Superfund Research Program

Microbial Degradation of PAH Mixtures

Project Leader: David Warshawsky (University of Cincinnati, Department of Environmental Health)
Grant Number: P42ES004908
Funding Period: 1995 - 2001

Project-Specific Links

Final Progress Reports

Year:   1999 

Since preliminary results indicated that utilizing the green alga Selenastrum capricornutum in conjunction with the bacteria Mycobacterium sp. strain RJGII.135 and Sphingomonas yanoikuyae strain B1 yielded greater degradation and mineralization of BaP, project investigators are interested in studying which aspect (s) of the degradation process are involved in this apparent enhancement. In particular, the bacterial strains with different dihydrodiols of BaP are being incubated to determine whether this will produce similar enhancement of degradation compared to BaP alone.

The researchers have completed the studies of pyrene degradation by Mycobacterium sp. strain RJGII.135 when grown with different concentrations of various metals. Lower concentrations of metals do not appear to affect pyrene degradation by strain 135 but higher concentrations seem to have a slight effect on overall degradation. These results are being confirmed for publication.

Using two separate PCR reactions to amplify bacterial DNA, potential polycyclic aromatic hydrocarbon degrading genes have been detected in Mycobacterium sp. strain RJGII.135 but not in Ralstonia sp. strain RJGII.123. These preliminary results indicate that the genes in Mycobacterium sp. strain RJGII.135 are similar to other known PAH degrading bacteria and that the genes from Ralstonia sp. strain RJGII.123 may be different from those already characterized. Similarly, DNA from the two carbazole degrading bacteria, Ralstonia sp. strain RJGII.123 and Burkholderia sp. strain 153, is being examined by southern blot analyses to determine whether these bacteria contain genes similar to other characterized dioxygenases. Furthermore, clones were constructed from Burkholderia sp. strain 153 and were then sequenced. To date, a number of sequences have been identified and two, in particular, show the most promise because of sequence similarity to other genes. Additionally, phylogenetic analyses have been used to determine that Burkholderia sp. strain 153 is most closely related to Burkholderia sp. strain JB1.