Isolation of Malathion degrading Pseudomonas xanthomarina with ...

Research Journal of Chemistry and Environment___________________________________Vol.17 (3) March (2013)
Res. J. Chem. Environ.
biotechnologies 33, 47 .
In the present study, the growth of all isolates was observed
in BSM media containing 0.5 mM Malathion. The growth
of bacterial culture DKM8 was rapid after 1 day in the
presence of 0.5 mM Malathion, showing exponential phase
of growth. After 4 days, the growth of DKM8 declined
which may be due to unavailability of Malathion as sole
carbon source or due to the production of some toxic
compound indicating the death phase.
The physiologically most active auxin in plants is indole-3acetic
acid (IAA), which is known to stimulate both rapid
(e.g. increases in cell elongation) and long-term (e.g. cell
division and differentiation) responses in plants. In the
present study, bacterial isolates DKM3, DKM5, DKM8 and
DKM9 were showing IAA production. The isolate DKM8
was showing more IAA production as compared to DKM9.
The IAA production ability of bacterial strain DKM8 was
also checked in the presence of Malathion. It was found
that there was no effect on IAA production in presence of
different concentration of Malathion (0.5 mM, 1.0 mM and
1.5 mM). Pseudomonas species have shown promising
results in the production of IAA as plant growth promotion
activites 42 .
Phosphate solubilizing microorganism (PSM) is present in
almost all soils, although their number varies depending
upon the soil and climatic conditions 22 . First time in 1903,
tricalcium phosphate (TCP) solubilization was
demonstrated by soil bacteria in liquid and in solid
medium 38 . However, the extent of phosphate solubilization
varies with the source of inorganic phosphate and the
micro-organisms involved 2 . PSM helps in utilization of
indigenous rock phosphates 20 . Thus, PSM causes the
release of nutrients into the soil for naturally balanced
proportion 6 and exerts beneficial effects on plant
development 14 . In the present study, all the ten bacterial
isolates were screened for phosphate solubilization activity.
The bacterial isolates DKM1, DKM3, DKM5, DKM8 and
DKM9 were forming clear zone on the Pikovaskaya
medium, considered as phosphate solubilizing bacteria. The
bacterial culture DKM8 was showing more phosphate
solubilization as compared to DKM1, DKM3, DKM5 and
DKM9. The phosphate solubilizing ability of DKM8 was
not adversely affected by the presence of Malathion.
Microbial community composition can also contribute to
the suppression of germination and mycelia growth of soil
fungi to a certain extent 9 . In the present study, out of ten,
only two bacterial strains (DKM8 and DKM9) showed
antifungal activity against Aspergillus sp. The antifungal
potential of Bacillus sp., Pseudomonas sp. and
Streptomyces sp. has also been reported to inhibit the
mycelial growth of many species of Aspergillus,
Penicillium and Fusarium 28, 30 .
For agricultural application, protease producing microorg-
(62)
anisms act as biological control agents for eradication of
some fungal plant pathogens 41 . Regulation of soil protease
activities in soil is important to maintain the fertility of
soil 46 . In the present study, out of ten bacterial isolates,
only two bacterial strains (DKM8 and DKM10) were
showing protease activity on skimmed milk agar medium.
The bacterial strain DKM8 showed more protease activity
as compared to DKM10.
The antibiotics produced by PGPR include: butyrolactones,
zwittermycin A, kanosamine, oligomycin A, oomycin A,
phenazine-1-carboxylic acid, pyoluteorin, pyrrolnitrin,
viscosinamide, xanthobaccin and 2, 4-diacetyl
phloroglucinol 48 . The DAPG is one of the most efficient
antibiotics in the control of plant pathogens 10 and can be
produced by various strains of Pseudomonas 35 . The isolates
DKM8 and DKM9 were resistant to antibiotic
(chloromphenicol, oxacillin, ampicillin, gentamycin,
vancomycin, amikacin, novobiocin, co-trimoxazole,
penicillin, azithromycin and tetracycline).
The resting cell study was performed to check the
quantitative degradation of Malathion. Resting cells of
Pseudomonas derived from cultures were grown on
diazinon or Malathion for extensive destruction of these
two organophosphates 36 . In the present study, from GC
analysis, it was found that the initial concentration of
Malathion (6.9 ppm) reduced to 4.74 ppm after 24 hr and
further reduced to 2.04 ppm after 48 hr indicating 70.5 %
depletion of Malathion by strain DKM8. It was reported
that a strain of Pseudomonas isolated from peppermill
effluents was capable of degrading Malathion cometabollically
up to Malathion mono carboxylic acid 39 .
Several species of Pseudomonas have been reported to
degrade organophosphorus pesticide 8,33 .
Conclusion
This research may have practical applications in
bioremediation of Malathion contaminated soil, waste
dump, industrial effluents and contaminated water
environment. Apart from this, bacterial strain DKM8 can
be used in the field of agriculture as a tool for plant growth
promotion. Manipulations of such bacterial strains in
relation to bioremediation and plant growth promotion are
promising areas for further development. The bacterial
strain DKM8 can be used as biofertilizer for sustainable
crop production system along with remediation of
Malathion under field conditions. Characterizing the
pathway for degradation, identifying the genes and
enzymes involved in this process represents areas for
further investigation.
References
1. Astrom B., Gustafsson A. and Gerhardson B., Characteristics
of a plant deleterious rhizosphere pseudomonad and its inhibitory
metabolites, J. App. Bacteriol., 74, 20 (1993)
2. Banik S. and Dey B. K., Available phosphate content of an