The environmental distribution of Dehalococcoides group organisms and their association with chloroethenecontaminated sites were examined. Samples from 24 chloroethene-dechlorinating sites scattered throughout North America and Europe were tested for the presence of members of the Dehalococcoides group by using a PCR assay developed to detect Dehalococcoides 16S rRNA gene (rDNA) sequences. Sequences identified by sequence analysis as sequences of members of the Dehalococcoides group were detected at 21 sites. Full dechlorination of chloroethenes to ethene occurred at these sites. Dehalococcoides sequences were not detected in samples from three sites at which partial dechlorination of chloroethenes occurred, where dechlorination appeared to stop at 1,2-cis-dichloroethene. Phylogenetic analysis of the 16S rDNA amplicons confirmed that Dehalococcoides sequences formed a unique 16S rDNA group. These 16S rDNA sequences were divided into three subgroups based on specific base substitution patterns in variable regions 2 and 6 of the Dehalococcoides 16S rDNA sequence. Analyses also demonstrated that specific base substitution patterns were signature patterns. The specific base substitutions distinguished the three sequence subgroups phylogenetically. These results demonstrated that members of the Dehalococcoides group are widely distributed in nature and can be found in a variety of geological formations and in different climatic zones. Furthermore, the association of these organisms with full dechlorination of chloroethenes suggests that they are promising candidates for engineered bioremediation and may be important contributors to natural attenuation of chloroethenes.The chloroethenes tetrachloroethene (PCE) and trichloroethene (TCE) are commonly used organic solvents and degreasing agents. As a result of past disposal practices and spills, chloroethenes are now widely distributed in the environment and are found in many sediments, soils, groundwater aquifers, and subsurface environments throughout the world (13,21,28). Traditional approaches to groundwater remediation practices, such as pump and treat methods, have been shown to be ineffective and costly when applied to chlorinated solvent plumes (2a, 2c, 23). Therefore, there is a need for microbebased remediation approaches that could provide an inexpensive way to clean up chlorinated solvent contamination.Chloroethene solvents were previously believed to be resistant to degradation by microorganisms. There now is rapidly accumulating laboratory and field evidence that microorganisms can transform chloroethenes to nontoxic products under a variety of environmental conditions (3, 8-10, 12, 15, 20, 22, 27, 28, 30, 31, 35). Maymó-Gatell et al. have isolated an organism from an anaerobic dechlorinating laboratory culture inoculated with municipal sewage sludge, which fully dechlorinates chlorinated ethenes (25,26). This organism, Dehalococcoides ethenogenes strain 195, was shown to meet its energy needs, which are essential for growth, by a process known as dehalore...
A multianalyte immunoassay for simultaneous detection of three analytes (hTSH, hCG and B-Gal) has been demonstrated using DNA-labeled antibodies and polymerase chain reaction (PCR) for amplification of assay response. The labeled antibodies were prepared by covalently coupling uniquely designed DNA oligonucleotides to each of the analyte-specific monoclonal antibodies. Each of the DNA oligonucleotide labels contained the same primer sequences to facilitate coamplification by a single primer pair. Assays were performed using a two-antibody sandwich assay format and a mixture of the three DNA-labeled antibodies. Dose-response relationships for each analyte were demonstrated. Analytes were detected at sensitivities exceeding those of conventional enzyme immunoassays by approximately three orders of magnitude. Detection limits for hTSH, 3-Gal and hCG were respectively 1 x 1O.19, 1 x 10-17 and 1 x 10-17 mol. Given the enormous amplification afforded by PCR and the existing capability to differentiate DNA based on size or sequence differences, the use of DNA-labeled antibodies could provide the basis for the simultaneous detection of many analytes at sensitivities greater than those of existing antigen detection systems. These findings in concert with previous reports suggest this hybrid technology could provide a new generation of ultra-sensitive multianalyte immunoassays.
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