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Bacterial strains
NOTE: Eighty strains were isolated from the aquatic environment and identified using an automated bacteria identification instrument (see the Table of Materials), including Escherichia coli, Pseudomonas aeruginosa, Salmonella spp., Vibrio spp., Klebsiella pneumoniae, and Aeromonas hydrophila (Table 1). Staphylococcus aureus (see the Table of Materials) was used as a negative nonmotile control; Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhimurium (see the Table of Materials) were used as positive control strains.
- Identify test bacterial strains to be used for motility analysis.
- Include negative nonmotile controls and motile positive control strains.
TTC-enhanced bacterial motility observation
- Pick single colonies of test bacteria from agar plates and inoculate them into the semisolid media with TTC (2,3,5-triphenyltetrazolium chloride ) by puncturing them with inoculating needles.
- Culture the tubes at 37 °C in the incubator for 24-48 h to observe the results.
- Observe the growth state: characterize the bacteria as nonmotile (-) if only the puncture line is red. Characterize the bacteria as motile (+) if the red color spreads lightly outward along the puncture line.
Table 1: Comparison of bacterial motility.
| Strain | Semisolid medium with 0.4% agar | Semisolid medium with 0.4% agar and 0.005% TTC |
| 24 h | 48 h | 24 h | 48 h |
| P. aeruginosa ATCC27853 | + | + | + | + |
| E. coli ATCC25922 | + | + | + | + |
| S. typhimurium ATCC14028 | + | + | + | + |
| S. aureus ATCC25923 | - | - | - | - |
| E. coli (15) | 12 | 14 | 13 | 14 |
| Salmonella spp. (8) | 7 | 8 | 8 | 8 |
| A. hydrophila (20) | 18 | 20 | 20 | 20 |
| Vibrio spp. (8) | 7 | 8 | 8 | 8 |
| P. aeruginosa (24) | 18 | 20 | 22 | 23 |
| K. pneumoniae (5) | -5 | -5 | -5 | -5 |
| Numbers indicate the numbers of positive strains (+) and negative stains (-). |