Poster presentation
249
SYNTHESIS OF BIOACTIVE COMPOUNDS OF LOCAL
BACTERIA AT DIFFERENT CONCENTRATIONS OF HEAVY
METAL IONS
A. Usmonkulova
1
, G. Kadirova
1
, M. Narmukhamedova
1
, D. Turaqulova
2
1) Institute of Microbiology of the Academy of Sciences, Tashkent, Uzbekistan;
2) Tashkent State Technical University;
e-mail: usmonkulova.aziza@mail.ru
Cadmium (Cd) and nickel (Ni) are among the most toxic metals and high levels of
Cd and Ni in soil have been observed in several studies to slow down plant growth,
mainly biomass, chlorophyll content and photosynthetic properties. Beneficial soil
bacteria are promising targets for reducing Cd and Ni toxicity
and increasing plant
tolerance to heavy metal stress.
In this study stimulating properties of plant productivity under conditions of heavy
metal stress were studied. Exopolysaccharid, Auxin and gibberellin synthesis at
different concentrations of heavy metal ions were determined.
Pseudomonas
aeruginosa,
Enterobacter
cloacae,
Bacillus
licheniformis,
Enterobacter ludwigii, Bacillus simplex
strains were used as research objects. Bacteria
were grown for 3-7 and 14 days in peptone broth added in concentrations up to added
57.3 mg/l, 95.7 mg/l and 191.4 mg/l and 2.44 mg/l, 4.1 mg/l and 8.2 mg/l
to the medium
of heavy metals (NiSO
4
× 7H
2
O and CdCl
2
× 2.5 H
2
O). Indole-3 acetic acid (IAA) and
gibberellin synthesis of bacteria was periodically determined for 3, 7 and 14 days
according to the spectrophotometric method recommended by Berrios et al. Synthesis of
exopolysaccharides by the strains was determined for 3, 7 and 9 days.
Pseudomonas aeruginosa
synthesized auxin 4, 4.8, 5.3 times higher amount
compared to control and
Enterobacter ludwigii
,
Bacillus licheniformis, Bacillus
simplex
synthesized auxin in equal amount compared to the control at
different concentrations of
Cd cation (2.4, 4.1, 8.2 mg/l). Gibberellin synthesis in the strains decreased with
increasing concentration of heavy metals (Cd(II) and Ni (II)).
Pseudomonas aeruginosa
synthesized 375 μg/ml gibberellin in the control and 390 μg/ml in the Ni
2+
95.7 mg/ml
concentration on the 7
th
day of cultivation, and
Enterobacter ludwigii
375 μg/ml in the
control and 380 μg/ml in the Cd
2+
4.2 mg/l concentration on the 3
rd
day of cultivation.
During experiments aimed at determining the synthesis of exopolysaccharides in
Bacillus atropheus
(4) and
Enterobacter ludwigii
(11) strains grown for 14
days at
concentration of 8.2 and 24.6 mg/l Cd(II) cation, EPS synthesis on the 7
th
and 14
th
days
of cultivation was increased to 26, 28 mg/l and 6, 11 mg/l.
Pseudomonas aeruginosa
(18) strain produced 78 mg/l EPS at the concentration of 24.6 mg/l Cd(II) cation on the
7
th
day of cultivation.
Using microorganisms tolerant of high concentrations of heavy metals and their
activity, bioremediation of ambience contaminated with heavy metals is possible.
Increased synthesis of phytohormones and exopolyccharides under heavy metal stress
conditions indicate that these microorganisms are promising objects in the future.