We live in a symbiotic world. All metaorganisms alike must have mechanisms in place to discriminate between microorganisms and to establish bacterial colonization during host development. However, the factors that are influencing the processes remain poorly understood.
In the first funding phase, the project of PI Hentschel (B1.1) focused on describing differential sponge responses to microorganisms by using an experimental approach in combination with transcriptome sequencing. Additionally, an experimentally tractable model for sponge symbioses was developed. In the project of PI Fraune (B1.2), co-occurrence networks indicated that bacterial interactions are dynamic throughout Nematostella development and certain competitive bacteria were shown to influence community structure over time. Re-colonization experiments indicated on one hand that bacteria-bacteria interactions are essential factors controlling colonization dynamics, while on the other hand RNA-Seq experiments indicated that the host might be involved in shaping initial colonization events.
In the second funding phase, we will build on these results and focus our efforts on two overarching aims:
(i) Do host mechanisms, especially phagocytosis, control bacterial colonization events in early branching metazoan taxa?
(ii) Which role do bacteria-bacteria interactions play in the assembly of the microbiome?
The new insights, which will be derived from in vitro and in vivo studies in both model systems, will unveil possibly ancient mechanisms of host-microbe cross talk and will provide insights into the patterns and successions that shape microbial colonization dynamics. As sponges and cnidaria preserved much of the genetic complexity of the common metazoan ancestor, our project promises to discover conserved mediators, which have evolved early in evolution as controls of bacterial colonization.
By combining our highly complementary expertise with respect to animal models and microbiology, we will be in a unique position to identify general rules of host-microbe and microbe-microbe interactions of which some may be conserved across all animal life while others may be unique to specific animal groups.