Molecular Mechanisms of Microbial Resistance to UnfavorableEnvironmental Conditions in Heavy Metal Bioremediation:Organic Solvents as Co-Contaminants in Groundwater

摘要

Sulfate-reducing bacteria (SRB) have been studied extensively for their potentialin the bioremediation of heavy metals and radionuclides in groundwater andsediments. Hydrocarbons and solvents, as frequent environmental co-contaminants,have been reported to inhibit microbial activities and thereby pose a challenge to thesuccess of bioremediation efforts. In order to understand the molecular mechanismsof microbial resistance to the presence of organic solvents, we studied the responsesof Desulfovibrio vulgaris as a model SRB to its exposure to the organic solventacetone. Genome-wide transcriptional profiling of D. vulgaris cultures followingacetone (5% v/v) treatment at 30 and 60 min revealed that genes encoding potassiumion transporters and flagella structural subunits are among the most highly upregulatedtranscripts. Molecular chaperones comprised another group of genes highlyinduced in the presence of acetone. Down-regulated genes spanned many genefunctional role categories, particularly energy metabolism and the biosynthesis ofprotein and DNA, suggesting the disruption of normal cell growth and metabolismupon acetone exposure. Results from this study confirmed previous indications thatorganic solvents adversely affect microorganism by impairing cell membraneintegrity and inactivating cellular proteins. Accordingly, this study shows that themechanisms to protect SRB from the toxicity of organic solvents include themaintenance of proper protein functions, restoration of ionic balance, and increasedcell mobility.