SEARCH · PubMed Health

Results for “Biodegradation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,423 records · Page 79Linked to original sources

PubMed1995

Role of competition for inorganic nutrients in the biodegradation of mixtures of substrates.

A study was conducted to determine whether competition for inorganic nutrients affects the biodegradation of mixtures of substrates. Little benzylamine was mineralized by Pseudomonas putida in solutions with no added P, but the substrate was degraded if the medium contained 100 nM P. The enhancement by P addition did not occur if the medium also contained caprolactam and a caprolactam-utilizing strain of Pseudomonas aeruginosa. The suppression by the second bacterium was overcome by a higher P concentration. The rate of caprolactam utilization by P. aeruginosa was reduced if benzylamine and P. putida were also present in media with 100 nM P, but the suppression was absent if the solution contained a higher P concentration. Glutamate increased and inorganic N plus P decreased the length of the acclimation phase prior to benzylamine mineralization in lake water. We suggest that the effect of one biodegradable substrate on the metabolism of a second often results from a competition for inorganic nutrients.

Benzylamines↗

PubMed1996

Identification of bacteria in a biodegraded wall painting by denaturing gradient gel electrophoresis of PCR-amplified gene fragments coding for 16S rRNA.

Medieval wall paintings are often affected by biodecay. An inventory of the existing microorganisms associated with the damage to the paintings is not yet an integral part of the restoration process. This stems from the lack of effective means for such a stocktaking. Nevertheless, fungi and bacteria cause severe damage through mechanical processes from growth into the painting and its grounding and through their metabolism. Detailed information on the bacterial colonization of ancient wall paintings is essential for the protection of the paintings. We used a molecular approach based on the detection and identification of DNA sequences encoding rRNA (rDNA) to identify bacteria present on an ancient wall painting without prior cultivation of the organisms, since it has been shown that most of these bacteria cannot be cultivated under laboratory conditions. To trace the noncultivated fraction of bacteria, total DNA from a biodegraded wall painting sample from a 13th century fresco was extracted and 194-bp fragments of the 16S rDNA were amplified with eubacterial primers. The 16S rDNA fragments of uniform length obtained from the different bacterial species were separated according to their sequence differences by denaturing gradient gel electrophoresis (DGGE). By sequencing excised and reamplified individual DNA bands, we characterized the phylogenetic affiliation of the corresponding bacteria. Using this approach, we identified members or close relatives of the genera Halomonas, Clostridium, and Frankia. To our knowledge, these groups of bacteria have not yet been isolated and implicated by conventional microbiological techniques as contributing to the biodegradation of wall paintings.

Bacteria↗

PubMed1996

Metabolic efficiency and turnover of soil microbial communities in biodegradation tests.

Biodegradability screening tests of soil commonly measure 14CO2 evolution from radiolabeled test compounds, and glucose has often served as a positive control. When constant amounts of radiolabel were added to soil in combination with increasing amounts of unlabeled substrates, glucose and some related hexoses behaved in an anomalous manner. In contrast to that of formate, benzoate, n-hexadecane, or bis(2-ethylhexyl) phthalate, dilution of glucose radiocarbon with unlabeled glucose increased rather than decreased the rate and extent of 14CO2 evolution. [14C]glucose incorporation into biomass and Vmax values were consistent with the interpretation that application of relatively high concentrations of glucose to soil shifts the balance of the soil microbial community from the autochthonous (humus-degrading) to the zymogeneous (opportunistic) segment. The higher growth and turnover rates that define zymogeneous microorganisms, combined with a lower level of carbon incorporation into their biomass, result in the evolution of disproportionate percentages of 14CO2. When used as positive controls, glucose and related hexoses may raise the expectations for percent 14CO2 evolution to levels that are not realistic for other biodegradable compounds.

Biodegradation, Environmental↗

PubMed1997

Nylon biodegradation by lignin-degrading fungi.

The biodegradation of nylon by lignin-degrading fungi was investigated. The fungus IZU-154 significantly degraded nylon-66 membrane under ligninolytic conditions. Nuclear magnetic resonance analysis showed that four end groups, CHO, NHCHO, CH3, and CONH2, were formed in the biodegraded nylon-66 membranes, suggesting that nylon-66 was degraded oxidatively.

Basidiomycota↗

PubMed1997

Plant compounds that induce polychlorinated biphenyl biodegradation by Arthrobacter sp. strain B1B.

Plant compounds that induced Arthrobacter sp. strain B1B to cometabolize polychlorinated biphenyls (PCBs) were identified by a screening assay based on the formation of a 4,4'-dichlorobiphenyl ring fission product. A chemical component of spearmint (Mentha spicata), l-carvone, induced Arthrobacter sp. strain B1B to cometabolize Aroclor 1242, resulting in significant degradation of 26 peaks in the mixture, including selected tetra- and pentachlorobiphenyls. Evidence for PCB biodegradation included peak disappearance, formation of a phenylhexdienoate ring fission product, and chlorobenzoate accumulation in the culture supernatant. Carvone was not utilized as a growth substrate and was toxic at concentrations of greater than 500 mg liter-1. Several compounds structurally related to l-carvone, including limonene, p-cymene, and isoprene, also induced cometabolism of PCBs by Arthrobacter sp. strain B1B. A structure-activity analysis showed that chemicals with an unsaturated p-menthane structural motif promoted the strongest cometabolism activity. These data suggest that certain plant-derived terpenoids may be useful for promoting enhanced rates of PCB biodegradation by soil bacteria.

Aroclors↗

PubMed1997

Biodegradation of petroleum hydrocarbons by psychrotrophic Pseudomonas strains possessing both alkane (alk) and naphthalene (nah) catabolic pathways.

Three hydrocarbon-degrading psychrotrophic bacteria were isolated from petroleum-contaminated Arctic soils and characterized. Two of the strains, identified as Pseudomonas spp., degraded C5 to C12 n-alkanes, toluene, and naphthalene at both 5 and 25 degrees C and possessed both the alk catabolic pathway for alkane biodegradation and the nah catabolic pathway for polynuclear aromatic hydrocarbon biodegradation. One of these strains contained both a plasmid slightly smaller than the P. oleovorans OCT plasmid, which hybridized to an alkB gene probe, and a NAH plasmid similar to NAH7, demonstrating that both catabolic pathways, located on separate plasmids, can naturally coexist in the same bacterium.

Alkanes↗

PubMed1998

Biodegradation of phosphonomycin by Rhizobium huakuii PMY1.

The biodegradation by Rhizobium huakuii PMY1 of up to 10 mM phosphonomycin as a carbon, energy, and phosphorus source with accompanying P(i) release is described. This biodegradation represents a further mechanism of resistance to this antibiotic and a novel, phosphate-deregulated route for organophosphonate metabolism by Rhizobium spp.

Anti-Bacterial Agents↗

PubMed1998

Biodegradation of metal-EDTA complexes by an enriched microbial population.

A mixed culture utilizing EDTA as the sole carbon source was isolated from a mixed inoculum of water from the River Mersey (United Kingdom) and sludge from an industrial effluent treatment plant. Fourteen component organisms were isolated from the culture, including representatives of the genera Methylobacterium, Variovorax, Enterobacter, Aureobacterium, and Bacillus. The mixed culture biodegraded metal-EDTA complexes slowly; the biodegradability was in the order Fe > Cu > Co > Ni > Cd. By incorporation of inorganic phosphate into the medium as a precipitant ligand, heavy metals were removed in parallel to EDTA degradation. The mixed culture also utilized a number of possible EDTA degradation intermediates as carbon sources.

Biodegradation, Environmental↗

PubMed1998

Biodegradation of aliphatic-aromatic copolyesters by Thermomonospora fusca and other thermophilic compost isolates.

Random aliphatic-aromatic copolyesters synthesized from 1,4-butanediol, adipic acid, and terephthalic acid (BTA) have excellent thermal and mechanical properties and are biodegradable by mixed cultures (e.g., in compost). Over 20 BTA-degrading strains were isolated by using compost as a microbial source. Among these microorganisms, thermophilic actinomycetes obviously play an outstanding role and appear to dominate the initial degradation step. Two actinomycete strains exhibited about 20-fold higher BTA degradation rates than usually observed in a common compost test. These isolates were identified as Thermomonospora fusca strains. They appeared to be particularly suitable for establishment of rapid degradation tests and were used in comparative studies on the biodegradation of various polyesters.

Actinomycetales↗

PubMed1999

Biodegradation of free phytol by bacterial communities isolated from marine sediments under aerobic and denitrifying conditions.

Biodegradation of (E)-phytol [3,7,11, 15-tetramethylhexadec-2(E)-en-1-ol] by two bacterial communities isolated from recent marine sediments under aerobic and denitrifying conditions was studied at 20 degrees C. This isoprenoid alcohol is metabolized efficiently by these two bacterial communities via 6,10, 14-trimethylpentadecan-2-one and (E)-phytenic acid. The first step in both aerobic and anaerobic bacterial degradation of (E)-phytol involves the transient production of (E)-phytenal, which in turn can be abiotically converted to 6,10,14-trimethylpentadecan-2-one. Most of the isoprenoid metabolites identified in vitro could be detected in a fresh sediment core collected at the same site as the sediments used for the incubations. Since (E)-phytenal is less sensitive to abiotic degradation at the temperature of the sediments (15 degrees C), the major part of (E)-phytol appeared to be biodegraded in situ via (E)-phytenic acid. (Z)- and (E)-phytenic acids are present in particularly large quantities in the upper section of the core, and their concentrations quickly decrease with depth in the core. This degradation (which takes place without significant production of phytanic acid) is attributed to the involvement of alternating beta-decarboxymethylation and beta-oxidation reaction sequences induced by denitrifiers. Despite the low nitrate concentration of marine sediments, denitrifying bacteria seem to play a significant role in the mineralization of (E)-phytol.

Aerobiosis↗

PubMed1999

Earthworm egg capsules as vectors for the environmental introduction of biodegradative bacteria.

Earthworm egg capsules (cocoons) may acquire bacteria from the environment in which they are produced. We found that Ralstonia eutropha (pJP4) can be recovered from Eisenia fetida cocoons formed in soil inoculated with this bacterium. Plasmid pJP4 contains the genes necessary for 2,4-dichlorophenoxyacetic acid (2,4-D) and 2, 4-dichlorophenol (2,4-DCP) degradation. In this study we determined that the presence of R. eutropha (pJP4) within the developing earthworm cocoon can influence the degradation and toxicity of 2,4-D and 2,4-DCP, respectively. The addition of cocoons containing R. eutropha (pJP4) at either low or high densities (10(2) or 10(5) CFU per cocoon, respectively) initiated degradation of 2,4-D in nonsterile soil microcosms. Loss of 2,4-D was observed within the first week of incubation, and respiking the soil with 2,4-D showed depletion within 24 h. Microbial analysis of the soil revealed the presence of approximately 10(4) CFU R. eutropha (pJP4) g-1 of soil. The toxicity of 2,4-DCP to developing earthworms was tested by using cocoons with or without R. eutropha (pJP4). Results showed that cocoons containing R. eutropha (pJP4) were able to tolerate higher levels of 2,4-DCP. Our results indicate that the biodegradation of 2, 4-DCP by R. eutropha (pJP4) within the cocoons may be the mechanism contributing to toxicity reduction. These results suggest that the microbiota may influence the survival of developing earthworms exposed to toxic chemicals. In addition, cocoons can be used as inoculants for the introduction into the environment of beneficial bacteria, such as strains with biodegradative capabilities.

2,4-Dichlorophenoxyacetic Acid↗

PubMed2001

Effects of low temperature and freeze-thaw cycles on hydrocarbon biodegradation in Arctic tundra soil.

Degradation of petroleum hydrocarbons was monitored in microcosms with diesel fuel-contaminated Arctic tundra soil incubated for 48 days at low temperatures (-5, 0, and 7 degrees C). An additional treatment was incubation for alternating 24-h periods at 7 and -5 degrees C. Hydrocarbons were biodegraded at or above 0 degrees C, and freeze-thaw cycles may have actually stimulated hydrocarbon biodegradation. Total petroleum hydrocarbon (TPH) removal over 48 days in the 7, 0, and 7 and -5 degrees C treatments, respectively, was 450, 300, and 600 microg/g of soil. No TPH removal was observed at -5 degrees C. Total carbon dioxide production suggested that TPH removal was due to biological mineralization. Bacterial metabolic activity, indicated by RNA/DNA ratios, was higher in the middle of the experiment (day 21) than at the start, in agreement with measured hydrocarbon removal and carbon dioxide production activities. The total numbers of culturable heterotrophs and of hydrocarbon degraders did not change significantly over the 48 days of incubation in any of the treatments. At the end of the experiment, bacterial community structure, evaluated by ribosomal intergenic spacer length analysis, was very similar in all of the treatments but the alternating 7 and -5 degrees C treatment.

Arctic Regions↗

PubMed2002

Impact of irradiation and polycyclic aromatic hydrocarbon spiking on microbial populations in marine sediment for future aging and biodegradability studies.

Experiments were carried out to develop methods to generate well-characterized, polycyclic aromatic hydrocarbon (PAH)-spiked, aged but minimally altered sediments for fate, biodegradation, and bioavailability experiments. Changes in indigenous bacterial populations were monitored in mesocosms constructed of relatively clean San Diego Bay sediments, with and without exposure to gamma radiation, and then spiked with five different PAHs and hexadecane. While phenanthrene and chrysene degraders were present in the unspiked sediments and increased during handling, PAH spiking of nonirradiated sediments led to dramatic increases in their numbers. Phenotypic characterization of isolates able to grow on phenanthrene or chrysene placed them in several genera of marine bacteria: Vibrio, Marinobacter or Cycloclasticus, Pseudoalteromonas, Marinomonas, and HALOMONAS: This is the first time that marine PAH degraders have been identified as the latter two genera, expanding the diversity of marine bacteria with this ability. Even at the highest irradiation dose (10 megarads), heterotrophs and endospore formers reappeared within weeks. However, while bacteria from the unirradiated sediments had the capacity to both grow on and mineralize 14C-labeled phenanthrene and chrysene, irradiation prevented the reappearance of PAH degraders for up to 4 months, allowing spikes to age onto the sediments, which can be used to model biodegradation in marine sediments.

Biodegradation, Environmental↗

PubMed2003

Role of soil pH in the development of enhanced biodegradation of fenamiphos.

Repeated treatment with fenamiphos (ethyl 4-methylthio-m-tolyl isopropylphosphoramidate) resulted in enhanced biodegradation of this nematicide in two United Kingdom soils with a high pH (>/= 7.7). In contrast, degradation of fenamiphos was slow in three acidic United Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result in enhanced biodegradation. Rapid degradation of fenamiphos was observed in two Australian soils (pH 6.7 to 6.8) in which it was no longer biologically active against plant nematodes. Enhanced degrading capability was readily transferred from Australian soil to United Kingdom soils, but only those with a high pH were able to maintain this capability for extended periods of time. This result was confirmed by fingerprinting bacterial communities by 16S rRNA gene profiling of extracted DNA. Only United Kingdom soils with a high pH retained bacterial DNA bands originating from the fenamiphos-degrading Australian soil. A degrading consortium was enriched from the Australian soil that utilized fenamiphos as a sole source of carbon. The 16S rRNA banding pattern (determined by denaturing gradient gel electrophoresis) from the isolated consortium migrated to the same position as the bands from the Australian soil and those from the enhanced United Kingdom soils in which the Australian soil had been added. When the bands from the consortium and the soil were sequenced and compared they showed between 97 and 100% sequence identity, confirming that these groups of bacteria were involved in degrading fenamiphos in the soils. The sequences obtained showed similarity to those from the genera Pseudomonas, Flavobacterium, and CAULOBACTER: In the Australian soils, two different degradative pathways operated simultaneously: fenamiphos was converted to fenamiphos sulfoxide (FSO), which was hydrolyzed to the corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos phenol. In the United Kingdom soils in which enhanced degradation had been induced, fenamiphos was oxidized to FSO and then hydrolyzed to FSO-OH, but direct conversion to fenamiphos phenol did not occur.

Biodegradation, Environmental↗

PubMed2006

Aerobic biodegradation of 2,2'-dithiodibenzoic acid produced from dibenzothiophene metabolites.

Dibenzothiophene is a sulfur heterocycle found in crude oils and coal. The biodegradation of dibenzothiophene through the Kodama pathway by Pseudomonas sp. strain BT1d leads to the formation of three disulfides: 2-oxo-2-(2-thiophenyl)ethanoic acid disulfide, 2-oxo-2-(2-thiophenyl)ethanoic acid-2-benzoic acid disulfide, and 2,2'-dithiodibenzoic acid. When provided as the carbon and sulfur source in liquid medium, 2,2'-dithiodibenzoic acid was degraded by soil enrichment cultures. Two bacterial isolates, designated strains RM1 and RM6, degraded 2,2'-dithiodibenzoic acid when combined in the medium. Isolate RM6 was found to have an absolute requirement for vitamin B12, and it degraded 2,2'-dithiodibenzoic acid in pure culture when the medium was supplemented with this vitamin. Isolate RM6 also degraded 2,2'-dithiodibenzoic acid in medium containing sterilized supernatants from cultures of isolate RM1 grown on glucose or benzoate. Isolate RM6 was identified as a member of the genus Variovorax using the Biolog system and 16S rRNA gene analysis. Although the mechanism of disulfide metabolism could not be determined, benzoic acid was detected as a transient metabolite of 2,2'-dithiodibenzoic acid biodegradation by Variovorax sp. strain RM6. In pure culture, this isolate mineralized 2,2'-dithiodibenzoic acid, releasing 59% of the carbon as carbon dioxide and 88% of the sulfur as sulfate.

Aerobiosis↗

PubMed1974

Biodegradation of cyanuric acid.

Cyanuric acid biodegrades readily under a wide variety of natural conditions, and particularly well in systems of either low or zero dissolved-oxygen level, such as anaerobic activated sludge and sewage, soils, muds, and muddy streams and river waters, as well as ordinary aerated activated sludge systems with typically low (1 to 3 ppm) dissolved-oxygen levels. Degradation also proceeds in 3.5% sodium chloride solution. Consequently, there are degradation pathways widely available for breaking down cyanuric acid discharged in domestic effluents. The overall degradation reaction is merely a hydrolysis; CO(2) and ammonia are the initial hydrolytic breakdown products. Since no net oxidation occurs during this breakdown, biodegradation of cyanuric acid exerts no primary biological oxygen demand. However, eventual nitrification of the ammonia released will exert its usual biological oxygen demand.

Aerobiosis↗

PubMed1991

Biodegradation of halogenated organic compounds.

In this review we discuss the degradation of chlorinated hydrocarbons by microorganisms, emphasizing the physiological, biochemical, and genetic basis of the biodegradation of aliphatic, aromatic, and polycyclic compounds. Many environmentally important xenobiotics are halogenated, especially chlorinated. These compounds are manufactured and used as pesticides, plasticizers, paint and printing-ink components, adhesives, flame retardants, hydraulic and heat transfer fluids, refrigerants, solvents, additives for cutting oils, and textile auxiliaries. The hazardous chemicals enter the environment through production, commercial application, and waste. As a result of bioaccumulation in the food chain and groundwater contamination, they pose public health problems because many of them are toxic, mutagenic, or carcinogenic. Although synthetic chemicals are usually recalcitrant to biodegradation, microorganisms have evolved an extensive range of enzymes, pathways, and control mechanisms that are responsible for catabolism of a wide variety of such compounds. Thus, such biological degradation can be exploited to alleviate environmental pollution problems. The pathways by which a given compound is degraded are determined by the physical, chemical, and microbiological aspects of a particular environment. By understanding the genetic basis of catabolism of xenobiotics, it is possible to improve the efficacy of naturally occurring microorganisms or construct new microorganisms capable of degrading pollutants in soil and aquatic environments more efficiently. Recently a number of genes whose enzyme products have a broader substrate specificity for the degradation of aromatic compounds have been cloned and attempts have been made to construct gene cassettes or synthetic operons comprising these degradative genes. Such gene cassettes or operons can be transferred into suitable microbial hosts for extending and custom designing the pathways for rapid degradation of recalcitrant compounds. Recent developments in designing recombinant microorganisms and hybrid metabolic pathways are discussed.

Bacteria↗

PubMed1998

A review of the occurrence, toxicity, and biodegradation of condensed thiophenes found in petroleum.

Condensed thiophenes comprise a significant portion of the organosulfur compounds in petroleum and in other products from fossil fuels. Dibenzothiophene (DBT) has served as a model compound in biodegradation studies for over two decades. However, until quite recently, few other organosulfur compounds were studied, and their fates in petroleum-contaminated environments are largely unknown. This paper presents a review of the types of organosulfur compounds found in petroleum and summarizes the scant literature on toxicity studies with condensed thiophenes. Reports on the biodegradation of benzothiophene, alkylbenzothiophenes, DBT, alkylDBTs, and naphthothiophenes are reviewed with a focus on the identification of metabolites detected in laboratory cultures. In addition, recent reports on quantitative studies with DBT and naphtho[2,1-b]thiophene indicate the existence of polar sulfur-containing metabolites that have escaped detection and identification.

Biodegradation, Environmental↗