Naphthalene biodegradation in environmental microcosms: estimates of degradation rates and characterization of metabolites

Abstract

Naphthalene biodegradation was investigated in microcosms containing sediment and water collected from three ecosystems which varied in past exposure to anthropogenic and petrogenic chemicals. Mineralization half-lives for naphthalene in microcosms ranged from 2.4 weeks in sediment chronically exposed to petroleum hydrocarbons to 4.4 weeks in sediment from a pristine environment. Microbiological analysis of sediments indicated that hydrocarbon-utilizing microbial populations also varied among ecosystems and were 5 to 12 times greater in sediment after chronic petrogenic chemical exposure than in sediment from an uncontaminated ecosystem. Sediment from an ecosystem exposed to agricultural chemicals had a mineralization half-life of 3.2 weeks for naphthalene and showed about a 30-fold increase in heterotrophic bacterial populations in comparison to uncontaminated sediments, but only a 2to 3-fold increase in hydrocarbon-degrading bacteria. Analysis of organic solvent-extractable residues from the microcosms by high-pressure liquid chromatography detected polar metabolites which accounted for 1 to 3% of the total radioactivity. Purification of these residues by thin-layer chromatography and further analysis by gas chromatography-mass spectrometry indicated that cis-1,2-dihydroxy-1,2-dihydronaphthalene, 1-naphthol, salicylic acid, and catechol were metabolites of naphthalene. These results provide useful estimates for the rates of naphthalene mineralization in different natural ecosystems and on the degradative pathway for microbial metabolism of naphthalene in freshwater and estuarine environments.

Metabolism of the Polycyclic Aromatic Hydrocarbon Fluoranthene by the Polychaete Capitella Capitata Species I

“…I (either in the digestive tract or on the body surface) were primarily responsible for the decline in worm body burden of fluoranthene that we observed in the present and previous [11] experiments. Although some variability among bacterial types in the formation of specific metabolites has been reported, in general, bacteria appear to employ similar PAH metabolic pathways (e.g., starting with an initial step involving dioxygenase) [35][36][37][38][39]. Assuming that bacteria living in association with worms would utilize similar metabolic pathways as those described by Kelley et al [25], it is therefore of importance that we could detect none of the metabolites shown in Table 1 in any of our samples.…”

Effects of chemical structure and exposure on the microbial degradation of polycyclic aromatic hydrocarbons in freshwater and estuarine ecosystems

“…Chemical analyses of the I4C residues in extracts from the microcosms by TLC and autoradiography detected the presence of some metabolites which were more polar than the six PAH substrates. We recently reported cis-l,2-dihydroxy- 1,2-dihydronaphthalene, 1-naphthol, salicylic acid and catechol as metabolites of naphthalene in sediment:water microcosms [31]. However, it should be noted that polar PAH residues represent a minor amount of the total radioactivity and accounted for only 0.1 to 6% of the total radioactivity after 8 wk of exposure.…”

Degradation of benzo[a]pyrene by bacterial isolates from human skin

“…Much of our current knowledge has been gathered using two model substances, naphthalene and benzo[a]pyrene (B[a]P). The first was the substrate of choice for numerous microbial biodegradability studies (Heitkamp et al, 1987;Juhasz & Naidu, 2000;Kimura et al, 2006;Toledo et al, 2006;Peng et al, 2008;Jones et al, 2011b), while the latter has been of particular interest as a typical cytochrome P450 (CYP)-activated carcinogen in eukaryotes (Supporting Information, Fig. S1a) (Dekant, 2009).…”