Succession of phenotypic, genotypic, and metabolic community characteristics during in vitro bioslurry treatment of polycyclic aromatic hydrocarbon-contaminated sediments

Dredged harbor sediment contaminated,vith polycyclic aromatic hydrocarbons (PAHs) was removed from the Milwaukee Confined Disposal Facility and examin ed for in situ biodegradative capacity. Molecular techniques were used to d etermine the successional characteristics of the indigenous microbiota duri ng a 4-month bioslurry evaluation. Ester-linked phospholipid fatty acids (P LFA), multiplex PCR of targeted genes, and radiorespirometry techniques wer e used to define in situ microbial phenotypic, genotypic, and metabolic res ponses, respectively. Soxhlet extractions revealed a lass in total PAH conc entrations of 52%, Individual PAHs showed reductions as great as 75% (i.e., acenapthene and fluorene), Rates of C-14-PAH mineralization (percent/day) were greatest for phenanthrene, followed by pyrene and then chrysene, There was no mineralization capacity for benzo[a]pyrene, Ester-linked phospholip id fatty acid analysis revealed a threefold increase in total microbial bio mass and a dynamic microbial community composition that showed a strong cor relation with observed changes in the PAH chemistry (canonical r(2) of 0.99 9). Nucleic acid analyses showed copies of genes encoding PAM-degrading enz ymes (extradiol dioxygenases, hydroxylases, and meta-cleavage enzymes) to i ncrease by as much as 4 orders of magnitude. Shifts in gene copy numbers sh owed strong correlations,vith shifts in specific subsets of the extant micr obial community. Specifically, declines in the concentrations of three-ring PAM moieties (i,e., phenanthrene) correlated,vith PLFA indicative of certa in gram-negative bacteria (i.e,, Rhodococcus spp, and/or actinomycetes) and genes encoding for naphthalene-, biphenyl-, and catechol-2,3-dioxygenase d egradative enzymes. The results of this study suggest that the intrinsic bi odegradative potential of an environmental site can be derived from the pol yphasic characterization of the in situ microbial community.