Detection of genotoxic substances
The term genotoxic describes reversible or irreversible damage to genetic material (DNA) by chemical substances or physical influences. The genotoxicity of metabolites is identified in addition to the genotoxic effects of the substances contained in the sample.
Our quick and proven biotest is used to analyse the mutagenic (genotoxic) potential of chemical substances and complex substance mixtures. The umu test offered by Food GmbH satisfies DIN 38415-T3, as well as analysis method 410 described in the Waste Water Ordinance (AbwV).
Our accredited laboratory offers genotoxicity analysis of the following sample materials:
- waste water,
- ground water and leachate,
- cooling water,
- soil eluates,
- sludge and sediment samples,
- flowing and stagnant waters
on short notice.
The test is based on the genetically modified salmonella typhymurium strain TA1535/pSK1002, a gramonegative, facultative anearobe bacterium from the family of enterobacteriaceae. It is modified in such a way:
- to improve penetration of chemicals through the cell walls, and
- to connect the induction of the cellular repair mechanism to a measurable detection system.
The test involves diluting the sample in increments and cultivating it with S. typhymurium. Genotoxic substances present in the sample during the growth phase induce the umuC gene (uv-mutagenesis) in the test strain. The umuC gene belongs to the cell’s SOS repair system and is activated in response to damaged DNA caused by genotoxic substances (analyte). A colour reaction (o-nitrophenol) can be used to measure activation of the repair system by genotoxic substances when a reporter gene (lacZ) is coupled to this repair response. However, this does not detect substances in a bacterium that in their initial state are harmless, but develop genotoxicity in mammals through enzyme catalysis. Therefore, additional cultivation using rat liver homogenate (S9 fraction, enzymatic preparation) is performed for substances that require enzymatic activation.
Besides the induction rate (IR), the growth factor (GF) is also used to evaluate the genotoxic potential of the sample. The findings are discounted if the bacterial growth inhibition is greater than 50% (GF < 0.5). The test result is expressed as the so-called total protein in urine factor (dilution stage G). This is the smallest value in dilution stage G, in which IR is < 1.5 and GF > 0.5. The smallest possible dilution G required in this test when using an undiluted water sample is 1.5 (i.e. TPU = 1.5); this finding states that the sample does not possess any genotoxic potential.
The umu test only permits statements on the genotoxicity (primary DNA damage) of substances contained in the sample. It does not provide any information on carcinogenity.
Sampling and sample volume
- Sample volume: 25–50 ml
- Sampling: Individual samples are taken by our trained and certified staff; customers may take their own samples in self-monitoring systems
- Transport: mandatory cooling and immediate transport to the analysis point