Microbiome derived acidity protects against microbial invasion inDrosophila

Abstract

Microbial invasions underlie host-microbe interactions that result in microbial pathogenesis and probiotic colonization. While these processes are of broad interest, there are still gaps in our understanding of the barriers to entry and how some microbes overcome them. In this study, we explore the effects of the microbiome on invasions of foreign microbes inDrosophila melanogaster. We demonstrate that gut microbesLactiplantibacillus plantarumandAcetobacter tropicalisimprove survival during invasion of a lethal gut pathogen and lead to a reduction in microbial burden. Using a novel multi-organism interactions assay, we report thatL. plantaruminhibits the growth of three invasive Gram-negative bacteria, whileA. tropicalisprevents this inhibition. A series ofin vitroandin vivoexperiments revealed that inhibition byL. plantarumis linked to its ability to acidify both internal and external environments, including culture media, fly food, and the gut itself, whileA. tropicalisdiminishes the inhibition by quenching acids. We propose that acid produced by the microbiome serves as an important gatekeeper to microbial invasions, as only microbes capable of tolerating acidic environments can colonize the host. The methods described herein will add to the growing breadth of tools to study microbe-microbe interactions in broad contexts.

Massively parallel mutant selection identifies genetic determinants ofPseudomonas aeruginosacolonization ofDrosophila melanogaster

“…Our previous work and other reports have highlighted a role for the microbiota in modulating enteric infection by bacteria, yeast, and viruses (48–52). We observed that colonization with a single member of the microbiota, Lactiplantibacillus plantarum , is sufficient to reduce mortality associated with S. marcescens , P. aeruginosa (41) and P. entomophila (51). Although symbiont-mediated augmentation of host defense has been proposed as the mechanism of this protective effect, a potential contribution of microbe-microbe interactions to pathogenesis has not been extensively explored in the fly (31, 53, 54).…”

Varying phylogenetic signal in susceptibility to four bacterial pathogens across species of Drosophilidae

“…Anecdotally, these species exhibited a relatively high survival to most of the bacteria (Figure 3). The microbiome can play an important role in priming the immune response and defending against bacterial infections [84, 85]. Gut probiotics such as Lactobacillus have demonstrated to reduce fly mortality caused by pathogenic bacteria [86].…”

The role of animal hosts in shaping gut microbiome variation

“…the surrounding environment is also used by commensal bacteria as a mechanism to control microbial invasion and protect the host [72]. On the contrary, the increase in pH, the high transit time in the ileum and rectum and the resulting accumulation of food content favour microbial proliferation [29] (table 2).…”