摘要：Microorganisms are known to tolerate and accumulate a wide range of heavy metals which are the common pollutants of soil. The earthworms, being the significant inhabitants of soil, bio-accumulate the heavy metals, detoxify them and improve the quality of soil. The gut micro flora of earthworms has been known to perform important roles like de-nitrification (in nitrogen fixation) and production of degradative enzymes (for decomposition of organic matter). Endogeic earthworms are often exposed to various kinds of stress which in turn could have a profound effect on the micro flora of its gut. Zinc is one of the largest heavy metal pollutants of the soil. In this study, we investigated the effect of zinc stress on the microbial communities of the gut of endogeic earthworms Pontoscolex corethrurus. The earthworms were subjected to zinc stress at increasing concentrations for a period of 15 days. Zinc had a deleterious effect on growth and development of the earthworms. It was observed that two bacterial species Aeromonas hydrophila and Bacillus cereus were selectively accumulated in the gut of earthworms that were exposed to metal stress when compared to the control earthworms. This study highlights the importance of association between earthworm and microorganisms with respect to bioremediation of soils contaminated with heavy metals.
