Bacteria on housefly eggs, Musca domestica, suppress fungal growth in chicken manure through nutrient depletion or antifungal metabolites

Abstract

Female houseflies, Musca domestica (Diptera: Muscidae), lay their eggs in ephemeral resources such as animal manure. Hatching larvae compete for essential nutrients with fungi that also colonize such resources. Both the well-known antagonistic relationship between bacteria and fungi and the consistent presence of the bacterium Klebsiella oxytoca on housefly eggs led us to hypothesize (1) that K. oxytoca, and possibly other bacteria on housefly eggs, help curtail the growth of fungal resource competitors and (2) that such fungi indeed adversely affect the development of housefly larvae. Bacteria washed from housefly eggs significantly reduced the growth of fungi in chicken manure. Nineteen bacterial strains and ten fungal strains were isolated from housefly eggs or chicken manure, respectively. Co-culturing each of all the possible bacterium-fungus pairs revealed that the bacteria as a group, but no single bacterium, significantly suppressed the growth of all fungal strains tested. The bacteria's adverse effect on fungi is due to resource nutrient depletion and/or the release of antifungal chemicals. Well-established fungi in resources significantly reduced the number of larval offspring that completed development to adult flies.

Semiochemical-Mediated Oviposition Avoidance by Female House Flies, Musca domestica, on Animal Feces Colonized with Harmful Fungi

“…Larval diet inoculated with mycelia and/or spores of the oviposition-inhibiting fungi Fusarium spp., Phoma spp., and Rhizopus spp. had detrimental effects on the number of house fly larvae that completed development (Lam et al 2009). This decrease in larval survival may not occur with other fungi [e.g., Fusarium spp.…”

“…Each fungal isolate with adverse effects on the development of house fly larvae (Lam et al 2009) emitted dimethyl trisulfide and 2-phenylethanol, each of which strongly reduced oviposition by house flies on feces. Neither of these two semiochemicals has been reported to affect oviposition decisions by flies, but 2-phenylethanol is a bacteria-derived putative oviposition semiochemical for Anopheles gambiae mosquitoes (Lindh et al 2008).…”

Fungal secondary metabolites as modulators of interactions with insects and other arthropods

“…Antagonistic interactions with other organisms co-occurring in the fungal habitat have an especially strong impact on fungal growth and reproduction, i.e., on evolutionary fitness. In decomposer systems, saprotrophic fungi may be engaged in competition with con-and heterospecifics and prokaryotic microorganisms (Vining, 1990), as well as saprophagous insects exploiting the same resource patches (Lam et al, 2009;Lussenhop and Wicklow, 1985;Trienens et al, 2010). Because fungi have the ability to accumulate high amounts of nitrogen and phosphorous, they are an important food source in soil ecosystems and are, thus, under heavy attack by fungivorous animals, especially arthropods, such as collembola, mites and insects (Boddy and Jones, 2008;Ruess and Lussenhop, 2005).…”

Personal immunity versus social immunity

“…Without the protection of this secretion, eggs would be killed by invasive fungi (Cardoza et al 2006). Similarly, houseflies that lay their eggs in manure cover the surface of their eggs with bacteria that inhibit the growth of fungi, which can affect larval development (Lam et al 2009). Burying beetles exhibit elaborate pre and posthatching parental care, one aspect of which involves preparing a vertebrate carcass for their offspring by covering it with anal exudates that have potent antibacterial activity .…”