Biomedical subjects

Steven D Siciliano

Publications and source records attributed to Steven D Siciliano.

At least 19 recordsLinked to original sources

PubMed2006

Fertilization stimulates anaerobic fuel degradation of antarctic soils by denitrifying microorganisms.

Human activities in the Antarctic have resulted in hydrocarbon contamination of these fragile polar soils. Bioremediation is one of the options for remediation of these sites. However, little is known about anaerobic hydrocarbon degradation in polar soils and the influence of bioremediation practices on these processes. Using a field trial at Old Casey Station, Antarctica, we assessed the influence of fertilization on the anaerobic degradation of a 20-year old fuel spill. Fertilization increased hydrocarbon degradation in both anaerobic and aerobic soils when compared to controls, but was of most benefit for anaerobic soils where evaporation was negligible. This increased biodegradation in the anaerobic soils corresponded with a shift in the denitrifier community composition and an increased abundance of denitrifiers and benzoyl-CoA reductase. A microcosm study using toluene and hexadecane confirmed the degradative capacity within these soils under anaerobic conditions. It was observed that fertilized anaerobic soil degraded more of this hydrocarbon spike when incubated anaerobically than when incubated aerobically. We conclude that denitrifiers are actively involved in hydrocarbon degradation in Antarctic soils and that fertilization is an effective means of stimulating their activity. Further, when communities stimulated to degrade hydrocarbons under anaerobic conditions are exposed to oxygen, hydrocarbon degradation is suppressed. The commonly accepted belief that remediation of polar soils requires aeration needs to be reevaluated in light of this new data.

Accidents, Occupational↗

PubMed2006

Identification of human fecal pollution sources in a coastal area: a case study at Oostende (Belgium).

From April to June 2001, a monitoring study at Oostende (Belgium) was conducted to obtain an insight into fecal pollution impairing water quality at this coastal area. Eight sampling sites were selected based on the historically low water quality at these sites compared to the remainder of the area. Indicator organisms such as fecal coliforms, Escherichia coli and fecal streptococci were monitored by plating. A real-time PCR assay for quantification of the human-specific HF183 Bacteroides 16S rRNA genetic marker was used to detect human fecal pollution at the sampling sites. Human fecal pollution was detected at all sampling sites. However, the frequency of detection ranged from 30-100% and the amount of human-specific Bacteroides markers recorded varied between the sampling sites. Concentrations of 10(7) human-specific Bacteroides markers per 1 to levels below the detection limit of the real-time PCR assay were recorded. Our results indicate that human fecal pollution is a re-occurring problem in certain areas. Of all the environmental parameters monitored during the study, only rainfall was strongly related to the detection of the indicator organisms and the human-specific Bacteroides marker.

Bacteria↗

PubMed2005

Abiotic production of methylmercury by solar radiation.

Methylmercury [MeHg(I) in the aerobic surface water of lakes is thought to be rapidly degraded, but contrary to expectations, we show that MeHg(I) concentrations often increase during sunlight hours or remain relatively constant. We hypothesized that there were water column processes that generated MeHg(I) and that these processes were linked to dissolved organic matter (DOM) and solar radiation. A 2-day diurnal pattern of MeHg(I) in surface water with corresponding bottled controls was assessed for two contrasting lakes in Kejimikujik, Nova Scotia, Canada. Following this study, a tangential ultrafiltrator was used to size-fractionate and generate a concentration gradient of DOM from four different lakes located near Lac Berthelot, Quebec, Canada. The watersheds of two of these lakes were not substantially logged whereas the other two had been extensively logged. Different size fractions of DOM as well as different concentrations of DOM were exposed to sunlight for varying periods of time. We observed that, in Keiimikujik, the concentration of MeHg(I) in surface waters peaked in the early afternoon. Furthermore, this also occurred in bottled water for one of the lakes, Puzzle, eliminating the possibility that in-lake mixing played a role in this pattern. The formation of MeHg(I) was found to be dependent on the size fraction and amount of DOM present in the water. Specifically, DOM less than 5 kDa or between 30 and 300 kDa generated MeHg(I) when exposed to sunlight, but larger fractions did not. Furthermore, although data are limited, we found that water from lakes with logged watersheds generated MeHg(I) when exposed to sunlight, whereas water from lakes with low levels of logging in the undisturbed watersheds did not. Our results demonstrate that MeHg(I) can be formed in freshwaters of certain lakes in response to solar radiation. This photoproduction of MeHg(I) is dependent on DOM concentrations and type, with the importance of water chemistry not yet clear. The significance of this process to freshwater lakes and the mechanism responsible for MeHg(I) photoproduction is still unclear, but a correction in the conventional wisdom that MeHg(I) is rapidly photodegraded is timely.

Animals↗

PubMed2005

Detection and quantification of the human-specific HF183 Bacteroides 16S rRNA genetic marker with real-time PCR for assessment of human faecal pollution in freshwater.

The human-specific HF183 Bacteriodes 16S rRNA genetic marker can be used to detect human faecal pollution in water environments. However, there is currently no method to quantify the prevalence of this marker in environmental samples. We developed a real-time polymerase chain reaction (PCR) assay using SYBR Green I detection to quantify this marker in faecal and environmental samples. To decrease the amplicon length to a suitable size for real-time PCR detection, a new reverse primer was designed and validated on human and animal faecal samples. The use of the newly developed reverse primer in combination with the human-specific HF183 primer did not decrease the specificity of the real-time PCR assay but a melting curve analysis must always be included. This new assay was more sensitive than conventional PCR and highly reproducible with a coefficient of variation of less than 1% within an assay and 3% between assays. As the Bacteroides species that carries this human-specific marker has never been isolated, a bacteria real-time assay was used to determine the detection efficiency. The estimated detection efficiency in freshwater ranged from 78% to 91% of the true value with an average detection efficiency of 83+/-4% of the true value. Using a simple filtration method, the limit of quantification was 4.7+/-0.3x10(5) human-specific Bacteroides markers per litre of freshwater. The aerobic incubation of the human-specific Bacteroides marker in freshwater for up to 24 days at 4 and 12 degrees C, and up to 8 days at 28 degrees C, indicated that the marker persisted up to the end of the incubation period for all incubation temperatures.

Bacteroides↗

PubMed2004

Liquid chromatography-mass spectrometry analysis of hydroxylated polycyclic aromatic hydrocarbons, formed in a simulator of the human gastrointestinal tract.

Described is a liquid chromatography-mass spectrometry (LC-MS) procedure for the determination of hydroxylated biotransformation products of polycyclic aromatic hydrocarbons (PAH) in the human gastrointestinal tract. The formation of hydroxylated PAHs was monitored upon incubation of PAHs with colon microbiota from the Simulator of the Human Intestinal Microbial Ecosystem (SHIME). The analytical method consisted of a biomass removal step followed by a solid phase extraction (SPE) step using C18 packed columns to remove non-digested food compounds and microbial metabolites that interfere with the detection of the target compounds. For quantification, 9-hydroxyphenanthrene (13)C(6)was used as the internal standard. The detection limits of the hydroxylated PAHs were generally in the range 0.36-14.09 microg x l(-1), based on a signal/noise ratio of 3:1. The recovery of hydroxylated PAHs in intestinal suspension was variable ranging from 45 to 107%, with relative standard deviation (R.S.D.) between 5 and 17%. The analytical procedure was used to show the microbial production of 1-hydroxypyrene and 7-hydroxybenzo(a)pyrene, metabolites that may give colon incubated PAHs bioactive properties.

Calibration↗

PubMed2004

Snowmelt sources of methylmercury to high arctic ecosystems.

Mercury in humans and other top predators living in the Arctic is present at elevated levels. Since only methylmercury (MeHg) bioaccumulates in food chains, sources of MeHg need to be identified. Recently, wetlands in the High Arctic were found to produce MeHg, and this was confirmed in laboratory soil incubations. In the present study both wetlands and snowmelt water were evaluated as sources of MeHg to Arctic ecosystems in Nunavut. Three substudies took place on Cornwallis Island, and one took place on Ellesmere Island. First, the effect of wetland presence in lake watersheds was evaluated by comparing four lakes with wetlands present to four lakes without wetlands present. Next, two individual wetlands were spatially and temporally investigated. Finally, three basin tributaries were evaluated for snowmelt MeHg sources. Catchments on Cornwallis Island with wetlands did not have an observable effect on MeHg levels in downstream lake water, but the wetland on Ellesmere Island contributed significant MeHg. In contrast, calculated yields of MeHg in tributaries draining snowmelt on Cornwallis Island were higher (ca. 1.5 mg km(-2) day(-1)) than those measured in temperate catchments characterized by wetlands. Methylmercury and total Hg concentrations in lakes, wetlands, and basin tributaries showed a strong temporal trend that corresponded to inputs from snowmelt water in late spring. This study revealed that wetland export of MeHg to downstream Arctic lakes is site dependent, and snowmelt water was the most significant source of MeHg to Arctic ecosystems located on Cornwallis Island.

Animals↗

PubMed2004

Impact of agricultural practices on the Zea mays L. endophytic community.

Agricultural practices are known to alter bulk soil microbial communities, but little is known about the effect of such practices on the plant endophytic community. We assessed the influence of long-term applications (20 years) of herbicides and different fertilizer types on the endophytic community of maize plants grown in different field experiments. Nested PCR-denaturing gradient gel electrophoresis (DGGE) analyses targeting general bacteria, type I or II methanotrophs, actinomycetes, and general fungi were used to fingerprint the endophytic community in the roots of Zea mays L. Low intraplant variability (reproducible DGGE patterns) was observed for the bacterial, type I methanotroph, and fungal communities, whereas the patterns for endophytic actinomycetes exhibited high intraplant variability. No endophytic amplification product was obtained for type II methanotrophs. Cluster and stability analysis of the endophytic type I methanotroph patterns differentiated maize plants cultivated by using mineral fertilizer from plants cultivated by using organic fertilizer with a 100% success rate. In addition, lower methanotroph richness was observed for mineral-fertilized plants than for organically fertilized plants. The use of herbicides could not be traced by fingerprinting the endophytic type I methanotrophs or by evaluating any other endophytic microbial group. Our results indicate that the effect of agrochemicals is not limited to the bulk microbial community but also includes the root endophytic community. It is not clear if this effect is due to a direct effect on the root endophytic community or is due to changes in the bulk community, which are then reflected in the root endophytic community.

Agriculture↗

PubMed2004

Biofuel cells select for microbial consortia that self-mediate electron transfer.

Microbial fuel cells hold great promise as a sustainable biotechnological solution to future energy needs. Current efforts to improve the efficiency of such fuel cells are limited by the lack of knowledge about the microbial ecology of these systems. The purposes of this study were (i) to elucidate whether a bacterial community, either suspended or attached to an electrode, can evolve in a microbial fuel cell to bring about higher power output, and (ii) to identify species responsible for the electricity generation. Enrichment by repeated transfer of a bacterial consortium harvested from the anode compartment of a biofuel cell in which glucose was used increased the output from an initial level of 0.6 W m(-2) of electrode surface to a maximal level of 4.31 W m(-2) (664 mV, 30.9 mA) when plain graphite electrodes were used. This result was obtained with an average loading rate of 1 g of glucose liter(-1) day(-1) and corresponded to 81% efficiency for electron transfer from glucose to electricity. Cyclic voltammetry indicated that the enhanced microbial consortium had either membrane-bound or excreted redox components that were not initially detected in the community. Dominant species of the enhanced culture were identified by denaturing gradient gel electrophoresis and culturing. The community consisted mainly of facultative anaerobic bacteria, such as Alcaligenes faecalis and Enterococcus gallinarum, which are capable of hydrogen production. Pseudomonas aeruginosa and other Pseudomonas species were also isolated. For several isolates, electrochemical activity was mainly due to excreted redox mediators, and one of these mediators, pyocyanin produced by P. aeruginosa, could be characterized. Overall, the enrichment procedure, irrespective of whether only attached or suspended bacteria were examined, selected for organisms capable of mediating the electron transfer either by direct bacterial transfer or by excretion of redox components.

Animals↗

PubMed2004

Methylmercury production in High Arctic wetlands.

Mercury is present at elevated levels in the top predators living in High Arctic ecosystems. Because only methylmercury (MeHg) bioaccumulates in food chains, the sources need to be identified. In temperate environments, wetlands are considered to be the principal sources of MeHg, with sulfate-reducing bacteria (SRB) thought to be responsible. The present study investigated whether High Arctic wetlands produced MeHg and whether SRB were involved in MeHg formation. Frozen soil was collected from 18 High Arctic wetlands before ground thaw, and when analyzed for MeHg, values were low, averaging 0.065 ng/g. When soils were incubated for 30 and 60 d at typical summer Arctic soil temperatures (4 degrees C and 8 degrees C), MeHg increased up to 100-fold. These laboratory observations were consistent with field measurements of wetland surface water, where MeHg concentrations increased from near detection limits (0.02 ng/L) at the inflow to an average of 1.21 ng/L at the outflow. Both laboratory and field data showed MeHg production in High Arctic wetlands. The prevalence of SRB in soil was low, however, and DNA analysis of the dissimilatory sulfate-reductase gene specific to SRB was positive at only one site. The present study showed that wetlands in the High Arctic can produce MeHg but that SRB may not the dominant mercury methylators.

Arctic Regions↗

PubMed2003

Continuous analysis of dissolved gaseous mercury (DGM) and mercury flux in two freshwater lakes in Kejimkujik Park, Nova Scotia: evaluating mercury flux models with quantitative data.

Diurnal patterns for dissolved gaseous mercury (DGM) concentration, mercury flux, several water variables (pH, oxidation reduction potential (ORP), water temperature), and meteorological variables (wind speed, air temperature, % relative humidity, solar radiation) were measured in two lakes with contrasting dissolved organic carbon (DOC) concentrations in Kejimkujik Park, Nova Scotia. A continuous analysis system made it possible to measure quick changes in DGM over time. Consistently higher DGM concentrations were found in the high DOC lake as compared to the low DOC lake. An examination of current mercury flux models using this quantitative data indicated some good correlations between the date and predicted flux (r ranging from 0.27 to 0.83) but generally poor fit (standard deviation of residuals ranging from 0.97 to 3.39). Cross-correlation analysis indicated that DGM dynamics changed in response to solar radiation with lag-times of 65 and 90 min. This relationship with solar radiation was used to develop new predictive models of DGM and mercury flux dynamics for each lake. We suggest that a generalized approach using time-shifted solar radiation date to predict DGM can be incorporated into existing mercury flux models. It is clear from the work presented that DOC and wind speed may also play important roles in DGM and mercury flux dynamics, and these roles have not been adequately accounted for in current predictive models.

Air Pollutants↗

PubMed2003

A microbial fuel cell capable of converting glucose to electricity at high rate and efficiency.

A microbial fuel cell containing a mixed bacterial culture utilizing glucose as carbon source was enriched to investigate power output in relation to glucose dosage. Electron recovery in terms of electricity up to 89% occurred for glucose feeding rates in the range 0.5-3 g l(-1) d(-1), at powers up to 3.6 W m(-2) of electrode surface, a five fold higher power output than reported thus far. This research indicates that microbial electricity generation offers perspectives for optimization.

Bacteria, Anaerobic↗

PubMed2003

Long-term effects of mineral versus organic fertilizers on activity and structure of the methanotrophic community in agricultural soils.

Agricultural practices, such as mineral nitrogen fertilization, have an impact on the soil's ability to oxidize methane, but little is known about the shifts in the methanotrophic community composition associated with these practices. Therefore, the long-term effect of both mineral (NH4NO3) and organic (manure and GFT-compost) fertilizer applications on the soil methanotrophic community activity and structure were investigated. Both high and low affinity methane oxidation rates were lower in the soil treated with mineral fertilizer compared to the other soils. An enhanced nitrate concentration was observed in the mineral fertilized soil but nitrate did not show a direct affect on the high affinity methane oxidation. In contrast, the low affinity methane oxidation was slowed down by increased nitrate concentrations, which suggests a direct effect of nitrate on low affinity methane oxidation. Denaturing gradient gel electrophoresis (DGGE) analysis of 16S rRNA gene fragments specific for methanotrophs revealed a distinct community between the mineral and organic fertilized soils as extra Type I methanotrophic bands (phylotypes) became visible in the organic fertilized soils. These phylotypes were not visible in the patterns of the added organic fertilizers suggesting an indirect effect of the organic fertilizers on the methanotrophic community. Additionally, a molecular analysis was performed after the low affinity methane oxidation test. The enhanced methane concentrations used in the test enriched certain low affinity methanotrophs in the organic fertilized soils but not in the mineral fertilized soil. Supporting the molecular and functional observations, fatty acids characteristic for methanotrophs were less abundant in the soil treated with mineral fertilizer compared to the soil treated with compost. In conclusion, the function and molecular and chemical composition of the methanotrophic community are all altered in soil fertilized with mineral fertilizer.

Alphaproteobacteria↗

PubMed2003

Cell density related H2 consumption in relation to anoxic Fe(0) corrosion and precipitation of corrosion products by Shewanella oneidensis MR-1.

In the absence of oxygen, a protective H2 film is formed around an Fe(0) surface, inhibiting the electron flow from this surface. Our study of anoxic corrosion of Fe(0) beads revealed that, in the presence of Shewanella oneidensis MR-1, H2 removal and precipitation of Fe mineral particles on the cell surface are determining processes for corrosion. These two biologically mediated processes were governed by cell density. H2 removal by Shewanella oneidensis was detected at cell concentrations of 1.0 x 10(6) live cells ml-1 and higher and H2 was electron donor for denitrification of NO3-. The removal of the protective H2 layer from Fe(0) beads by Shewanella oneidensis, resulted in an increase of Fe release out of the Fe(0) beads from 153 +/- 25 mg l(-1) to 196 +/- 7 mg l-1 after 20 h. When the cell concentration exceeded 1.0 x 10(8) live cells ml-1, precipitation of iron minerals on the cell surface was characteristic for the greatest percentage of MR-1 cells, whereas micrometre-scale iron precipitates not associated with culturable cell biomass significantly decreased in number. Addition of supernatant of a corrosion assay with high cell concentration induced metabolic activity in a corrosion assay with low cell concentration, resulting in increased H2 consumption and Fe release from Fe(0) beads. Homoserine lactone-like molecules were detected in the supernatant by a bio-assay, suggesting the involvement of a quorum-sensing regulatory mechanism.

4-Butyrolactone↗

PubMed2003

Changes in microbial community composition and function during a polyaromatic hydrocarbon phytoremediation field trial.

The purpose of this study was to investigate the mechanism by which phytoremediation systems promote hydrocarbon degradation in soil. The composition and degradation capacity of the bulk soil microbial community during the phytoremediation of soil contaminated with aged hydrocarbons was assessed. In the bulk soil, the level of catabolic genes involved in hydrocarbon degradation (ndoB, alkB, and xylE) as well as the mineralization of hexadecane and phenanthrene was higher in planted treatment cells than in treatment cells with no plants. There was no detectable shift in the 16S ribosomal DNA (rDNA) composition of the bulk soil community between treatments, but there were plant-specific and -selective effects on specific catabolic gene prevalence. Tall Fescue (Festuca arundinacea) increased the prevalence of ndoB, alkB, and xylE as well as naphthalene mineralization in rhizosphere soil compared to that in bulk soil. In contrast, Rose Clover (Trifolium hirtum) decreased catabolic gene prevalence and naphthalene mineralization in rhizosphere soil. The results demonstrated that phytoremediation systems increase the catabolic potential of rhizosphere soil by altering the functional composition of the microbial community. This change in composition was not detectable by 16S rDNA but was linked to specific functional genotypes with relevance to petroleum hydrocarbon degradation.

Bacteria↗

PubMed2003

Bioaugmentation as a tool to protect the structure and function of an activated-sludge microbial community against a 3-chloroaniline shock load.

Bioaugmentation of bioreactors focuses on the removal of xenobiotics, with little attention typically paid to the recovery of disrupted reactor functions such as ammonium-nitrogen removal. Chloroanilines are widely used in industry as a precursor to a variety of products and are occasionally released into wastewater streams. This work evaluated the effects on activated-sludge reactor functions of a 3-chloroaniline (3-CA) pulse and bioaugmentation by inoculation with the 3-CA-degrading strain Comamonas testosteroni I2 gfp. Changes in functions such as nitrification, carbon removal, and sludge compaction were studied in relation to the sludge community structure, in particular the nitrifying populations. Denaturing gradient gel electrophoresis (DGGE), real-time PCR, and fluorescent in situ hybridization (FISH) were used to characterize and enumerate the ammonia-oxidizing microbial community immediately after a 3-CA shock load. Two days after the 3-CA shock, ammonium accumulated, and the nitrification activity did not recover over a 12-day period in the nonbioaugmented reactors. In contrast, nitrification in the bioaugmented reactor started to recover on day 4. The DGGE patterns and the FISH and real-time PCR data showed that the ammonia-oxidizing microbial community of the bioaugmented reactor recovered in structure, activity, and abundance, while the number of ribosomes of the ammonia oxidizers in the nonbioaugmented reactor decreased drastically and the community composition changed and did not recover. The settleability of the activated sludge was negatively influenced by the 3-CA addition, with the sludge volume index increasing by a factor of 2.3. Two days after the 3-CA shock in the nonbioaugmented reactor, chemical oxygen demand (COD) removal efficiency decreased by 36% but recovered fully by day 4. In contrast, in the bioaugmented reactor, no decrease of the COD removal efficiency was observed. This study demonstrates that bioaugmentation of wastewater reactors to accelerate the degradation of toxic chlorinated organics such as 3-CA protected the nitrifying bacterial community, thereby allowing faster recovery from toxic shocks.

Ammonia↗

PubMed2003

Characterization of an autotrophic nitrogen-removing biofilm from a highly loaded lab-scale rotating biological contactor.

In this study, a lab-scale rotating biological contactor (RBC) treating a synthetic NH(4)(+) wastewater devoid of organic carbon and showing high N losses was examined for several important physiological and microbial characteristics. The RBC biofilm removed 89% +/- 5% of the influent N at the highest surface load of approximately 8.3 g of N m(-2) day(-1), with N(2) as the main end product. In batch tests, the RBC biomass showed good aerobic and anoxic ammonium oxidation (147.8 +/- 7.6 and 76.5 +/- 6.4 mg of NH(4)(+)-N g of volatile suspended solids [VSS](-1) day(-1), respectively) and almost no nitrite oxidation (< 1 mg of N g of VSS(-1) day(-1)). The diversity of aerobic ammonia-oxidizing bacteria (AAOB) and planctomycetes in the biofilm was characterized by cloning and sequencing of PCR-amplified partial 16S rRNA genes. Phylogenetic analysis of the clones revealed that the AAOB community was fairly homogeneous and was dominated by Nitrosomonas-like species. Close relatives of the known anaerobic ammonia-oxidizing bacterium (AnAOB) Kuenenia stuttgartiensis dominated the planctomycete community and were most probably responsible for anoxic ammonium oxidation in the RBC. Use of a less specific planctomycete primer set, not amplifying the AnAOB, showed a high diversity among other planctomycetes, with representatives of all known groups present in the biofilm. The spatial organization of the biofilm was characterized using fluorescence in situ hybridization (FISH) with confocal scanning laser microscopy (CSLM). The latter showed that AAOB occurred side by side with putative AnAOB (cells hybridizing with probe PLA46 and AMX820/KST1275) throughout the biofilm, while other planctomycetes hybridizing with probe PLA886 (not detecting the known AnAOB) were present as very conspicuous spherical structures. This study reveals that long-term operation of a lab-scale RBC on a synthetic NH(4)(+) wastewater devoid of organic carbon yields a stable biofilm in which two bacterial groups, thought to be jointly responsible for the high autotrophic N removal, occur side by side throughout the biofilm.

Anaerobiosis↗

PubMed2003

Use of 16S-23S rRNA intergenic spacer region PCR and repetitive extragenic palindromic PCR analyses of Escherichia coli isolates to identify nonpoint fecal sources.

Despite efforts to minimize fecal input into waterways, this kind of pollution continues to be a problem due to an inability to reliably identify nonpoint sources. Our objective was to find candidate source-specific Escherichia coli fingerprints as potential genotypic markers for raw sewage, horses, dogs, gulls, and cows. We evaluated 16S-23S rRNA intergenic spacer region (ISR)-PCR and repetitive extragenic palindromic (rep)-PCR analyses of E. coli isolates as tools to identify nonpoint fecal sources. The BOXA1R primer was used for rep-PCR analysis. A total of 267 E. coli isolates from different fecal sources were typed with both techniques. E. coli was found to be highly diverse. Only two candidate source-specific E. coli fingerprints, one for cow and one for raw sewage, were identified out of 87 ISR fingerprints. Similarly, there was only one candidate source-specific E. coli fingerprint for horse out of 59 BOX fingerprints. Jackknife analysis resulted in an average rate of correct classification (ARCC) of 83% for BOX-PCR analysis and 67% for ISR-PCR analysis for the five source categories of this study. When nonhuman sources were pooled so that each isolate was classified as animal or human derived (raw sewage), ARCCs of 82% for BOX-PCR analysis and 72% for ISR-PCR analysis were obtained. Critical factors affecting the utility of these methods, namely sample size and fingerprint stability, were also assessed. Chao1 estimation showed that generally 32 isolates per fecal source individual were sufficient to characterize the richness of the E. coli population of that source. The results of a fingerprint stability experiment indicated that BOX and ISR fingerprints were stable in natural waters at 4, 12, and 28 degrees C for 150 days. In conclusion, 16S-23S rRNA ISR-PCR and rep-PCR analyses of E. coli isolates have the potential to identify nonpoint fecal sources. A fairly small number of isolates was needed to find candidate source-specific E. coli fingerprints that were stable under the simulated environmental conditions.

Animals↗

PubMed2002

Bioaugmenting bioreactors for the continuous removal of 3-chloroaniline by a slow release approach.

The survival and activity of microbial degradative inoculants in bioreactors is critical to obtain successful biodegradation of non- or slowly degradable pollutants. Achieving this in industrial wastewater reactors is technically challenging. We evaluated a strategy to obtain complete and stable bioaugmentation of activated sludge, which is used to treat a 3-chloroaniline (3-CA) contaminated wastewater in a lab-scale semi-continuous activated sludge system. A 3-CA metabolizing bacterium, Comamonas testosteroni strain I2, was mixed with molten agar and encapsulated in 4 mm diameter open-ended silicone tubes of 3 cm long. The tubes containing the immobilized bacteria represented about 1% of the volume of the mixed liquor. The bioaugmentation activity of a reactor containing the immobilized cells was compared with a reactor with suspended I2gfp cells. From day 25-30 after inoculation, the reactor with only suspended cells failed to completely degrade 3-CA because of a decrease in metabolic activity. In the reactors with immobilized cells, however, 3-CA continued to be removed. A mass balance indicated that ca. 10% of the degradation activity was due to the immobilized cells. Slow release of the growing embedded cells from the agar into the activated sludge medium, resulting in a higher number of active 3-CA-degrading I2 cells, was responsible for ca. 90% of the degradation. Our results demonstrate that this simple immobilization procedure was effective to maintain a 3-CA-degrading population within the activated sludge community.

Aniline Compounds↗