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PubMed2004

Enhanced microbial degradation of cadusafos in soils from potato monoculture: demonstration and characterization.

Rapid degradation of cadusafos was evident in soils collected from previously-treated field sites from a potato monoculture area in northern Greece. The slower degradation of cadusafos observed in corresponding antibiotic-treated soils as well as in soils from an adjacent previously-untreated field demonstrated the microbial involvement in the rapid degradation of cadusafos in the soils from the previously-treated sites. Application of the non-specific antibacterial antibiotic chloramphenicol or of the Gram+ bacteria-inhibiting antibiotics penicillin + lyncomycin + vancomycin significantly inhibited the rapid biodegradation of cadusafos suggesting that soil bacteria and probably Gram+ bacteria are mainly responsible for the rapid biodegradation of cadusafos in the specific soil. Further experiments showed that the bacterial population of the cadusafos-adapted soil was also able to rapidly degrade the chemically related nematicide ethoprophos but not fenamiphos and oxamyl. This is the first report of the occurrence of enhanced biodegradation of cadusafos in potato fields. In addition, the finding of cross-enhancement between cadusafos and ethoprophos significantly reduces the number of available chemicals which could be alternated to prevent the development of enhanced biodegradation and thus intensifies the problem in potato monoculture areas like the one in northern Greece.

Analysis of Variance↗
PubMed1990

Microbial degradation of trichloroethylene in the rhizosphere: potential application to biological remediation of waste sites.

The possibility that vegetation may be used to actively promote microbial restoration of chemically contaminated soils was tested by using rhizosphere and nonvegetated soils collected from a trichloroethylene (TCE)-contaminated field site. Biomass determinations, disappearance of TCE from the headspace of spiked soil slurries, and mineralization of [14C]TCE to 14CO2 all showed that microbial activity is greater in rhizosphere soils and that TCE degradation occurs faster in the rhizosphere than in the edaphosphere. Thus, vegetation may be an important variable in the biological restoration of surface and near-surface soils.

Biodegradation, Environmental↗
PubMed2006

Microbial degradation of styrene: biochemistry, molecular genetics, and perspectives for biotechnological applications.

Large quantities of the potentially toxic compound styrene are produced and used annually by the petrochemical and polymer-processing industries. It is as a direct consequence of this that significant volumes of styrene are released into the environment in both the liquid and the gaseous forms. Styrene and its metabolites are known to have serious negative effects on human health and therefore, strategies to prevent its release, remove it from the environment, and understand its route of degradation were the subject of much research. There are a large number of microbial genera capable of metabolizing styrene as a sole source of carbon and energy and therefore, the possibility of applying these organisms to bioremediation strategies was extensively investigated. From the multitude of biodegradation studies, the application of styrene-degrading organisms or single enzymes for the synthesis of value-added products such as epoxides has emerged.

Bacteria↗
PubMed1995

Novel 26-oxygenated products in microbial degradation of ergosterol.

In order to investigate the effect of the different stereochemistry of C-24 on the microbial C-26 oxidation of sterol side-chain the genetically modified Mycobacterium sp. BCS 396 strain was used to transform erogsterol. Ergosterol was converted to 3-oxo-4,22-ergostadien-26-oic acid methyl ester, 3-oxo-1,4,22-ergostatrien-26-oic acid methyl ester, and 3-oxo-1,4,22-ergostatrien-26-oic acid, the structures of which have been determined by IR, 1H NMR, 13C NMR, and mass spectroscopy. The X-ray structure of 3-oxo-4,22-ergostadien-26-oic acid methyl ester revealed that oxidation at C-26 of the ergostane side-chain generates a chiral center with S-configuration at C-25 as a result of chiral induction of the C-24 center.

Ergosterol↗
PubMed2004

[Microbial degradation of Abamectin in soil].

Incubation test on the degradation dynamics of Abamectin in soil showed that the half-life of its non-biodegradation plus microbial biodegradation, non-biodegradation, and microbial biodegradation was 34.8, 277.3 and 49.9 d, respectively, and its degradation in soil was mostly by microbes. A dominant bacterium which could effectively degrade Abamectin was isolated from test soil, and identified as Stenotrophomonas maltrophilia by 16S rDNA. The crude enzyme extracted from the dominant bacteria had a Michaelis-Menten's constant 6.78 nmol x ml(-1) and a maximum rate 81.5 nmol x min(-1) x mg(-1).

Biodegradation, Environmental↗
PubMed2006

Microbial degradation of penoxsulam in flooded rice field soils.

The degradation of penoxsulam [2-(2,2-difluoroethoxy)-N-5,8-dimethoxy[1,2,4]triazolo[1,5-C]pyrimidin-2-yl-6-(trifluoromethyl)benzene-sulfonamide] was studied in flasks simulating flooded rice field conditions using four representative rice field soils from the Sacramento Valley. Degradation half-lives (t(1/2) values) ranged between 2 and 13 days. Increased degradation rates were observed in flask systems with steeper redox gradients between the flooded soil layer and the overlaying water. Two transient metabolites were identified that were temporarily formed in amounts exceeding 5% of the total initial mass of penoxsulam. The results of high-performance liquid chromatography/(14)C radiodetection studies indicate that the degradation of the triazolopyrimidine system and its substituents is the main pathway of microbial transformation processes. Microbial activity, as measured by dehydrogenase activity, was not affected by penoxsulam concentrations corresponding to the proposed maximum annual use rate of 40 g active ingredient/ha.

Bacteria↗
PubMedDate not supplied

Aerobic and anaerobic microbial degradation of poly-beta-hydroxybutyrate produced by Azotobacter chroococcum.

Food industry wastewater served as a carbon source for the synthesis of poly-beta-hydroxybutyrate (PHB) by Azotobacter chroococcum. The content of polymer in bacterial cells grown on the raw materials reached 75%. PHB films were degraded under aerobic, microaerobic, and anaerobic conditions in the presence and absence of nitrate by microbial populations of soil, sludges from anaerobic and nitrifying/denitrifying reactors, and sediment from a sludge deposit site. Changes in molecular mass, crystallinity, and mechanical properties of PHB were studied. Anaerobic degradation was accompanied by acetate formation, which was the main intermediate utilized by denitrifying bacteria or methanogenic archaea. On a decrease in temperature from 20 to 5 degrees C in the presence of nitrate, the rate of PHB degradation was 7.3 times lower. Under anaerobic conditions and in the absence of nitrate, no PHB degradation was observed, even at 11 degrees C. The enrichment cultures of denitrifying bacteria obtained from soil and anaerobic sludge degraded PHB films for a short time (3-7 d). The dominant species in the enrichment culture from soil were Pseudomonas fluorescens and Pseudomonas stutzeri. The rate of PHB degradation by the enrichment cultures depended on the polymer molecular weight, which reduced with time during biodegradation.

Aerobiosis↗
PubMed1994

[Microbial degradation of xenobiotics in the environment].

Biodegradation of naturally occurring organic compounds follows their synthesis. In contrast, man-made compounds, also known as xenobiotics, are often refractory to degradation. The main reason is that they cannot be recognized by naturally present organisms and therefore do not enter common metabolic pathways. The physical and chemical characteristics of the compounds, as well as environmental factors, may influence their biodegradability. Some compounds may be transformed only in the presence of another compound which appears as a carbon and energy source. Very often compounds are degraded sequentially through the activity of a series of different organisms. The main degraders in nature are microorganisms, mostly bacteria and some fungi. These organisms, due to their rapid rates of multiplication and great metabolic potential, are able to adapt to new substrates. Selection of degradative potent microorganisms and their successive adaptation to a naturally persistent compound might be a powerful means for environmental detoxification. Although numerous laboratory experiments have given positive results, very few are applicable on a large scale. It is necessary to select microorganisms or microbial communities capable of controlled degradation of persistent organic chemicals without their transformation to other, more hazardous compounds. Better understanding of metabolic pathways for the biodegradation of specific organic compounds as well as more thorough knowledge of degrading microorganisms will make purposeful application of biodegradation possible.

Bacteria↗
PubMed1995

Microbial degradation and humification of the lawn care pesticide 2,4-dichlorophenoxyacetic acid during the composting of yard trimmings.

The fate of the widely used lawn care herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) during the composting of yard trimmings consisting of primarily leaves and grass is an important unexplored question. In this study, we determined the extent of 2,4-D mineralization, incorporation into humic matter, volatilization, and sorption during the composting of yard trimmings. Yard trimmings (2:1 [wt/wt] leaves-grass) were amended with 14C-ring-labeled 2,4-D (17 mg/kg of dry weight) and composted in a temperature-controlled laboratory scale compost system. During composting, thermophilic microbes were numerically dominant, reaching a maximum of 2 x 10(11)/g. At the end of composting, 46% of the organic matter (OM) present in the yard trimmings was lost and the compost was stable, with an oxygen uptake rate of 0.09 mg of O2 per g of OM per h, and was well humified (humification index, 0.39). Mineralization of the OM temporally paralleled mineralization of 2,4-D. In the final compost, 47% of the added 2,4-D carbon was mineralized, about 23% was complexed with high-molecular-weight humic acids, and about 20% was not extractable (humin fraction). Less than 1% of the added 14C was present in water expressed from the finished compost, suggesting a low potential for leaching of 2,4-D. Very little volatilization of 2,4-D occurred during composting. It is of interest that our results indicate active mineralization of 2,4-D at composting temperatures of 60 degrees C because microbial 2,4-D degradation at thermophilic temperatures has not been previously documented.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2002

Parallel characterization of anaerobic toluene- and ethylbenzene-degrading microbial consortia by PCR-denaturing gradient gel electrophoresis, RNA-DNA membrane hybridization, and DNA microarray technology.

A mesophilic toluene-degrading consortium (TDC) and an ethylbenzene-degrading consortium (EDC) were established under sulfate-reducing conditions. These consortia were first characterized by denaturing gradient gel electrophoresis (DGGE) fingerprinting of PCR-amplified 16S rRNA gene fragments, followed by sequencing. The sequences of the major bands (T-1 and E-2) belonging to TDC and EDC, respectively, were affiliated with the family Desulfobacteriaceae. Another major band from EDC (E-1) was related to an uncultured non-sulfate-reducing soil bacterium. Oligonucleotide probes specific for the 16S rRNAs of target organisms corresponding to T-1, E-1, and E-2 were designed, and hybridization conditions were optimized for two analytical formats, membrane and DNA microarray hybridization. Both formats were used to characterize the TDC and EDC, and the results of both were consistent with DGGE analysis. In order to assess the utility of the microarray format for analysis of environmental samples, oil-contaminated sediments from the coast of Kuwait were analyzed. The DNA microarray successfully detected bacterial nucleic acids from these samples, but probes targeting specific groups of sulfate-reducing bacteria did not give positive signals. The results of this study demonstrate the limitations and the potential utility of DNA microarrays for microbial community analysis.

Bacteria↗
PubMed1965

Microbial Degradation of the Sulfonate of Dodecyl Benzene Sulfonate.

It has been observed that the sulfonate portion of alkyl benzene sulfonate (ABS) will undergo microbial attack in certain pure and mixed cultures if an energy source, such as glucose, is available. The evidence for this is provided by the stoichiometric relationship between the reduction of ABS concentration and the appearance of inorganic sulfur compounds.

Journal Article↗
PubMed1999

Functional and Structural Responses of a Degradative Microbial Community to Substrates with Varying Degrees of Complexity in Chemical Structure.

Abstract The objective of the present study was to determine whether cultivation of a degradative community on substrates with varying degrees of chlorination and complexity in chemical structure, as well as cultivation in batch and flow cell culture, would alter the community's functional capability. The community was isolated from oil-contaminated soil and maintained in the laboratory on 2,4,6-trichlorobenzoic acid for 5 months before its ability to grow on 15 different chemicals as sole carbon source was evaluated in batch and flow cell systems. While the community could grow and develop biofilms in flow cells on all the substrates, only 11 of the 15 substrates could support growth in batch culture. Although biofilm development was less extensive on chemicals such as pentachlorophenol (2.09% average area covered by biofilm; average biofilm depth = 3 µm) than on 2,4,6-trichlorobenzoic acid (50.84% area covered; biofilm depth = 6.4 µm), no correlation was observed between the degree of chlorination, or number of rings, and the number of planktonic cells or biofilm biomass. In contrast, physicochemical characteristics such as the octanol/water partition coefficient had a significant effect on the development of biofilm biomass. In the case of planktonic communities, the degree of chlorination and ring number also had no effect on the BIOLOG carbon utilization profiles of the resulting communities. Although the sessile communities generally clustered separately from their planktonic counterparts, principal component analysis of carbon utilization profiles of the sessile communities showed different grouping between growth on chlorinated and nonchlorinated substrates. Analysis of the degradative community maintained on 2,4,6-trichlorobenzoic acid over an extended period further showed that adaptation to a new chemical environment is a rather slow process, since the substrate utilization profiles did not stabilize even after 12 months. These results demonstrate the flexibility in metabolic ability and community structure found in microbial communities.http://link.springer-ny.com/link/service/journals/00248/bibs/38n3p215.html</hea

Journal Article↗
PubMed1984

Aerobic microbial degradation of glucoisosaccharinic Acid.

alpha-Glucoisosaccharinic acid (GISA), a major by-product of kraft paper manufacture, was synthesized from lactose and used as the carbon source for microbial media. Ten strains of aerobic bacteria capable of growth on GISA were isolated from kraft pulp mill environments. The highest growth yields were obtained with Ancylobacter spp. at pH 7.2 to 9.5. GISA was completely degraded by cultures of an Ancylobacter isolate. Ancylobacter cell suspensions consumed oxygen and produced carbon dioxide in response to GISA addition. A total of 22 laboratory strains of bacteria were tested, and none was capable of growth on GISA. GISA-degrading isolates were not found in forest soils.

Journal Article↗
PubMed1996

Measurement of hydrocarbon-degrading microbial populations by a 96-well plate most-probable-number procedure.

A 96-well microtiter plate most-probable-number (MPN) procedure was developed to enumerate hydrocarbon-degrading microorganisms. The performance of this method, which uses number 2 fuel oil (F2) as the selective growth substrate and reduction of iodonitrotetrazolium violet (INT) to detect positive wells, was evaluated by comparison with an established 24-well microtiter plate MPN procedure (the Sheen Screen), which uses weathered North Slope crude oil as the selective substrate and detects positive wells by emulsification or dispersion of the oil. Both procedures gave similar estimates of the hydrocarbon-degrader population densities in several oil-degrading enrichment cultures and sand samples from a variety of coastal sites. Although several oils were effective substrates for the 96-well procedure, the combination of F2 with INT was best, because the color change associated with INT reduction was more easily detected in the small wells than was disruption of the crude oil slick. The method's accuracy was evaluated by comparing hydrocarbon-degrader MPNs with heterotrophic plate counts for several pure and mixed cultures. For some organisms, it seems likely that a single cell cannot initiate sufficient growth to produce a positive result. Thus, this and other hydrocarbon-degrader MPN procedures might underestimate the hydrocarbon-degrading population, even for culturable organisms.

Bacteria↗
PubMed2003

Characterization of hydrocarbon-degrading microbial populations in contaminated and pristine Alpine soils.

Biodegradation of petroleum hydrocarbons in cold environments, including Alpine soils, is a result of indigenous cold-adapted microorganisms able to degrade these contaminants. In the present study, the prevalence of seven genotypes involved in the degradation of n-alkanes (Pseudomonas putida GPo1 alkB; Acinetobacter spp. alkM; Rhodococcus spp. alkB1, and Rhodococcus spp. alkB2), aromatic hydrocarbons (P. putida xylE), and polycyclic aromatic hydrocarbons (P. putida ndoB and Mycobacterium sp. strain PYR-1 nidA) was determined in 12 oil-contaminated (428 to 30,644 mg of total petroleum hydrocarbons [TPH]/kg of soil) and 8 pristine Alpine soils from Tyrol (Austria) by PCR hybridization analyses of total soil community DNA, using oligonucleotide primers and DNA probes specific for each genotype. The soils investigated were also analyzed for various physical, chemical, and microbiological parameters, and statistical correlations between all parameters were determined. Genotypes containing genes from gram-negative bacteria (P. putida alkB, xylE, and ndoB and Acinetobacter alkM) were detected to a significantly higher percentage in the contaminated (50 to 75%) than in the pristine (0 to 12.5%) soils, indicating that these organisms had been enriched in soils following contamination. There was a highly significant positive correlation (P < 0.001) between the level of contamination and the number of genotypes containing genes from P. putida and Acinetobacter sp. but no significant correlation between the TPH content and the number of genotypes containing genes from gram-positive bacteria (Rhodococcus alkB1 and alkB2 and Mycobacterium nidA). These genotypes were detected at a high frequency in both contaminated (41.7 to 75%) and pristine (37.5 to 50%) soils, indicating that they are already present in substantial numbers before a contamination event. No correlation was found between the prevalence of hydrocarbon-degradative genotypes and biological activities (respiration, fluorescein diacetate hydrolysis, lipase activity) or numbers of culturable hydrocarbon-degrading soil microorganisms; there also was no correlation between the numbers of hydrocarbon degraders and the contamination level. The measured biological activities showed significant positive correlation with each other, with the organic matter content, and partially with the TPH content and a significant negative correlation with the soil dry-mass content (P < 0.05 to 0.001).

Altitude↗
PubMed1989

Sequential photochemical and microbial degradation of organic molecules bound to humic Acid.

We studied the effects of photochemical processes on the mineralization by soil microorganisms of [2-C]glycine bound to soil humic acid. Microbial mineralization of these complexes in the dark increased inversely with the molecular weight of the complex molecules. Sunlight irradiation of glycine-humic acid complexes resulted in loss of absorbance in the UV range and an increase in the amount of C-labeled low-molecular-weight photoproducts and the rate and extent of mineralization. More than half of the radioactivity in the low-molecular-weight photoproducts appears to be associated with carboxylic acids. Microbial mineralization of the organic carbon increased with solar flux and was proportional to the loss of A(330). Mineralization was proportional to the percentage of the original complex that was converted to low-molecular-weight photoproducts. Only light at wavelengths below 380 nm had an effect on the molecular weight distribution of the products formed from the glycine-humic acid complexes and on the subsequent microbial mineralization. Our results indicate that photochemical processes generate low-molecular-weight, readily biodegradable molecules from high-molecular-weight complexes of glycine with humic acid.

Journal Article↗
PubMed2006

Using real-time PCR to assess changes in the hydrocarbon-degrading microbial community in Antarctic soil during bioremediation.

A real-time polymerase chain reaction (PCR) method to quantify the proportion of microorganisms containing alkane monooxygenase was developed and used to follow changes in the microbial community in hydrocarbon-contaminated Antarctic soil during a bioremediation field trial. Assays for the alkB and rpoB genes were validated and found to be both sensitive and reproducible (less than 2% intrarun variation and 25-38% interrun variation). Results from the real-time PCR analysis were compared to analysis of the microbial population by a culture-based technique [most probable number (MPN) counts]. Both types of analysis indicated that fertilizer addition to hydrocarbon-contaminated soil stimulated the indigenous bacterial population within 1 year. The proportion of alkB containing microorganisms was positively correlated to the concentration of n-alkanes in the soil. After the concentration of n-alkanes in the soil decreased, the proportion of alkane-degrading microorganisms decreased, but the proportion of total hydrocarbon-degrading microorganisms increased, indicating another shift in the microbial community structure and ongoing biodegradation.

Antarctic Regions↗