US EPA

7663732 

Journal Article 

Naphthalene degradation and mineralization by nitrate-reducing and denitrifying pure cultures 

Rockne, KJ; Chee-Sanford, JC; Sanford, RA; Hedlund, B; Staley, JT; Strand, SE; , 

1999 

5 

191-196 

English 

WOS:000082417200032 

Although most PAHs with fewer than five rings are known to be biodegraded under aerobic conditions, most contaminated sediments and soils are anaerobic. In these environments, aerobic bioremediation may be difficult to implement because of the problems associated with oxygen delivery to the subsurface. With recent results clearly demonstrating some bicyclics and PAHs can be degraded without oxygen, further progress in understanding this process will be achieved by the identification of pure cultures of anaerobic PAH degrading bacteria. We attempted to isolate pure bacterial cultures from a denitrifying enrichment that anaerobically degrades phenanthrene, naphthalene, and biphenyl with stoichiometric nitrate reduction. After enrichment and screening, four pure cultures were obtained. The isolates were assayed for the ability to degrade naphthalene or phenanthrene as the sole source of carbon and energy in the presence of nitrate. Two pure cultures demonstrated unambiguous naphthalene biodegradation ability, designated NAP-3-1 and NAP-4. Both NAP-4 and NAP-3-1 transformed naphthalene, and the transformation was nitrate dependent. No significant removal of naphthalene occurred in nitrate-limited incubations or in cell-free controls. Both cultures partially mineralized naphthalene, representing 12-15% of the initial added C-14-labeled naphthalene. Isolate NAP-3-1 was a denitrifier, as shown by gas production in a denitrification assay. In contrast, NAP-4 did not produce gas, but did produce significant amounts of nitrite. The complete 16s rDNAs of NAP-3-1 and NAP-4 were sequenced and compared to other PAH- and non-PAM degrading bacteria. NAP-4 was phylogenetically closely related to Vibrio spp, and NAP-3-1 was phylogenetically closely related to Pseudomonas spp., results which suggest that anaerobic bicyclic degradation ability may be more widely spread within the proteobacteria. 

5th International In Situ and On-Site Bioremediation Symposium 

SAN DIEGO, CA