When Not to Kill Your Host in Competitive Bust-Boom Environments

Temperate phages, which can either kill their host cells or integrate into them, struggle to compete with purely virulent phages in environments with plenty of available hosts. This suggests that their survival strategy is fine-tuned for unstable conditions, where they hedge their bets between immediate replication and long-term persistence as an integrated prophage. In this study, we explored how temperate phages make these life-or-death decisions, both in isolation and when competing with other phages. We found that when temperate phages compete with each other, those with relatively stable lysogens survive better. Environments with competitive temperate phages further select for lower lysogeny frequency. Our findings suggest that dosage-dependent lysogeny choice is adapted to competing phages with overlapping immunity. In environments where phages can disperse between separate sub-systems that fluctuate independently, temperate phages struggle to survive against virulent phages.