Showing papers on "Microbial biodegradation published in 1980"

Studies on the degradation of atrazine by bacterial communities enriched from various biotopes

Abstract: Degradation of14C-ring labeled atrazine (2-choloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) by bacterial populations from soil, waters and activated sludges was investigated and compared with non-biological decomposition in sterile solutions. Within two weeks, 0.6% Cl-deethyl- and 0.1% Cl-deisopropylatrazine had been formed in sterile 0.02 M phosphate buffer, pH 7.2. In biodegradation studies, bacterial populations were enriched and incubated in media containing atrazine and high or low levels of nutrients. Nutrient supply had a strong effect on the fate of atrazine in bacterial cultures, whereas the origin of bacteria was of minor importance. In 31 of 33 mixed populations investigated, the herbicide was largely converted to unidentified compounds. Incubation with high levels of nutrients resulted in 17% to 57% of these compounds being constant after one and two weeks of incubation. In parallel experiments with low nutrient supply, the compounds were present in amounts of 7% to 57% after one week. The proportions of the unidentified compounds dropped within the second week of incubation, while atrazine reappeared correspondingly. The amounts of dealkylated metabolites generally did not exceed those of sterile solutions. The results indicate that atrazine is not degraded by bacteria but bound, thus simulating biodegradation. Evidence is presented that physicochemical decomposition of the herbicide is more significant than microbial degradation.

Microbial transformation of low-level radioactive waste

Abstract: Microorganisms play a significant role in the transformation of the radioactive waste and waste forms disposed of at shallow-land burial sites. Microbial degradation products of organic wastes may influence the transport of buried radionuclides by leaching, solubilization, and formation of organoradionuclide complexes. The ability of indigenous microflora of the radioactive waste to degrade the organic compounds under aerobic and anaerobic conditions was examined. Leachate samples were extracted with methylene chloried and analyzed for organic compounds by gas chromatography and mass spectrometry. In general, several of the organic compounds in the leachates were degraded under aerobic conditions. Under anaerobic conditions, the degradation of the organics was very slow, and changes in concentrations of several acidic compounds were observed. Several low-molecular-weight organic acids are formed by breakdown of complex organic materials and are further metabolized by microorganisms; hence these compounds are in a dynamic state, being both synthesized and destroyed. Tributyl phosphate, a compound used in the extraction of metal ions from solutions of reactor products, was not degraded under anaerobic conditions.

Bacterial Degradation of Crude Oil and Oil Components in Pure and Mixed Culture Systems

Abstract: Since the eventual removal from land and water of spilled hydrocarbons depends upon microbial oxidation, any situation in which there is no oil degrading bacteria, no oxygen available for that oxidation, or too low a temperature for bacterial growth will result in the oil remaining virtually undegraded. It is already known that oil-degrading bacteria exist at low levels in most ecological habitats and that even in Arctic conditions microbial degradation occurs. The only possible limitation, other than time, could be available oxygen, that is, if we assume that the spilt oil does not contain or release compounds which are toxic to the bacterial population.

Rapid assays for microbial degradation of 2-chlorophenol

Abstract: Until recently it has been impossible to characterize the microbial subpopulations of complex ecosystems on the basis of their metabolic characteristics. This study presents two simple procedures for estimating the size of microbial subpopulations and their ability to degrade 2-chlorophenol. The assay techniques were used to study shifts in microbial subpopulations identified as sensitive or resistant to the toxic effects of 2chlorophenol. The studies also show the effect of cosubstrate metabolism on degradation of 2-chlorophenol by pure cultures. Adaptation or acclimation to a normally toxic environment results in a shift in microbial subpopulations. Once the subpopulations were established in acclimated cultures, their response to the pulsed addition of 2chlorophenol was much less than was the response of a paired unacclimated culture. The screening procedure indicated that increased resistance to 2-chlorophenol paralleled the increased 2-chlorophenol degrading capability of the microbial subpopulations. The assays make possible rapid and accurate estimation of 2-chlorophenol resistance and degradation in microbial populations.