Outline of the life cycle experimental evolution of M. xanthus with either 1% (stringent) or 15% (relaxed) population bottlenecks. Four different colonies of M. xanthus (GV1) were used to establish four parallel evolving lines. One generation of the complex life cycle with multiple social traits involved the growth of M. xanthus populations in nutrient-rich CTT liquid (with gentamycin) medium till O.D. 600 nm reached 0.3–0.4. These cultures were then spotted on starvation TPM hard agar (1.5% agar) plate for sporulation and fruiting body development. Next, only the spores (and not vegetative cells that failed to sporulate) were harvested by first incubating the M. xanthus populations at 50°C, after which they were transferred onto TPM hard agar (supplemented with 0.025% glucose) beds overlaid with Escherichia coli lawns in flasks for germination and predation. After incubation for 4 days on E. coli lawns, populations were harvested by adding 4 mL TPM buffer, shaking at 200 rpm, and either (0.04 mL) 1%, or (0.6 mL) 15% of harvested populations were transferred to fresh CTT liquid media with gentamycin (M. xanthus is naturally resistant to gentamycin whereas E. coli is sensitive to it). This selection regimen was repeated for 10 cycles.
Population bottlenecks shape the evolution of #cooperative traits in #Myxococcus via #LifeCycle trade-offs. @iamsamayp.bsky.social &co show that stringent bottlenecks favor growth & sporulation, while relaxed bottlenecks favor predation & germination @plosbiology.org 🧪 plos.io/3N1nia7
