The prokaryotes (bacteria and archaea) that make up the majority of our microbial inhabitants (the microbiota) are known to engage in horizontal gene transfer (HGT) i.e., gene transfer among lineally unrelated individuals. The ‘holobiont’ perspective considers the human (or other macroscopic organism) and the associated microbial community as a composite organism. Can ecological and evolutionary considerations inform our analyses of gene transfer within the prokaryotic component of the microbiota, and do these analyses gain from a holobiontic perspective? This is the theme of my synthetic review published in Microbiome.

When we look back at 2018, it will lay strong claim to the title 'annus mirabilis' with respect to the discovery of novel bacterial anti-phage defenses.