PJB-2020-455
INDOLE-3-ACETIC ACID (IAA) PRODUCTION BY MERCURY RESISTANT AND NITROGEN FIXING BACTERIAL STRAINS ISOLATED FROM DIFFERENT AREAS OF PUNJAB, PAKISTAN
DR. AATIF AMIN
Abstract
Pollution of heavy metals such as mercury (Hg) in the rhizosphere poses serious danger to plant growth and yield and then ultimately human health. In the present study, a total 30 bacterial isolates were qualitatively screened out on the basis of resistance against mercury at the concentration of 30 µg/ml of HgCl2 and growth on selective medium i.e. nitrogen free mannitol (NFM) for nitrogen fixing bacteria (NFB). All bacterial isolates were checked for their ability to produce indole-3-acetic acid (IAA). Out of 30, six Hg-resistant and NFB isolates, UM-3, UM-5, UM-7, UM-11, UM-26 and UM-28 were selected for high production of IAA as 18.6, 16.7, 16, 18.7, 14 and 16 µg/ml respectively (p<0.05). The biochemical and plant growth promoting characterization of selected Hg-resistant and IAA producing NFB isolates was performed by using different tests such as Gram staining, morphological characterization, triple sugar iron (TSI), catalase, oxidase, HCN and H2S production and then phosphate and potassium solubilization. The 16S rDNA ribotyping and phylogenetic analysis of six highly Hg-resistant and IAA producing NFB isolates was performed by PCR-amplification of 16S rRNA gene and characterized as Exiguobacterium sp. (KJ736011), Bacillus cereus (KJ736012), B. subtilis (KJ736013), Enterobacter cloacae (KJ736014) and Pseudomonas aeruginosa (KJ736016 and KJ736017). B. cereus UM-5 gave promising resistance against HgCl2 (30 µgml-1) due to the presence of merB gene. The structural determination of MerB protein was carried out using bioinformatics tools i.e. Protparam, Pfam, InterProScan, STRING, Jpred4, PSIPRED, I-TASSER, COACH server and ERRAT. These tools predicted the structural based functional homology of MerB protein (organomercury lyase) in association with MerA (mercuric reductase) in bacterial Hg-detoxification system.
To Cite this article:
Download
