pathogens such as E. coli. and discusses issue 56:5’s Editor’s Choice article, Organic farming promotes biotic resistance to foodborne human pathogens by Jones et al.

Outbreaks of food poisoning, whether due to Escherichia coli (E. coli) or other food-borne pathogens continually pop-up in the news at what seems to be an ever-increasing rate. These outbreaks inevitably prompt discussion on how to best protect the food supply meant for human consumption. One such effort to enhance food safety calls for a constructing a barrier, physical or by other means, between the crop meant for consumption and any livestock or wild animals. The idea being that the faeces from these animals can potentially contaminate a food crop with any number of foodborne pathogens. Since organic farms tend to be more biodiverse or are managed in an integrated manner with livestock, these systems should be ideal for promoting foodborne pathogens given the above reasoning. Thus, to decrease foodborne pathogen incidence and increase food safety, we should remove any surrounding biodiverse habitat that attracts wild animals as well as reduce livestock presence. Under this rubric, food safety and biodiversity constitute conflicting objectives. This mode of thinking is also in direct conflict with the ecosystem services that farmland biodiversity may provide such as pollination and/or pest control. Jones et al. in their article “Organic farming promotes biotic resistance to food-borne human pathogens” convincingly demonstrate that these two objectives are not in conflict but instead act in concert such that biodiversity promotes food safety.

Photo by Matt Jones

Using a series of surveys and laboratory experiments, Jones et al. show that organic farming promotes coprophagic communities both above and below ground that, in turn, better suppress pathogenic strains of E. coli. Across the 70 commercial vegetable fields surveyed, there was greater dung beetle biodiversity in organic as compared to conventional fields. When the authors placed pig faeces, which is a vector for food-born pathogens, in these fields, the biodiverse communities removed the faeces at a quicker rate. Using the three most common dung beetles found in their surveys, the authors conducted a series of laboratory experiments that show that two of the species, the native Onthophagus taurus and the invasive O. nuchicornis decreased pathogenic populations in E. coli contaminated faeces. However, the native dung beetle decreased the population by greater than 90% as compared to a less than 50% reduction by the invasive beetle. For the below-ground community, organic farms had greater soil microbial diversity and, in the lab, these soils did a much better job of suppressing E. coli numbers in contaminated faeces. Together, these results demonstrate that a more biodiverse coprophagic community better protects crops against potential food-borne pathogen vectors.

By promoting a more diverse coprophagic community, organic farming’s list of potential ecosystem services may have grown to include food safety. However, as the article highlights, there is more work to be done. For instance, there are potential links between the above-ground and below-ground communities such that dung beetles that bury their dung balls may enhance contact with the soil microbiota and further decrease food-borne pathogen populations. Future research will undoubtedly seek to explore these connections and their importance in agricultural systems. Overall, Jones et al.’s research establishes that biodiversity, in particular, coprophagic biodiversity may be just what the doctor ordered.

The Editor’s Choice article, Organic farming promotes biotic resistance to foodborne human pathogens is free to read for a limited time in issue 55:5 of Journal of Applied Ecology.

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