This photograph depicts three test tubes, each containing a motility medium with triphenyl tetrazolium chloride (TTC), as a growth indicator. The far left tube was inoculated with an ATCC control strain of non-motile Staphylococcus bacteria, and incubated for a 24 hour time period. The middle tube was inoculated with an ATCC control strain for non-pathogenic, motile, Escherichia coli bacteria, and also incubated for a 24 hour time period. The far right tube was also inoculated with the ATCC control strain for non-pathogenic, motile, Escherichia coli bacteria, but allowed to grow for a 5-day time period, which allowed for the bacterial swarm, in order to represent what would happen had Salmonella enterica serovar Typhimurium bacteria been used in place of the E. col.
You’re able to see that the organisms in tube #1, i.e., non-motile Staphylococcus, remained affixed to the tract, and fracture lines formed by the inoculating needle, upon their introduction to the motility medium. While those organisms in tube #2, i.e., motile E, coli, are seen to have begun migrating away from the needle tract, out into the surrounding medium. Finally, those organisms in tube #3, again motile E. coli, were permitted to migrate throughout the tube, given their 5-day, elongated incubation period.