Author

Wai Ki Chung

Date of Award

12-2001

Level of Access

Open-Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Microbiology

Advisor

Gary M. King

Second Committee Member

Clare S. Darling

Third Committee Member

Katherine Boettcher

Abstract

Polycyclic aromatic hydrocarbons (PAH) are significant environmental pollutants and represent a severe health threat. Many cosmopolitan areas including coastal environments are heavily impacted by PAH. This research investigates the isolation of PAH-degrading bacteria from burrow sediment of marine benthic macrofauna and their potential in bioremediation. Macrofaunal burrow sediment is biogeochemically distinct from bulk sediment and has high microbial activities. Samples were collected from a local uncontaminated cove and PAH degradation potential was measured by incubating sediment slurries with exogenous PAH. Burrow sediments from two polychaetes and a mollusc showed significantly higher PAH degradation potential than the bulk sediment. The degradation potential was sensitive to the oxygen level during incubation. Prolonged anoxia arrested the PAH degradation in the slurries however degradation resumed when oxygen became available. Periodic anoxia only slowed the rate of degradation, These results indicated that burrow sediments likely harbored bacteria which degraded PAH using oxygen. The presence of PAH-degrading bacteria from burrow sediments was confirmed by enrichment culture of the burrow sediment slurries. Isolate LC8 was isolated from Nereis burrow sediment and isolate M4-6 was isolated from Mya burrow sediment. These isolates were characterized using phenotypic and phylogenetic techniques. The combined results suggested that LC8, Lutibacterium anuloederans (nov.gen., novsp.), is a novel genus most closely related to the genus Erythrobacter. M4-6, Cycloclasticus spirillensus, is a new species of Cycloclasticus which is an established PAH-degrading genus. To study the potential for the two isolates to serve as bioremediation agents, LC8 and M4-6 were re-introduced into a sediment matrix and the degradation potential of the inoculated slurries was measured. Although both strains were isolated from the same locale, LC8-inoculated slurries showed much better PAH degradation potential in both uncontaminated and heavily polluted sediments. M4-6-inoculated slurries showed similar PAH degradation but the rate declined rapidly with time. Moreover, M4-6 seemed to be sensitive to other pollutants in the system. In summary, two novel PAH degraders were isolated from marine macrofaunal burrow sediments. They degraded PAH under laboratory conditions and when re- introduced into a sediment matrix. However, M4-6 will not be a suitable bioremediation agent due to its sensitivity to other pollutants which may be present in the environment.

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