The COMETS project focuses on mobile genetic elements—both conjugative and mobilizable, whether episomal or integrated—found in bacterial genomes. It will specifically target Bacillota, a bacterial group widely present in the gut microbiota. Within this group, a paradoxical observation drives the study: mobilizable elements, which cannot transfer autonomously, are far more abundant than conjugative elements. This imbalance raises a central biological question: What mechanisms explain their evolutionary success?
To unravel this mystery, COMETS conducts a systematic, large-scale exploration of the distribution, abundance, and diversity of these two types of elements in Bacillota. The goal is to determine whether their prevalence varies across taxonomic groups, including uncultivable species within the human gut microbiota. The project will also investigate two foundational hypotheses to explain the unexpected evolutionary success of mobilizable elements:
1. They may exploit the machinery of multiple conjugative elements—plasmids and integrated elements—to maximize their dissemination. COMETS will decode the partnerships between these elements by analyzing their co-occurrence patterns and preferential interactions.
2. Their persistence may rely on optimized vertical transmission, enhanced by "cargo" genes that provide a selective advantage to their bacterial hosts. By predicting the function of these genes, COMETS will assess their key role in bacterial adaptation to their environment and their contribution to the long-term maintenance of mobilizable elements.
The COMETS project will shed light on the evolutionary dynamics and ecological mechanisms underlying the success of conjugative and mobilizable elements, shaping the genomes of Bacillota and, likely, the composition of the gut microbiota.