Aerobic Biodegradation of Natural and Xenobiotic Organic Compounds by Subsurface Microbial Communities

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 I4CO2 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-chlorophenol, rn-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 ( K l ) ranged from lo-' to h-' for the natural compounds and from low3 to 10W6 h-' 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 firstorder. The results show that uptake into cell biomass represents a large fraction of total metabolism for many of the xenobiotic compounds. ''C-most-probable-number (MPN) of substrate degraders was calculated. MPNs for naturally occurring compounds ranged from 10' to lo6 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.

Adaptation of aquifer microbial communities to the biodegradation of xenobiotic compounds: Influence of substrate concentration and preexposure

“…Differences in degradative capabilities are expected at different sites and indeed have been shown among samples from the same soil stratum of the Lula aquifer [1,12,19]. In our experiments, the Lula community did not degrade toluene, whereas at the Traverse City site, microbes with no previous exposure to hydrocarbon contamination, as well as those that had been previously exposed, were able to degrade toluene even at low concentrations.…”

Supplemental Carbon Use by Microorganisms Degrading Toxic Organic Compounds and the Concept of Specific Toxicity

“…High concentrations of easily metabolized carbon substrates have been shown to repress the catabolic enzyme systems needed by bacteria to degrade less desirable organic substrates until no easily metabolizable substrate remains (diauxic growth; 16). Swindoll et al (17) studied the variability in biodégradation of four toxic organic substrates upon addition of supplementary nutrients. Addition of ancillary carbon sources (e.g., glucose) was found to inhibit mineralization of the toxic substrates presumably due to preferential utilization of the more easily degraded carbon supplements.…”

A comparison of microbial community characteristics among petroleum-contaminated and uncontaminated subsurface soil samples

“…Since then, research into the metabolic capabilities of aquifer microbial communities has been prolific. Aquifer microbial communities can degrade a broad range of naturally occurring and xenobiotic compounds under a broad range of environmental conditions [20,22,24,31,32,42,44,45]: Two reviews of the research on subsurface microbial ecology were presented by Ghiorse and Wilson [18] and by Dobbins et al [11]. The results of these studies and many others led to the understanding that indigenous, aquifer, microbial populations could biodegrade environmental pollution and affect remediation of contaminated sites.…”