Materials and MethodsChemicals.1,2,

Materials and Methods
Chemicals.1,2,3,4,7,8-HxCDF (98+%), 1,2,3,4-TeCDF, and
1,3,7,8-tetrachlorodibenzofuran (1,3,7,8-TeCDF) were purchased from Ultra Scientific (North Kingstown, RI). The 2,2′,5-trichlorobiphenyl (2,2′,5-TrCB) and OCDD and standard
solutions of 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PeCDF), 1,2,3,7,8-pentachlorodibenzofuran (1,2,3,7,8-PeCDF), and 2,3,7,8-tetrachlorodibenzofuran (2,3,7,8-TeCDF)
were purchased from AccuStandard, Inc. (New Haven, CT).
A 1,2,3,4,8-pentachlorodibenzofuran (1,2,3,4,8-PeCDF) standard solution was purchased from Cambridge Isotope
Laboratories, Inc. (Andover, MA). Standard solutions of
1,2,4,7,8-pentachlorodibenzofuran (1,2,4,7,8-PeCDF), 1,3,4,7,8-pentachlorodibenzofuran (1,3,4,7,8-PeCDF), 2,3,6,8-tetrachlorodibenzofuran (2,3,6,8-TeCDF), 1,4,7,8-tetrachlorodibenzofuran (1,4,7,8-TeCDF), 1,3,4,8-tetrachlorodibenzofuran
(1,3,4,8-TeCDF), 1,2,4,7-tetrachlorodibenzofuran (1,2,4,7-TeCDF), and 1,2,4,8-tetrachlorodibenzofuran (1,2,4,8-TeCDF)
were purchased from Wellington Laboratories, Inc. (Guelph,
Ontario, Canada). The 1,2,3,4-tetrachlorobenzene (1,2,3,4-TeCB) was purchased from Sigma-Aldrich, Inc. (St. Louis,
MO), and PCE (99.9+%), TCE (99.5+%), and butyric acid
(99+%) were obtained from Aldrich Chemical Company
(Milwaukee, WI). The cis-1,2-DCE was purchased from
Supelco, Inc. (Bellefonte, PA). VC (99.5+%) was obtained
from Fluka Chemie GmbH (Germany). Ethene (99%) was
purchased from Matheson Tri-Gas, Inc. (Montgomeryville,
PA).
Culture Preparation.A mixed culture containingD.
ethenogenesstrain 195 was grown at 25°C on PCE and butyric
acid using methods described previously (23, 31, 32).
Dechlorination experiments were carried out in 60 mL serum
bottles. A dry sterile sediment (0.375 g) prepared as previously
described (23) was added to each bottle. The sediment was
completely wetted by 0.35 mL of a 535 µM (200 mg/L)
1,2,3,4,7,8-HxCDF-toluene stock solution. The toluene was
allowed to volatilize under sterile N2, leaving behind a coating
of 1,2,3,4,7,8-HxCDF on the sediment carrier. The culture
(37.5 mL) was transferred to each bottle under anoxic and
sterile conditions, resulting in a final nominal 1,2,3,4,7,8-HxCDF concentration of 5µM (1.87 mg/L). Each bottle also
received 100 µM butyric acid as an electron donor and
hydrogen source and 15µL of a 50 g/L fermented yeast extract
solution (31, 32) as a nutrient source on days 6, 25, 51, 74,
111, 144, and 165. A vitamin stock solution (31, 32) was added
at set up. Four sets of triplicate treatments were established.
One set of bottles received 1,2,3,4,7,8-HxCDF as the sole
halogenated substrate. Because we do not know if PCDD/Fs
are growth substrates forD. ethenogenesstrain 195, in addition
to the 1,2,3,4,7,8-HxCDF, one set of triplicate bottles was
amended with PCE, a known growth compound, as an
additional substrate on the same days when butyric acid
and fermented yeast extract were amended. One set of
triplicate bottles was spiked with 1,2,3,4-TeCB, which is also
a growth-supporting substrate forD. ethenogenesstrain 195,
but only on days 0 and 76. The nominal concentrations of
PCE and 1,2,3,4-TeCB added to the culture bottles were 25
µM. The fourth set of triplicate bottles was autoclaved for 1 h
on each of 3 consecutive days to serve as killed controls.
Parallel treatments were prepared with OCDD as the PCDD/F
substrate at 5µM, using the same experimental protocol as
described for 1,2,3,4,7,8-HxCDF. The bottles were shaken in
the dark at 120 rpm at 28°C and sampled periodically over
195 days.
To ascertain the dechlorination intermediates of 1,2,3,4,7,8-HxCDF, two separate experiments were performed using