Excised Band Substrate Division (or subdivision) Nearest Taxon Accession no. Similarity (%) 1 LB Firmicutes Bacillus pumilus JQ353824 99 2 LB Gammaproteobacteria Stenotrophomonas maltophilia JX867287 100 3 LB Gammaproteobacteria Stenotrophomonas sp JQ917790 99 4 LB Firmicutes Lysinibacillus sphaericus JQ744637 99 5 LB Actinobacteria Actinobacterium JN049471 99 6 LB Firmicutes Bacillus sp HM026204 98 7 LB Gammaproteobacteria Acinetobacter johnsonii JQ039983 100 8 LB Gammaproteobacteria Pseudomonas putida JQ781586 100 9 LB Betaproteobacteria Delftia sp HE716888 100 10 LB Firmicutes Clostridiales bacterium GQ922846 97 11 LB Actinobacteria Kineococcus radiotolerans CP000750 100 12 LB Gammaproteobacteria Shewanella aquimarina FJ589034 100 13 LB Firmicutes Lactobacillus helveticus CP003799 100 14 LB Gammaproteobacteria Marinobacterium JQ670704 100 15 LB Gammaproetobacteria Pseudidomarina sp GQ202579 98 16 UB Epsilonproteobacteria Epsilonproteobacterium HQ607532 100 17 UB Betaproteobacteria Massilia sp JQ014560 100 18 UB Firmicutes Clostridium sp FR872934 99 19 UB Actinobacteria Nocardiodes islandensis NR044235 100 LB= Labeled benzene, UB-= unlabeled benzene

Table 2A: Summary of bacterial 16S rRNA partial sequences obtained from excised DGGE profiles (Figure 1A) of unlabeled and labeled benzene microcosms.