Rock-weathering bacteria isolated from rock surface and its role inecological restoration on exposed carbonate rocks

Carbonate rock is widely distributed in the world. Most of the carbonate rock mining areas have been seriously degraded by destructive human activities, resulting in soil erosion, deterioration of vegetation cover, and bare rock. Microbial weathering of minerals is one of the important processes that can promote ecological restoration of such areas. However, bacterial strains vary in their mineral weathering abilities as well as their function in releasing nutrients. Thus, isolation of effective bacterial strains and studies of their mechanism of weathering processes are critical to promote ecological restoration on abandoned carbonate mine land. We isolated the Bacillus megatherium NL-7 from weathered rock surface and screened out as the most efficient strain for the ecological rehabilitation of rocky mine soil. In this study, we found that the rock sample released more Ca2+, Mg2+ with a significant reduction of pH value in fermentation broth cultivated with NL-7 than with inactivated NL-7 (control group, CK). In combination with the results of high performance liquid chromatography (HPLC), acetic acid produced by bacterial metabolism was thereby considered as the effective component of promoting rock dissolution. This research also demonstrated that NL-7 releases essential elements (phosphorus and potassium) for plant establishment and growth from rocks. Our results indicated that Bacillus megatherium NL-7 can promote rock weathering and increase nutrient elements in the environment, therefore to improve soil formation and plant growth. We suggest its application may solve the present problems of environmental remediation technologies in environments damaged by carbonate rock mines. (C)2017 Elsevier B.V. All rights reserved.