Ac. Layton et al., MOLECULAR DIAGNOSTICS AND CHEMICAL-ANALYSIS FOR ASSESSING BIODEGRADATION OF POLYCHLORINATED-BIPHENYLS IN CONTAMINATED SOILS, Journal of industrial microbiology, 13(6), 1994, pp. 392-401
The microbial populations in PCB-contaminated electric power substatio
n capacitor bank soil (TVA soil) and from another PCB-contaminated sit
e (New England soil) were compared to determine their potential to deg
rade PCB. Known biphenyl operon genes were used as gene probes in colo
ny hybridizations and in dot blots of DNA extracted from the soil to m
onitor the presence of PCB-degrading organisms in the soils. The micro
bial populations in the two soils differed in that the population in N
ew England soil was enriched by the addition of 1000 p.p.m. 2-chlorobi
phenyl (2-CB) whereas the population in the TVA capacitor bank soil wa
s not affected. PCB degradative activity in the New England soil was i
ndicated by a 50% PCB disappearance (gas chromatography), accumulation
of chlorobenzoates (HPLC), and (CO2)-C-14 evolution from C-14-2CB. Th
e PCB-degrading bacteria in the New England soil could be identified b
y their positive hybridization to the bph gene probes, their ability t
o produce the yellow meta-cleavage product from 2,3-dihydroxybiphenyl
(2,3-DHB), and the degradation of specific PCB congeners by individual
isolates in resting cell assays. Although the TVA capacitor bank soil
lacked effective PCB-degrading populations, addition of a PCB-degradi
ng organism and 10 000 p.p.m. biphenyl resulted in a >50% reduction of
PCB levels. Molecular characterization of soil microbial populations
in laboratory scale treatments is expected to be valuable in the desig
n of process monitoring and performance verification approaches for fu
ll scale bioremediation.