Abstract

Heavy metals are silent killer of mankind and the cause of environmental pollution. The ability of some microorganisms to resist heavy metals makes them useful in bioremediation. The aim of this study was to molecularly characterize heavy metal-resistant Proteus species isolated from the soil of a cement factory. Proteus species were tested for resistance to lead, chromium, copper and iron at concentrations 0.00, 0.25, 0.50, 0.75, 1.00, 1.25 and 1.50 mg/L. Minimum inhibitory concentration (MIC) was determined at mg/mL. Plasmid profiling was done. Genomic DNA was extracted using DNA Kit by Zymo Research USA. The concentration of genomic DNA was determined using NanoDrop Spectrophotometer. Twenty-five microlitre was used for polymerase chain reaction. Amplicons were electrophoresed and sequenced.  Nucleotide sequences were blasted at the NCBI website. Proteus species showed resistance to the test heavy metals. MIC was determined for lead, copper, partly for iron and not for chromium. Plasmid profiling showed that six Proteus species harbor high molecular weight plasmids. Concentration of genomic DNA ranged between 1.88 and 2.03 ng/µl. Electrophoresis revealed 16S rRNA genes amplified at 1500 base pair. Blast analysis revealed that six was Proteus mirabilis and one was Proteus terrae.  Phylogeny constructed and study revealed that these Proteus species may be useful as bioremediation agents.

Key words: Proteus species, resistance, heavy metal, 16S rRNA gene, bioremediation.