An anaerobic bacterium, strain PCP-lT (T = type strain), which dechlorinates pentachlorophenol (PCP) to 3-chlorophenol, was isolated from a methanogenic consortium. This organism is a spore-forming rod-shaped bacterium that is nonmotile, asaccharolytic, and Gram stain negative but Gram type positive as determined by electron microscopic observations. Inorganic electron acceptors, such as sulfite, thiosulfate, and nitrate (but not sulfate), stimulate growth in the presence of pyruvate and yeast extract. The optimum pH and optimum temperature for growth are 7.5 and 38"C, respectively. The dechlorination pathway is: PCP -+ 2,3,4,5-tetrachlorophenol + 3,4,5-trichlorophenoI + 3,5-dichlorophenol + 3-chlorophenol. This bacterium dechlorinates several different chlorophenols at ortho, meta, and para positions; exceptions to this are 2,3-dichlorophenol, 2,5-dichlorophenol, 3,4-dichlorophenol, and the monochlorophenols. The time course of PCP dechlorination suggests that two enzyme systems are involved in dehalogenation in strain PCP-lT. One system is inducible for ortho dechlorination, and the second system is inducible for meta and para dechlorinations. A 16s rRNA analysis revealed that strain PCP-lT exhibits 95% homology with Desu@tobacterium dehalogenans JW/IU-DCl, an anaerobic bacterium which can dehalogenate chlorophenols only in ortho positions. These results suggest that strain PCP-lT is a member of a new species and belongs to the recently proposed genus DesuZjhbacteriurn. Strain PCP-lT differs from D. dehalogenans JW/IU-DCl by its broader range of chlorophenol dechlorination. Strain PCP-1 is the type strain of the new species, DesuEftobacterium frappieri.Only a few anaerobic bacteria that can reductively dechlorinate chlorophenols have been isolated in pure culture. Desulfornonile tiedjei DCB-1 is the best-described dechlorinating anaerobic bacterium to date (7). This organism is a strictly anaerobic, gram-negative, sulfate-reducing bacterium that obtains energy for growth from reductive dehalogenation of 3-chlorobenzoate with formate as an electron donor (8, 19). In the presence of 3-chlorobenzoate, this strain can also dechlorinate rneta-substituted halobenzoates (9, 15) and chlorophenols (18). Madsen and Licht (16) isolated a Clostridium-like microorganism, strain DCB-2, that can dechlorinate 2,4,6-chlorophenol to 2,4-chlorophenol and finally to 4-chlorophenol; removal of rneta-substituted chlorine has been observed only with 3,s-chlorophenol. DesulJitobacteriurn dehalogenans JWf IU-DC1, a gram-positive anaerobic bacterium, can dehalogenate a wide range of chlorophenols, including pentachloropheno1 (PCP) and related compounds, at the ortho position (22, 23). This strain can use various alternative electron acceptors, including sulfur, sulfoxy anions (except sulfate), nitrate, and fumarate. Recently, a novel, gram-negative, facultatively anaerobic, rod-shaped bacterium which can grow anaerobically via reductive dehalogenation of 2-chlorophenol was isolated (5). This microaerophilic bacterium is a member of th...

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Pentachlorophenol (PCP) dechlorination by a methanogenic consortium was observed when glucose, formate, lactate, or yeast extract was present in the mineral medium as a secondary carbon source. Acetate was not a good substrate to sustain dechlorination. The consortium was able to dechlorinate the different monochlorophenols, although the chlorine in position ortho and meta was removed more readily than in para position. Dechlorination was most efficient at 37 degrees C. At 45 degrees C, the first PCP dechlorination steps were very rapid, but 3,5-dichlorophenol (3,5-DCP) was not further dechlorinated. At 15 and 4 degrees C, dechlorination was very slow. The dechlorination of PCP to 3-chlorophenol (3-CP) was still observed after the consortium had been subjected to heat treatment (80 degrees C, 60 min), suggesting that spore-forming bacteria were responsible. The dechlorinating activity of the consortium was significantly reduced by the presence of hydrogen, 2-bromoethanosulfonic acid (BESA), or sulfate but not of nitrate. The dechlorination of 3-CP was completely inhibited by heat treatment or the presence of BESA, suggesting that a syntrophic microorganism would be involved. Vigorous agitation of the consortium stopped the dechlorination, but the presence of DEAE-Sephacel acting as a support was very efficient in restoring the activity, suggesting that association between certain members of the consortium was important.

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Animal cells were incubated in the presence of Clostridium M‐55 spores, extracts derived therefrom, or filtrates in test tubes and in Petri dishes. Cytotoxicity was determined either by the dye exclusion test or the adhesiveness efficiency, while the animal cells growth reduction was estimated either by the plating efficiency or the doubling time. Clostridium M‐55 spores, mixed with animal cells in suspension, reduced the heteroploid malignant cell viability to 35% after 28 hours' contact. Increasing the multiplicity index of spores to animal cells resulted in a greater degree of cytotoxicity. Allowing the animal cells to sediment and stretch on the bottom of the Petri dishes showed that M‐55 spores exerted a slight cytotoxic activity on the murine malignant cell lines while not significantly on the human malignant cell line and the simian cells prepared from normal animals. An important cell growth reduction was observed on all malignant cell lines as determined by plating efficiency. Increasing the multiplicity index of spores to animal cells did not lead to any significant further reduction in plating efficiency. Spore extracts were as effective as the spores themselves in reducing the heteroploid malignant cell growth. The M‐55 culture filtrates were very active and reduced malignant cell growth as determined by their plating efficiency and their doubling time. Filtrates prepared from extracted vegetative forms of Clostridium M‐55 bacilli were not active. Neither cytotoxicity nor cell growth reduction was observed in any way on diploid kidney cells derived from normal healthy monkeys.