BENZENE-INDUCED EXPRESSION OF PROTEINS IN A RHODOCOCCUS SPECIES REVEALED BY ANALYSIS OF HIGHLY PURIFIED SUBCELLULAR FRACTIONSTONY GUTIERREZ AND IAIN COUPERWHITEAbstract Benzene, a constituent of petroleum, is an important solvent in the chemical industry and a ubiquitous environmental pollutant. Its inherent toxicity and high solubility often limits its degradation and ultimate removal from contaminated sites. Rhodococcus sp. 33, a gram positive bacterium, can both degrade and tolerate super saturating concentrations of benzene (>1780 mg/L). Previous work by our group demonstrated the important role of this organisms exopolymer and membrane fatty acids in conferring tolerance to benzene. In this study, we investigated protein expression patterns in the cell wall and plasma membrane of this organism before and after exposure to benzene. For this, we developed methods to isolate highly purified subcellular fractions from this Rhodococcus. Cells were found to induce an increase in their total content of wall and membrane proteins, as well as up-regulate several proteins during exposure to benzene. These changes are thought to provide the cell wall and plasma membrane with greater structural rigidity, thereby mitigating benzenes potential to cause damage to the cells. The activities of cis-benzene dihydrodiol dehydrogenase and catechol 1,2-dioxygenase were detected in only cytoplasmic fractions of cells grown with benzene, suggesting that, like for other species of benzene-catabolizing bacteria, the expression of these enzymes is confined to the cytoplasm of this organism.
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