Coli Inhibition Research Articles

Pattern of organotin inhibition of methanogenic bacteria

Seven organotin compounds and tin chloride were tested for their effects on the methanogenic bacteria Methanococcus thermolithotrophicus, Methanococcus deltae delta LH, and Methanosarcina barkeri 227. The methanogens were strongly inhibited by triethyltin, tripropyltin, and monophenyltin compounds, generally at concentrations below 0.05 mM. Less inhibition by tributyltin and diphenyltin was observed at levels below 0.1 mM, but complete inhibition was observed at a 1 mM concentration. Tin chloride inhibited all methanogens, with nearly complete inhibition at a 1 mM concentration. There was no inhibition by tetra-n-butyltin and triphenyltin compounds even at 2 mM, the highest concentration tested. The 50 and 100% inhibitory concentrations of all compounds were estimated; these values varied with both the compound tested and the bacterium tested. The 50% inhibitory concentration estimate generally decreased (i.e., giving a higher toxicity) as the total surface area of the alkyltin molecules decreased. These results differ considerably from those reported previously for aerobic microorganisms (G. Eng, E. J. Tierney, J. M. Bellama, and F. E. Brinckman, Appl. Organometallic Chem. 2:171-175, 1988), where a clear correlation between increasing total molecular surface area and increasing toxicity was documented with a variety of organisms. Using the same procedures as for the methanogens, we examined the effects of organotin compounds on Escherichia coli growing aerobically or anaerobically. The E. coli inhibition pattern clearly resembled that seen in the data of Eng et al., under both aerobic and anaerobic conditions.

A comparison of QSARs proposed for the inhibition of dihydropteroate synthase by substituted 4-aminodiphenylsulfones

Recently DeBenedetti et al. [1] synthesized and tested some substituted 4-aminodiphenylsulfones as Escherichia coli dihydropteroate synthase inhibitors. The findings from this assay have been shown to correlate highly with the measured inhibition potencies of dihydropteroate synthase from Mycobacterium lufu by Seydel and coworkers [2]. The resulting QSARs proposed by DeBenedetti et al. and Seydel et al. are compared to one another as well as to the QSARs proposed from an analysis of the M. lufu inhibition data. Intramolecular conformational entropy, S, is found to be the key correlation property, which can also be used to construct a QSAR for the E. coli inhibition data.