Bottleneck size drives the evolution of cooperative traits in an aggregative multicellular myxobacterium

Sep 29, 2026

Repeated population bottlenecks shape cooperation, yet it is unclear whether bottlenecks favor all cooperative traits or only a subset. Using laboratory evolution on Myxococcus xanthus, a social bacterium with multiple cooperative behaviors, researchers compared repeated stringent versus relaxed bottlenecks while all four traits were under selection. Stringent bottlenecks favored fruiting body formation and growth; relaxed bottlenecks reversed the pattern, promoting predation and germination. Relaxed regimes improved fitness across the life cycle and maintained higher trait variation, with coexistence of cooperative and exploitative strategies. Genomic analyses linked adaptations to mutations in regulatory proteins specific to each regimen, while similar trade-offs appear in natural populations.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages33

Reading Time1 h 23 min

AccessFree to download

Abstract

Key results

Genomic findings

Broader implications and trade-offs

OPEN ACCESS Citation: Kalathera J, Jaiswal P, Mandal N, Patel V, Guttal V, Krishna S, et al. (2026) Bottleneck size drives the evolution of cooperative traits in an aggregative multicellular myxobacterium. PLoS Biol 24(1): e3003499 . [https://doi.org/10.1371/journal.pbio.3003499](https://doi.org/10.1371/journal.pbio.3003499) [Academic Editor:](Academic Editor: J. Arjan G. M. de Visser)[ J. Arjan G. M. de Visser](Academic Editor: J. Arjan G. M. de Visser), Wageningen University, NETHERLANDS, KINGDOM OF THE Received: August 5, 2025 Accepted: October 31, 2025 Published: January 6, 2026 Copyright: © 2026 Kalathera et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data availability statement: All excel data sheets, R codes, Matlab codes, and whole genome sequence data are available from the figshare database (DOI: [https://doi](https://doi). org/10.6084/m9.figshare.c.7975292) . RESEARCH ARTICLE Bottleneck size drives the evolution of cooperative traits in an aggregative multicellular myxobacterium Jyotsna Kalathera1*, Prakhar Jaiswal2, Neha Mandal1, Vishwa Patel1, Vishwesha Guttal2, Sandeep Krishna3, Samay Pande1* 1 Bacterial Ecology and Evolution group, Department of Microbiology and Cell Biology, Indian Institute of Science, Bengaluru, India, 2 Theoretical Ecology and Evolution laboratory, Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, India, 3 Simons Centre for the Study of Living Machines, National Centre for Biological Sciences-TIFR, Bengaluru, India * [jyotsnak@iisc.ac.in](jyotsnak@iisc.ac.in) (JK); [samayrp@gmail.com](samayrp@gmail.com) (SP) Abstract Repeated population bottlenecks influence the evolution and maintenance of cooperation. However, it remains unclear whether bottlenecks select all cooperative traits expressed by an organism or only a subset of them. Myxococcus xanthus, a social bacterium, displays multiple cooperative traits, including growth, predation, sporulation in multicellular fruiting bodies, and germination. Using laboratory evolution experiments, we investigated the effect of repeated stringent versus relaxed population bottlenecks on the evolution of these four cooperative traits when they were all under selection. We found that only fruiting body formation and growth were positively selected under the stringent regimen, while the other two traits were selected against. The pattern was reversed in the relaxed regimen. Populations propagated under the relaxed regimen also exhibited greater fitness across the entire life cycle and maintained higher trait variations, including coexistence of cooperative and exploitative strategies. Genomic analyses identified mutations in σ54 interacting protein and DNA binding response regulator protein associated with adaptations in stringent and relaxed regimens, respectively. Furthermore, similar trade-offs, for example, between sporulation and germination, are also seen among natural populations of M. xanthus. Overall, we demonstrate that different bottleneck sizes drive the evolution of cooperative life history traits in distinct ways, often via trade-offs that constrain their joint optimization. Author summary Population bottlenecks have long been known to stabilize cooperation. However, we show that repeated bottlenecks affect different cooperative traits in distinct PLOS Biology | [https://doi.org/10.1371/journal.pbio.3003499](https://doi.org/10.1371/journal.pbio.3003499) January 6, 2026 1 / 33 Funding: The authors thank DST-FIST for support to the Department of Microbiology and Cell Biology, UGC Centre for Advanced Study, and the DBT-IISc partnership. This study was supported by the funds from India Alliance Intermediate fellowship ([https://www.indiaal](https://www.indiaal)[liance.org/fellowshiptype/basicbiom

FAQs

What question does the study address about bottlenecks and cooperation?

It tests whether repeated population bottlenecks select all cooperative traits or only specific subsets in a multicellular aggregative bacterium.

How did stringent versus relaxed bottlenecks affect the four cooperative traits?

Stringent bottlenecks positively selected fruiting body formation and growth, while relaxed bottlenecks reversed the pattern by favoring predation and germination.

What role did genomic analyses play in the findings?

Genomic analyses identified mutations in regulatory proteins that were associated with adaptations occurring under stringent versus relaxed bottleneck regimens.

Sep 29, 2026

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