
Fruiting body formation in Myxococcus xanthus provides valuable insights into microbial life, its complexities, and its ecological significance. The transition from single cells to multicellular structures involves intricate developmental processes. Studying these mechanisms can provide insights into cellular differentiation and development in other organisms. The Shaevitz Lab at Princeton investigated the interplay between nematic and polar order in M. xanthus colonies and how this interplay governs the mechanical events that trigger the transition from a monolayer to a multilayer colony structure. Polar order refers to the distinct orientation of individual bacterial cells with a defined "front" and "back" along their long axis. In contrast, nematic order describes the alignment of multiple bacterial cells parallel to each other without necessarily having a defined polarity within each cell. The paper describes the following results:

- Polarity fluctuations, rather than just nematic order, trigger the formation of new cell layers in M. xanthus colonies.
- M. xanthus controls the formation of new cell layers by tuning its cell reversal frequency, with non-reversing cells producing stronger traction fluctuations that promote layer formation.
- Even in reversing strains, there are regions with strong and weak local polar order, leading to a broad distribution of local traction forces.
Nematic and polar order coexistence in M. xanthus colonies. Polar order fluctuations drive stronger forces and flows than nematic stresses, and the colony's ability to control its morphology by tuning cell reversal time to modulate local polar order.
Han E, Fei C, Alert R, Copenhagen K, Koch MD, Wingreen NS, Shaevitz JW. Local polar order controls mechanical stress and triggers layer formation in Myxococcus xanthus colonies. Nat Commun. 2025 Jan 22;16(1):952. doi: 10.1038/s41467-024-55806-6. PMID: 39843452. https://www.nature.com/articles/s41467-024-55806-6
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