TitleAnaerobic benzene degradation in culture and hydrocarbon degradation in the subsurface environment
NameOka, Amita R. (author), Young, Lily (chair), Kerkhof, Lee (internal member), Strom, Peter (internal member), Phelps, Craig (internal member), Jaffe, Peter (outside member), Rutgers University, Graduate School - New Brunswick,
DescriptionUnderstanding of microorganisms and pathways involved in anaerobic benzene degradation is limited. Stable isotope probing of DNA was used to identify key members of a previously characterized, sulfate-reducing benzene degrading consortium. DNA extracts of cultures incubated with [13C6]- or [12C6]benzene were separated into 13C- and 12C-labeled fractions by CsCl density gradient centrifugation. Sequencing and Terminal Restriction Fragment Length Polymorphism (T-RFLP) analysis of the 16S rRNA gene identified TRF 270 (bp), a Desulfobacterium like phylotype, which was first to derive the bulk of the 13C label for DNA synthesis, and is thus likely involved in activation of benzene degradation.
To understand the pathway of anaerobic benzene metabolism, degradation and inhibition tests were used. Based on these tests toluene was eliminated, and benzoate was identified as a possible intermediate. Metabolites detected in cultures amended with [13C6]benzene or [13C6]phenol indicate that in this consortium there are 2 different pathways of benzoate formation, one forms universally labeled ([13C-UL]benzoate), and the other forms ring labeled benzoate. Pathway that forms [13C-UL]benzoate is dominant during benzene degradation in which the benzene ring is carboxylated by a carbon derived from another benzene ring. This pathway is different from the proposed pathway of benzene degradation via phenol, as the labeling pattern of 13C-labeled benzoate formed from [13C6]benzene or [13C6]phenol is not identical. In conclusion, a novel pathway that activates one benzene ring through its reaction with products of another benzene ring likely exists in this consortium.
Groundwater impacted by a manufacturing gas plant site was used for detection and quantification of metabolic intermediates of polycyclic aromatic hydrocarbons and gene analogues encoding alpha subunit of benzylsuccinate synthase (bssA), as evidence for natural attenuation. Highest concentrations of metabolic intermediates of anaerobic naphthalene and 2-methylnaphthalene degradation were detected in an impacted monitoring well (MW)-24, near the source. Quantitative analysis of 16S rRNA gene indicated that bacterial population was enriched in the impacted wells, while bssA gene containing bacterial community was enriched in MW-24. Detection of not one, but two different indicators specific to the presence and activity of microorganisms provides strong evidence for in situ anaerobic microbial processes.
NoteIncludes bibliographical references
Noteby Amita R. Oka
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.