Investigating Multi-Species Interactions and Spatial Structure of Gut-Bacterial Communities using Live Imaging
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Date
2022-10-26
Authors
Sundarraman, Deepika
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Publisher
University of Oregon
Abstract
Animal intestines harbor hundreds of microbial species that play a crucial role in host health and development. Despite their importance, many questions about the rules that govern community assembly in these complex environments remain unanswered and almost impossible to study in humans. For example, is it possible to construct multi-species communities from an understanding of pairwise interactions? What is the role of spatial structure and timing in community assembly? How do species' spatial structure and interactions affect the host? We focus on addressing these questions using a consortium of gut bacterial species, native to the vertebrate model organism of larval zebrafish. We first characterize pairwise interactions between a consortium of 5 gut bacterial isolates in 2-species and 5-species competition experiments using an interaction model and find evidence for higher order interactions that dampened strong pairwise competition and enabled coexistence in 5-species communities.
We next focus on a specific pair showing strong pairwise competition in 2-species experiments.Using light sheet fluorescence microscopy, we illuminate on the role of spatial structure in the competition between two highly aggregated species localized in the intestinal midgut, namely strains of genera \textit{Aeromonas} (AE) and \textit{Enterobacter} (EN). We test whether altering aggregation and localization behavior impact this interaction using a bacterial strain \textit{Aeromonas-MB4}, derived from parental AE and composed mostly of planktonic cells that are anterior localized. When AE-MB4 invades fish colonized with EN, it induces disaggregation of the highly aggregated EN strain, an effect weakened in the presence of the other 4 species. Additionally, we observe that AE-MB4 induces increased inflammation compared to the aggregated parental AE strain, suggesting possible links between spatial structure and host inflammation.
These studies illustrate the complex ways in which species interact with each other and impact the host and that multi-species gut bacterial communities are capable of showing resilience by dampening strong competition effects.
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Keywords
aggregation, gut microbiome, interactions, multi-species, spatial structure, zebrafish