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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Here, we present a protocol to detect bacterial motility based on a color reaction. Key advantages of this method are that it is easy to evaluate and more accurate, and does not require specialized equipment.

Abstract

Bacterial motility is crucial for bacterial pathogenicity, biofilm formation, and drug resistance. Bacterial motility is crucial for the invasion and/or dissemination of many pathogenic species. Therefore, it is important to detect bacterial motility. Bacterial growth conditions, such as oxygen, pH, and temperature, can affect bacterial growth and the expression of bacterial flagella. This can lead to reduced motility or even loss of motility, resulting in the inaccurate evaluation of bacterial motility. Based on the color reaction of 2,3,5-triphenyl tetrazolium chloride (TTC) by intracellular dehydrogenases of living bacteria, TTC was added to traditional semisolid agar for bacterial motility detection. The results showed that this TTC semisolid agar method for the detection of bacterial motility is simple, easy to operate, and does not involve large and expensive instruments. The results also showed that the highest motility was observed in semisolid medium prepared with 0.3% agar. Compared with the traditional semisolid medium, the results are easier to evaluate and more accurate.

Introduction

Bacterial motility plays a critical role in bacterial pathogenicity, biofilm formation, and drug resistance1. Bacterial motility is closely associated with pathogenicity and is necessary for bacterial colonization during early infection of host cells2. Biofilm formation is closely related to bacterial motility, where bacteria adhere to the surface of solid media through motility. Bacterial motility has long been considered to be positively correlated with biofilm formation. A high degree of bacterial drug resistance due to biofilm can lead to persistent infections that are a threat to human health3

Protocol

1. Preparation of semisolid medium

  1. Traditional semisolid agar
    1. Prepare the traditional semisolid agar according to the bacterial motility test medium recipe using the basic ingredients11. Dissolve 10 g of Tryptose, 15 g of NaCl, 4 g of agar in enough distilled water, adjust the pH to 7.2 ± 0.2, and make up the final volume to 1,000 mL.
    2. Autoclave the agar at 121 °C for 20 min, and dispense it into 10 mL test tubes as a 3-.......

Representative Results

Both standard strains and isolated strains were compared for motility detection, and the results are shown in Table 1. Due to the absence of flagella, Staphylococcus aureus and Klebsiella pneumoniae only grew along the inoculated line on both traditional and TTC semisolid media. In contrast, Pseudomonas aeruginosa, Escherichia coli, and Salmonella typhimurium showed growth in all directions around the inoculated line after culturing for 24 h on TTC semisolid m.......

Discussion

The detection of bacterial motility by the semisolid medium method is affected by many factors13,14. Bacterial growth conditions, such as oxygen (aerobic on agar surface, nonaerobic at the bottom of the tube with the semisolid medium), pH, and temperature, can affect the viability of bacterial flagella, which can lead to reduced motility or even loss of motility15. In addition, some mucus-type bacteria as their motility can be affected by .......

Acknowledgements

This study was supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD) and Teaching Reform Research Project of China Pharmaceutical University (2019XJYB18).

....

Materials

NameCompanyCatalog NumberComments
Bacto AgarDifco
Escherichia coliATCCATCC25922Positive control
Pseudomonas aeruginosaATCCATCC27853Positive control
Salmonella typhimuriumATCCATCC14028Positive control
Staphylococcus aureusATCCATCC25923Negative nonmotile control
Tryptose OXOID
TTCSigma298-96-4
VITEK 2 automated microbial identification systemBio Mérieux

References

  1. Jordan, E. O., Caldwell, M. E., Reiter, D. Bacterial motility. Journal of Bacteriology. 27 (2), 165 (1934).
  2. Lai, S. L., Hou, H., Jiang, W. Bacterial motility and its role during initial stage of pathogenesis. Journal of Microbiolo....

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