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PubMed2000

Survival and conjugation of Bacillus thuringiensis in a soil microcosm.

The survival and conjugation ability of sporogenic and asporogenic Bacillus thuringiensis strains were investigated in broth, in non-amended sterile clay soil monoculture and in mixed soil culture. The 75 kb pHT73 plasmid carrying an erythromycin resistance determinant and a cry1Ac gene was transferred in mating broth and soil microcosm. Survival of strains was assessed in soil monoculture and in mixed soil culture for up to 20 days. Sporogenic strains rapidly formed viable spores which were maintained until the end of the experiment. The asporogenic strains were no longer recovered after 8 days of incubation. This study shows that the environmental impact of asporogenic B. thuringiensis strains is lower than that of sporogenic B. thuringiensis strains. Thus, the use of asporogenic strains may significantly reduce any potential risk (gene transfer, soil and plant contamination) due to the dissemination of B. thuringiensis-based biopesticides in the environment.

Journal Article↗
PubMed1991

Effects of surfactant adsorption and biodegradability on the distribution of bacteria between sediments and water in a freshwater microcosm.

A microcosm containing resuspended river sediment was used to investigate the effect of anionic surfactants on the distribution of bacteria between planktonic and attached populations. Freshwater river sediment containing viable bacteria was preequilibrated in the microcosm, which was subsequently supplemented with biodegradable or recalcitrant surfactants and a non-surface-active carbon and energy source. Population dynamics of both free-living and attached bacteria were measured by epifluorescence microscopy with simultaneous analysis of the residual solution concentration of the xenobiotic carbon source. The addition of the readily biodegradable anionic surfactants sodium decyl sulfate and sodium dodecyl sulfate in separate experiments caused an increase in the number of attached bacteria and a concomitant decrease in the number of free-living bacteria. As biodegradation of the surfactants progressed, these trends reversed and the bacterial populations had returned to their preaddition values by the time when biodegradation was completed. In contrast, sodium tetradecyl sulfate or sodium dodecane sulfonate did not stimulate bacterial association with sediment, nor were they biodegraded in the microcosm. Sodium pyruvate, a non-surface-active carbon and energy source, was readily utilized but caused no bacterial attachment to the sediment. These results indicate that for an anionic surfactant to induce bacterial attachment to river sediment, it must be biodegradable. The bacterial attachment to the sediment appears to be reversible and may be dependent on the accumulation of the surfactant at the surface or as a result of alteration of the surface free energies.

Adsorption↗
PubMed2003

Genetic transfer of the mcd gene in soil.

AIMS: To investigate the role of horizontal gene transfer of mcd (methylcarbamate-degrading) gene in high genetic diversity of carbofuran-degrading bacteria. METHODS AND RESULTS: The actuality of genetic transfer from degraders to an Agrobacterium tumefaciens strain was determined in liquid medium. The mcd gene was chosen for transfer experiments. Transconjugants were obtained irrespective of the type of the donor strain (Gram-positive or Gram-negative), size of the inoculum, or nature and concentration of the pesticide in the medium. Soil microcosms, inoculated with or without the donor and/or recipient strains were used. The size of the initial degrading population (treated or untreated soil) and the nature of the inoculated donor strains were considered. More transconjugants were isolated in the previously treated soil than in the untreated soil. Agrobacterium transconjugants were isolated even when the donor strain was not inoculated, probably as a result of gene transfer from indigenous degrading population to the recipient strain. Moreover, potential transconjugants belonging to the Pseudomonas genus were isolated. CONCLUSIONS: Our results seem to demonstrate that the mcd gene is transferable in soil among bacterial populations. SIGNIFICANCE AND IMPACTS OF THE STUDY: The transfer of the mcd gene is partly responsible for the high genetic diversity of micro-organisms able to catabolize carbofuran.

Agrobacterium tumefaciens↗
PubMed1998

Cu-Cd interactions in earthworms maintained in laboratory microcosms: the examination of a putative copper paradox.

Earthworms (Lumbricus rubellus) from Ecton (predominantly Cu-contaminated), Shipham (Cd-contaminated) and Dinas Powys (uncontaminated, reference) were maintained in the laboratory on soil from the sampling sites. Two principle exposure protocols were used: (1) a 4-week 'no pre-exposure experiment', where batches of earthworms were maintained on soils from each habitat and (2) a 'pre-exposure experiment' where uncontaminated control worms were maintained on Shipham soil for 4 weeks (the pre-exposure period), and then transferred to Ecton soil for a further 4 weeks, and vice versa. In summary, there were two primary findings. Firstly, exposure of worms to Cd-rich soil (Shipham) before exposure to Cu-rich soil (Ecton) increased the Cu burden and secondly, biochemical analysis of metal binding proteins in analogous earthworm populations indicated that Cu and Cd, but not Zn, are bound to a metallothionein homologue. These observations are consistent with the hypothesis that Cu does not induce thionein synthesis efficiently in earthworm tissues, but may bind avidly to Cd-induced thionein by substituting for Cd in the molecule because Cu-thionein is a more stable complex.

Animals↗
PubMed2001

Galactosides in the rhizosphere: utilization by Sinorhizobium meliloti and development of a biosensor.

Identifying the types and distributions of organic substrates that support microbial activities around plant roots is essential for a full understanding of plant-microbe interactions and rhizosphere ecology. We have constructed a strain of the soil bacterium Sinorhizobium meliloti containing a gfp gene fused to the melA promoter which is induced on exposure to galactose and galactosides. We used the fusion strain as a biosensor to determine that galactosides are released from the seeds of several different legume species during germination and are also released from roots of alfalfa seedlings growing on artificial medium. Galactoside presence in seed wash and sterile root washes was confirmed by HPLC. Experiments examining microbial growth on alpha-galactosides in seed wash suggested that alpha-galactoside utilization could play an important role in supporting growth of S. meliloti near germinating seeds of alfalfa. When inoculated into microcosms containing legumes or grasses, the biosensor allowed us to visualize the localized presence of galactosides on and around roots in unsterilized soil, as well as the grazing of fluorescent bacteria by protozoa. Galactosides were present in patches around zones of lateral root initiation and around roots hairs, but not around root tips. Such biosensors can reveal intriguing aspects of the environment and the physiology of the free-living soil S. meliloti before and during the establishment of nodulation, and they provide a nondestructive, spatially explicit method for examining rhizosphere soil chemical composition.

Base Sequence↗
PubMed1989

Survival and activity of a 3-chlorobenzoate-catabolic genotype in a natural system.

A chlorobenzoate-degrading Alcaligenes strain, BR60, was introduced to flowthrough lake microcosms and exposed to 3-chlorobenzoate (3Cba) concentrations from 0 to 25 muM. A DNA probe specific for BR60 chlorobenzoate catabolic genes was used with the most probable number (MPN) technique to enumerate bacteria harboring this genetic information. This MPN-DNA hybridization method combined with [U-C]3Cba uptake rate measurements allowed the correlation of the size and activity of a specific catabolic population in a natural mixed community for the first time. An experiment involving the release of a streptomycin-resistant strain of BR60 indicated that estimates of bacteria carrying the introduced catabolic genotype often outnumbered plate count estimates of viable BR60 by as much as 3 orders of magnitude, particularly when 3Cba inputs were high. The MPN-DNA hybridization method provided catabolic population estimates highly correlated to 3Cba exposure levels and the [U-C]3Cba uptake rates in the microcosms. Plate counts of BR60 were poorly correlated with both 3Cba exposure levels and uptake rates. In the absence of chlorobenzoate selection, the catabolic genotype declined to very low levels by the MPN-DNA hybridization technique after 8 weeks in the microcosms.

Journal Article↗
PubMed2004

Response of Archaeal communities in beach sediments to spilled oil and bioremediation.

While the contribution of Bacteria to bioremediation of oil-contaminated shorelines is well established, the response of Archaea to spilled oil and bioremediation treatments is unknown. The relationship between archaeal community structure and oil spill bioremediation was examined in laboratory microcosms and in a bioremediation field trial. 16S rRNA gene-based PCR and denaturing gradient gel analysis revealed that the archaeal community in oil-free laboratory microcosms was stable for 26 days. In contrast, in oil-polluted microcosms a dramatic decrease in the ability to detect Archaea was observed, and it was not possible to amplify fragments of archaeal 16S rRNA genes from samples taken from microcosms treated with oil. This was the case irrespective of whether a bioremediation treatment (addition of inorganic nutrients) was applied. Since rapid oil biodegradation occurred in nutrient-treated microcosms, we concluded that Archaea are unlikely to play a role in oil degradation in beach ecosystems. A clear-cut relationship between the presence of oil and the absence of Archaea was not apparent in the field experiment. This may have been related to continuous inoculation of beach sediments in the field with Archaea from seawater or invertebrates and shows that the reestablishment of Archaea following bioremediation cannot be used as a determinant of ecosystem recovery following bioremediation. Comparative 16S rRNA sequence analysis showed that the majority of the Archaea detected (94%) belonged to a novel, distinct cluster of group II uncultured Euryarchaeota, which exhibited less than 87% identity to previously described sequences. A minor contribution of group I uncultured Crenarchaeota was observed.

Biodegradation, Environmental↗
PubMed2006

Fluctuation in the physical environment as a mechanism for reinforcing evolutionary transitions.

We hypothesize a mechanism for reinforcing transitions between levels of selection, involving physiological homeostasis and amplification of variation in the physical environment. Groups experience a stronger selection pressure than individuals for homeostasis with respect to reproductively limiting variables, because their greater longevity exposes them more often to suboptimal physical conditions, and greater physical size means they encompass a larger fraction of any resource/nutrient gradient. Groups achieve homeostasis by differentiation into microcosms with specialist functions, e.g. cell types. Such differentiation is more limited in individuals due to their smaller size and shorter lifespan. Hence tolerance of fluctuation in certain physical variables is proposed to be weaker in individuals than in groups. We show that a trait providing increased tolerance (alpha) to fluctuation (V-V(opt)) in a limiting abiotic variable (V), at relative fitness cost (C), can increase from rarity if the condition alpha.mid R:V-V(opt)|>C is met. Groups also sequester larger absolute quantities of resource than individuals, and group death is less frequent, hence the population dynamics of groups cause resource/nutrient availability to fluctuate with greater amplitude than that of individuals. Increasing the amplitude of fluctuation in a reproductively limiting environmental variable is proposed as a mechanism by which a group can limit reproduction of parasitic "cheat" individuals. Enhancing physical fluctuation is frequency dependent, hence only an increase in tolerance to fluctuation can explain the group's increase from rarity. However, once groups reach intermediate frequencies, a positive feedback process can be initiated in which a differentiated group enhances physical fluctuation beyond the tolerance of any "cheat", and in so doing enhances the selection pressure it experiences for homeostasis. This may help explain the persistence of transitions in individuality, and the coincidence of some such transitions with periods of change and oscillation in global scale environmental variables.

Altruism↗
PubMed2003

Novel use of soil moisture samplers for studies on anaerobic ammonium fluxes across lake sediment-water interfaces.

Small soil suction samplers have been used for several years to sample soil solution for chemical analysis in laboratory and glasshouse experiments. They are very cheap, effective and convenient. Here we describe for the first time their use in studies on sediment porewater. Bulk sediment from West Lake, a shallow hypereutrophic lake in Hangzhou, Zhejiang Province, China, was placed in laboratory microcosms and incubated in the dark at 25 degrees C for 182 days to evaluate the feasibility of using the samplers to extract sediment porewater and to estimate NH4+ flux across the sediment-water interface under anaerobic conditions. The results show that the samplers were capable of sequentially extracting sediment porewater, 15 ml of which could be readily extracted for analysis within 30-45 min by vacuum applied using a plastic syringe. The NH4+ flux under laboratory conditions was characterized by a fast phase during the initial 18 days of incubation followed by a slower linear phase, with average release rates of 11.6 and 3.6 mg N m(-2) d(-1), respectively.

Anaerobiosis↗
PubMed2005

Combined effects of discharge, turbidity, and pesticides on mayfly behavior: experimental evaluation of spray-drift and runoff scenarios.

The effects of the pyrethroid-insecticide cypermethrin (CYP), increased flow speed (Flow), and increased suspended particles (Part) on drift behavior and activity of mayfly nymphs (Baetis harrisoni) were investigated both individually and in combination in a laboratory stream microcosm. Spray-drift trials were performed by exposing the nymphs to 1 microg/L of CYP. During runoff trials (CYP x Part), contaminated sediment containing 2,000 microg/kg of CYP was introduced to the microcosm at a concentration of 500 mg/L. Both trials were carried out under high-flow (CYP x Flow and CYP x Part x Flow) and low-flow (CYP and CYP x Part) conditions, and for all cases, control experiments were performed. Drift rate, drift density (for any treatments with increased flow), and activity were used as behavioral endpoints. Multifactorial analysis of variance shows that CYP exposure significantly increased the drift, whereas Part and Flow trials significantly decreased the drift (p < 0.05). In addition, activity decreased significantly under high-flow conditions. The CYP x Part and CYP x Flow treatments resulted in increased drift rate and drift density, respectively, whereas Part x Flow and CYP x Part x Flow treatments resulted in decreased drift density. The CYP x Part and CYP x Flow trials had a significant antagonistic, interactive effect on drift rate and drift density, respectively, with measured levels being lower than expected levels. The reduction in bioavailability of CYP in the presence of increased flow and sediment levels suggests that mayflies are more likely to be affected by spray-drift exposure (CYP) than by runoff exposure (CYP x Part x Flow). Results indicate that mayflies reacted actively in response to flow conditions and passively in response to pesticide exposure.

Analysis of Variance↗
PubMed1986

A laboratory microcosm (artificial mouth) for the culture and continuous pH measurement of oral bacteria on surfaces.

A laboratory microcosm has been designed for the cultivation of bacteria on surfaces subjected to an adjustable supply of fluids. Bacteria are grown as a microbial film on halved premolar teeth, mounted back to back. Synthetic saliva is dropped slowly over the teeth throughout experiments. A nutrient supplement is provided at regular intervals. The drops of fluid retained by the teeth can be sampled for metabolic end-products. Alternatively, a miniature glass electrode may be set into one half of a tooth assembly to monitor the pH continuously at the stagnation site between tooth segments. Up to six replicate culture flasks and six electrodes can be accommodated in a single experiment. Satisfactory electrode performance was maintained during 66 h experiments. In initial 48 h experiments, teeth were inoculated with Streptococcus rattus BHT or 'Streptococcus mitior' LPA-1 in pure culture and provided with 1% (w/v) glucose for 1 h every 6 h. Bacteria produced typical responses to glucose feeds leading to the formation of 'Stephan'-like curves of pH-fall. Under these conditions, 'Strep. mitior' was more acidogenic than Strep. rattus and the pattern of acid production was distinct for each organism.

Bacteriological Techniques↗
PubMed2001

Rates and quantities of carbon flux to ectomycorrhizal mycelium following 14C pulse labeling of Pinus sylvestris seedlings: effects of litter patches and interaction with a wood-decomposer fungus.

We used a novel digital autoradiographic technique that enabled, for the first time, simultaneous visualization and quantification of spatial and temporal changes in carbon allocation patterns in ectomycorrhizal mycelia. Mycorrhizal plants of Pinus sylvestris L. were grown in microcosms containing non-sterile peat. The time course and spatial distribution of carbon allocation by P. sylvestris to mycelia of its mycorrhizal partners, Paxillus involutus (Batsch) Fr. and Suillus bovinus (L.): Kuntze, were quantified following 14C pulse labeling of the plants. Litter patches were used to investigate the effects of nutrient resource quality on carbon allocation. The wood-decomposer fungus Phanerochaete velutina (D.C.: Pers.) Parmasto was introduced to evaluate competitive and territorial interactions between its mycelial cords and the mycelial system of S. bovinus. Growth of ectomycorrhizal mycelium was stimulated in the litter patches. Nearly 60% of the C transferred from host plant to external mycorrhizal mycelium (> 2 mm from root surfaces) was allocated to mycelium in the patches, which comprised only 12% of the soil area available for mycelial colonization. Mycelia in the litter patch most recently colonized by mycorrhizal mycelium received the largest investment of carbon, amounting to 27 to 50% of the total 14C in external mycorrhizal mycelium. The amount of C transfer to external mycelium of S. bovinus following pulse labeling was reduced from a maximum of 167 nmol in systems with no saprotroph to a maximum of 61 nmol in systems interacting with P. velutina. The 14C content of S. bovinus mycelium reached a maximum 24-36 h after labeling in control microcosms, but allocation did not reach a peak until 56 h after labeling, when S. bovinus interacted with mycelium of P. velutina. The mycelium of S. bovinus contained 9% of the total 14C in the plants (including mycorrhizae) at the end of the experiment, but this was reduced to 4% in the presence of P. velutina. The results demonstrate the dynamic manner in which mycorrhizal mycelia deploy C when foraging for nutrients. The inhibitory effect of the wood-decomposer fungus P. velutina on C allocation to external mycorrhizal mycelium has important implications for nutrient cycling in forest ecosystems.

Autoradiography↗
PubMed1999

Effect of novel biosurfactants on biodegradation of polychlorinated biphenyls by pure and mixed bacterial cultures.

A study was conducted to determine the potential positive effect of novel biosurfactants on the enhancement of Aroclor 1248 metabolization in both in vitro and in situ experiments. Among two lipopeptides tested the highest activity was found in experiments with a hydrolytically opened form of lichenysin A. Lichenysin A itself did not enhance the degradation activity of chosen microorganism-degraders and in most cases inhibited their PCB mineralization rates. Glucolipid surfactant from marine bacterium Alcanivorax borkumensis showed in several tests a strong enhancing effect on microbial metabolization of Aroclor 1248 congeners. Biosurfactants appeared to act very specifically, i.e. depending on strain and concentration used. Experiments set up with soil samples did not give a clear answer whether bioemulsifiers applied at low concentration could sufficiently increase the rates of biodegradation in situ. Only A. borkumiensis glucose lipid caused the most marked enhancement of Aroclor 1248 metabolization in soil microcosm. We suggest that taking into account the specificity of surface- and biological activities of various biosurfactants they may promote the mineralization of sorbed PCBs in polluted soils, when the optimized biosurfactant-degrader combination is used.

Aroclors↗
PubMed2004

Freshwater microcosms-based assessment of eco-toxicological effects of a chemical effluent from the Pilcam industry in Cameroon.

We studied the acute toxicity of a raw effluent from a battery manufacturing plant (Pilcam) in Douala, Cameroon, to a freshwater fish (Oreochromis niloticus), and subsequently evaluated its sub-acute effects on water quality and the biota in freshwater microscosms. The acute toxicity test was based on 96 hrs static renewal bioassays that resulted in 96-h LC50 and LC90 values of 16 and 20.7% (v/v), respectively. The sub-acute experiments were conducted by exposing several species of aquatic organisms (plankton, macroinvertebrates and mollusks) to lower effluent concentrations [1.6%, 8.0%, 16% (v/v)] for six weeks, and monitoring their survival rates, as well as the physical and chemical characteristics of water. These concentrations were based on 10%, 50%, and 100% of the 96 h - median lethal concentrations (LC50) of the effluent to the freshwater fish, Oreochromis niloticus. Significant effects on functional parameters, such as, chlorophyll-a and total protein could not be demonstrated. However, the activity of alkaline phosphatase was significantly inhibited at all concentrations tested. Phytoplankton, zooplankton, macro-invertebrate communities and snails were negatively affected by the effluent application at concentrations ? 8% (v/v), with chlorophyta, ciliates, ostracoda, annelida, planaria and snails being the most sensitive groups. The snails were eliminated after 24 h exposure from microcosms treated with effluent at concentration ? 8% (v/v). Effluent exposure also caused significant effects on water quality parameters (DO, pH, hardness, conductivity, color, turbidity, ammonia) in general at concentrations ? 8% (v/v). Temperature and alkalinity were not significantly affected. Overall, data from this research indicate that a dilution of the Pilcam effluent down to 1.6% does not provide protection against chronic toxicity to aquatic organisms. Further studies are needed to determine the no observable adverse effect level (NOAEL), as well as a chronic reference concentration for this effluent.

Animals↗
PubMed2004

The relative impacts of spills of two alternative fuels on the microalgae of a sandy site: a microcosm study.

Electric power generation in the United States uses substantial amounts of fuel oil #6. Orimulsion, an emulsion of bitumen, water, and a surfactant, is an alternative. A portion of the information that managers need to compare the two fuels is their relative environmental impacts. Both fuels are shipped by sea, so the impact of spills on the marine benthos is a concern. We used microcosms to assess the relative impacts of simulated spills of these fuels on the microalgae of shallow subtidal sandy bottoms. Response variables included microalgal abundance, primary productivity, ratio of chlorophyll a to phaeophytin, and ratio of primary production to chlorophyll a. During our 88-day experiment, we found no significant differences between the fuels for any variable. We suggest that weathering before the spill reaches the shore removes the most toxic components, rendering the fuels essentially equal in their impact on benthic microalgae.

Chlorophyll↗
PubMed2001

Effects of microcosm scaling and food resources on growth and survival of larval Culex pipiens.

BACKGROUND: We used a simple experimental design to test for the effects of microcosm scaling on the growth and survival of the mosquito, Culex pipiens. Microcosm and mesocosm studies are commonly used in ecology, and there is often an assumption that scaling doesn't affect experimental outcomes. The assumption is implicit in the design; choice of mesocosms may be arbitrary or based on convenience or cost. We tested the hypothesis that scale would influence larvae due to depth and surface area effects. Larvae were predicted to perform poorly in microcosms that were both deep and had small openings, due to buildup of waste products, less exchange with the environment, and increased competition. To determine if the choice of scale affected responses to other factors, we independently varied leaf litter quantity, whose effects on mosquitoes are well known. RESULTS: We found adverse effects of both a lower wall surface area and lower horizontal surface area, but microcosm scale interacted with resources such that C. pipiens is affected by habitat size only when food resources are scarce. At low resource levels mosquitoes were fewer, but larger, in microcosms with smaller horizontal surface area and greater depth than in microcosms with greater horizontal surface area and shallower depth. Microcosms with more vertical surface area/volume often produced larger mosquitoes; more food may have been available since mosquitoes browse on walls and other substrates for food. CONCLUSIONS: The interaction between habitat size and food abundance is consequential to aquatic animals, and choice of scale in experiments may affect results. Varying surface area and depth causes the scale effect, with small horizontal surface area and large depth decreasing matter exchange with the surrounding environment. In addition, fewer resources leads to less leaf surface area, and the effects of varying surface area will be greater under conditions of limiting resources. This leads to smaller size, which limits fecundity and survival. Choice of container size, either by ovipositing females or researchers, interacts with a major aspect of the ecology of animals; obtaining resources in a resource-limited environment.

Analysis of Variance↗
PubMed1999

Intraguild predation among larval treehole mosquitoes, Aedes albopictus, Ae. aegypti, and Ae. triseriatus (Diptera: Culicidae), in laboratory microcosms.

We compared the tendency for 4th-instar larvae to prey on newly hatched larvae, and the vulnerability of those 1st instars to such predation for Aedes triseriatus (Say), Ae. aegypti (L.), and Ae. albopictus (Skuse), all container-breeding mosquitoes. The latter 2 species were introduced to North America and are now sympatric with Ae. triseriatus, a native species in eastern North America. The experiment also enabled the assessment of species-specific influences of food supplements and spatial heterogeneity on predatory behavior. Ae. triseriatus was substantially more predatory and less susceptible to attack than the other 2 species. These differences were amplified in food-deprived and spatially simple conditions, indicating that Ae. triseriatus predatory behavior may have important retarding effects on the colonization of occupied treehole habitats by Ae. albopictus. Ae. aegypti and Ae. albopictus were similar in imposing little (Ae. aegypti) or almost no (Ae. albopictus) predation on 1st instars and in being susceptible to predation by Ae. triseriatus. The general lack of species-specific differences between Ae. aegypti and Ae. albopictus indicates that interspecific predation is not a likely explanation for the rapid displacement of Ae. aegypti by Ae. albopictus in domestic containers in the southeastern United States.

Aedes↗
PubMed2006

Benzene oxidation under sulfate-reducing conditions in columns simulating in situ conditions.

The oxidation of benzene under sulfate-reducing conditions was examined in column and batch experiments under close to in situ conditions. Mass balances and degradation rates for benzene oxidation were determined in four sand and four lava granules filled columns percolated with groundwater from an anoxic benzene-contaminated aquifer. The stoichiometry of oxidized benzene, produced hydrogen carbonate and reduced sulfate correlated well with the theoretical equation for mineralization of benzene with sulfate as electron acceptor. Mean retention times of water in four columns were determined using radon ((222)Rn) as tracer. The retention times were used to calculate average benzene oxidation rates of 8-36 microM benzene day(-1). Benzene-degrading, sulfide-producing microcosms were successfully established from sand material of all sand filled columns, strongly indicating that the columns were colonized by anoxic benzene-degrading microorganisms. In general, these data indicate a high potential for Natural Attenuation of benzene under sulfate-reducing conditions at the field site Zeitz. In spite of this existing potential to degrade benzene with sulfate as electron acceptor, the benzene plume at the field site is much longer than expected if benzene would be degraded at the rates observed in the column experiment, indicating that benzene oxidation under sulfate-reducing conditions is limited in situ.

Benzene↗