UMU-ChromoTest™ (umuC Assay)
A rapid ISO 13829 microplate genotoxicity bioassay using a genetically engineered strain of Salmonella typhimurium TA1535 [pSK1002] to detect DNA damage in water, wastewater, effluents, chemicals, and environmental samples — with quantitative results in a single working day.
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The UMU-ChromoTest™ employs Salmonella typhimurium TA1535 [pSK1002], a genetically engineered strain in which the umuC SOS repair gene is fused to the lacZ reporter gene. When a genotoxic compound damages DNA, the SOS repair pathway is activated, triggering simultaneous production of β-galactosidase. The enzyme acts on the colourless substrate ONPG (o-nitrophenyl-β-D-galactopyranoside), converting it to the yellow product o-nitrophenol. The darker the yellow colour, the greater the genotoxicity — the bacteria are working harder to repair damaged DNA. Results closely correlate with the traditional Ames test while requiring only a single bacterial strain. The procedure follows ISO 13829, allowing direct comparison of results between laboratories worldwide.
- Test organismSalmonella typhimurium TA1535 [pSK1002] (umuC::lacZ fusion; rfa + uvrB mutations)
- EndpointumuC SOS induction — β-galactosidase activity; darker yellow = more genotoxic
- ChromogenONPG (o-nitrophenyl-β-D-galactopyranoside) → yellow o-nitrophenol product
- Detection wavelength420 nm (β-galactosidase) and 580 nm (turbidity correction)
- Incubation time1.5 hours exposure + 2 hours recovery + 30 minutes substrate development
- Format96-well microplate; 6 samples per plate in triplicate with 4 dilutions
- Tests per kitUp to 6 samples including dilutions and controls; small sample volumes (360 µL)
- Metabolic activationCompatible with S9 liver fraction for pro-mutagen testing (+/− S9 design)
- StandardISO 13829 — Water Quality: Determination of Genotoxicity Using the umu-test
- Ames correlationResults agree closely with traditional Ames mutagenicity tests; single strain advantage
- Sample matricesWater, wastewater, effluents, sediment extracts, chemicals, food, cosmetics, air extracts
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🍁 Ships from Burlington, Ontario, Canada · International shipping available · Cold-chain packaging included
How the UMU-ChromoTest™ Works
When a genotoxic compound enters a Salmonella typhimurium TA1535 [pSK1002] cell and damages DNA, the SOS repair pathway is activated. In this strain, the umuC gene is fused to the lacZ gene — so SOS induction simultaneously produces β-galactosidase. This enzyme converts the colourless substrate ONPG into the yellow product o-nitrophenol. The darker the yellow, the greater the genotoxicity — the bacteria are working harder to repair DNA damage. Colour intensity decreases across the dilution series as the genotoxic load is reduced. Strain TA1535 [pSK1002] contains both the rfa mutation (more permeable cell membrane for better sample uptake) and the uvrB mutation (eliminates error-free excision repair, forcing error-prone SOS repair), maximizing the assay’s sensitivity.
ProcedureAssay Procedure — Completed in One Working Day
Expose
Add sample dilutions (360 µL) to S. typhimurium TA1535 [pSK1002]; incubate 1.5 hours at 37°C
Recover
Dilute exposure cultures into fresh growth medium; allow a further 2 hours growth at 37°C for umuC gene expression
Develop
Lyse bacteria; add ONPG substrate; incubate 30 minutes at 37°C for yellow colour development
Read & Calculate
Measure absorbance at 420 nm (β-galactosidase) and 580 nm (turbidity); calculate Induction Factor (IF) using EBPI’s bioinformatics spreadsheet
Fig. 1 — UMU-ChromoTest™ 96-Well Plate Result
The photograph below shows a typical UMU-ChromoTest™ result. ONPG is the yellow chromogen — the colourless substrate is converted to the yellow product o-nitrophenol by β-galactosidase. The darker the yellow colour, the greater the genotoxicity of the sample. Deep yellow wells indicate heavy DNA damage repair activity; pale yellow or colourless wells indicate low genotoxicity or cytotoxicity. Colour intensity decreases with increasing dilution as the genotoxic concentration is reduced, producing the characteristic dose–response gradient visible across the plate.
Reading the Plate Result
Colourless / Very Pale
No or minimal ONPG conversion. Either no genotoxicity (negative control or clean sample) or acute cytotoxicity — bacteria killed before SOS induction can be measured.
Pale Yellow
Low to moderate β-galactosidase activity. Low genotoxicity — limited SOS induction at this sample concentration. Typically seen at higher dilutions in a dose–response series.
Deep Yellow
High genotoxicity. Significant ONPG → o-nitrophenol conversion driven by strong SOS induction. Bacteria are working hard to repair damaged DNA. Darker yellow = more genotoxic.
Genotoxicity Screening for Drinking Water & Wastewater
The UMU-ChromoTest™ is the ISO 13829 standardized method for determining genotoxicity in water and wastewater. EBPI has supported Canadian and international water quality programs, environmental agencies, and universities in applying the umuC assay to water quality monitoring for over 20 years.
💧 Drinking Water & Source Water
Disinfection by-products (DBPs) formed during chlorination, chloramination, and ozonation can have genotoxic activity. The UMU-ChromoTest™ provides ISO 13829–standardized genotoxicity screening for:
- Treated drinking water and distribution system monitoring
- Source water and reservoir genotoxicity assessment
- Disinfection by-product (DBP) genotoxicity profiling
- Groundwater contamination and remediation monitoring
- Source Water Protection Plan (SWPP) investigations
- Comparison of treatment processes for DBP reduction
See also: Microbial Source Tracking for fecal source identification in source water catchments.
🏭 Wastewater & Effluent Monitoring
Industrial and municipal effluents frequently contain genotoxic contaminants including PAHs, nitroaromatics, pharmaceuticals, pesticides, and heavy metal complexes. ISO 13829 compliance enables the UMU-ChromoTest™ to be used for:
- Municipal WWTP influent and effluent genotoxicity
- Industrial effluent characterization and compliance
- Pharmaceutical and hospital wastewater genotoxicity
- Combined sewer overflow (CSO) event monitoring
- Mining, leachate, and tailings effluent screening
- Pre/post-treatment genotoxicity comparison
Complement with the Toxi-ChromoTest™ for a combined acute toxicity + genotoxicity battery on the same sample.
⚙️ Metabolic Activation with S9 Fraction — Pro-Mutagen Testing
Many genotoxic compounds require metabolic activation before they become genotoxically active. The UMU-ChromoTest™ is designed to be run with or without S9 metabolic activation. The S9 mix (included in the S9 activation kit) contains S9A MgCl₂/KCl, S9B glucose-6-phosphate, S9C NADP, S9D phosphate buffer, and S9F lyophilized S9 fraction. Adding S9 allows detection of pro-mutagens such as benzo[a]pyrene, aflatoxins, and aromatic amines that would otherwise give false-negative results.
Why Use the UMU-ChromoTest™?
🏢 ISO 13829 Standardized
Fully compliant with ISO 13829, enabling direct comparison of results between laboratories worldwide and supporting regulatory submissions.
⚡ Completed in One Day
Rapid 1.5-hour exposure + 2-hour recovery + 30-minute substrate step. Results, including quantitative Induction Factor calculation, within a single working day.
📈 Quantitative & Qualitative
Visual qualitative interpretation plus spectrophotometric quantification at 420 nm and 580 nm. EBPI’s bioinformatics spreadsheet calculates Induction Factor (IF) automatically.
🔬 Single Strain Design
Only one bacterial strain required — compared to the five-strain Ames test. Simpler, faster, and more cost-effective for routine screening applications.
🧪 Ready-to-Use Reagents
All reagents and consumables supplied ready-to-use for a non-specialized laboratory. Small sample volumes (360 µL) minimize sample requirements.
🧬 Ames Test Correlation
Results agree closely with traditional Ames mutagenicity tests. Strong correlation validated across hundreds of published studies for environmental and industrial samples.
Full Range of UMU-ChromoTest™ Applications
Environmental Water Monitoring
ISO 13829–compliant genotoxicity testing of drinking water, groundwater, surface water, and sediment pore water.
Industrial & Municipal Effluents
Effluent characterization, discharge compliance, and pre/post-treatment genotoxicity comparison.
Chemicals & Raw Materials
Rapid genotoxicity screening of industrial chemicals, process intermediates, pesticides, and raw materials.
Food, Cosmetics & Pharmaceuticals
Genotoxicity screening of food additives, cosmetic ingredients, pharmaceutical compounds, and packaging extracts.
Sediment & Soil Extracts
Aqueous extracts of contaminated sediment and soil. See also: umuC Direct Contact Sediment Genotoxicity Test (Product No. 7021).
Research & Education
Used in universities across North America for over 20 years. Contact EBPI for educational kit pricing and protocols.
Kit Specifications & Performance Characteristics
| Parameter | Detail |
|---|---|
| Product Number | 5021 |
| Product Name | UMU-ChromoTest™ (umuC Assay) |
| Test Organism | Salmonella typhimurium TA1535 [pSK1002] (umuC::lacZ operon fusion; rfa mutation + uvrB mutation) |
| Assay Endpoint | umuC SOS induction; β-galactosidase converts ONPG to yellow o-nitrophenol. Darker yellow = more genotoxic. Colourless = no induction (clean sample) or cytotoxicity |
| Chromogen | ONPG (o-nitrophenyl-β-D-galactopyranoside) → yellow o-nitrophenol product |
| Detection | Spectrophotometric at 420 nm (β-galactosidase activity) and 580 nm (turbidity correction); visual qualitative evaluation also possible |
| Incubation Protocol | 1.5 hours exposure at 37°C + 2 hours recovery in fresh media + 30 minutes ONPG substrate development |
| Plate Format | 96-well microplate; 6 samples per plate in triplicate with 4 dilution steps |
| Sample Volume | 360 µL per well (small volume requirement) |
| Metabolic Activation | +/− S9 design; S9 components (S9A–S9F) available for pro-mutagen activation |
| International Standard | ISO 13829 — Water Quality: Determination of the Genotoxicity of Water and Waste Water Using the umu-test |
| Ames Test Correlation | Closely correlated with traditional Salmonella Ames mutagenicity tests; single strain simplicity |
| Kit Contents | All reagents and disposable plastics ready-to-use for up to 6 samples with dilutions and controls |
| Manufacturer | EBPI — Environmental Bio-Detection Products Inc., Burlington ON, Canada |
Technical Resources
Procedure Presentation
Step-by-step presentation of the UMU-ChromoTest™ procedure and ISO 13829 protocol
⬇️ Download PDFExcel Worksheet
EBPI’s bioinformatics spreadsheet for Induction Factor (IF) calculation and data recording
⬇️ Download PDFAssay Flow Chart
Quick-reference bench flowchart for the UMU-ChromoTest™ procedure
⬇️ Download PDFOther Genotoxicity & Toxicity Testing Kits
Contact EBPI for pricing, volume discounts, educational kit options, or technical support for the UMU-ChromoTest™.