Diversity of anaerobic microbial processes in chlorobenzoate degradation: nitrate, iron, sulfate and carbonate as electron acceptors.
ABSTRACT The utilization of monochlorobenzoate isomers (2-, 3- and 4-chlorobenzoate) by anaerobic microbial consortia in River Nile sediments was systematically evaluated under denitrifying, Fe-reducing, sulfidogenic and methanogenic conditions. Loss of all three chlorobenzoates was noted in denitrifying cultures; furthermore, the initial utilization of chlorobenzoates was fastest under denitrifying conditions. Loss of 3-chlorobenzoate was seen under all four reducing conditions and the degradation of chlorobenzoates was coupled stoichiometrically to NO3- loss, Fe2+ production, SO4(2-) loss or CH4 production, indicating that the chlorobenzoates were oxidized to CO2. To our knowledge, this is the first observation of halogenated aromatic degradation coupled to Fe reduction.
Article: Dehalogenation and biodegradation of brominated phenols and benzoic acids under iron-reducing, sulfidogenic, and methanogenic conditions.[show abstract] [hide abstract]
ABSTRACT: The anaerobic biodegradation of monobrominated phenols and benzoic acids by microorganisms enriched from marine and estuarine sediments was determined in the presence of different electron acceptors [i.e., Fe(III), SO4(2-), or HCO3-]. Under all conditions tested, the bromophenol isomers were utilized without a lengthy lag period whereas the bromobenzoate isomers were utilized only after a lag period of 23 to 64 days. 2-Bromophenol was debrominated to phenol, with the subsequent utilization of phenol under all three reducing conditions. Debromination of 3-bromophenol and 4-bromophenol was also observed under sulfidogenic and methanogenic conditions but not under iron-reducing conditions. In the bromobenzoate-degrading cultures, no intermediates were observed under any of the conditions tested. Debromination rates were higher under methanogenic conditions than under sulfate-reducing or iron-reducing conditions. The stoichiometric reduction of sulfate or Fe(III) and the utilization of bromophenols and phenol indicated that biodegradation was coupled to sulfate or iron reduction, respectively. The production of phenol as a transient intermediate demonstrates that reductive dehalogenation is the initial step in the biodegradation of bromophenols under iron- and sulfate-reducing conditions.Applied and Environmental Microbiology 11/1997; 63(10):3911-5. · 3.83 Impact Factor
Article: Reductive dehalogenation and mineralization of 3-chlorobenzoate in the presence of sulfate by microorganisms from a methanogenic aquifer.[show abstract] [hide abstract]
ABSTRACT: We investigated the anaerobic biodegradation of 3-chlorobenzoate (3CBz) by microorganisms from an aquifer where chloroaromatic compounds were previously found to resist decay in the presence of sulfate. After a lengthy lag period, 3CBz was degraded in the presence of sulfate and concurrently with sulfate reduction. Chlorine removal from 2,5- or 3,5-dichlorobenzoates and the transient appearance of benzoate from 3CBz confirmed that reductive dehalogenation was the initial fate process for these substrates. Sulfate did not influence 3CBz degradation rates in acclimated enrichment cultures but accelerated the development of 3CBz degradation activity in fresh transfers. Benzoate degradation was more rapid in the presence of sulfate regardless of the enrichment history. Nitrate, sulfite, and a headspace of air inhibited 3CBz dehalogenation, while thiosulfate had no effect. Mass balance determinations revealed that 71 to 107% of the theoretically expected amount of methane was produced from 3CBz and benzoate oxidation in the absence of sulfate. In parallel cultures containing 15 mM sulfate, methanogenesis was reduced to 48 to 71% of that theoretically expected, while sulfate reduction accounted for 12 to 50% of the reducing equivalents. In either the presence or absence of sulfate, steady-state dissolved hydrogen concentrations were similar to those reported for sulfate-reducing or methanogenic environments, respectively. Molybdate inhibited sulfate reduction and 3CBz dehalogenation to a similar extent but did not affect benzoate biodegradation. Sulfate-dependent 3CBz biodegradation was not observed. We conclude that reductive dehalogenation and sulfate reduction occur concurrently in these enrichments and that the sulfate-dependent stimulation in fresh transfers was likely due to the acceleration of benzoate oxidation.Applied and Environmental Microbiology 08/1997; 63(7):2785-91. · 3.83 Impact Factor
Article: Isolation and characterization of diverse halobenzoate-degrading denitrifying bacteria from soils and sediments.[show abstract] [hide abstract]
ABSTRACT: Denitrifying bacteria capable of degrading halobenzoates were isolated from various geographical and ecological sites. The strains were isolated after initial enrichment on one of the monofluoro-, monochloro-, or monobromo-benzoate isomers with nitrate as an electron acceptor, yielding a total of 33 strains isolated from the different halobenzoate-utilizing enrichment cultures. Each isolate could grow on the selected halobenzoate with nitrate as the terminal electron acceptor. The isolates obtained on 2-fluorobenzoate could use 2-fluorobenzoate under both aerobic and denitrifying conditions, but did not degrade other halobenzoates. In contrast, the 4-fluorobenzoate isolates degraded 4-fluorobenzoate under denitrifying conditions only, but utilized 2-fluorobenzoate under both aerobic and denitrifying conditions. The strains isolated on either 3-chlorobenzoate or 3-bromobenzoate could use 3-chlorobenzoate, 3-bromobenzoate, and 2- and 4-fluorobenzoates under denitrifying conditions. The isolates were identified and classified on the basis of 16S rRNA gene sequence analysis and their cellular fatty acid profiles. They were placed in nine genera belonging to either the alpha-, beta-, or gamma-branch of the Proteobacteria, namely, Acidovorax, Azoarcus, Bradyrhizobium, Ochrobactrum, Paracoccus, Pseudomonas, Mesorhizobium, Ensifer, and Thauera. These results indicate that the ability to utilize different halobenzoates under denitrifying conditions is ubiquitously distributed in the Proteobacteria and that these bacteria are widely distributed in soils and sediments.Applied and Environmental Microbiology 09/2000; 66(8):3446-53. · 3.83 Impact Factor