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Dirk Springael

Publications and source records attributed to Dirk Springael.

At least 19 recordsLinked to original sources
PubMed2007

Overview of on-farm bioremediation systems to reduce the occurrence of point source contamination.

Contamination of ground and surface water puts pressure on the use of pesticides. Pesticide contamination of water can often be linked to point sources rather than to diffuse sources. Examples of such point sources are areas on farms where pesticides are handled and filled into sprayers, and where sprayers are cleaned. To reduce contamination from these point sources, different kinds of bioremediation system are being researched in various member states of the EU. Bioremediation is the use of living organisms, primarily microorganisms, to degrade the environmental contaminants into less toxic forms. The systems available for biocleaning of pesticides vary according to their shape and design. Up till now, three systems have been extensively described and reported: the biobed, the Phytobac and the biofilter. Most of these constructions are excavations or different sizes of container filled with biological material. Typical overall clean-up efficiency exceeds 95%, realising even more than 99% in many cases. This paper provides an overview of the state of the art of these bioremediation systems and discusses their construction, efficiency and drawbacks.

Agriculture↗
PubMed2006

Comparison of mineralization of solid-sorbed phenanthrene by polycyclic aromatic hydrocarbon (PAH)-degrading Mycobacterium spp. and Sphingomonas spp.

The mineralization of 14C-phenanthrene, sorbed to porous synthetic amberlite sorbents, i.e., IRC50, XAD7-HP, and XAD2, by three phenanthrene-degrading Mycobacterium soil isolates, i.e., strains VM552, VM531, and VM451 and three phenanthrene-degrading Sphingomonas soil isolates, i.e., strains LH162, EPA505 and LH227, was compared. In P-buffer and in the presence of IRC50, for all strains the maximum rate of mineralization of 14C-phenanthrene was significantly higher (1.1-1.9 ng ml(-1) h(-1)) than the initial abiotic desorption rate (0.2 ng ml(-1) h(-1)), indicating that both Mycobacterium and Sphingomonas utilize sorbed phenanthrene with a higher rate than can be explained by abiotic desorption. Because all Mycobacterium and Sphingomonas strains belonged to different species, it can be suggested that this feature is intrinsic to those genera rather than a specific feature of a particular strain. The final mineralization extent in P-buffer in the presence of IRC50 was about a factor of two higher for the Mycobacterium strains compared to the Sphingomonas strains. Moreover, a significantly higher normalized phenanthrene mineralization ratio in the presence of IRC50 to the control (without IRC50) was found for the Mycobacterium strains compared to the normalized ratio found for the Sphingomonas strains. Addition of minimal nutrients had a more beneficial effect on phenanthrene mineralization by Sphingomonas compared to Mycobacterium, resulting into similar mineralization extents and rates for both types of strains in the presence of IRC50. Our results show that Mycobacterium is better adapted to utilization of sorbed phenanthrene compared to Sphingomonas, especially in nutrient-poor conditions.

Biodegradation, Environmental↗
PubMed2006

Distribution of the Mycobacterium community and polycyclic aromatic hydrocarbons (PAHs) among different size fractions of a long-term PAH-contaminated soil.

Summary Mycobacterium is often isolated from polycyclic aromatic hydrocarbon (PAH)-contaminated soil as degraders of PAHs. In model systems, Mycobacterium shows attachment to the PAH substrate source, which is considered to be a particular adaptation to low bioavailability as it results into increased substrate flux to the degraders. To examine whether PAH-degrading Mycobacterium in real PAH-contaminated soils, in analogy with model systems, are preferentially associated with PAH-enriched soil particles, the distribution of PAHs, of the PAH-mineralizing capacity and of Mycobacterium over different fractions of a soil with an aged PAH contamination was investigated. The clay fraction contained the majority of the PAHs and showed immediate pyrene- and phenanthrene-mineralizing activity upon addition of (14)C-labelled pyrene or phenanthrene. In contrast, the sand and silt fractions showed a lag time of 15-26 h for phenanthrene and 3-6 days for pyrene mineralization. The maximum pyrene and phenanthrene mineralization rates of the clay fraction expressed per gram fraction were three to six times higher than those of the sand and silt fractions. Most-probable-number (MPN)-polymerase chain reaction demonstrated that Mycobacterium represented about 10% of the eubacteria in the clay fraction, while this was only about 0.1% in the sand and silt fractions, indicating accumulation of Mycobacterium in the PAH-enriched clay fraction. The Mycobacterium community composition in the clay fraction represented all dominant Mycobacterium populations of the bulk soil and included especially species related to Mycobacterium pyrenivorans, which was also recovered as one of the dominant species in the eubacterial communities of the bulk soil and the clay fraction. Moreover, Mycobacterium could be identified among the major culturable PAH-degrading populations in both the bulk soil and the clay fraction. The results demonstrate that PAH-degrading mycobacteria are mainly associated with the PAH-enriched clay fraction of the examined PAH-contaminated soil and hence, that also in the environmental setting of a PAH-contaminated soil, Mycobacterium might experience advantages connected to substrate source attachment.

Genes, Bacterial↗
PubMed2006

Long-term exposure to elevated zinc concentrations induced structural changes and zinc tolerance of the nitrifying community in soil.

A series of long-term Zn-contaminated soils was sampled around a galvanized pylon. The potential nitrification rate (PNR) was unaffected by the soil total Zn concentrations up to 25 mmol Zn kg(-1) whereas spiking the uncontaminated control soil with ZnCl(2) to identical total concentrations completely eliminated nitrification. The larger sensitivity of the PNR to spiked ZnCl(2) than to the Zn added in the field was equally found when relating the PNR to the Zn concentrations in the pore water of these soils, suggesting differences in Zn tolerance of the nitrifying communities. Zinc tolerance in the long-term Zn-contaminated soil was demonstrated by showing that (i) the nitrifying community of long-term Zn-contaminated soil samples was less sensitive to Zn than that of the uncontaminated control soil when both communities were inoculated in sterile ZnCl(2)-contaminated soil samples, and, that (ii) addition of ZnCl(2) to the long-term Zn-contaminated soil samples affected nitrification less than equal additions of ZnCl(2) to uncontaminated control samples. Denaturing gradient gel electrophoresis fingerprinting of polymerase chain reaction amplified 16SrRNA gene fragments of ammonia-oxidizing bacteria showed that the community structure in uncontaminated and long-term contaminated soil samples was different and could be related to soil Zn concentrations.

Adaptation, Physiological↗
PubMed2006

Effect of bioaugmentation and supplementary carbon sources on degradation of polycyclic aromatic hydrocarbons by a soil-derived culture.

The degradation of polycyclic aromatic hydrocarbons (PAHs) by an undefined culture obtained from a PAH-polluted soil and the same culture bioaugmented with three PAH-degrading strains was studied in carbon-limited chemostat cultures. The PAHs were degraded efficiently by the soil culture and bioaugmentation did not significantly improve the PAH degrading performance. The presence of PAHs did, however, influence the bacterial composition of the bioaugmented and non-bioaugmented soil cultures, resulting in the increase in cell concentration of sphingomonad strains. the initial enhancement of the degradation of the PAHs by biostimulation gradually disappeared and only the presence of salicylate in the additional carbon sources had a lasting slightly stimulating effect on the degradation of phenanthrene. The results suggest that bioaugmentation and biostimulation have limited potential to enhance PAH bioremediation by culture already proficient in the degradation of such contaminants.

Bacteria↗
PubMed2006

PCR-DGGE method to assess the diversity of BTEX mono-oxygenase genes at contaminated sites.

tmoA and related genes encode the alpha-subunit of the hydroxylase component of the major group (subgroup 1 of subfamily 2) of bacterial multicomponent mono-oxygenase enzyme complexes involved in aerobic benzene, toluene, ethylbenzene and xylene (BTEX) degradation. A PCR-denaturing gradient gel electrophoresis (DGGE) method was developed to assess the diversity of tmoA-like gene sequences in environmental samples using a newly designed moderately degenerate primer set suitable for that purpose. In 35 BTEX-degrading bacterial strains isolated from a hydrocarbon polluted aquifer, tmoA-like genes were only detected in two o-xylene degraders and were identical to the touA gene of Pseudomonas stutzeri OX1. The diversity of tmoA-like genes was examined in DNA extracts from contaminated and non-contaminated subsurface samples at a site containing a BTEX-contaminated groundwater plume. Differences in DGGE patterns were observed between strongly contaminated, less contaminated and non-contaminated samples and between different depths, suggesting that the diversity of tmoA-like genes was determined by environmental conditions including the contamination level. Phylogenetic analysis of the protein sequences deduced from the amplified amplicons showed that the diversity of TmoA-analogues in the environment is larger than suggested from described TmoA-analogues from cultured isolates, which was translated in the DGGE patterns. Although different positions on the DGGE gel can correspond to closely related TmoA-proteins, relationships could be noticed between the position of tmoA-like amplicons in the DGGE profile and the phylogenetic position of the deduced protein sequence.

Bacteria↗
PubMed2006

Effect of short-term exposure to methyl-tert-butyl ether and tert-butyl alcohol on the hatch rate and development of the African catfish, Clarias gariepinus.

Methyl tert-butyl ether (MTBE), a synthetic chemical used as a fuel additive, has been detected more frequently in the environment than previously. In this study, we examine the effects of MTBE (up to 100 mg/L) and its primary metabolite tertbutyl alcohol (TBA) (up to 1,400 mg/L) on the hatch rate and larval development of the African catfish Clarias gariepinus. Exposure to higher MTBE concentrations resulted in deformed eyes, mouthparts, and spinal cord and in increased larval mortality. Methyl tert-butyl ether exposure had no significant impact on egg viability, whereas TBA induced a decline of hatch rate. The MTBE can be regarded as a pollutant with toxicological effects on catfish larvae at concentrations above 50 mg/L. Although such concentrations greatly surpass present-day concentrations found in surface water (0.088 mg/L), concentrations up to 200 mg/L have been detected in groundwater.

Abnormalities, Drug-Induced↗
PubMed2006

Long-term exposure to environmentally relevant doses of methyl-tert-butyl ether causes significant reproductive dysfunction in the zebrafish (Danio rerio).

Methyl-tert-butyl ether (MTBE), an anthropogenic chemical used as a gasoline additive, is being detected at an increasing frequency in the environment. The acute lethal concentration that kills 50% of the fish test population and the chronic effects of exposure to MTBE were investigated in the zebrafish (Danio rerio). Chronic exposure over three weeks to effective MTBE conceritrations as low as 0.11 mg/L induced a significant increase in the vitellogenin concentration of male fish. The impact of a chronic, eight-week exposure at effective concentrations ranging from 0.44 to 220 mg/L had no significant effect on fecundity, fertilization, or hatch rate but highly significant impacts on sperm motility. Spermatozoa of all MTBE-exposure groups showed a significantly lower straight-line velocity and lower average path velocity compared to those of the nonexposed group. These results suggest that chronic exposure to MTBE negatively affects fish sperm motility at concentrations that are environmentally relevant and several orders of magnitude lower than concentrations inducing acute effects.

Animals↗
PubMed2005

DsrB gene-based DGGE for community and diversity surveys of sulfate-reducing bacteria.

A denaturing gradient gel electrophoresis (DGGE) method was developed to assess the diversity of dsrB (dissimilatory sulfite reductase beta-subunit)-genes in sulfate-reducing communities. For this purpose a PCR primer pair was optimized for the amplification of a approximately 350 bp dsrB gene fragment that after DGGE gel electrophoresis enabled us to discriminate between dsrB genes of different SRB-subgroups,-genera and -species. The dsrB-DGGE method revealed considerable genetic diversity when applied to DNA extracts obtained from aquifer samples that were derived from monitoring wells of an in situ metal precipitation (ISMP) pilot project conducted at the site of a non-ferrous industry or from environmental heavy metal contaminated samples. The sequences of the excised and sequenced DGGE bands represented dsrB genes of different SRB-subgroups,-genera and -species, thus confirming the broad applicability of the PCR primer pair. Linking the results of the physico-chemical follow-up of the field and lab experiments to the dsrB-DGGE data will provide a better understanding of the contribution of the SRB populations to the ongoing ISMP processes.

Base Sequence↗
PubMed2005

Combined removal of chlorinated ethenes and heavy metals by zerovalent iron in batch and continuous flow column systems.

The combined removal of chlorinated ethenes and heavy metals from a simulated groundwater matrix by zerovalent iron (ZVI) was investigated. In batch, Ni (5-100 mg L(-1)) enhanced trichloroethene (TCE, 10 mg L(-1)) reduction by ZVI (100 g L(-1)) due to catalytic hydrodechlorination by bimetallic Fe0/Ni0. Cr(VI) or Zn (5-100 mg L(-1)) lowered TCE degradation rates by a factor of 2 to 13. Cr(VI) (100 mg L(-1)) in combination with Zn or Ni (50-100 mg L(-1)) inhibited TCE degradation. Addition of 20% H2(g) in the headspace, or of Zn (50-100 mg L(-1)), enhanced TCE removal in the presence of Ni and Cr(VI). Sorption of Zn to ZVI alleviated the Cr(VI) induced inhibition of bimetallic Fe0/Ni0 apparently due to release of protons necessary for TCE hydrodechlorination. In continuous ZVI columns treating tetrachloroethene (PCE, 1-2 mg L(-1)) and TCE (10 mg L(-1)), and a mixture of the metals Cr(VI), Zn(II), and Ni(II) (5 mg (L-1)), the PCE removal efficiency decreased from 100% to 90% in columns operated without heavy metals. The PCE degradation efficiency remained above 99% in columns receiving heavy metals as long as Ni was present. The findings of this study indicate the feasibility and limitations of the combined treatment of mixtures of organic and inorganic pollutants by ZVI.

Catalysis↗
PubMed2005

Alternative primer sets for PCR detection of genotypes involved in bacterial aerobic BTEX degradation: distribution of the genes in BTEX degrading isolates and in subsurface soils of a BTEX contaminated industrial site.

Eight new primer sets were designed for PCR detection of (i) mono-oxygenase and dioxygenase gene sequences involved in initial attack of bacterial aerobic BTEX degradation and of (ii) catechol 2,3-dioxygenase gene sequences responsible for meta-cleavage of the aromatic ring. The new primer sets allowed detection of the corresponding genotypes in soil with a detection limit of 10(3)-10(4) or 10(5)-10(6) gene copies g(-1) soil, assuming one copy of the gene per cell. The primer sets were used in PCR to assess the distribution of the catabolic genes in BTEX degrading bacterial strains and DNA extracts isolated from soils sampled from different locations and depths (vadose, capillary fringe and saturated zone) within a BTEX contaminated site. In both soil DNA and the isolates, tmoA-, xylM- and xylE1-like genes were the most frequently recovered BTEX catabolic genes. xylM and xylE1 were only recovered from material from the contaminated samples while tmoA was detected in material from both the contaminated and non-contaminated samples. The isolates, mainly obtained from the contaminated locations, belonged to the Actinobacteria or Proteobacteria (mainly Pseudomonas). The ability to degrade benzene was the most common BTEX degradation phenotype among them and its distribution was largely congruent with the distribution of the tmoA-like genotype. The presence of tmoA and xylM genes in phylogenetically distant strains indicated the occurrence of horizontal transfer of BTEX catabolic genes in the aquifer. Overall, these results show spatial variation in the composition of the BTEX degradation genes and hence in the type of BTEX degradation activity and pathway, at the examined site. They indicate that bacteria carrying specific pathways and primarily carrying tmoA/xylM/xylE1 genotypes, are being selected upon BTEX contamination.

Actinobacteria↗
PubMed2005

Occurrence and community composition of fast-growing Mycobacterium in soils contaminated with polycyclic aromatic hydrocarbons.

Fast-growing mycobacteria are considered essential members of the polycyclic aromatic hydrocarbons (PAH) degrading bacterial community in PAH-contaminated soils. To study the natural role and diversity of the Mycobacterium community in contaminated soils, a culture-independent fingerprinting method based on PCR combined with denaturing gradient gel electrophoresis (DGGE) was developed. New PCR primers were selected which specifically targeted the 16S rRNA genes of fast-growing mycobacteria, and single-band DGGE profiles of amplicons were obtained for most Mycobacterium strains tested. Strains belonging to the same species revealed identical DGGE fingerprints, and in most cases, but not all, these fingerprints were typical for one species, allowing partial differentiation between species in a Mycobacterium community. Mycobacterium strains inoculated in soil were detected with a detection limit of 10(6) CFU g(-1) of soil using the new primer set as such, or approximately 10(2) CFU g(-1) in a nested PCR approach combining eubacterial and the Mycobacterium specific primers. Using the PCR-DGGE method, different species could be individually recognized in a mixed Mycobacterium community. This approach was used to rapidly assess the Mycobacterium community structure of several PAH-contaminated soils of diverse origin with different overall contamination profiles, pollution concentrations and chemical-physical soil characteristics. In the non-contaminated soil, most of the recovered 16SrRNA gene sequence did not match with previous described PAH-degrading Mycobacterium strains. In most PAH-contaminated soils, mycobacteria were detected which were closely related to fast-growing species such as Mycobacterium frederiksbergense and Mycobacterium austroafricanum, species that are known to include strains with PAH-degrading capacities. Interestingly, 16S rRNA genes related to M. tusciae sequences, a Mycobacterium species so far not reported in relation to biodegradation of PAHs, were detected in all contaminated soils.

DNA Primers↗
PubMed2005

Effect of humic acids on heavy metal removal by zero-valent iron in batch and continuous flow column systems.

The effects of Aldrich humic acids (HA) on the removal of Zero-valent iron (ZVI) was investigated in laboratory systems. In batch, the removal rate of Zn and Ni (5 mg l(-1)) was, respectively, 2.8 and 2.4 times lower in the presence of HA (20 mg l(-1)) than in the absence of HA, presumably due to the formation of HA-heavy metal complexes which prevented the removal reactions at the ZVI surface. Chromate removal was not affected. In a column test, two parallel systems were supplemented with a continuous input of simulated groundwater containing a mixture of the heavy metals Zn, Ni and Cr(VI) (5 mg l(-1) each), with or without HA (at 20 mg l(-1)). Initially, the two column systems efficiently (>90%) removed the heavy metals from the simulated groundwater. When the input heavy metal concentration was increased to 8-10 mg l(-1), a significant breakthrough of Ni and Zn, up to 80%, occurred in the column system fed with HA. Chromate and HA did not significantly break through. After 60 weeks, the effect of HA on leaching of the accumulated metals (approx. 2 mg g(-1)) was investigated. No significant leaching was observed. The results of this study suggest that the impact of dissolved organic matter on the efficiency and lifetime of a ZVI barrier for in situ removal of heavy metals should be considered in the design of the barrier.

Adsorption↗
PubMed2005

Dynamics of an oligotrophic bacterial aquifer community during contact with a groundwater plume contaminated with benzene, toluene, ethylbenzene, and xylenes: an in situ mesocosm study.

An in situ mesocosm system was designed to monitor the in situ dynamics of the microbial community in polluted aquifers. The mesocosm system consists of a permeable membrane pocket filled with aquifer material and placed within a polypropylene holder, which is inserted below groundwater level in a monitoring well. After a specific time period, the microcosm is recovered from the well and its bacterial community is analyzed. Using this system, we examined the effect of benzene, toluene, ethylbenzene, and xylene (BTEX) contamination on the response of an aquifer bacterial community by denaturing gradient gel electrophoresis analysis of PCR-amplified 16S rRNA genes and PCR detection of BTEX degradation genes. Mesocosms were filled with nonsterile or sterile aquifer material derived from an uncontaminated area and positioned in a well located in either the uncontaminated area or a nearby contaminated area. In the contaminated area, the bacterial community in the microcosms rapidly evolved into a stable community identical to that in the adjacent aquifer but different from that in the uncontaminated area. At the contaminated location, bacteria with tmoA- and xylM/xylE1-like BTEX catabolic genotypes colonized the aquifer, while at the uncontaminated location only tmoA-like genotypes were detected. The communities in the mesocosms and in the aquifer adjacent to the wells in the contaminated area consisted mainly of Proteobacteria. At the uncontaminated location, Actinobacteria and Proteobacteria were found. Our results indicate that communities with long-term stability in their structures follow the contamination plume and rapidly colonize downstream areas upon contamination.

Actinobacteria↗
PubMed2004

Influence of the carbon/nitrogen/phosphorus ratio on polycyclic aromatic hydrocarbon degradation by Mycobacterium and Sphingomonas in soil.

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) in the environment is often limited due to unfavorable nutrient conditions for the bacteria that use these PAHs as sole source of carbon and energy. Mycobacterium and Sphingomonas are 2 PAH-degrading specialists commonly present in PAH-polluted soil, but not much is known about their specific nutrient requirements. By adding different inorganic supplements of nitrogen (N) and phosphorus (P), affecting the overall carbon/nitrogen/phosphorus ratio of soil in soil slurry degradation tests, we investigated the impact of soil inorganic N and P nutrient conditions on PAH degradation by PAH-degrading Sphingomonas and Mycobacterium strains. The general theoretically calculated C/N/P ratio of 100/10/1 (expressed in moles) allowed rapid PAH metabolization by Sphingomonas and Mycobacterium strains without limitation. In addition, PAH-degradation rate and extent was not affected when ca. ten times lower concentrations of N and P were provided, indicating that Sphingomonas and Mycobacterium strains are capable of metabolizing PAHs under low nutrient conditions. Nor does PAH-degradation seem to be affected by excesses of N and P creating an imbalanced C/N/P ratio. However, supplements of N and P salts increased the salinity of soil slurry solutions and seriously limited or even completely blocked biodegradation.

Biodegradation, Environmental↗
PubMed2004

Competition for sorption and degradation of chlorinated ethenes in batch zero-valent iron systems.

The sorption and degradation of the chlorinated ethenes tetrachloroethene (PCE, 5 mg L(-1)) and trichloroethene (TCE, 10 mg L(-1)) were investigated in zero-valent iron systems (ZVI, 100 g L(-1)) in the presence of compounds common to contaminated groundwater with varying physicochemical properties. The potential competitors were chlorinated ethenes, monocyclic aromatic hydrocarbons, and humic acids. The effect of a complex matrix was tested with landfill contaminated groundwater. Nonlinear Freundlich isotherms adequately described chloroethene sorption to ZVI. In the presence of the more hydrophobic PCE (5 mg L(-1)), TCE sorption and degradation decreased by 33% and 30%, respectively, while TCE (10 mg L(-1)) decreased PCE degradation by 30%. In the presence of nonreactive hydrophobic hydrocarbons (i.e., benzene, toluene, and m-xylene at 100 mg L(-1)), TCE and PCE sorption decreased by 73% and 55%, respectively. The presence of the hydrocarbons had no effect on TCE degradation and increased PCE reduction rates by 50%, suggesting that the displacement of the chloroethenes from the sorption sites by the aromatic hydrocarbons enhanced the degradation rates. Humic acids did not interfere significantly with chloroethene sorption or with TCE degradation but lowered PCE degradation kinetics by 36% when present at high concentrations (100 mg L(-1)). The landfill groundwater with an organic carbon content of 109 mg L(-1) C had no effect on chloroethene sorption but inhibited TCE and PCE degradation by 60% and 70%, respectively.

Adsorption↗
PubMed2004

Horizontal gene transfer and microbial adaptation to xenobiotics: new types of mobile genetic elements and lessons from ecological studies.

The characterization of bacteria that degrade organic xenobiotics has revealed that they can adapt to these compounds by expressing 'novel' catabolic pathways. At least some of them appear to have evolved by patchwork assembly of horizontally transmitted genes and subsequent mutations and gene rearrangements. Recent studies have revealed the existence of new types of xenobiotic catabolic mobile genetic elements, such as catabolic genomic islands, which integrate into the chromosome after transfer. The significance of horizontal gene transfer and patchwork assembly for bacterial adaptation to pollutants under real environmental conditions remains uncertain, but recent publications suggest that these processes do occur in a polluted environment.

Adaptation, Physiological↗