Screening of Antibiotics and Heavy Metals Resistant Nitrogen Fixating Bacteria for Efficient Phytoremediation

Use of sewage water and agriculture biocides for cultivation has resulted in soil pollution with antibiotic and heavy metal in Pakistan. These two major contaminants hinder Rhizobia survival, nitrogenase enzyme activity and nodulation. Therefore, to explore novel resistant Rhizobia species for biological nitrogen fixation (BNF) and phytoremediation current study was undertaken. Through root nodulation assay 19 chickpea and 12 green pea nodulating bacteria were isolated and tested for resistance to 6 antibiotics and 8 heavy metals. Minimum inhibitory concentrations (MIC), Resistance percentage, resistance, and principal component analysis (PCA). Most of chickpea isolate were inhibited at higher antibiotic concentrations whereas green pea Rhizobia at moderate concentration. Maximum chickpea is isolates (40%) were resistant against erythrosine, while green pea isolates (35%) were resistant against erythrosine and chloramphenicol. Studied Rhizobia of chickpea were more diverse than green pea isolates for heavy metal tolerance. Among chickpea nodulating Rhizobia 95% were found resistant against Ag, Pb, Mn, Cu and Zn whereas only 10% for Hg. In case green pea isolates, 100% isolates were resistant against Ag, Pb, Mn, Cu and Zn and only 18% for Hg. According to principle components analysis kanamycin, Ag, Pb, Mn, Cu, Co and Zn were most important coefficients for chickpea Rhizobia diversity while chloramphenicol and ampicillin were the major source of variation for green pea Rhizobia. Isolates 13cp 24cp, 27cp, 26cp and 4gp24gp 27gp are the candidate isolates to be used in polluted soils as these possesses more resistance for antibiotic and heavy metals then commercial strain