Anti-fungal properties of bacteria present in secretions of the burying beetle nicrophorus orbicollis

Competition for carrion can be intense, including between animals and microbes, which rely heavily on the availability of these resources for survival and reproduction. Burying beetles use a small vertebrate carcass for reproduction and offspring development and prevent carcass decomposition by continuously covering it with oral and anal secretions. A common competitor for vertebrate carcasses was found to be fungi, leading us to predict that oral and anal secretions of the burying beetle Nicrophorous orbicollis would have anti-fungal properties. The zone of inhibition assays showed that oral and anal secretions inhibited the growth of fungi and filter sterilization of these secretions resulted in no anti-fungal activity confirming the role of bacteria as an anti-fungal agent in the secretions. The anti-fungal properties of oral and anal secretions could be attributed to the presence of Gram negative bacteria Enterobacter aerogenes. When isolated and cultured, E. aerogenes had activity similar to oral and anal secretions. E. aerogenes was found in the oral and anal secretions of both breeding and non-breeding beetles. Our study clearly demonstrates the mutualistic symbiosis between the burying beetle Nicrophorus orbicollis and the bacteria it harbors in the secretions