Genetic Monitoring of Microbes in Soils Amended with Fly Ash

Abstract

Coal fly ash may prove as a valuable soil amendment agent especially to coarsetexture soils mainly due to the presence of silt and clay like particles and plant nutrients. Its effect on soil chemical and physical properties has been studied, but little is known regarding its effect on soil microbial community. Present study was focused to monitor the behavior of inoculated transformant S2: pMMB277 in pure soil and soil amended with flyash @ 0, 5, 10, 20 and 30% (w/w basis) under sterile and non-sterile conditions over a period of four weeks and also to study the effect of fly ash in general on soil microbial activity. Phosphate solubilizing bacteria (S2) isolated form fly ash affected soil was transformed with a wide host range, low copy number plasmid containing cat and LacZ gene responsible for chloramphenicol resistance and functional b-galactosidase which were used as molecular markers. Dehydrogenase activity was used as an indicator of total microbial activity in soil. Application of fly ash @ 10% in conjunction with bacterium S2: pMMB277 had optimum effect on its establishment and colonization and provides favorable environment for the growth of native as well as inoculated bacterium. Addition of fly ash causes an increase in the electrical conductivity of soils and heavy metals Pb, Fe, Zn, Co, Ni, Cu, Cd and Cr content increased as proportion of fly ash was increased in soil from 5 to 30%. Also there was an increase in available phosphorus, available sulphur and organic carbon content of soil with concomitant increase in the fly ash percentage. Application of unweathered fly ash @ 10 % (w/w) basis has positive impact in soil on soil biological properties where as at higher concentration it had negative impact.