USE OF BIOLOG FOR THE ANALYSIS OF MICROBIAL COMMUNITIES FROM ZINC-CONTAMINATED SOILS

The BIOLOG procedure, a useful method for assessing differences in com munity structure between sad microbial communities, could be used to d etermine the impact of metal contamination of soils and reclamation of these soils; however, high metal levels may affect the results of the BIOLOG assay. This project det ermined that Zn in soils interfered wi th extraction of soils with phosphate buffer by forming an insoluble p recipitate. High Zn levels were also shown to prevent color formation and to cause false positive readings in the BIOLOG assay. The objectiv es of this project were developing and validating a modified BIOLOG me thod for use in the presence of high Zn concentrations. Substitution o f 0.1 M Tris buffer for phosphate buffer prevented precipitate formati on during the extraction step; however, extraction with Tris buffer co uld result in high Zn concentrations in the BIOLOG inoculant. Zinc con centrations of >50 mg L-1 in the inoculant were shown to result in fal se positive readings due to production of a precipitate in the wells. Raising the pH of the extractant to above 7.0 or removal of the Zn wit h cation exchange resin relieved this problem. Analyses of BIOLOG data showed that neither raising the extractant pH nor using cation exchan ge resin resulted in observable changes in BIOLOG metabolic profiles. However, use of Tris buffer in place of phosphate buffer did result in a slight change in BIOLOG metabolic profiles. Thus, the nature of the extracting buffer most be considered when analyzing experimental resu lts. The methods developed herein allow use of the BIOLOG procedure fo r soils with high metal concentrations.