Abstract
Interactions between species and their environment play a key role in the evolution of diverse communities, and numerous studies have emphasized that interactions among microbes and among trophic levels play an important role in maintaining microbial diversity and ecosystem functioning. In this study, we investigate how two of these types of interactions, public goods cooperation through the production of iron scavenging siderophores and predation by the social amoeba Dictyostelium discoideum, mediate competition between two strains of Pseudomonas fluorescens that were co-isolated from D. discoideum. We find that although we are able to generally predict the competitive outcomes between strains based on the presence and absence of either D. discoideum or iron, predator-by-environment interactions result in unexpected competitive outcomes. This suggests that while both cooperation and predation can mediate the competitive abilities and potentially the coexistence of these strains, predicting how combinations of different environments affect even the relatively simple microbiome of D. discoideum remains challenging.
Highlights
Interactions within and between microbial species play an important role in mediating competition and shaping their evolutionary histories
We find that the Pf2 gacA mutant and Pf3 behave across all our experimental treatments and reach similar bacterial densities (t = −1.18, p > 0.24) (Figure 2 and Table 3)
It is important to note that changes to the GacS/GacA system may affect more than just pyochelin production and edibility, so some of the competitive fitness differences we observe may be due to other functions of GacS/GacA
Summary
Interactions within and between microbial species play an important role in mediating competition and shaping their evolutionary histories. Predation can be important in preventing the spread of new genetic mutants such as microbial cheaters, if the cheaters that no longer produce anti-predator toxins are preferentially eaten (Jousset et al, 2009; Friman et al, 2013). This suggests that predation can have a variety of effects on both interacting microbes and Bacterial Competition in the Microbiome complex microbial communities. Interactions between trophic levels may play a key role in determining the species composition of diverse populations of interacting microbes
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