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Degradation of
dichlorodiphenyltrichloroethane (DDT)
by bacterial isolates from cultivated and uncultivated soil
Kinuthia Mwangi, Hamadi I.
Boga*, Anne W. Muigai, Ciira Kiiyukia and Muniru K. Tsanuo
Jomo
Kenyatta University of Agriculture and Technology, P.O. Box
62000 (00200) Nairobi, Kenya.
*Corresponding author.
E-mail:
hboga@fsc.jkuat.ac.ke.
Accepted 3 December, 2009 |
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The
re-introduction of
dichlorodiphenyltrichloroethane
(DDT) to control mosquitos was recommended by the World
Health Organization in 2007. In this study, the potential
for biodegradation of DDT by soil microorganisms through
enrichment and isolation of DDT biodegraders from soils
without a history of prior exposure to DDT
was done. Microorganisms from cultivated and uncultivated
soils grew in minimal media with DDT (100 ppm) as the only
carbon source. Six bacteria coded as isolates 101, 102, 103,
104, 105 and 110 degraded DDT to
l, l-dichloro-2, 2-bis (p-chlorophenyl)
ethane (DDD).
None of the isolates degraded DDT into
l, l-dichloro-2,2-bis (p-chlorophenyl)
ethylene
(DDE). Degradation by
the mixed culture of the six isolates
was higher
(82.63%) than that of any individual isolates whose range
was 28.48 - 58.08%. The identity of the isolates was
determined through
biochemical, morphological, physiological and molecular
techniques. Isolate 101 was a member of the genus
Bacillus; isolates 102 and 110 belonged to the genus
Staphylococcus while isolates 103, 104 and 105 clustered
with members of the genus Stenotrophomonas. This
study showed that there are microorganisms in the soil that
can degrade DDT and that the rate of degradation is
dependent on the presence and numbers of microbes in the
soil with the required degradative ability, environmental
factors and access of the microbes to DDT.
Key words:
DDT, biodegradation, bacterial isolates, phylogenetic
analysis. |
