JoVE Encyclopedia of Experiments
Microbiology
0 views • 2:37 min • September 26th, 2025
Begin with two bacterial strains, a reference and a competitor, each expressing a distinct fluorescent marker for strain identification.
Mix the strains in equal proportions and spot the mixture onto an agar plate.
Incubate the plate to allow the strains to grow and interact.
The competitor outcompetes the reference strain through either contact-dependent or contact-independent mechanisms.
In contact-dependent competition, the competitor uses specialized secretion systems to deliver toxins directly into the reference strain.
In contact-independent competition, the competitor releases toxins that diffuse into the surrounding medium and enter the reference strain.
These toxins disrupt essential processes in the reference strain, including cell wall synthesis, DNA replication, and protein synthesis, leading to growth arrest, cell death, and reduced fluorescence expression.
After incubation, examine the plate under a fluorescence microscope.
Reduced fluorescence in the reference strain, compared to the brighter fluorescence of the competitor, indicates competitive interactions.
To mix the reference strain and competitor strain in a one to one ratio, add 100 microliters of each strain normalized
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