GROWTH PROMOTING ATTRIBUTES OF CHROMIUM (VI) RESISTANT BACILLUS STRAINS FOR TRITICUM AESTIVUM L.
H. Shahbaz, B. Ali and S. Sultan*
Department of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore-54590, Pakistan.
*Corresponding Author: sikandersultan.mmg@pu.edu.pk
ABSTRACT
Hexavalent chromium (Cr) is carcinogenic, mutagenic and causes many health hazards. Some bacteria are capable of resisting high concentrations of hexavalent Cr by converting it into trivalent form, which is non-toxic. The purpose of this study was to isolate Bacillus strains resistant to Cr (VI) and also proficient to promote plant growth. The strains B. rhizosphaerae KAC5, B. clausii KSC6 and B. cereus SLC9 were capable to grow at 500 to 4000 µg/ml Cr (VI). The strains showed growth over wide range of pH (pH 5-11), temperature (32-55ºC) and sodium chloride concentration (up to 5% (w/v). The Bacillus strains showed 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and produced indole-3-acetic acid (IAA) up to 152 µg/ml. The strains were also positive for phosphate solubilization and siderophore synthesis. Seeds of Triticum aestivum L. treated with Bacillus strains were grown in pots having Cr (VI) concentrations 0, 200 and 500 mg/kg of soil. The Bacillus strains significantly improved the growth of T. aestivum by increasing its shoot length, number of tillers, spike length, number of spikelets, number of grains and seed weight. Hence, the Cr (VI) resistant Bacillus strains showed potential to be used for the growth promotion of plants under chromium stress.
Keywords: ACC-deaminase activity, Bacterial auxin production, Chromium resistant bacteria, Bacillus, Cr (VI) reduction, plant growth promoting bacteria.
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