Population Bottlenecks Shape the Evolution of Cooperation in Bacterial Societies – IISc Study
Bengaluru | Science & Research
Cooperation is a fundamental feature of microbial life, where individual cells invest resources for the collective benefit of the group. However, such cooperation often faces a challenge from “cheater” cells that exploit shared benefits without contributing. A new study from the Indian Institute of Science (IISc), Bengaluru, published in the prestigious journal PLOS Biology, reveals that population bottlenecks play a critical role in maintaining and shaping cooperative behaviour in bacteria.
The research focuses on Myxococcus xanthus, a well-known social bacterium that exhibits complex group behaviours such as coordinated hunting and spore formation within multicellular fruiting bodies. By conducting long-term laboratory evolution experiments, IISc researchers investigated how repeated population bottlenecks influence the evolution of cooperative traits.
A population bottleneck refers to a sudden and drastic reduction in population size and genetic diversity. Such events commonly occur in nature due to floods, forest fires, or other environmental disruptions.
Key Findings of the Study
The researchers compared two experimental conditions:
- Stringent bottlenecks, where only a few bacterial cells survived each generation
- Relaxed bottlenecks, where a larger number of cells were allowed to persist
Four major cooperative traits were analysed: sporulation, germination, predation, and growth.
The study found that:
- Stringent bottlenecks favoured fruiting body formation and growth
- Predation and germination abilities declined under stringent bottlenecks
- Populations became more genetically uniform and cooperation-oriented
- Relaxed bottlenecks led to increased competition and reduced cooperative stability
According to Jyotsna Kalathera, first author of the study and former PhD student at IISc, bottlenecks can effectively help eliminate cheater cells, thereby stabilising cooperative behaviour.
Dr Samay Pande, Assistant Professor at the Department of Microbiology and Cell Biology, IISc, noted that microorganisms offer a powerful model to understand evolutionary processes that are difficult to study in larger ecosystems.
Why This Research Matters
The findings provide valuable insights into:
- The evolution and stability of cooperation in microbial communities
- How population dynamics influence genetic and behavioural traits
- Broader principles underlying multicellularity and biological organisation
“Cooperation is central to the evolution of life—from genes forming chromosomes to cells forming multicellular organisms,” Dr Pande added.
Reference
Kalathera J., Jaiswal P., Mandal N., Patel V., Guttal V., Krishna S., Pande S.
Bottleneck size drives the evolution of cooperative traits in an aggregative multicellular myxobacterium, PLOS Biology (2025)
