The second objective of this research was to determine which species of bacteria are present in the cultures, and which are active in the benzene degradation process. Direct correlation of an active species to benzene degradation rates was not possible using these methods; and molecular investigations revealed the presence of numerous organisms thought to be carrying out side-reactions in the cultures. Stoichiometry and molecular evidence also pointed towards the involvement of anammox in benzene degradation under nitrate-reducing conditions.Characterization of benzene-degrading nitrate-reducing enrichment cultures was carried out using both biochemical and molecular methods.The first objective of this research was to gain a better understanding of conditions under which benzene degradation is promoted or inhibited in order to improve consistent benzene degradation in the nitrate-reducing cultures. Fe(II), H2, resazurin, and nitrite were observed to inhibit benzene degradation, while acetate addition was shown to promote faster benzene degradation.