Phototaxis as a Collective Phenomenon in Cyanobacterial Colonies

Cyanobacteria are a diverse group of photosynthetic bacteria that exhibit phototaxis, or motion in response to light. Cyanobacteria such as Synechocystis sp. secrete a mixture of complex polysaccharides that facilitate cell motion, while their type 4 pili allow them to physically attach to each othe...

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Bibliographic Details
Published in:Scientific reports 2017-12, Vol.7 (1), p.17799-10, Article 17799
Main Authors: Varuni, P., Menon, Shakti N., Menon, Gautam I.
Format: Article
Language:English
Subjects:
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631/326
631/57
Bacteria
Cell Movement - physiology
Colonies
Cyanobacteria
Cyanobacteria - physiology
Humanities and Social Sciences
Light
Light sources
multidisciplinary
Phototaxis
Phototaxis - physiology
Pili
Polysaccharides
Quorum Sensing - physiology
Saccharides
Science
Science (multidisciplinary)
Signal Transduction - physiology
Synechocystis - physiology
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Summary:Cyanobacteria are a diverse group of photosynthetic bacteria that exhibit phototaxis, or motion in response to light. Cyanobacteria such as Synechocystis sp. secrete a mixture of complex polysaccharides that facilitate cell motion, while their type 4 pili allow them to physically attach to each other. Even though cells can respond individually to light, colonies are observed to move collectively towards the light source in dense finger-like projections. We present an agent-based model for cyanobacterial phototaxis that accounts for slime deposition as well as for direct physical links between bacteria, mediated through their type 4 pili. We reproduce the experimentally observed aggregation of cells at the colony boundary as a precursor to finger formation. Our model also describes the changes in colony morphology that occur when the location of the light source is abruptly changed. We find that the overall motion of cells toward light remains relatively unimpaired even if a fraction of them do not sense light, allowing heterogeneous populations to continue to mount a robust collective response to stimuli. Our work suggests that in addition to bio-chemical signalling via diffusible molecules in the context of bacterial quorum-sensing, short-ranged physical interactions may also contribute to collective effects in bacterial motility.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-017-18160-w