Similartowhatwasfoundwith C. xestobii,ourstudies also indicate that B. simplex uses metolachlor as a sole source of C and energy for growth. However, neither microorganism had the ability to degrade some of the proposed main metabolites of metolachlor, MESA or MOA. Under aerobic conditions, only partial biodegradation of metolachlor by bacteria was previously reported, and it has been proposed that degradation proceeds through a co metabolic process in the presence of other C sources. How ever, the catabolism of metolachlor by B. simplex does not appear to be due to a co metabolic process, because it occurred in MM without other added carbon substrates and with only a single microorganism present. Despite this, the transformation of metolachlor by B.

simplex was not complete, and this may be related,inpart,totheapparentpersistenceofmetolachlorinsoils. Forexample,inlaboratoryincubationexperimentsKonopkaand Turco reportedthatmetolachlor wasnot degraded over a period of 128 days in vadose zone samples obtained from an agricultural field. Nevertheless, our data indicate that partial PARP Inhibitors transformation of this herbicide was still sufficient to supply this bacterium with sufficient C and energy for growth. Degradation of Acetochlor and Alachlor by C. xestobii. The degradation of relatively high concentrations of acetochlor and alachlor by C. xestobii was also examined, and the disappearance of both of these substrates was also determined to be due to the result of microbial metabolism. Results in Figure 5 show that 50% of the added acetochlor was degraded by C.

xestobii in the first 15 h of growth, and the concentration decreased by 60% after 312 h. In the resting cell assays, however, about 80% of the acetochlor was degraded in 15 h, but the degradation was also incomplete, and there p53 Signaling Pathway was no degradation after that time. Whereas acetochlor was previously shown to be completely degraded by a consortium of eight microorganisms after 4 days, no single isolate was able to degrade acetochlor efficiently. Results in Figure 6 show that C. xestobii also transformed ??70% of the initial concentration of alachlor after 3 days of growth, after which time degradation was much slower. In the restingcellassays,however,degradationproceededmorequickly, and ??80% was transformed after 2 days. Whereas Xu et al.

reported that 63 and 39% of alachlor and metolachlor, respec tively, were degraded by mixed microbial consortia after 21 days of incubation, C. xestobii surpassed those AMPK Signaling degradation amounts in shorter incubation periods. Control media, which were not inoculated, did not exhibit acetochlor or alachlor disappearance. A summary of the degradation of acetanilide herbicides by the isolated microorganisms is shown in Table 1. Mineralization of Metolachlor and Alachlor by C. xestobii and B. simplex. Growth of C. xestobii in the presence of meto lachlor showed that up to 25% of the ring labeled compound was converted into CO 2 after 10 days of growth. Like catabolism, the mineralization of metolachlor by C. xestobii was not complete, and no further mineralization occurred even after 360 h of incubation.

Interestingly, mineralization of metolachlor in MM amended with yeast extract was greater than that seen in MM containing only metolachlor. In the former case, PLK miner alization started after 4 days of incubation and reached only 6% after 240 days of incubation, whereas mineralization started 24 h earlier in resting cells assays, indicating a direct relationship between cell numbers and mineralization rate. Growth of C. xestobii in the presence of alachlor showed that up to 20% of the ring labeled compound was mineralized to CO 2 after 48 h. After that time, mineralization proceeded much more slowly, and 40% was transformed after 336 h of incubation. Whereas white rot fungi were previously reported to The colored product was not seen in NaOH vials in control uninoculated biometer flasks containing alachlor or metolachlor mineralization studies.

Whereas B. simplex has the ability to use metolachlor as the sole C and energy sources for growth, the bacterium failed to mineralize this herbicide, at least the C ring labeled PARP atoms. This indicated that B. simplex likely uses a different degradation path way for metolachlor than does C. xestobii. In some ways, this result is similar to those reported by Saxena et al., who failed to isolate bacteria that could mineralize metolachlor. However, these authors did report that strains of Bacillus circulans, Bacillus megaterium, and an actinomycete were able to transform metola chlor into several metabolites. Although Stamper and Tuovinen postulated that miner alization of metolachlor may not be the major route for its dissipation in natural systems, results are currently contradictory. For example, Staddon et al. reported that 4% of metola chlor was mineralized after 46 days, but Krutz et al. reported that 40% of metolachlor was mineralized after 63 days in a soil.