Abstract:
BACKGROUND: Excessive metals in the soil have
become one of the most significant environmental
problems. Phytoremediation has received considerable
attention as a method for restoring the contaminated soils.
The microbes having remarkable metal tolerance and plant
growth-promoting abilities could also play a significant
role in remediation of metal-contaminated soils, because
bioaugmentation with such microbes could promote
phytoextraction of metals. Therefore, the present study was
focused on evaluating the phytoextraction of heavy metals
(Co, Pb and Zn) in Helianthus annuus (sunflower) induced
by bioaugmentation of a phosphate solubilizing bacterium.
METHODS AND RESULTS: A phosphate solubilizing
bacterium was isolated from metal-contaminated soils
based on the greater halo size (>3 mm) with solid NBRIP
agar medium containing 10 g glucose, 5 g Ca3(PO4)2, 5 g
MgCl2⋅6H2O, 0.25 g MgSO4.7H2O, 0.2 g KCl, 0.1 g
(NH4)2SO4 in 1 L distilled water. Isolated bacterial strain
was assessed for their resistance to heavy metals;
CoCl2.6H2O, 2PbCO3.Pb(OH)2, and ZnCl2 at various
concentrations ranging from 100-400 µg/mL (Co, Pb and
Zn) using the agar dilution method. A pot experiment was
conducted with aqueous solutions of different heavy metals
(Co, Pb and Zn) to assess the effect of bacterial strain on
growth and metal uptake by Helianthus annuus (sunflower).
The impact of bacterial inoculation on the mobility of
metals in soil was investigated under laboratory conditions
with 50 mL scaled polypropylene centrifuge tubes. The
metal contents in the filtrate of plant extracts were
determined using an atomic absorption spectrophotometer
(Perkinelmer, Aanalyst 800, USA).
CONCLUSION: Inoculation with Enterobacter ludwigii
PSB 28 resulted in increased shoot and root biomass and
enhanced accumulation of Co, Pb and Zn in Helianthus
annuus plants. The strain was found to be capable of
promoting metal translocation from the roots to the shoots
of H. annuus. Therefore, Enterobacter ludwigii PSB 28
could be identified as an effective promoter of phytoextraction
of Co, Pb and Zn from metal-contaminated soils
