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The increasing use of silver nanoparticles (AgNPs) due to its excellent antimicrobial activity in commercial products prompting concerns about their fate in the environment. The toxicity of AgNPs is mainly the result of Ag+ ions. In this study, soil was experimentally contaminated with 100 mg kg-1 of AgNO3 to investigate its effect on fungal soil community. Deoxyribonucleic acid (DNA) from the soil was extracted at the 6th, 12th, and 24th month of observation and assessed by Illumina Next Generation Sequencing (NGS). The results show that, the pollutant change fungal community in soil. After 12 months incubated the number of fungal species in the soil reduced significantly and 40% of the community was dominated by one species.

Current non-invasive biomonitoring techniques to measure heavy metal exposure in free ranging birds using eggs, feathers and guano are problematic because essential metals copper (Cu) and zinc (Zn) deposited in eggs and feathers are under physiological control, feathers accumulate metals from surface contamination and guano may contain faecal metals of mixed bioavailability. This paper reports a new technique of measuring lead (Pb), Cu and Zn in avian urate spheres (AUS), the solid component of avian urine. These metal levels in AUS (theoretically representing the level of metal taken into the bloodstream, i.e. bioavailable to birds) were compared with levels in eggs (yolk and shell), feathers and whole guano from chickens (Gallus gallus domesticus) exposed to a heavy metal-contaminated soil (an allotment soil containing Pb 555 mg kg−1 dry mass (dm), Cu 273 mg kg−1 dm and Zn 827 mg kg−1 dm). The median metal levels (n = 2) in AUS from chickens exposed to this contaminated soil were Pb 208 μg g−1 uric acid, Cu 66 μg g−1 uric acid and Zn: 526 μg g−1 uric acid. Lead concentrations in egg yolk and shell samples (n = 3) were below the limit of detection (

In this study, three different soils with contrasting features, spiked with 300 mg benzo[a]pyrene (BaP)/kg dry soil, were incubated at 20 °C and 60% water holding capacity for 540 days. At different time points, BaP and DNA were extracted and quantified, and DNA adducts were quantified by 32P-postlabelling. After 540 days incubation, 69.3, 81.6 and 83.2% of initial BaP added remained in Cruden Bay, Boyndie and Insch soils, respectively. Meanwhile, a significantly different amount of DNA–BaP adducts were found in the three soils exposed to BaP over time. The work demonstrates the concept that DNA adducts can be detected on DNA extracted from soil. Results suggest the technique is not able to directly reflect bioavailability of BaP transformation products. However, this new method provides a potential way to detect mutagenic compounds in contaminated soil and to assess the outcomes of soil remediation.

A study of soil polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/F) concentrations was undertaken in the vicinity of a municipal solid waste incinerator (MSWI) in Newcastle upon Tyne as a result of concerns raised by local residents about potential contamination from fugitive and stack emissions. The study area was divided into four sectors (north-east (NE), south-east (SE), north-west (NW) and south-west (SW)) around the MSWI, and sampling sites were located up to a distance of 2.25 km. Based on air dispersion modelling, the sampling density was four times greater in the NE (downwind) sector compared to the SW (upwind) direction, and twice as great in the NW and SE sectors. PCDD/F concentrations found in soil samples ranged from 6 to 1911 ng I-TEQ/kg DW with a median of 32 ng I-TEQ/kg DW. There was no evidence of elevated concentrations downwind of the MSWI compared to other directions, nor of any trend in concentration at increasing distance from the MSWI. We concluded, therefore, that the MSWI fugitive and stack emissions were not a major source of PCDD/F contamination. Analysis of PCDD/F homologue profiles showed that samples exhibiting furan-dominated and OCDD-dominated profiles and a profile characteristic of the MSWI ash occurred in distinct clusters. Those samples showing the furan-dominated profile had the largest PCDD/F concentrations measured as I-TEQ, followed by samples with the incinerator profile, the deposition profile, and the OCDD-dominated profile. We identified some contamination hotspots located in the SW and SE sampling sectors (upwind of the MSWI), and potential sources for these hotspots were sought by using historic land use data from maps of the locality dating back to 1856. We concluded that the cluster of very high concentrations of PCDD/F in soils showing the furan homologue profile were most likely to have resulted from the disposal of graphite electrode sludges from brine electrolysis carried out at a chemical works between the 1890s and the 1930s.

The potential of using ozone for the removal of phenanthrene from several different soils, both alone and in combination with biodegradation using a microbial inoculant (Pseudomonas alcaligenes PA-10), was examined. The greater the water content of the soil the less effective the ozone treatment, with air-dried soils showing the greatest removal of phenanthrene; while soils with higher levels of clay also reduced the effectiveness of the ozone treatments. However, at least a 50% reduction in phenanthrene levels was achieved in air-dried soil after an ozone treatment of 6 h at 20 ppm, with up to 85% removal of phenanthrene achieved in sandy soils. The biodegradation results indicate that P. alcaligenes PA-10 may be useful as an inoculant for the removal of PAHs from contaminated soils. Under the conditions used in our experiments, however, pre-ozonation did not enhance subsequent biodegradation of phenanthrene in the soils. Similar levels of phenanthrene removal occurred in both non-ozonated and ozonated Cruden Bay soil inoculated with P. alcaligenes PA-10. However, the biodegradation of phenanthrene in ozonated Boyndie soil was much slower. This may be due to the release of toxic products in this soil during ozonation.

Benzo[a]pyrene (BaP) is a significant environmental pollutant and rapid, accurate methods to quantify this compound in soil for both research and environmental investigation purposes are required. In this work, solvent extracts from five contrasting soils spiked with four different polycyclic aromatic hydrocarbons (PAHs) were rapidly analysed by using a synchronous fluorescence spectroscopy (SFS) method. The SFS method was validated using HPLC with ultraviolet detection. A good correlation for the quantification of BaP in soil extracts by the two methods was observed. The detection limit of the SFS method was 1.6 x 10(-9) g/ml in CTAB micellar medium (7.8 mmol/l). The work demonstrates that SFS has potential as a sensitive, accurate, rapid, simple and economic methodology and an efficient alternative to HPLC for fast confirmation and quantification of BaP in complex soil extracts.

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds that have accumulated in the natural environment mainly as a result of anthropogenic activities such as the combustion of fossil fuels. Interest has surrounded the occurrence and distribution of PAHs for many decadesdue to their potentially harmful effects to human health. This concern has promptedresearchers to address ways to detoxify/remove these organic compounds from the natural environment. Bioremediation is one approach that has been used to remediate contaminated land and waters, and promotes the natural attenuation of the contaminants using the in situ microbial community of the site. This review discusses the variety of fungi and bacteria that are capable of these transformations, describes the major aerobic and anaerobic breakdown pathways, and highlights some of the bioremediation technologies that are currently available.  2005 Society of Chemical Industry

DDT [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] is a major environmental pollutant and economical methods to remove DDT from the environment are required. In this work we used seaweed (dried and ground) to enhance DDT transformation in waterlogged soils. Initial daily rates of DDT biodegradation increased in the following order relating to the percentage by weight of added seaweed to soil 0.5 > 1 > 0 > 3 > 5 > 13 (w/w). The actual percentages of DDT biodegradation occurring within 6 weeks were 80, 64, 60, 50, 40 and 34 respectively. During soil incubation DDD [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] was the major metabolite found with small amounts of DDE [1,1,1-trichloro-2,2-bis (p-chlorophenyl) ethane] produced. The maximum amount of 4,4′-dichlorobenzophenone (DBP) (2.5%) produced was found in soil amended with 0.5% (w/w) seaweed, indicating that further degradation of DDD occurred. High levels of dissolved organic carbon (DOC), between 309 and 509 mg kg−1 soil, were present in soil amended with 3–13% (w/w) seaweed immediately after seaweed addition. It is possible that the high levels of DOC in soils amended with larger amounts of seaweed significantly retarded DDT biodegradation, possibly due to binding of DDT to DOC and subsequently decreasing the bioavailability of DDT to soil microbes. Copyright © 2004 Society of Chemical Industry

This study was conducted to assess whether the addition of exogenous nutrients and bioaugmentation by arsenic (As) methylating fungi could accelerate the rate of As volatilisation in cattle dip soils containing mixed As and DDT contamination. Increasing levels of manure application resulted in a greater loss of As from contaminated soils [30% (w/w) > 15% (w/w) > 5% (w/w) manure]. Loss of As was more pronounced at 75% of field capacity than at 35% of field capacity. The supplement of 30% (w/w) manure at 75% field capacity exerted the greatest reduction of As (8.3% loss of total As) in a contaminated dip soil containing 1390 mg As kg −1 and 194 mg DDT kg −1 over a 5-month incubation. The rates of As loss and microbial respiration (CO 2 production) were correlated with the levels of manure amendment ( P ≤0.05). Augmentation by As methylating fungi ( Penicillium sp. and Ulocladium sp.) was able to enhance arsine evolution rates in field contaminated soils and in freshly spiked soils. The amounts of arsine dissipated in augmented long-term contaminated soils and soils spiked with As alone were 3.7 and 8.3 orders of magnitude greater than uninoculated soils, respectively. DDT appears to inhibit the rates of microbial formation of arsine in the contaminated dip soils.

This work examined the effect of long-term arsenic (As) and DDT contamination on soil microbial properties at 11 cattle dip sites in northern New South Wales, Australia. Total As in the surface (0-10 cm) soils from these sites ranged from 34 to 2941 mg As kg(-1) soil and hexane-extractable DDT concentrations ranged between 2.9 and 7673 mg DDT kg(-1) soil. The concentrations of water and oxalate-extractable As were positively correlated with total As. Oxalate-extractable As was more strongly correlated (r(2)=0.87) with total As than water-extractable As (r(2)=0.34). A weak positive relationship was observed between the level of nutrient (organic carbon and nitrogen) and microbial biomass C (r(2)=0.61 and 0.45, respectively). There was a highly significant difference between the microbial properties of polluted and unpolluted sites (P0.001). In comparison to unpolluted soils, fungal counts, microbial biomass C, and respiration were dramatically reduced (P0.05) in polluted soils. However, the bacterial population between polluted and unpolluted soils were not different (P0.05). The results of this study suggested that (a) long-term contamination of soils adjacent to former cattle dipping sites by As and DDT adversely affected soil microbial properties with the fungal populations being the most sensitive and (b) there was little regeneration of microbiota despite 25 years of field ageing of the soils.

Soil metal contamination is an international problem and there is a recognised need for methods to detect the effects of such pollution. To this end, we investigated the use of soil protein extraction, quantification and expression as indicators of cadmium contamination of soil. A variety of methods to extract total soil protein were examined and the effects of cadmium and lime treatment on total soil protein, protein expression and microbial biomass were determined. A simple snap freeze protein extraction technique (using liquid nitrogen) was found to extract the most protein from soil samples compared to a bead beating method used commonly for DNA extraction from soil. Using the snap freeze method, cadmium (Cd) contamination was observed to significantly decrease total soil protein levels compared to an uncontaminated control soil (16 μg g−1 cf. 24 μg g−1) whilst liming significantly increased total soil protein in the control and contaminated treatments (35 and 22 μg g−1). These results were related to similar, but less pronounced, changes in microbial biomass in Cd contaminated and limed control soils. Limed Cd contaminated soils had similar amounts of total soil protein to unlimed control soils. The protein profiles (SDS-PAGE) of extracted soil protein from control and cadmium contaminated soils concentrated by both acetone precipitation and heating showed no obvious changes in protein expression between treatments. However, large amounts of presumably low molecular weight proteins (

With greater understanding of microbial diversity and the development of bioengineering, bioremediation is taking its place as a cost-effective technique in integrated environmental restoration efforts. The major reasons for the control of water and soil pollution and the consideration of bioremediation are first and foremost, public health concerns; second, environmental conservation; and finally, the cost of decontamination. A major aim of bioremediation, or any other remediation technology, must be the reduction of toxicity associated with the environmental contaminant, that is, the abatement of environmental impact. Bioremediation solutions can be used to reduce the impacts of environmental persistence of contaminants and thus to alleviate problems associated with chronic toxicity. The broadest classification of environmental pollutants is into two categories: organic and inorganic. Quantitatively, the organic pollutants of most concern are the hydrocarbons in their various forms. The most common are petroleum hydrocarbons, chlorinated solvents, surfactants, biocides, and a host of other compounds specific to particular industries, e.g., nitroaromatics from munitions. Fortunately, many of these pollutants are biodegradable by microorganisms in soils and waters. The biodegradability of environmental pollutants, and hence the degree of persistence of contaminants in natural environments, is influenced by various factors, most important of which are the chemical structure of the contaminant, the presence of a viable microbial population able to degrade the contaminant(s), and environmental conditions suitable for microbial biodegradative activities.

Bioremediation is recognised as an economically viable method to treat contaminated soil and the use of microbial inoculants, in particular, white-rot fungi, has been proposed to enhance the remediation process. During bioremediation, a variety of pollutant transformation products will be created which may have toxic synergistic interactions and may not at all be detected by chemical analysis. This work examined the potential for formation of toxic breakdown products during pentachlorophenol (PCP) transformation in soil after inoculation with Phanerochaete chrysosporium ; a frequently used fungal inoculant. To monitor toxicity during bioremediation, changes in soil dehydrogenase activity and effects of soil methanol extracts on the growth of a common soil bacterium Bacillus megaterium in liquid culture were determined. After 6 weeks of remediation, soil PCP levels had dropped from an initial 250 mg kg −1 to 2 mg kg −1 , and inoculation with P. chrysoporium did not improve PCP remediation over uninoculated PCP-contaminated soil. Soil dehydrogenase activity remained very low in all soils containing PCP and did not recover throughout the experiment (6 weeks) despite the decrease in PCP levels. Soil methanol extracts varied in their toxicity towards growth of B. megaterium and were most toxic after 6 weeks incubation when extracts obtained from PCP-contaminated soil inoculated with P. chrysosporium completely inhibited B. megaterium . A longer incubation time would probably result in removal of toxic products and as soil methanol extracts were used in growth inhibition studies, the bioavailability of these toxic compounds remains in question. However, this work indicates that toxic transformation products may be formed during bioremediation and that ecotoxicological assays are useful to complement chemical analysis during bioremediation of contaminated soil.

Petroleum hydrocarbons are widespread environmental pollutants. Although biodegradation of petroleum hydrocarbons has been the subject of numerous investigations, information on their toxicity to microorganisms in soil is limited, with virtually no work conducted on soil algae. We carried out a screening experiment for total petroleum hydrocarbons (TPH) and their toxicity to soil algal populations, microbial biomass, and soil enzymes (dehydrogenase and urease) in a long-term TPH-polluted site with reference to an adjacent unpolluted site. Microbial biomass, soil enzyme activity, and microalgae declined in medium to high-level (5,200-21,430 mg kg(-1) soil) TPH-polluted soils, whereas low-level (2,120 mg kg(-1) soil) pollution stimulated the algal populations and showed no effect on microbial biomass and enzymes. However, inhibition of all the tested parameters was more severe in soil considered to have medium-level pollution than in soils that were highly polluted. This result could not be explained by chemical analysis alone. Of particular interest was an observed shift in the species composition of algae in polluted soils with elimination of sensitive species in the medium to high polluted soils. Also, an algal growth inhibition test carried out using aqueous eluates prepared from polluted soils supported these results. Given the sensitivity of algae to synthetic pollutants, alteration in the algal species composition can serve as a useful bioindicator of pollution. The results of this experiment suggest that chemical analysis alone is not adequate for toxicological estimations and should be used in conjunction with bioassays. Furthermore, changes in species composition of algae proved to be more sensitive than microbial biomass and soil enzyme activity measurements.

Fenamiphos is a commonly and widely used nematicide and insecticide in agriculture but information on its effects on microorganisms in soil is scarce. The microbial role in the persistence of fenamiphos in soil was determined by comparing the relative rate of its degradation in autoclaved and unautoclaved soil. Nearly 80% of added fenamiphos disappeared in unautoclaved soil during a 20-day incubation. In autoclaved soil incubated under similar conditions the recovery of fenamiphos was about 91%. This indicates the involvement of microorganisms in the degradation of this compound. Fenamiphos in general was not toxic to the soil algal community and soil enzymes (dehydrogenase, phosphatase and β-glucosidase). Therefore fenamiphos at field application rates may not endanger non-target microorganisms and their activities in soil.

Concern from local residents about possible contamination with metals and PCDD/F (dioxins and furans) from fugitive and stack emissions from the Byker municipal solid waste incinerator in Newcastle upon Tyne led the City Council to initiate a study of the concentration of these pollutants in soils. We report here the results for the metals and arsenic. Soils were sampled at distances up to 2.25 km from the incinerator stack. The intensity of sampling in concentric zones was four times greater in the northeast (down-wind) direction, and twice as great in the northwest and southeast directions, compared to the southwest (up-wind) direction. In total 163 samples were collected and analyzed for total As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Concentrations were generally elevated above background levels, but were typical of those found in other urban areas. For As, Cd, Cu, Hg, Pb, and Zn, contamination hotspots were identified. These were spread throughout the sampling area, and there was no evidence of greater concentrations down-wind of the incinerator compared to other directions, nor of any trend in concentration at increasing distance from the incinerator. We concluded that metal contamination resulting from the incinerator could not be detected in an environment with generally elevated concentrations. Potential sources for many of the hotspots of contamination were identified in a survey of historic land use based on maps of the locality dating back to 1856. Detailed investigations of particular areas with serious contamination will now be undertaken by the local authorities using the CLEA (Contaminated Land Exposure Assessment) model.

We investigated the phospholipid fatty acid (PLFA) pattern and dehydrogenase activity (DHA) in soil samples from three sites (designated as low, medium, and high based on the level of chromium) in a long-term (25 years after last waste input) tannery waste-contaminated area rich in Cr. Soil samples, collected from different soil depths (0-100 cm), at each site were used in this study. In general, soil samples from all three contaminated sites had elevated pH, electrical conductivity, organic carbon (OC), total Cr, and hexavalent Cr [Cr(VI)]. The maximum total Cr concentration in surface soils (0-10 cm) at the highly contaminated site was 102 gkg(-1), with 4.6 mgkg(-1) present as the bioavailable water-soluble Cr. More than 50% of soluble Cr was in the form of Cr(VI) (2.7 mgkg(-1)). DHA (normalized to OC) was inhibited to a greater extent in soil samples from the highly contaminated site than in low- and medium-contaminated soil samples. PLFA analyses of surface soils indicated that there was a shift in PLFA patterns. PLFAs specific for bacteria (i15:0, a15:0, 15:0, i16:0, a17:0, and cy17:0) decreased significantly (P

Introduction Laboratory-based studies have shown that fungi are able to degrade a wide range of organic pollutants (see other chapters) and have great potential for use as inoculants to remediate contaminated soil. However, soil is a heterogeneous environment and it is to be expected that experiments using fungal inocula to remove pollutants will show varying degrees of success. For example, soil environmental conditions such as pH, nutrient and oxygen levels may not be optimal for fungal growth or for activity of the fungal extracellular enzymes involved in pollutant transformation. In addition, results from laboratory studies on fungal transformation of persistent organic pollutants (POPs) carried out under optimal conditions in nutritionally defined liquid media are likely to be different from those obtained in the soil environment. Despite this, fungi have been shown to transform a wide variety of POPs in soil and have been used on a large scale to remediate contaminated sites (Lamar et al ., 1994). This chapter will first highlight some important issues faced by researchers when using fungi for soil remediation, provide a critical review of previous work concerning fungal transformation of organic pollutants in soil, and then discuss actual field studies using fungal inocula to remediate contaminated soil. Throughout this chapter ‘pollutant’ refers to persistent organic pollutants only.

One DDT-contaminated soil and two uncontaminated soils were used to enumerate DDT-resistant microbes (bacteria, actinomycetes and fungi) by using soil dilution agar plates in media either with 150 mug DDT ml(-1) or without DDT at different temperatures (25, 37 and 55 degreesC). Microbial populations in this study were significantly (p actinomycetes>bacteria. Bacteria from contaminated soil were more resistant to DDT than bacteria from uncontaminated soils. Microbes isolated at different temperatures also demonstrated varying degrees of DDT resistance. For example, bacteria and actinomycetes isolated at all incubation temperatures were sensitive to DDT. Conversely fungi isolated at all temperatures were unaffected by DDT. (C) 2001 Elsevier Science B.V. All rights reserved.

DDT (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane) and its principle metabolites, DDE (1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene) and DDD (1,1-dichloro-2,2-bis(p-chlorophenyl)ethane) are widespread environmental contaminants but little information is available concerning their effects on non-target microflora (especially microalgae and cyanobacteria) and their activities in long-term contaminated soils. For this reason a long-term DDT-contaminated soil was screened for DDT residues and toxicity to microorganisms (bacteria, fungi, algae), microbial biomass and dehydrogenase activity. Also, five pure cultures isolated from various sites (two unicellular green algae and three dinitrogen-fixing cyanobacteria) were tested for their ability to metabolise DDT. Viable counts of bacteria and algae declined with increasing DDT contamination while fungal counts, microbial biomass and dehydrogenase activity increased in medium-level contaminated soil (27 mg DDT residues kg(-1) soil). All the tested parameters were greatly inhibited in high-level contaminated soil (34 mg DDT residues kg(-1) soil). Species composition of algae and cyanobacteria was altered in contaminated soils and sensitive species were eliminated in the medium and high contaminated soils suggesting that these organisms could be useful as bioindicators of pollution. Microbial biomass and dehydrogenase activity may not serve as good bioindicators of pollution since these parameters were potentially influenced by the increase in fungal (probably DDT resistant) counts. All the tested algal species metabolised DDT to DDE and DDD; however, transformation to DDD was more significant in the case of dinitrogen-fixing cyanobacteria.

Pentachlorophenol (PCP), a major industrial chemical, has been extensively used throughout the world as a pesticide and general biocide in agriculture and industry. The worldwide production of PCP was estimated to be 5 x 10 7 kg by 1983 (Crosby et al. 1981). The major use of PCP (about 80%) was as a timber preservative and it has been estimated that there were over 500 wood preserving operations in the United States utilizing about 36 million kg PCP (Cirelli 1978). As a consequence of high usage and persistence, PCP is still found as a major global pollutant in the soils around timber treatment facilities. PCP has been listed as a priority pollutant by the US Environmental Protection Agency (Keith and Telliard 1979). Given the toxicity of PCP and the global distribution of PCP contamination it is important to examine the effects of the compound on soil microorganisms and essential soil functions.

Soil contamination by silver nanoparticles (AgNP) is of potential environmental concern but little work has been carried out on the effect of such contamination on ectomycorrhizal fungi (EMF). EMF are essential to forest ecosystem functions as they are known to enhance growth of trees by nutrient transfer. In this study, soil was experimentally contaminated with AgNP (0, 350 and 790 mg Ag/kg) and planted with Bishop pine seedlings. The effect of AgNP was subsequently measured, assessing variation in pine growth and ectomycorrhizal diversity associated with the root system. After only 1 month, the highest AgNP level had significantly reduced the root length of pine seedlings, which in turn had a small effect on above ground plant biomass. However, after 4 months growth, both AgNP levels utilised had significantly reduced both pine root and shoot biomass. For example, even the lower levels of AgNP (350 mg Ag/kg) soil, reduced fresh root biomass by approximately 57 %. The root systems of the plants grown in AgNP-contaminated soils lacked the lateral and fine root development seen in the control plants (no AgNP). Although, only five different genera of EMF were found on roots of the control plants, only one genus Laccaria was found on roots of plants grown in soil containing 350 mg AgNP/kg. At the higher levels of AgNP contamination, no EMF were observed. Furthermore, extractable silver was found in soils containing AgNP, indicating potential dissolution of silver ions (Ag+) from the solid AgNP. Electronic supplementary material The online version of this article (doi:10.1007/s11051-015-3246-4) contains supplementary material, which is available to authorised users.

Bioremediation is a potential option to treat 1, 1, 1-trichloro-2, 2-bis (4-chlorophenyl) ethane (DDT) contaminated sites. In areas where suitable microbes are not present, the use of DDT resistant microbial inoculants may be necessary. It is vital that such inoculants do not produce recalcitrant breakdown products e.g. 1, 1-dichloro-2, 2-bis (4-chlorophenyl) ethylene (DDE). Therefore, this work aimed to screen DDT-contaminated soil and compost materials for the presence of DDT-resistant microbes for use as potential inoculants. Four compost amended soils, contaminated with different concentrations of DDT, were used to isolate DDT-resistant microbes in media containing 150 mg l−1 DDT at three temperatures (25, 37 and 55°C). In all soils, bacteria were more sensitive to DDT than actinomycetes and fungi. Bacteria isolated at 55°C from any source were the most DDT sensitive. However DDT-resistant bacterial strains showed more promise in degrading DDT than isolated fungal strains, as 1, 1-dichloro 2, 2-bis (4...