Environ. Sci. Technol. 2005, 39, 1974-1979
Microbial Catabolic Diversity in Soils Contaminated with Hydrocarbons and Heavy Metals W E I S H I , * ,†,§ M A R I A N N E B I S C H O F F , ‡ RONALD TURCO,‡ AND ALLAN KONOPKA† Department of Biological Sciences and Department of Agronomy, Purdue University, West Lafayette, Indiana 47907
Understanding indigenous microbial function in contaminated soil is crucial to the successful development and use of bioremediation technologies. We measured the catabolic diversity of indigenous microbial communities in soils with a 30-yr history of Pb, Cr, and hydrocarbon (HC) contamination using a modified substrate-induced respiration method. There were characteristic differences of microbial respirations in the response of highly versus less contaminated soils to the range of organic substrates used. The catabolic response to glucose as compared to succinic acid was approximately 1:5 in less contaminated soils, but 1:25 in highly contaminated soils. In contrast, the response ratio to glucose versus aromatics was about 1:0.4 in less contaminated soils and 1:1 in highly contaminated soils. Principal components analysis (PCA) of the responses confirmed that catabolic diversity differed between highly and less contaminated soils. Univariate analysis also indicated that catabolic diversity was reduced in highly contaminated soils. This catabolic difference was strongly associated with the alteration of microbial community composition. Statistical analyses suggested that the variation in microbial community catabolic diversity was attributed to HCs more than to Pb and Cr.
breadth of metabolic function (as well as phylogenetic diversity) is presumed to enhance resistance to environmental stress and disturbance. Metabolic function has been studied in soils under environmental stress from either heavy metals (6-8) or HCs (9-11), but rarely has it been studied in soils contaminated with both. On theoretical grounds, the presence of multiple contaminants may provide a more restricted niche because the microbes must tolerate both heavy metals and toxic HCs. In addition, there may be a synergistic interaction between these multiple stresses (12), because HCs can affect membranes, thereby increasing ion permeability. As a result, the toxicity of heavy metals may be enhanced. Microbial activity and functional diversity under the pressure of multiple contaminants may not equal the sums of responses to single stresses. Community level physiological profiling (CLPP) with BIOLOG plates has been applied to differentiate soil microbial metabolic diversity of various land-use systems (13, 14) and been extended to examine soil habitats contaminated with HCs and heavy metals (8, 10, 15, 16). However, the method has an intrinsic problem: extended incubation means that the culturable community (typically
