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PubMed2002

Complete dechlorination of tetrachloroethene to ethene in presence of methanogenesis and acetogenesis by an anaerobic sediment microcosm.

An anaerobic consortium taken from brackish sediments, enriched by PCE/CH3OH sequential feeding, was capable of completely dechlorinating tetrachloroethene (PCE) to ethene (ETH). In batch experiments, PCE (0.5 mM) was dechlorinated to ethene (ETH) in approximately 75 h with either CH3OH or H2 as the electron donor. When VC (0.5 mM) was added instead of PCE it was dechlorinated without any initial lag by the PCE/CH3OH enriched consortium, although at a lower dechlorination rate. In batch tests H2 could readily replace CH3OH for supporting PCE dechlorination, with a similar PCE dechlorination rate and product distribution with respect to those observed with methanol. This indicates that H2 production during CH3OH fermentation was not the rate-limiting step of PCE or VC dechlorination. Acetogenesis was the predominant activity when methanol was present. A remarkable homoacetogenic activity was also observed when hydrogen was supplied instead of methanol.

Anaerobiosis↗

PubMed1998

Response of single species biofilms and microcosm dental plaques to pulsing with chlorhexidine.

The aim of this study was to determine the effect of pulsing chlorhexidine gluconate, at concentrations commonly used in mouthwashes, on Streptococcus sanguis biofilms and microcosm dental plaques in vitro. Biofilms were grown on bovine enamel and nutrients were supplied in the form of artificial saliva. Pulsing experiments were carried out on steady-state biofilms using 0.05 or 0.2% chlorhexidine solutions delivered twice daily for 1 min. In a separate study, the enamel discs on which the biofilms were formed were pre-treated with chlorhexidine and pulsed directly after inoculation and then at regular intervals. With both concentrations of chlorhexidine used, a c.2 log10 reduction in the viable counts of S. sanguis was achieved with the initial pulse, but as pulsing continued, the bacterial population recovered, albeit not to the previous level. A c.1 log10 reduction in the total viable counts of the microcosm plaques was seen after the first pulse with 0.2% chlorhexidine. The total count then recovered rapidly and, after the fifth pulse, the total viable counts were not significantly different from those before pulsing. The total counts then remained at a similar level throughout the course of the experimental runs. Pre-treatment of the enamel discs with 0.2% chlorhexidine before inoculation produced viable counts of c.10(5) cfu/mm2, a 1 log10 reduction compared with untreated discs. After pulsing with 0.2% chlorhexidine at 8 h, a 3 log10 reduction was seen in the total aerobic and anaerobic counts, but again the viable counts subsequently increased despite twice-daily chlorhexidine pulsing. Regardless of the nature of the biofilm, pulsing initially achieved substantial kills, but the viability of the biofilms subsequently increased despite continued pulsing. Chlorhexidine was effective at reducing the viability of microcosm plaques when it was applied to the substratum before exposure to bacteria and subsequently pulsed on to the biofilms.

Animals↗

PubMed2001

Transformation of 2,4,6-trinitrotoluene (TNT) by immobilized Phanerochaete chrysosporium under fed-batch and continuous TNT feeding conditions.

The cometabolic transformation of 2,4,6-trinitrotoluene (TNT) by an immobilized Phanerochaete chrysosporium culture was investigated under different TNT and/or glycerol feeding conditions in a 5-L reactor. In the fed-batch feeding mode, as a result of four spiking events at an average feeding rate of 20 mg TNT L(-1) d(-1) and 250 mg glycerol L(-1) d(-1), the initial TNT transformation rate and the glycerol uptake rate of the 7-day-old immobilized cell culture were 2.41 mg L(-1) h(-1) and 16.6 mg L(-1) h(-1), respectively. Thereafter, the TNT fed into the reactor depicted a negative effect on the cell physiology of P. chrysosporium, i.e., both rates decreased constantly. At 32 mg TNT L(-1) d(-1) feeding rate, also in the presence of glycerol (200 mg L(-1) d(-1)), this effect on the fungal cell metabolism was even more significant. When TNT was fed alone at 3.7 mg L(-1) d(-1), it showed an initial 0.75 mg L(-1) h(-1) rate of TNT transformation, i.e., one-third the initial level observed in the presence of glycerol. In contrast, in the continuous feeding mode (dilution rate, D = 0.11 d(-1)), at 5.5 mg TNT L(-1) d(-1) and 220 mg glycerol L(-1) d(-1), the immobilized cell culture exhibited a constant TNT transformation rate for cultivation periods of 50 and 61 days, under uncontrolled and controlled pH conditions, respectively. Thereafter, during the latter experiment, 100% TNT biotransformation was achieved at 1,100 mg L(-1) d(-1) glycerol feeding rate. Immobilized cells (115-day-old), sampled from a continuous TNT feeding experiment, mineralized [(14)C]-TNT to a level of 15.3% following a 41-day incubation period in a microcosm.

Bioreactors↗

PubMed1993

Plasmid DNA in a groundwater aquifer microcosm--adsorption, DNAase resistance and natural genetic transformation of Bacillus subtilis.

Prokaryotes can exchange chromosomal and plasmid genes via extracellular DNA in a process termed genetic transformation. This process has been observed in the test tube for several bacterial species living in the environment but it is not clear whether transformation occurs in natural bacterial habitats. A major constituent of terrestrial environments are solid particles such as quartz, silt and clay, which have considerable surface areas and which make up the solid-liquid interfaces of the habitat. In previous experiments the adsorption of DNA to chemically purified quartz and clay minerals was shown and the partial protection of adsorbed DNA against DNAase I. In a microcosm consisting of natural groundwater aquifer material (GWA) sampled directly from the environment and groundwater (GW) both linear duplex and supercoiled plasmid DNA molecules bound rapidly and quantitatively to the minerals. The divalent cations required to form the association were those present in the GWA/GW microcosm. The association was stable to extended elution over one week at 23 degrees C. Upon adsorption, the DNA became highly resistant against enzymatic degradation. About 1000 times higher DNAase I concentrations were needed to degrade bound DNA to the same extent as DNA dissolved in GW. Furthermore, chromosomal and plasmid DNA bound on GWA transformed competent cells of Bacillus subtilis. However, in contrast to DNA in solution, on GWA the chromosomal DNA was more active in transformation than the plasmid DNA. The studies also revealed that in the transformation of B. subtilis Mg2+ can be replaced by Na+, K+ or NH4+. The observations suggest that in soil and sediment environments, mineral material with inorganic precipitates and organic matter can harbour extracellular DNA leaving it available for genetic transformation.

Bacillus subtilis↗

PubMed1993

Natural Transformation of Acinetobacter calcoaceticus by Plasmid DNA Adsorbed on Sand and Groundwater Aquifer Material.

It is known that plasmid DNA and linear duplex DNA molecules adsorb to chemically purified mineral grains of sand and to particles of several clay fractions. It seemed desirable to examine whether plasmid DNA would also adsorb to nonpurified mineral materials taken from the environment and, particularly, whether adsorbed plasmid DNA would be available for natural transformation of bacteria. Therefore, microcosms consisting of chemically pure sea sand plus buffered CaCl(2) solution were compared with microcosms consisting of material sampled directly from a groundwater aquifer (GWA) plus groundwater (GW) with respect to the natural transformation of Acinetobacter calcoaceticus by mineral-associated DNA. The GWA minerals were mostly sand with inorganic precipitates and organic material plus minor quantities of silt and clay (illite and kaolinite). The amount of plasmid DNA which adsorbed to GWA (in GW) was about 80% of the amount which adsorbed to purified sand (in buffered CaCl(2) solution). Plasmid DNA adsorbed on sand transformed A. calcoaceticus significantly less efficiently than did plasmid DNA in solution. In contrast, the transformation by sand-adsorbed chromosomal DNA was as high as that by DNA in solution. In GWA/GW microcosms, the efficiency of transformation by chromosomal DNA was similar to that in sand microcosms, whereas plasmid transformation was not detectable. However, plasmid transformants were found at a low frequency when GWA was loaded with both chromosomal and plasmid DNA. Reasons for the low transformation efficiency of plasmid DNA adsorbed to mineral surfaces are discussed. Control experiments showed that the amounts of plasmid and chromosomal DNA desorbing from sand during incubation with a cell-free filtrate of a competent cell suspension did not greatly contribute to transformation in sand microcosms, suggesting that transformation occurred by direct uptake of DNA from the mineral surfaces. Taken together, the observations suggest that plasmid DNA and chromosomal DNA fragments which are adsorbed on mineral surfaces in a sedimentary or soil habitat may be available (although with different efficiencies for the two DNA species) for transformation of a naturally competent gram-negative soil bacterium.

Journal Article↗

PubMed2004

Analysis of methanotrophic bacteria in Movile Cave by stable isotope probing.

Movile Cave is an unusual groundwater ecosystem that is supported by in situ chemoautotrophic production. The cave atmosphere contains 1-2% methane (CH4), although much higher concentrations are found in gas bubbles that keep microbial mats afloat on the water surface. As previous analyses of stable carbon isotope ratios have suggested that methane oxidation occurs in this environment, we hypothesized that aerobic methane-oxidizing bacteria (methanotrophs) are active in Movile Cave. To identify the active methanotrophs in the water and mat material from Movile Cave, a microcosm was incubated with a 10%13CH4 headspace in a DNA-based stable isotope probing (DNA-SIP) experiment. Using improved centrifugation conditions, a 13C-labelled DNA fraction was collected and used as a template for polymerase chain reaction amplification. Analysis of genes encoding the small-subunit rRNA and key enzymes in the methane oxidation pathway of methanotrophs identified that strains of Methylomonas, Methylococcus and Methylocystis/Methylosinus had assimilated the 13CH4, and that these methanotrophs contain genes encoding both known types of methane monooxygenase (MMO). Sequences of non-methanotrophic bacteria and an alga provided evidence for turnover of CH4 due to possible cross-feeding on 13C-labelled metabolites or biomass. Our results suggest that aerobic methanotrophs actively convert CH4 into complex organic compounds in Movile Cave and thus help to sustain a diverse community of microorganisms in this closed ecosystem.

Carbon Radioisotopes↗

PubMed2002

Engineering bacterial competitiveness and persistence in the phytosphere.

Several tactics exist to improve the survival of an introduced microorganism of interest in the plant environment. One, derived from studies on the Agrobacterium-plant interaction and the role of opines in this interaction, proposes to promote growth of the inoculant in the plant environment via the establishment of a bias in the rhizosphere. It is supported by the occurrence of natural biases, such as those generated by opine-like molecules, by calestegins, or by mimosine. Opine-mediated biases have allowed several investigators to favor the growth of opine-degrading bacteria or communities under sterile or axenic environments or in microcosms mimicking near field conditions. Another way to favor a given microbe consists in impeding growth of competing microorganisms. Experiments performed using detergent or bacteriostatic agents as amendments under field or near field conditions yielded promising results. Research perspectives for engineering plant-microbe interactions also include specific engineering of predation and strategies designed to interfere with some of the signals perceived by the microbes, provided these signals control the expression of functions central to microbial fitness. In this respect, quorum-sensing signal molecules, such as N-acyl-homoserine lactones, may be valuable targets for the development of biocontrol agents and procedures.

Bacteria↗

PubMed1990

Volunteerism and community building in continuing care retirement communities.

In summary, CCRCs are arenas in which four types of natural helping and volunteerism occur. The CCRC may, therefore, be a microcosm of a community system, serving multiple functions in a campus setting. Volunteer program coordinators can benefit from the experiences of others, and research into helping patterns and the process of community building may provide insight as new CCRCs develop.

Aged↗

PubMed2006

Uncertainties in sediment erodibility estimates due to a lack of standards for experimental protocols and data interpretation.

Quantitative prediction of the erodibility of muds and mud-sand mixtures is, at present, seldom possible without resorting to direct measurements, preferably in situ. A variety of devices and protocols have been developed for erosion testing, but a considerable degree of uncertainty remains with regard to the accuracy and comparability of the resulting data. This paper argues that differences in experimental protocols and data analysis procedures are a major contributing factor to uncertainty in estimates of sediment erodibility. In particular, the likelihood of a time-dependent erosion rate response under typical erosion testing conditions means that the time history of applied forcing and the chosen protocols for analyzing and interpreting data directly affect derived erosion parameters. Several straightforward ways to address this problem are suggested, including standardization of experimental design and data analysis protocols, explicit recognition and adoption of appropriate erosion model(s), and allowing for potential time/depth changes in erodibility. Experimentalists should also archive and share erosion-test time series, not just derived parameters, so that data sets may be reanalyzed within a different framework if necessary. An example is presented from an intercomparison experiment between the Virginia Institute of Marine Sciences Sea Carousel and the University of Maryland Center for Environmental Science Microcosm System, carried out in the upper Chesapeake Bay (Maryland, USA) in May 2002. Derived parameters appear to be incompatible when the data are analyzed using different procedures, but real similarities and differences are readily apparent when the data are analyzed using the same procedures.

Conservation of Natural Resources↗

PubMed2002

Fate of 14C-chlorpyrifos in the tropical estuarine environment.

The distribution and fate of 14C-chlorpyrifos were investigated in microcosms simulating the conditions of the tropical estuarine environment of North Vietnam. The microcosms containing brackish water, sediment, clams (Meretrix meretrix) and green algae (Gracilaria verucosa) from the Red River estuary, were maintained for 30 days. The results show that chlorpyrifos released into the water was rapidly adsorbed onto sediment. However, only 1-2% of the initial amount of 14C-chlorpyrifos could be detected in the sediment by the end of the experiment. The accumulation of chlorpyrifos in fauna and flora attained, respectively, a maximum of 5.8% and 2.2% of the initial activity observed at days 3 and 2 after application. The compound 3,4,5-trichloro-2pyridinol (TCP) was the major transformation product of chlorpyrifos found in the microcosm. TCP accumulated in the clam's soft tissues, and, 3 days after application, reached a maximum of 0.5% of the total 14C-activity. The balance of the 14C-activity at the end of the experiment suggests that the main loss of the insecticide from the system was through volatilisation of chlorpyrifos and escape to the atmosphere. The persistence half-time of the compound in the aquatic microcosms was computed at 5 days.

Animals↗

PubMed2006

The impact of sampling techniques on soil pore water carbon measurements of an Icelandic Histic Andosol.

The carbon in soil pore water from a Histic Andosol from Western Iceland was studied at three different scales; in the field, in undisturbed outdoor mesocosms and in laboratory repacked microcosms. Pore water was extracted using suction cup lysimeters and hollow-fibre tube sampler devices (Rhizon samplers). There were significant differences in all measured variables, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and pH values between the scales of the experiment. Gaseous constituents of soil solution and pH were more susceptible to changes in scale and the type of sampling devices used. Dissolved inorganic carbon concentrations did not differ significantly between field and mesocosm solutions but where up to 14 times lower in microcosms compared to mesocosms solutions. Rhizon samplers yielded solutions with up to 4.7 times higher DIC concentrations than porous cup lysimeters. Mesocosm surface horizon DOC concentrations were 20 and 2 times higher than in field and microcosms respectively. There was difference in DOC concentration between sampling methods (up to 8 times higher in suction cups than rhizon samplers) above 50 cm depth. Soil solution pH values did not differ between field and mesocosms and mesocosms and microcosms respectively down to 80 cm depth. Direct comparison between field and microcosms was not possible due to the nature of sampling devices. Soil solutions sampled with Rhizon samplers yielded lower pH values (up to 1.3 pH units) than those sampled with suction cups. Twenty percent of annually bound organic carbon at the soils surface under field conditions was lost by leaching of DOC and through decomposition to DIC in disturbed non-vegetated microcosms. This percentage increased to 38% in undisturbed vegetated mesocosms highlighting the importance of surface vegetation in importing carbon to soils. Increased influx of nutrients will increase growth and photosynthesis but decrease carbon sequestration in near surface horizons. Although field studies considering long-term anthropogenic changes in pedogenesis require considerable experimental duration, more rapid experiments can be conducted with confidence in micro- and mesocosms as in this research.

Aluminum↗

PubMed1996

Experimental studies on the infectivity of non-culturable forms of Campylobacter spp. in chicks and mice.

The significance of non-culturable forms of Campylobacter spp., especially with regard to the epidemiology of this organism in poultry flocks, was explored. Two different experiments were conducted to produce non-culturable Campylobacter spp. and test their ability to colonize the animal gut. In the first experiment a mixture of 28 different strains of Campylobacter spp. from various sources was inoculated in both sterilized surface water and potassium phosphate buffer and stored at 4 degrees C. After Campylobacter spp. were no longer detectable by culture in the microcosms, the mixtures of non-culturable cells were used to challenge both chicks and mice. Recovery of non-culturable Campylobacter spp. from the animals was not successful at 4 weeks after administration. In the second experiment the survival of six individual strains of Campylobacter spp. in sterilized surface water at 4 degrees C was studied and the resulting non-culturable cells were used to challenge chicks. None of the campylobacter strains could be recovered from the chicks at 2 weeks after administration. We conclude that occurrence of non-culturable forms of Campylobacter spp. capable of colonizing chicks is not a common phenomenon and that non-culturable forms of Campylobacter spp. are likely to be insignificant for importantly to the epidemiology of the organism in Dutch broiler flocks.

Animals↗

PubMed2003

Solar inactivation of mesophilic Aeromonas by exogenous photooxidation in high-rate algal pond treating waste water.

AIMS: Investigations were carried out to observe the effect of sunlight on the survival of mesophilic Aeromonas (A. caviae, A. hydrophila and A. sobria) in high-rate algal pond. METHODS AND RESULTS: Light damage was estimated by loss of bacterial culturability, using simple beaker experiments. Survival of the strains studied under illuminated conditions was highly affected by the physico-chemical conditions within the microcosms. The inactivation of Aeromonas increased strongly as dissolved oxygen was increased, and was dependent on exogenous sensitizers. This process was enhanced by the high pH of water. Die-off of bacteria was prevented by adding catalase and pyruvate (H2O2 scavengers) into the microcosms. CONCLUSIONS: The damage of Aeromonas was mainly due to exogenous photooxidation. Hydrogen peroxide at least was involved in light-induced damage of bacteria. Aeromonas sobria appeared to be slightly less sensitive to photooxidation than A. hydrophila and A. caviae. SIGNIFICANCE AND IMPACT OF STUDY: The present study could explain the relative resistance of A. sobria to treatment in wastewater stabilization ponds.

Aeromonas↗

PubMed1992

Use of a novel plasmid to monitor the fate of a genetically engineered Pseudomonas putida strain.

Plasmid pSI30 was constructed to increase the sensitivity of detection of a genetically engineered micro-organism (GEM) and its recombinant DNA in environmental samples. This broad host-range, mobilizable plasmid contained chlorocatechol (clc) degradative genes, antibiotic resistance genes (ampicillin and kanamycin) and a fragment of eukaryotic DNA. The clc genes encode enzymes that convert 3-chlorocatechol to maleylacetic acid permitting the host, Pseudomonas putida RC-4, to grow on 3-chlorobenzoate. This catabolic phenotype was exploited using enrichment procedures to detect RC-4(pSI30) cells, free-living in the water column or when irreversibly bound to surfaces. The eukaryotic DNA sequence provided a unique target allowing positive identification by DNA:DNA hybridization. Using the eukaryotic DNA sequence as a probe, no transfer of the plasmid to indigenous bacteria was detected. Persistence of RC-4(pSI30) and its ability to multiply upon addition of 3-chlorobenzoate were demonstrated 78 days after its addition to natural freshwater. In flow-through microcosms RC-4(pSI30), undetectable as free-living cells, was found by enrichment as irreversibly bound sessile forms. These experiments revealed the stability of pSI30 and its utility in a 'combination' detection system for tracking the survival of a GEM and its DNA in environmental samples.

Biodegradation, Environmental↗

PubMed2006

Symbiotic bacteria as a determinant of plant community structure and plant productivity in dune grassland.

Symbiotic interactions are thought to play a key role in ecosystems. Empirical evidence for the impact of symbiotic bacteria on plant communities is, however, extremely scarce because of experimental constraints. Here, in three complementary experiments, we show that nitrogen-fixing rhizobia bacteria act as a determinant of plant community structure and diversity. Grassland microcosms inoculated with a mixture of rhizobia had a higher above-ground plant productivity (+35%), contained more nitrogen (+85%) and had significant higher community evenness (+34%) than control microcosms without rhizobia. Moreover, three of the four studied legume species required rhizobia to successfully coexist with other plant species. In contrast, the growth and survival of three grass and five forb species were not affected by the presence or absence of rhizobia. Finally, our results also showed that the legume species largely relied on symbiotically fixed nitrogen, both in the field and in the microcosms. This indicates that results in the microcosms are indicative for processes occurring in the field. It is concluded that symbiotic interactions between plants and prokaryotes can contribute to plant productivity, plant community structure and acquisition of limiting resources in legume-rich grassland communities.

Asteraceae↗

PubMedDate not supplied

Application of a slow-release fertilizer for oil bioremediation in beach sediment.

A 105-d field experiment was conducted to determine the potential of the slow-release fertilizer, Osmocote (Scotts, Marysville, OH), to stimulate the indigenous microbial biodegradation of petroleum hydrocarbons in an oil-spiked beach sediment on an intertidal foreshore in Singapore. Triplicate microcosms containing 80 kg of weathered sediment, spiked with 5% (w/w) Arabian light crude oil and 1.2% (w/w) Osmocote pellets, were established, together with control microcosms minus Osmocote. Relative to the control, the presence of the Osmocote sustained a significantly higher level of nutrients (NH(4)(+)-N, NO(3)(-)-N, and PO(4)(3-)-P) in the sediment pore water over the duration of the experiment. The metabolic activity of the indigenous microbial biomass, as measured using an intracellular dehydrogenase enzyme assay, was also significantly enhanced over the duration of the experiment in amended sediments. The loss of total recoverable petroleum hydrocarbons (TRPH) and biodegradation of total n-alkanes (C(10)-C(33)), branched alkanes (pristane and phytane), as well as total target polycyclic aromatic hydrocarbons (PAHs) (two- to six-ring), in both the control and Osmocote-amended sediments, followed a first-order biodegradation model. The first-order loss rate of total recoverable petroleum hydrocarbons was 2.57 times greater than that of the control. The hopane-normalized rate constants for total n-alkane, branched alkane, and total target PAH biodegradation in the Osmocote-treated sediments were 3.95-, 5.50-, and 2.45-fold higher than the control, respectively. Overall, the presence of Osmocote was able to significantly enhance and accelerate the biodegradation of aliphatics and PAHs in oil-contaminated sediments under natural field conditions in an intertidal foreshore environment.

Biodegradation, Environmental↗

PubMed2000

Determination of metabolic activity of streptomycetes in soil microcosms.

Two Streptomyces griseus strains were isolated from different soil types. S. griseus CAG17 strain was isolated from an agricultural area with low organic matter but rich in phosphorus content and S. griseus 26K strain was isolated from a forest area rich in organic matter with a low phosphorus content. The survival and metabolic activity of these isolates were studied in dynamic sterile soil microcosm systems. The fitness of each isolate was studied by re-inoculation in a soil type different from its origin. Maximum percentage of germination and respiration rates occurred within the first 48 h after each soil turnover (removal and addition of certain soil volumes). Data suggested that S. griseus CAG17 survived better independently of the soil type in comparison with S. griseus 26K which sporulated within the first 12 h after inoculation. Incubation temperatures did affect the lifecycles in relation to soil type. For example, the lowest temperature tested, 22 degrees C, was more favourable for extended germination and adaptation in general but revealed lesser spore numbers in the 'foreign' soil environment. Monitoring metabolic activity by estimation of urease, phosphatases and dehydrogenase-specific activities, between 18 and 35 degrees C incubation temperatures, was a reliable method for studying the survival and growth of streptomycete populations in soil. Results also confirmed that respiration rate and enzyme-specific activity corresponded with spore counts in long-term experiments which were designed for the investigation of survival and growth of S. griseus CAG17. Under selective pressure by heavy metals, in soil microcosm systems, metabolic activity proved a useful tool for the investigation of streptomycete activity. These methods could also be applied in agricultural field studies for monitoring microbial populations under conditions where various 'pollutants' are present in soil samples.

Colony Count, Microbial↗

PubMed2001

Use of green fluorescent protein and luciferase biomarkers to monitor survival and activity of Arthrobacter chlorophenolicus A6 cells during degradation of 4-chlorophenol in soil.

The recently isolated novel species Arthrobacter chlorophenolicus A6 is capable of growth on and degradation of high concentrations of 4-chlorophenol (up to 350 microg ml(-1)) as the sole carbon and energy source. This strain shows promise for bioremediation of environmental sites contaminated with high levels of chlorophenols. In this study, green fluorescent protein (gfp) or luciferase (luc) genes were used as biomarkers for monitoring cell number and activity, respectively, during degradation of 4-chlorophenol by A. chlorophenolicus cells. The individual marked strains, Arthrobacter chlorophenolicus A6L (luc-tagged) and Arthrobacter chlorophenolicus A6G (gfp-tagged), were monitored during degradation of 250 microg ml(-1) 4-chlorophenol in pure culture and 175 microg g(-1) 4-chlorophenol in soil microcosms. Both gene-tagged strains were capable of cleaning up the contaminated soil during 9 d incubation. During the bioremediation experiments, the luc-tagged cells were monitored using luminometry and the gfp-tagged cells using flow cytometry, in addition to selective plate counting for both strains. The cells remained at high population levels in the soil (evidenced by GFP-fluorescent cell counts) and the A. chlorophenolicus A6L population was metabolically active (evidenced by luciferase activity measurements). These results demonstrate that the Arthrobacter chlorophenolicus A6 inoculum is effective for cleaning-up soil containing high concentrations of 4-chlorophenol.

Arthrobacter↗