Bioindicators are organisms that monitor environmental health and changes by producing molecular signals. Genotoxic compounds are DNA-damaging agents that affect replication and activate the SOS response, leading to the expression of specific genes. The document discusses using the SOS response as a bioindicator by constructing plasmid vectors to detect DNA damage through gene expression and fluorescent markers.

1. Bioindicators of
Genotoxic Compounds
Submitted to-
Dr. R. D. Gupta
Submitted by-
Virendra Singh

2. Bioindicators
Bioindicators are defined as organisms used to
monitors the health of, or changes in, their
surroundings or ecosystem.
This can be plants, animals or bacteria that
regularly produce certain molecular signals in
response to changes in their environmental
conditions.
Bioindicators are also known as biomarkers.

3. Genotoxic Compounds
Toxic to life
DNA damaging compounds
Difficult to metabolize as they contain
molecular arrangement that are not normally
encountered in nature.
e.g., Ethyl methane sulphate (EMS), methyl
methane sulphate (MMS), mitomycin C (MMC),
hydrogen peroxide, formaldehyde, N-methyl-N-
nitro-N-nitrosoguanidine.

4. Single stranded and double stranded DNA damage
potentially caused by genotoxic compounds.

5. Types of mutations caused by genotoxic compounds

6. How genotoxic compounds affect DNA?
Replication
Genotoxic compounds
Activation of SOS Response Gene
Rec A
Rec A –SS DNA

7. SOS Response
Rec A autocatalytic activity
Cleavage of Lex A repressor at Ala-Gly peptide bond
SOS response gene express
SOS induces damage inducible (din) gene or sos
gene has 20 nucleotide long “SOS-box” near its
promoter/operator site, to which Lex A repressor
protein bound, preventing RNA polymerase binding
and gene expresson.

8. SOS response can be used as
Bioindicator
Construct a plasmid vector in which din gene
promoter fused with lac Z gene .
• In normal condition lacZ gene not express due to
genotoxic compound.
• But din gene express in the presence of toxic
compound
• When lacZ gene construct with din promotor it
express in this condition.

9. Detection of SOS-Induced Genes
din gene Lac Z gene
P
P
Din gene
lac Z gene
Vector
Transfer into E. coli

10. Detection of SOS-Induced Genes
DNA damage No expression of β-galactosidase
If Lac Z gene expressed with din promoter then formation
of β-galactosidase start in response to DNA damage.
If Lac Z gene replaced by GFP gene then it produces GFP.
With the help of fluorescent GFP present can be detected.

11. THANK YOU
FOR
ATTENTION