Preprint / Loss of dispersal via ice nucleation activity constrains microbial evolution

Cet article est un preprint et n'a donc pas été certifié par des pairs

Jacobs, J.M., Konkel, Z., Poelstra, J.W., Butchachas, J., Ebeling-Koning, L., Renzer, G., Meister, K., Slot, J.C., Cohen, S.P., Roman-Reyna, V., Morris, C.E. (2026) Loss of dispersal via ice nucleation activity constrains microbial evolution. bioRxiv, 2026.02.11.704803. DOI:10.64898/2026.02.11.704803 https://doi.org/10.64898/2026.02.11.704803

Résumé : The ability to disperse over long distances through the atmosphere is a common trait across the tree of life, facilitating resource access and increasing long-range gene flow. Loss of dispersal mechanisms, viz. flight, can occur in animals found on islands where documented phenotypic changes like loss of wingspan impedes longer distance travel to mate with the metapopulation. Bacteria also experience atmospheric flight and descend via bioprecipitation by catalyzing the freezing of cloud droplets with protein InaZ. InaZ triggers ice nucleation at temperatures near 0_∘C(1). This ice nucleation activity (INA), a biophysical trait, enhances bacterial deposition through precipitation. The role of InaZ-mediated ice nucleation on bacterial dispersal is well documented, but the impact of loss of INA and thus reduction or loss of atmospheric dispersal on bacterial ecology and evolution has not been described. Here we show that the loss of the ancestral inaZ gene restricts bacterial dispersal and leads to significant genetic and ecological isolation across multiple genera. Through the analysis of available complete genomes, we demonstrate that lineages lacking functional inaZ experience major gene loss events, reduced recombination rates and a marked dependence on human-mediated or insect transmission. These INA-lacking bacteria exhibit an increased ecological signature of isolation that parallels the distribution of geographically isolated animals. Our results establish InaZ as a keystone biophysical trait that defines microbial dispersal strategies. We anticipate these findings will provide a framework for understanding how shifts in biophysical traits drive niche differentiation and changes in dispersal with downstream consequences for Earth system processes.