High transposase abundance in the deep ocean is linked to a particle-associated lifestyle

Abstract

AbstractTransposases are mobile genetic elements (MGEs) that move within and between genomes, enabling genomic plasticity within microorganisms. Transposases often carry functional genes, termed cassette sequences, when they migrate within and between genomes. In marine microbial communities, transposase abundance increases with depth, but the reasons for this trend are unclear. Through analysis of metagenomes from the Tara Oceans and Malaspina Expeditions, we identify the particle-associated lifestyle as a main covariate for the high occurrence of transposases in the deep ocean. The abundance of biofilm-associated genes correlates with transposases in a strong and depth-independent manner, suggesting that MGEs readily propagate among microbial communities in crowded biofilms. We show that particle association positively correlates with larger genome size, which is linked to higher transposase abundance. Genes related to defense mechanisms are enriched in cassette sequences associated with transposons and are more highly expressed in the deep sea. Thus, while transposons spread at the expense of their microbial hosts, they introduce novel genes and potentially benefit the hosts in accessing heavily contested resources. Together, our results reveal an emerging picture of deep ocean particles as gene sharing highways that result in expanded and defensively oriented microbial genomes.