Colorimetric Detection of a Bacterial Biomarker Using a Modified Litmus Test
Published: February 29, 2024
Abstract
Source: Tram, K., et al. Colorimetric Detection of Bacteria Using Litmus Test. J. Vis. Exp. (2016).
This video demonstrates a colorimetric E. coli detection method, involving an E. coli biomarker activating a DNAzyme, leading to cleavage of RNA linkage and detachment of a DNAzyme-urease conjugate. A subsequent colorimetric assay detects the E. coli biomarker through ammonia-induced pH changes.
Protocol
1. Preparing E. coli Cells for Testing For a desired cell suspension, transfer 1 ml of cultured stock to a 1.5 ml microfuge tube. Centrifuge the cells at 6,000 x g for 10 min at 4 °C. Carefully remove the supernatant without disturbing the cell pellet. Add 10 µl of reaction buffer to the cell pellet and resuspend the cells. Sonicate the cell suspension for 5 min. Transfer the cell suspension to an ice box for 5 min. Sonicate the cell s…
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The authors have nothing to disclose.
Materials
| Ethylenediaminetetraacetic acid (EDTA) | VWR AMRESCO | 105 | |
| Sodium Hydroxide (NaOH) pellets | BIO BASIC CANADA INC | SB6789 | |
| Tris-base | VWR AMRESCO | 497 | |
| Urea | VWR AMRESCO | M123 | |
| Xylenecyanol FF | SIGMA-ALDRICH | X-4126 | |
| 0.04% Phenol red | SIGMA-ALDRICH | P3532 | |
| 10x T4 polynucleotide kinase reaction buffer | Lucigen | 30061-1 | |
| E. coli K12 (MG1655) | ATCC | ATCC700926 | |
| Magnetic Bead (BioMag) | Bangs Laboratories Inc | ||
| Magnetic Seperation Rack | New England BioLabs | S1506S | |
| Microfuge tubes | Sarstedt | 72.69 | |
| Cell culture incubator | Eppendorf Scientific | M13520000 | |
| Branson Ultrasonic cleaner | Branson | N/A |
