No abstract

Studies were conducted to characterize the diversity of degradative abilities of microbial communities from pristine aquifer solids samples. Biodegradation was measured in aquifer solids slurries as both the conversion of radiolabeled substrate to 14CO2 and the incorporation of label into cell biomass. Under aerobic conditions, the microbial community metabolized the following naturally occurring compounds: acetic acid, amino acids, cellulose, cinnamic acid, glucosamine and glucose. The xenobiotic compounds aniline hydrochloride, chlorobenzene, p‐chloro‐phenol, m‐cresol, ethylene dibromide, naphthalene, phenol, toluene and trichlorobenzene were also biodegraded. Several kinetic parameters were calculated from the uptake and mineralization data. First‐order rate constants (K1) ranged from 10−2 to 10−4 h−1 for the natural compounds and from 10−3 to 10−6 h−1 for the xenobiotic compounds. Turnover times ranged from 47 to more than 1,900 h for natural compounds and from 806 to 60,000 h for xenobiotic compounds. For some compounds, respiratory enzymes became saturated, whereas incorporation into biomass was first‐order. The results show that uptake into cell biomass represents a large fraction of total metabolism for many of the xenobiotic compounds. 14C‐most‐probable‐number (MPN) of substrate degraders was calculated. MPNs for naturally occurring compounds ranged from 102 to 106 per gram of soil. There were generally fewer than 10 xenobiotic degraders per gram of soil. The biodegradative activity of the subsurface community appears to differ in both rate and product distribution from the activities of aquatic or surface‐soil communities.

Although pentamidine (1,5bis(4'-amidinophenoxy)pentane) is currently in use for the treatment of a variety of parasitic infections, including acquired immune deficiency syndrome-related Pneumocystis carinii pneumonia, its metabolism is still under investigation. Positive-ion fast atom bombardment mass spectrometry was used with highenergy collision-activated dissociation (CAD) and linked scanning at constant B/E to obtain tandem mass spectra of protonated molecules of pentamidine and seven synthetic oxygenated derivatives, which are known metabolites of pentamidine. Charge-initiated fragmentation produced abundant fragment ions of m/z 120 and 137 and loss of neutral ammonia from the protonated analyte that characterized the amidinophenoxy group. The structures of isomeric Zhydroxypentamidine, 3-hydroxypentamidine and N-hydroxypentamidine could be distinguished based on charge-remote fragmentation that produced a series of fragment ions of the pentyl chain and permitted the exact location of the hydroxyl group in each molecule to be determined. Next, tandem mass spectra were obtained and the charge-initiated and charge-remote fragmentation discussed for four other metabolites of pentamidine, including N,N-dihydroxypentamidine, 5-(4'-amidinophenoxy)pentanoic acid, 5-(4'-amidinophenoxy) pentan-1-01, and p-hydroxybenzamidine. Finally, tandem mass spectrometry was used to identify pentamidine and three pentamidine metabolites contained in high-performance liquid chromatographic (HPLC) fractions from rat liver perfusate and rat urine following treatment with pentamidine. Pentamidine metabolites identified in rat urine and liver perfusate using mass spectrometry and HPLC retention times included Zhydroxypentamidine,