Transcript Mutagenic Properties of Pesticides

Mutagenic Properties of
Pesticides
Kimberly Champine
Pesticide Usage
Pesticide use by farmers in southeast Missouri
provides many opportunities for pesticide
contamination of ground water. The ideal outcome
of pesticide use occurs when it accomplishes its
purpose then breaks down into harmless
components such as CO2 and H2O. The breakdown
of various pesticide chemicals varies with time and
can be affected by factors such as persistence,
formulation or soil characteristics.
Groundwater Contamination
Groundwater is the water that
that lies below the soil
surface and fills the pore
spaces in and around rock,
sand, gravel and other
materials. Groundwater
moves through water
saturated zones called
aquifers. The upper level of
the aquifer is the water table
and fluctuates throughout
the year. Contamination
occurs when unwanted
substances move into the
saturated zone.
Classification and Examples of
Pesticides
Pesticides
Insecticides
Organophosphate
Herbicides
Carbamates
Triazine
Malathion
Aldicarb
Atrazine
Parathion
Carbaryl
Hexazinone
Diazinon
Propoxur
Simazine
Parathion

Parathion is an
organophosphate compound
and is one of the most toxic
insecticides registered with
the EPA. Is is a broad
spectrum insecticide,
nematocide, acaricide, and
fumigant. Parathion is used
on alfalfa, barley, corn,
cotton, soybeans and wheat.
Aldicarb

Aldicarb is a member of the
carbamate class of
chemicals. It is a toxic,
systemic insecticide used to
control mites, nematodes,
and aphids. It is applied
directly to the soil and is
used on cotton, peanut, and
soybean crops.
Atrazine

Atrazine is a member of the
triazine class of chemicals.
It is a broad-leaf preemergence herbicide
commonly applied to
agricultural fields containing
corn, apples and grapes.
Eighty million pounds of
atrazine are applied annually
to soils in the US.
Testing Contaminated Ground
Water for Mutagenesis Using
the Ames Test
Ames Test


Used to evaluate the mutagenicity
of chemicals
Assay is based on the reversion of
mutations in the histidine (His)
operon in the bacterium
Salmonella typhimurium

Mutations are changes in the DNA
sequence of a gene
Salmonella typhimurium



The His operon encodes enzymes
required for the biosynthesis of
the amino acid histidine
Strains with mutations in the His
operon are unable to grow without
added histidine
Revertants that restore His+
phenotype will grow without
added histidine
Step 1 – Inoculating Plates
Spread 0.05 ml (1 drop)
of mutant strain of
Salmonella to the
surface of Minimal Media
without Histidine
Step 2 – Apply Groundwater
Add a sterile paper disk to the
center of the plate
Apply 0.1 ml of Groundwater, or
other suspected mutagen, to the
center of the disk
Only cells that are mutated a
second time will be able to
synthesize Histidine and be able to
grow
Typical Results
The larger white disk in the
middle is impregnated with the
mutagen
The smaller dots are colonies
of revertant bacteria.
The more growth indicates a
stronger mutagen
Various strains can be used to
test for different types of
mutations
Interpreting Results
Revertant bacterial growth around a disc impregnated
with contaminated ground water could indicate possible
carcinogenic affects in human beings. The more
colonies observed, the higher degree of health risk in
the water sample.
Bibliography and Links
http://www.ultranet.com/~jkimball/BiologyPages/A/AmesTest.html
http://www.ag.ohio-state.edu/~ohioline/b820_1.html
http://www.labmed.umn.edu/umbbd/atr/atr_map.html
http://ace.ace.orst.edu/info/extoxnet/pips/aldicarb.htm
http://w3.one.net/~cornette/pthn/pthn_map.html