Environmental Science & Engineering - www.esemag.com - November 2002
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Teaching bacteria to consume PCBs
A research team from the University of British Columbia
and Purdue University is “teaching”
microorganisms to break down polychlorinated
biphenyls (PCBs) into ecologically safe molecules,
a process known as bioremediation.
Scientists have identified one of the key stumbling blocks
that prevent microorganisms from decomposing PCBs, a
family of persistent hazardous industrial chemicals that is
widespread in the environment. They have persisted for decades
because decomposers, such as bacteria and fungi, do
not consume them very well.
PCBs were manufactured and used in industry for decades
for their insulating qualities, but the 1960s and 1970s
brought increased awareness of their toxicity to animals and
mass poisonings linked to PCB contaminated food. PCBs
are no longer manufactured in Canada and the United States,
but their persistence makes them a worldwide problem.
Many clean-up methods, such as incineration, are ineffective
and may generate other toxic compounds such as
dioxins.
“The globe’s entire surface is now contaminated with
PCBs,” said Jeffrey Bolin, professor of biological sciences
and a member of Purdue’s Markey Center for Structural
Biology and Cancer Center. “PCB molecules actually look
very similar to many organic molecules that certain bacteria
eat,” Bolin said. “But there are enough little differences that
bacteria can’t quite digest them. The process of digestion
requires a long chain of chemical steps, and if the bacteria
can’t accomplish one of those steps, the chain is broken and
digestion can’t occur,” Bolin said. “What we have done is
isolate one of the steps that causes problems for the bacteria,
a clog in the biochemical pipeline if you will.”
Bolin and his research partner, Lindsay Eltis, associate
professor of microbiology and biochemistry at the University
of British Columbia, predict that microorganisms can
learn to consume PCBs if properly bred.
“A species will fit itself to a new environment, given many
generations to adapt,” said Eltis. “In the case of bacteria,
you can get new generations once every few minutes under
proper laboratory conditions. We hope to use certain species
of bacteria with a slight taste for PCBs and improve
this trait through breeding until it’s strong enough to make
them consume PCBs as a food source.”
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