Longitudinal studies are equally relevant for studying the dynamics of microbiomes outside the human body (FIG. 2). For example, one study explored the interplay between viral and microbial populations in human-controlled aquatic environments (aquaculture and solar saltern ponds)39. Theoretical models predict that such communities should follow ‘kill-the-winner’ dynam-ics: as a microbial species becomes more dominant, its
interactions with predatory phages increase, ultimately leading to population decline. The cycle then repeats for the next microbial species rising to dominance, always driving the community away from a homogeneous state. Contrary to this model, earlier empirical observations had shown that similar communities maintained sur-prisingly stable composition and metabolic potential. By using temporal metagenomic analysis, this apparent paradox was resolved by demonstrating that although composition remained stable at the species level, dis-tinct microbial strains within those species displayed kill-the-winner dynamics, as predicted by the theoretical model. Therefore, although the net abundance of strains within a species remained stable, individual strains grew or declined according to strain-specific phage predation. These findings highlight the advantages of integrating strain-level profiling with longitudinal sampling and serve as a reminder of the benefits of considering alternative metagenomic sequencing strategies (FIGS 1,2).