Microorganisms occurring naturally in coastal
mudflats have an essential role to play in cleaning up
pollution by breaking down petrochemical residues.
Research by Dr. Efe Aganbi and colleagues from the University of Essex, presented at the Society for General
Microbiology's meeting at Harrogate reveals essential differences
in the speed of degradation of the chemicals depending on
whether or not oxygen is present.
In aerobic conditions (where oxygen is present), benzene, toluene
and naphthalene, which all occur in petroleum, were rapidly
degraded by microbes. In the absence of oxygen degradation was
slower and only toluene was significantly broken down. This
means that in a healthy marine ecosystem where the water is
oxygenated, petrochemical contamination can be biodegraded by
microorganisms, but if the oxygen supply is depleted by pollution
and other processes leading to the breakdown of organic matter
in the soil, the contamination will persist.
While almost all known aromatic hydrocarbons (the
petroleum breakdown products) are degraded with oxygen only a
few can be completely broken down in the absence of oxygen.
However, in a contaminated environment oxygen is quickly
depleted and anaerobic breakdown (without oxygen) becomes an
important mechanism for getting rid of contaminants. The
scientists also investigated the impact of the three chemicals on
the make-up of different estuarine microbial communities. Over
time the types of microorganisms changed as the compounds were degraded. In aerobic conditions, benzene and toluene did
not appear to affect community structure but naphthalene
stimulated the growth of Cycloclasticus spirillensus, a bacterium
known to break down oil residues. These bacteria might be used
as a natural way of cleaning up pollution.
"Our work shows that microbes are very versatile and
can live on most types of chemicals" said Dr. Aganbi, "More
work is needed to identify bacteria in these mud sediments as
little is known about the range of bacteria present. Estuaries are
ideal locations for refineries and petrochemical facilities, it is
essential that mudflats are preserved to provide a natural clean-up
area for pollution".
Source: www.physorg.com
ENVIS
CENTRE Newsletter Vol.7,Issue 4 October 2009
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