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Peer-reviewedCC BY 4.0PLOS One

Bacterial expression of human small GTPases induces stochastic predatory responses and motility interference in Physarum polycephalum

  • Rui Saiki1
  • Rion Iimura2
  • Makoto Ichimura3
  • Yoshihito Osada4
  • Ken-Ichi Sano5
5 affiliations
  1. 1Department of Applied Chemistry, Faculty of Fundamental Engineering, Nippon Institute of Technology, Saitama, Japan
  2. 2Tochigi Prefectural Oyama High School, Oyama, Tochigi, Japan
  3. 3Department of Innovative System Engineering, Faculty of Engineering, Nippon Institute of Technology, Saitama, Japan
  4. 4Glycometabolic Biochemistry Laboratory, RIKEN, Saitama, Japan
  5. 5Department of Sustainable Biological Chemistry, Faculty of Fundamental Engineering, Nippon Institute of Technology, Saitama, Japan
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Abstract

We investigated the behavioral responses of the slime mold Physarum polycephalum to Escherichia coli expressing human small GTPases to elucidate how internalized proteins affect its actomyosin-based motility machinery. We found that prey bacteria expressing hKRAS WT or hRhoA triggered a deterministic “conflict” behavior, in which P. polycephalum failed to complete ingestion despite physical contact. Notably, the oncogenic hKRAS G12C mutation induced a transition to stochastic switching among predation, conflict, and sampling-mediated rejection, whereas hRac1 expression showed a tendency toward diversified behavioral outcomes. To explain this, we propose a working model centered on molecular jamming or local perturbation of intracellular oscillatory dynamics, in which non-prenylated G-domains act as decoys that decouple the contractile machinery from leading-edge actin dynamics. This behavioral stochasticity likely reflects physical noise arising from the specific conformational states and functional heterogeneity of the expressed proteins. Our results suggest that P. polycephalum functions as a sensitive biological sensor of the biophysical properties of prey proteins, providing a unique platform for exploring the co-evolutionary arms race and molecular survival strategies between bacteria and amoeboid predators.

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Cite

BibTeXRIS
BibTeX
@article{saiki2026bacterial,
  title = {{Bacterial expression of human small GTPases induces stochastic predatory responses and motility interference in Physarum polycephalum}},
  author = {Rui Saiki and Rion Iimura and Makoto Ichimura and Yoshihito Osada and Ken-Ichi Sano},
  journal = {PLOS One},
  year = {2026},
  month = sep,
  doi = {10.1371/journal.pone.0359275},
  url = {https://doi.org/10.1371/journal.pone.0359275},
  note = {CC BY 4.0},
}
RIS
TY  - JOUR
TI  - Bacterial expression of human small GTPases induces stochastic predatory responses and motility interference in Physarum polycephalum
AU  - Rui Saiki
AU  - Rion Iimura
AU  - Makoto Ichimura
AU  - Yoshihito Osada
AU  - Ken-Ichi Sano
PY  - 2026
DA  - 2026/09/24
JO  - PLOS One
DO  - 10.1371/journal.pone.0359275
UR  - https://doi.org/10.1371/journal.pone.0359275
AB  - We investigated the behavioral responses of the slime mold Physarum polycephalum to Escherichia coli expressing human small GTPases to elucidate how internalized proteins affect its actomyosin-based motility machinery. We found that prey bacteria expressing hKRAS WT or hRhoA triggered a deterministic “conflict” behavior, in which P. polycephalum failed to complete ingestion despite physical contact. Notably, the oncogenic hKRAS G12C mutation induced a transition to stochastic switching among predation, conflict, and sampling-mediated rejection, whereas hRac1 expression showed a tendency toward diversified behavioral outcomes. To explain this, we propose a working model centered on molecular jamming or local perturbation of intracellular oscillatory dynamics, in which non-prenylated G-domains act as decoys that decouple the contractile machinery from leading-edge actin dynamics. This behavioral stochasticity likely reflects physical noise arising from the specific conformational states and functional heterogeneity of the expressed proteins. Our results suggest that P. polycephalum functions as a sensitive biological sensor of the biophysical properties of prey proteins, providing a unique platform for exploring the co-evolutionary arms race and molecular survival strategies between bacteria and amoeboid predators.
SN  - 1932-6203
ER  -