Submitted to: Biodegradation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/7/2003
Publication Date: 10/1/2003
Citation: OH, B., SHEA, P.J., DRIJBER, R.A., VASILYEVA, G., SARATH, G. TNT BIOTRANSFORMATION AND DETOXIFICATION BY A PSEUDOMONAS AERUGINOSA STRAIN. BIODEGRADATION. 2003. Interpretive Summary: Bioremediation of man-made toxins represents vast, potentially untapped resource for alleviating present and future ecological problems. One means to approaching this exciting science is to screen, identify and study microorganisms isolated from contaminated ecosystems. We had previously isolated a Pseudomonas aeruginosa strain MX, from munitions-contaminated soil and shown that this organism was capable of metabolizing TNT. However, successful microbial-mediated remediation requires transformation pathways that maximize metabolism and minimize the accumulation of toxic products. In this study the optimal growth conditions for TNT biodegradation by strain MX were evaluated and the major metabolites of TNT identified. Of the many breakdown products of TNT some were toxic such as 2-amino-4,6-dinitrotoluene and some non-toxic. Manipulations to the growth media could change the relative abundance of TNT-derived metabolites resulting from a shift in underlying biochemical processes of the cells. These data point to the possible cellular machinery involved in TNT metabolism, and thus provide future targets for study.
Technical Abstract: Successful microbial-mediated remediation requires transformation pathways that maximize metabolism and minimize the accumulation of toxic products. Pseudomonas aeruginosa strain MX, isolated from munitions-contaminated soil, degraded 100 mg TNT L-1 in culture medium within 10 h under aerobic conditions. The major TNT products were 2-amino-4,6-dinitrotoluene (2ADNT, primarily in the supernatant) and 2,2' -azoxytoluene (2,2'AZT, primarily in the cell fraction), which accumulated as major products via the intermediate 2-hydroxylamino-4,6-dinitrotoluene (2HADNT). The 2HADNT and 2,2'AZT were relatively less toxic to the strain than TNT and 2ADNT. Aminodinitrotoluene (ADNT) production increased when yeast extract was added to the medium. While TNT transformation rate was not affected by pH, more HADNTs accumulated at pH 5.0 than at pH 8.0 and AZTs did not accumulate at the lower pH. The appearance of 2,6-diamino-4-nitrotoluene (2,6DANT) and 2,4-diamino-6-nitrotoluene (2,4DANT); dinitrotoluene (DNT) and nitrotoluene (NT); and 3,5-dinitroaniline (3,5DNA) indicated various routes of TNT metabolism and detoxification by P. aeruginosa strain MX.