Dataset for the submitted manuscript "Fitness-driven virulence evolution in Bacillus via group selection bypasses classic trade-off"

Social evolution theories of virulence posit a trade-off between pathogen replication and the cost of producing public goods, which are susceptible to exploitation by cheating mutants. This conflict constrains stable investment in shared virulence factor. Here, we demonstrate that group selection can circumvent this evolutionary constraint. Using the entomopathogenic Bacillus thuringiensis, which is safe for humans, as a model, we conducted ~200 generations of alternating serial passage in vivo (within insect host) and in vitro. This group selection yielded a stably inherited lineage with a virulence increase of over 20%, while other lineages showed fluctuating but non-significant changes in virulence. The virulent enhancement was uncoupled from changes in public goods (toxin) production and did not trade-off against replication or sporulation. Instead, higher virulence was attributable to increase within-host fitness: increased survival in the host midgut and more efficient translocation into the hemocoel. Furthermore, the competitive fitness of virulence-increased lineage was also stronger in their population. Pool-Sequencing Time Series analysis revealed that the higher virulence lineage showed the frequencies of certain genes remained at a low level, while other lineages showed more similar polymorphism with in vitro passaged control. This divergence in evolutionary trajectory underscores that the adaptation to the host was the primary driver of increased virulence. Our findings reveal a non-canonical evolutionary trajectory to virulence that operates through group-selected fitness benefits without public goods trade-offs.毒力的社会演化理论指出，病原体复制与公共产物生产成本之间存在权衡，而公共产物极易被欺骗性突变体利用。这种冲突制约了对共享毒力因子的稳定投入。本研究证明，群体选择能够规避这一演化约束。本研究以对人类安全的昆虫病原性苏云金芽孢杆菌（Bacillus thuringiensis）为模型，开展了约200代的体内（昆虫宿主内）与体外交替连续传代实验。该群体选择获得了稳定遗传的谱系，其毒力提升超过20%；而其他谱系的毒力则呈现波动但无统计学显著性的变化。该毒力增强与公共产物（毒素）的产量变化解偶联，且未与复制或芽孢形成产生权衡关系。相反，更高的毒力可归因于宿主内适合度的提升：宿主中肠内的存活率提高，且更高效地易位至血腔。此外，毒力提升谱系在其种群中的竞争适合度也更强。混合测序时间序列（Pool-Sequencing Time Series）分析显示，高毒力谱系中部分基因的频率维持在较低水平，而其他谱系的多态性与体外传代对照组更为相似。这种演化轨迹的差异凸显出，对宿主的适应是毒力增强的主要驱动因素。本研究结果揭示了一条非典型的毒力演化轨迹：其通过群体选择获得的适合度优势实现，且无需付出公共产物权衡的代价。