SOS/umu-Test as

A Tool for Genotoxicity Assessment

By 劉文堅Advisor: 袁如馨防災與水環境研究中心

Why umu-test ? A low cost experiment assay: no high cost chemicals

and complicated apparatus is needed in conducting the experiment.

High-throughput: umu-test enable high amount of sample to be tested at a time.

Short time requirement: umu-test utilizes bacteria which has short life cycle.

High sensitivity: accuracy of umu-test has been proven

Theory of umu-test

β-galactosidase

IR calculation

Mutagen exposure

Sos response

umuC-LacZ fused protein

translation

Enzyme production

ONPG o-nitrophenyl(colourless) (Yellow-colored)

Absorbance measurement

• Firstly, Salmonella typhimuium TA1535/pKK1002 will be exposed to genotoxicants

• As soon as the bacteria senses genotoxicity existance, SOS response is transmitted to produce umuC-LacZ fused protein

• The protein will produce β-galactosidase• ONPG is used as color indicator• ONPG (colorless) will be converted into o-

nitrophenyl (yellow color) by the existance of β-galactosidase

• Absorbance measurement is done under spectrophotometer

• The amount of β-galactosidase correlates to the level of toxicity

• Induction ratio obtained by calculation

Genotoxicity test of 4-NQO

The recent conducted toxicity test result on 4-NQO (well known genotoxicants) indicates the ability of umu test in toxic assessment.

The Dashed line represent concentration of 4-NQO at 2-fold greater than the control response, which tells us every black point (IR point) that is higher than the dashed line are considered to be genotoxic.

4-NQO (mg/L)

1052.

51.

250.

625

0.31

25

0.15

625

0.07

815

-g

alac

tosi

das

e ac

tivi

ty (

un

it)

0

200

400

600

800

1000

1200

1400

1600

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Ind

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rat

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14

-galactosidase activityInduction ratio

Future Study Application of umu-test on various toxic samples in

the environment. Continuous cooperation with the inventor of the

umu-test to increase the efficiency of the test by experimenting on different strains of Salmonella.

Comparison of the genotoxicity result by umu-test with those by Comet assay, to establish the database of potential genotoxicants from industrial wastewater.