Biosurfactant polysaccharide drives dispersal of exopolysaccharide-coated myxospores in Myxococcus xanthus
- 1Institut National de la Recherche Scientifique, Centre Armand-Frappier Sante Biotechnologie
Abstract
Bacterial spores are highly resilient cell forms, yet the organization of their protective surface layers in diderm species remains largely unexplored. For the social predatory soil bacterium Myxococcus xanthus, myxospore formation within multicellular fruiting body structures is a key ecological adaptation to surviving conditions of nutrient deprivation. These myxospores were long thought to be outwardly coated with so-called major spore coat (MASC) polysaccharide. Using polysaccharide-deficient mutant strains, electron microscopy, surface hydrophobicity assays, dye binding, and functional swarm complementation, we show that MASC instead forms a protective sub-surface outer-cortex layer, while the exopolysaccharide (EPS) glycocalyx inherited from vegetative cells constitutes the true outermost myxospore coat. EPS mediates inter-myxospore adhesion and supports collective behaviors, whereas secretion of biosurfactant polysaccharide (BPS) reduces myxospore surface stickiness, preventing excessive aggregation. BPS-deficient myxospores form persistent clumps, while EPS-deficient myxospores fail to aggregate or restore EPS-dependent swarm motility of vegetative cells. These results reveal a mechanistic interplay in which MASC serves as a sub-surface protective layer, EPS defines the exterior interface, and BPS tunes surface accessibility to regulate dispersal. Our findings overturn long-standing assumptions about myxospore architecture and illustrate a polysaccharide-driven strategy for controlling aggregation and readiness for germination. More broadly, these results highlight how social diderm bacteria leverage inherited and dynamically remodeled polysaccharide surfaces to coordinate multicellular development, in contrast to the rigid protein-based spore surfaces of Gram-positive species.
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BibTeX
@misc{bignet2026biosurfactant,
title = {{Biosurfactant polysaccharide drives dispersal of exopolysaccharide-coated myxospores in Myxococcus xanthus}},
author = {A. Bignet and N. Rezania and A. A. Kezzo and N. Saraf and A. Nakamura and G. Sharma and F. J. Veyrier and S. T. Islam},
howpublished = {bioRxiv},
year = {2026},
month = sep,
doi = {10.64898/2026.09.26.754727},
url = {https://www.biorxiv.org/content/10.64898/2026.09.26.754727v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Biosurfactant polysaccharide drives dispersal of exopolysaccharide-coated myxospores in Myxococcus xanthus
AU - A. Bignet
AU - N. Rezania
AU - A. A. Kezzo
AU - N. Saraf
AU - A. Nakamura
AU - G. Sharma
AU - F. J. Veyrier
AU - S. T. Islam
PY - 2026
DA - 2026/09/26
PB - bioRxiv
DO - 10.64898/2026.09.26.754727
UR - https://www.biorxiv.org/content/10.64898/2026.09.26.754727v1
AB - Bacterial spores are highly resilient cell forms, yet the organization of their protective surface layers in diderm species remains largely unexplored. For the social predatory soil bacterium Myxococcus xanthus, myxospore formation within multicellular fruiting body structures is a key ecological adaptation to surviving conditions of nutrient deprivation. These myxospores were long thought to be outwardly coated with so-called major spore coat (MASC) polysaccharide. Using polysaccharide-deficient mutant strains, electron microscopy, surface hydrophobicity assays, dye binding, and functional swarm complementation, we show that MASC instead forms a protective sub-surface outer-cortex layer, while the exopolysaccharide (EPS) glycocalyx inherited from vegetative cells constitutes the true outermost myxospore coat. EPS mediates inter-myxospore adhesion and supports collective behaviors, whereas secretion of biosurfactant polysaccharide (BPS) reduces myxospore surface stickiness, preventing excessive aggregation. BPS-deficient myxospores form persistent clumps, while EPS-deficient myxospores fail to aggregate or restore EPS-dependent swarm motility of vegetative cells. These results reveal a mechanistic interplay in which MASC serves as a sub-surface protective layer, EPS defines the exterior interface, and BPS tunes surface accessibility to regulate dispersal. Our findings overturn long-standing assumptions about myxospore architecture and illustrate a polysaccharide-driven strategy for controlling aggregation and readiness for germination. More broadly, these results highlight how social diderm bacteria leverage inherited and dynamically remodeled polysaccharide surfaces to coordinate multicellular development, in contrast to the rigid protein-based spore surfaces of Gram-positive species.
ER -