Vibrio fischeri
Free-swimming in the ocean at low density, it's invisible - producing no light.
Vibrio fischeri lives in two worlds. Free-swimming in the ocean at low density, it's invisible - producing no light. Colonizing a squid's light organ at high density (10^10 cells/mL), it glows brilliantly, creating counter-illumination camouflage for its host. The difference is quorum sensing: cells continuously secrete a chemical autoinducer (3-oxo-C6-HSL) that accumulates in confined spaces. When the concentration crosses threshold, every cell simultaneously activates its bioluminescence genes. The entire colony lights up as one.
This is where quorum sensing was first discovered - Woody Hastings at Princeton in the 1960s documenting how bacteria coordinate collective behavior through chemical signaling. The genius is efficiency: bioluminescence consumes ~20% of cellular energy budget. Individual cells in the open ocean waste that energy producing invisible light. But packed in the squid's light organ where diffusion is restricted, accumulated autoinducer triggers synchronized production - creating visible light that benefits the host, who provides nutrients in return. Threshold-triggered collective behavior optimized for context.
The strategic principle is fundamental: Expensive behaviors should activate only when collective participation makes them effective. Vibrio fischeri demonstrates that broadcast communication wastes resources unless density guarantees reception. Slack's presence indicators work identically - showing online status only when enough teammates are active to make synchronous communication worthwhile. Don't signal to an empty room.
Notable Traits of Vibrio fischeri
- Quorum-sensing bioluminescence
- AHL autoinducer signaling
- Density-dependent gene expression
- First organism where quorum sensing was discovered
- Produces bioluminescence only at high density (~10^7-10^10 cells/mL)
- Uses 3-oxo-C6-HSL (lactone) as autoinducer
- Symbiotic relationship with squid provides mutual benefit
- Light production consumes ~20% of cell energy budget
Vibrio fischeri Appears in 2 Chapters
Vibrio fischeri demonstrates quorum sensing for coordinated bioluminescence, where accumulated autoinducer triggers synchronized light production only at high population density.
How density triggers collective behavior →Vibrio fischeri is the organism where quorum sensing was first discovered, showing how bacteria invest in expensive bioluminescence only when population density makes it worthwhile.
How bacteria coordinate through chemistry →