Abstract. The case-based reasoning (CBR) methodology can be augmented with the ability to determine the confidence in the correctness of individual solutions. A confidence calculation can be added to the REUSE portion of the CBR methodology. The confidence calculation takes confidence indicators, like "number of cases retrieved with best solution" and "average similarity of cases which suggest an alternative solution," and generates a confidence value. The information gain algorithm C4.5 can be used to select the best confidence indicators by evaluating their usefulness in historical cases. A genetic algorithm can be used to optimize and maintain the confidence calculation.
Several bacterial isolates were characterized based on their abilities to degrade specific polychlorinated biphenyls (PCBs) and their 16s rRNA gene sequences. The members of one group of bacteria consisting of Alcaligenes species, including the PCB-degrading bacterium Alcaligenes eutrophus H850, had strong abilities to degrade a broad range of PCBs but not the di-para-chlorine-substituted congeners. The members of another group, which included the PCB-degrading bacterium originally classified as Corynebacterium sp. strain MB1, had strong abilities to degrade di-para-chlorine-substituted PCBs. These bacteria were most likely different members of Rhodococcus species.Aerobic microbial degradation of polychlorinated biphenyls (PCBs) is well documented and has been characterized at the genetic level for several bacterial isolates (6, 12, 16, 19). Various PCB-degrading bacteria isolated from PCB-contaminated Hudson River sediment have significant differences in their abilities to degrade various PCB congeners (8). However, very little is known about the identities or phylogenetic relatedness of these bacterial isolates. A phylogenetic classification of these bacteria would be useful for understanding the diversity of PCB-degrading microorganisms and possibly for identifying any correlation with PCB-degradative ability.Current molecular biology techniques, in conjunction with Ribosomal Database Project (RDP) data, have permitted rapid classification of microorganisms and delineation of their evolutionary relationships (1 1, 18). Pseudomonas sp. strain LB400 (4) andAlcaZigenes eutrophus H850 (3) have been shown to contain nearly identical genes coding for the PCB-degradative enzymes, which are different from the enzymes in Pseudomonas cepacia, Pseudomonas testosteroni, Alcaligenes faecalis, and Coiynebacterium sp. strain MB1 (14, 19). In this paper, we report on a phylogenetic analysis of eight PCB-degrading bacterial isolates in which 16s rRNA gene analysis was used. In addition, two isolates previously classified as Arthrobacter sp. strain M5 (7) and Corynebacterium sp. strain MB1 (3) are reclassified.Bacterial strains 2AV, 2A2,2A42,6S48, and 2N40 (Table 1) were isolated from PCB-contaminated Hudson River sediment (8). A Biolog GN Microplate assay (Biolog, Inc., Haywood, Calif.) was used to characterize these isolates, in addition to PCB biodegradation and 16s rRNA gene phylogenetic analyses.PCB biodegradation. Resting cell assays (2) were performed to examine the abilities of the different strains to degrade PCBs and determine if there is a correlation between the phylogenetic relationships of these organisms and their specific PCBdegradative abilities. The abilities of the various bacterial strains to degrade selected PCB congeners during resting cell assays are shown in Table 1. The predominant mechanism of PCB degradation by the strains involves an initial 2,3-dioxyge-* Corresponding author. Mailing address: GE Research and Development Center, P.O. Box 8, Schenectady, NY 12301. ~~ nase attack, followed by a second...
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