Addition of allochthonous fungi to a historically contaminated soil affects both remediation efficiency and bacterial diversity

Bioaugmentation of Native Fungi, an Efficient Strategy for the Bioremediation of an Aged Industrially Polluted Soil With Heavy Hydrocarbons

The concurrence of structurally complex petroleum-associated contaminants at relatively high concentrations, with diverse climatic conditions and textural soil characteristics, hinders conventional bioremediation processes. Recalcitrant compounds such as high molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) and heavy alkanes commonly remain after standard soil bioremediation at concentrations above regulatory limits. The present study assessed the potential of native fungal bioaugmentation as a strategy to promote the bioremediation of an aged industrially polluted soil enriched with heavy hydrocarbon fractions. Microcosms assays were performed by means of biostimulation and bioaugmentation, by inoculating a defined consortium of six potentially hydrocarbonoclastic fungi belonging to the genera Penicillium, Ulocladium, Aspergillus, and Fusarium, which were isolated previously from the polluted soil. The biodegradation performance of fungal bioaugmentation was compared with soil biostimulation (water and nutrient addition) and with untreated soil as a control. Fungal bioaugmentation resulted in a higher biodegradation of total petroleum hydrocarbons (TPH) and of HMW-PAHs than with biostimulation. TPH (C14-C35) decreased by a 39.90 ± 1.99% in bioaugmented microcosms vs. a 24.17 ± 1.31% in biostimulated microcosms. As for the effect of fungal bioaugmentation on HMW-PAHs, the 5-ringed benzo(a)fluoranthene and benzo(a)pyrene were reduced by a 36% and 46%, respectively, while the 6-ringed benzoperylene decreased by a 28%, after 120 days of treatment. Biostimulated microcosm exhibited a significantly lower reduction of 5- and 6-ringed PAHs (8% and 5% respectively). Higher TPH and HMW-PAHs biodegradation levels in bioaugmented microcosms were also associated to a significant decrease in acute ecotoxicity (EC50) by Vibrio fischeri bioluminiscence inhibition assays. Molecular profiling and counting of viable hydrocarbon-degrading bacteria from soil microcosms revealed that fungal bioaugmentation promoted the growth of autochthonous active hydrocarbon-degrading bacteria. The implementation of such an approach to enhance hydrocarbon biodegradation should be considered as a novel bioremediation strategy for the treatment of the most recalcitrant and highly genotoxic hydrocarbons in aged industrially polluted soils.

Ecology of Contaminant Biotransformation in the Mycosphere: Role of Transport Processes

Fungi and bacteria often share common microhabitats. Their co-occurrence and coevolution give rise to manifold ecological interactions in the mycosphere, here defined as the microhabitats surrounding and affected by hyphae and mycelia. The extensive structure of mycelia provides ideal "logistic networks" for transport of bacteria and matter in structurally and chemically heterogeneous soil ecosystems. We describe the characteristics of the mycosphere as a unique and highly dynamic bacterial habitat and a hot spot for contaminant biotransformation. In particular, we emphasize the role of the mycosphere for (i) bacterial dispersal and colonization of subsurface interfaces and new habitats, (ii) matter transport processes and contaminant bioaccessibility, and (iii) the functional stability of microbial ecosystems when exposed to environmental fluctuations such as stress or disturbances. Adopting concepts from ecological theory, the chapter disentangles bacterial-fungal impacts on contaminant biotransformation in a systemic approach that interlinks empirical data from microbial ecosystems with simulation data from computational models. This approach provides generic information on key factors, processes, and ecological principles that drive microbial contaminant biotransformation in soil. We highlight that the transport processes create favorable habitat conditions for efficient bacterial contaminant degradation in the mycosphere. In-depth observation, understanding, and prediction of the role of mycosphere transport processes will support the use of bacterial-fungal interactions in nature-based solutions for contaminant biotransformation in natural and man-made ecosystems, respectively.

Overview on the Biochemical Potential of Filamentous Fungi to Degrade Pharmaceutical Compounds

Pharmaceuticals represent an immense business with increased demand due to intensive livestock raising and an aging human population, which guarantee the quality of human life and well-being. However, the development of removal technologies for these compounds is not keeping pace with the swift increase in their use. Pharmaceuticals constitute a potential risk group of multiclass chemicals of increasing concern since they are extremely frequent in all environments and have started to exhibit negative effects on micro- and macro-fauna as well as on human health. In this context, fungi are known to be extremely diverse and poorly studied microorganisms despite being well suited for bioremediation processes, taking into account their metabolic and physiological characteristics for the transformation of even highly toxic xenobiotic compounds. Increasing studies indicate that fungi can transform many structures of pharmaceutical compounds, including anti-inflammatories, β-blockers, and antibiotics. This is possible due to different mechanisms in combination with the extracellular and intracellular enzymes, which have broad of biotechnological applications. Thus, fungi and their enzymes could represent a promising tool to deal with this environmental problem. Here, we review the studies performed on pharmaceutical compounds biodegradation by the great diversity of these eukaryotes. We examine the state of the art of the current application of the Basidiomycota division, best known in this field, as well as the assembly of novel biodegradation pathways within the Ascomycota division and the Mucoromycotina subdivision from the standpoint of shared enzymatic systems, particularly for the cytochrome P450 superfamily of enzymes, which appear to be the key enzymes in these catabolic processes. Finally, we discuss the latest advances in the field of genetic engineering for their further application.

Mycoremediation of hydrocarbons with basidiomycetes-a review

The literature on hydrocarbon remediation with basidiomycetes was reviewed. Two ecological groups are considered for bioremediation, the saprotrophic basidiomycetes (white-rot and brown-rot fungi) and the ectomycorrhizal basidiomycetes. A remarkable capacity of basidiomycetes for in vitro degradation of simple and recalcitrant hydrocarbons, such as PAH, persistent organic pollutants (POPs), halogenated HC, aromatic HC and phenols, explosives and dyes was reported for many species. However, there is a need for more studies on the practical feasibility of field applications with basidiomycetes.

Comparative assessment of fungal augmentation treatments of a fine-textured and historically oil-contaminated soil

The removal of aged hydrophobic contaminants from fine-textured soils is a challenging issue in remediation. The objective of this study was to compare the efficacy of augmentation treatments to that of biostimulation in terms of total aliphatic hydrocarbon (TAH) and toxicity removal from a historically contaminated clay soil and to assess their impact on the resident microbial community. To this aim, Pleurotus ostreatus, Botryosphaeria rhodina and a combination of both were used as the inoculants while the addition of a sterilized lignocellulose mixture to soil (1:5, w/w) was used as a biostimulation approach. As opposed to the non-amended control soil, where no changes in TAH concentration and residual toxicity were observed after 60days, the activation of specialized bacteria was found in the biostimulated microcosms resulting in significant TAH removal (79.8%). The bacterial community structure in B. rhodina-augmented microcosms did not differ from the biostimulated microcosms due to the inability of the fungus to be retained within the resident microbiota. Best TAH removals were observed in microcosms inoculated with P. ostreatus alone (Po) and in binary consortium with B. rhodina (BC) (86.8 and 88.2%, respectively). In these microcosms, contaminant degradation exceeded their bioavailability thresholds determined by sequential supercritical CO2 extraction. Illumina metabarcoding of 16S rRNA gene showed that the augmentation with Po and BC led to lower relative abundances of Gram(+) taxa, Actinobacteria in particular, than those in biostimulated microcosms. Best detoxification, with respect to the non-amended incubation control, was found in Po microcosms where a drop in collembola mortality (from 90 to 22%) occurred. At the end of incubation, in both Po and BC, the relative abundances of P. ostreatus sequences were higher than 60% thus showing the suitability of this fungus in bioaugmentation-based remediation applications.

Biodegradation of phthalic acid esters by a newly isolated Mycobacterium sp. YC-RL4 and the bioprocess with environmental samples

Bacterial strain YC-RL4, capable of utilizing phthalic acid esters (PAEs) as the sole carbon source for growth, was isolated from petroleum-contaminated soil. Strain YC-RL4 was identified as Mycobacterium sp. by 16S rRNA gene analysis and Biolog tests. Mycobacterium sp. YC-RL4 could rapidly degrade dibutyl phthalate (DBP), diethyl phthalate (DEP), dimethyl phthalate (DMP), dicyclohexyl phthalate (DCHP), and di-(2-ethylhexyl) phthalate (DEHP) under both individual and mixed conditions, and all the degradation rates were above 85.0 % within 5 days. The effects of environmental factors which might affect the degrading process were optimized as 30 °C and pH 8.0. The DEHP metabolites were detected by HPLC-MS and the degradation pathway was deduced tentatively. DEHP was transformed into phthalic acid (PA) via mono (2-ethylhexyl) phthalate (MEHP) and PA was further utilized for growth via benzoic acid (BA) degradation pathway. Cell surface hydrophobicity (CSH) assays illuminated that the strain YC-RL4 was of higher hydrophobicity while grown on DEHP and CSH increased with the higher DEHP concentration. The degradation rates of DEHP by strain YC-RL4 in different environmental samples was around 62.0 to 83.3 % and strain YC-RL4 survived well in the soil sample. These results suggested that the strain YC-RL4 could be used as a potential and efficient PAE degrader for the bioremediation of contaminated sites.

Effects of RAMEB and/or mechanical mixing on the bioavailability and biodegradation of PCBs in soil/slurry

Microbial remediation is preferred as a clean and cost-effective method for restoring environments polluted by organics. But the biodegradation rates of hydrophobic organic contaminants (HOCs) are usually extremely restricted by their low bioavailability, especially in soil. Here, a physical method (mechanical mixing) and a chemical method (randomly methylated-β-cyclodextrins, RAMEB) were adopted to improve the bioavailability and biodegradation of polychlorinated biphenyls (PCBs) of an aged soil. The bioavailability of tri-CBs was increased by adding RAMEB in soil/slurry or assisting mechanical mixing in slurry, but these methods had no effects on the bioavailability of tetra-CBs and high chlorinated PCBs (Cl > 4). The degradation rate of tri-CBs could be obviously enhanced by adding RAMEB in soil or assisting mechanical mixing in slurry. The highest removal amount of tri-CBs reached 43.8% in 100 d with a first-order decay kinetics constant of 0.0059 d(-1). But the removal of tetra-CBs and high chlorinated PCBs (Cl > 4) were not significant in all mesocosms, possibly due to the lack or weakness of the native degrading microflora. Based on the analysis of the richness and diversity of bacterial communities, the characteristics of the heatmap and the variation of bphC copy numbers in the soil/slurry mesocosms, it could be inferred that there was no obvious corresponding relationship between the variation of the bacterial communities and the physical/chemical measures.

Pyrosequencing reveals the effect of mobilizing agents and lignocellulosic substrate amendment on microbial community composition in a real industrial PAH-polluted soil

Bacterial and fungal biodiversity throughout different biostimulation and bioaugmentation treatments applied to an industrial creosote-polluted soil were analyzed by means of polyphasic approach in order to gain insight into the microbial community structure and dynamics. Pyrosequencing data obtained from initial creosote polluted soil (after a biopiling step) revealed that Alpha and Gammaproteobacteria were the most abundant bacterial groups, whereas Fusarium and Scedosporium were the main fungal genera in the contaminated soil. At the end of 60-days laboratory scale bioremediation assays, pyrosequencing and DGGE data showed that (i) major bacterial community shifts were caused by the type of mobilizing agent added to the soil and, to a lesser extent, by the addition of lignocellulosic substrate; and (ii) the presence of the non-ionic surfactant (Brij 30) hampered the proliferation of Actinobacteria (Mycobacteriaceae) and Bacteroidetes (Chitinophagaceae) and, in the absence of lignocellulosic substrate, also impeded polycyclic aromatic hydrocarbons (PAHs) degradation. The results show the importance of implementing bioremediation experiments combined with microbiome assessment to gain insight on the effect of crucial parameters (e.g. use of additives) over the potential functions of complex microbial communities harbored in polluted soils, essential for bioremediation success.

Bioaugmentation of sewage sludge with Trametes versicolor in solid-phase biopiles produces degradation of pharmaceuticals and affects microbial communities

The use of sludge (biosolids) in land application may contribute to the spread of organic micropollutants as wastewater treatments do not completely remove these compounds. Therefore, the development of alternative strategies for sludge treatment is a matter of recent concern. The elimination of pharmaceuticals at pre-existent concentrations from sewage sludge was assessed, for the first time, in nonsterile biopiles by means of fungal bioaugmentation with Trametes versicolor (BTV-systems) and compared with the effect of autochthonous microbiota (NB-systems). The competition between the autochthonous fungal/bacterial communities and T. versicolor was studied using denaturing gradient gel electrophoresis (DGGE) and the cloning/sequencing approach. An inhibitory effect exerted by T. versicolor over bacterial populations was suggested. However, after 21 days, T. versicolor was no longer the main taxon in the fungal communities. The elimination profiles revealed an enhanced removal of atorvastatin-diclofenac-hydrochlorothiazide (during the whole treatment) and ranitidine-fenofibrate (at short periods) in the BTV biopiles in respect to NB biopiles, coincident with the presence of the fungus. For ibuprofen-clarithromycin-furosemide, the elimination profiles were similar irrespective of the system, and with carbamazepine no significant degradation was obtained. The results suggest that a fungal treatment with T. versicolor could be a promising process for the remediation of some pharmaceuticals in complex matrices such as biosolids.

A diversified approach to evaluate biostimulation and bioaugmentation strategies for heavy-oil-contaminated soil

A diversified approach involving chemical, microbiological and ecotoxicity assessment of soil polluted by heavy mineral oil was adopted, in order to improve our understanding of the biodegradability of pollutants, microbial community dynamics and ecotoxicological effects of various bioremediation strategies. With the aim of improving hydrocarbon degradation, the following bioremediation treatments were assayed: i) addition of inorganic nutrients; ii) addition of the rhamnolipid-based biosurfactant M(AT10); iii) inoculation of an aliphatic hydrocarbon-degrading microbial consortium (TD); and iv) inoculation of a known hydrocarbon-degrading white-rot fungus strain of Trametes versicolor. After 200 days, all the bioremediation assays achieved between 30% and 50% total petroleum hydrocarbon (TPH) biodegradation, with the T. versicolor inoculation degrading it the most. Biostimulation and T. versicolor inoculation promoted the Brevundimonas genus concurrently with other α-proteobacteria, β-proteobacteria and Cytophaga-Flexibacter-Bacteroides (CFB) as well as Actinobacteria groups. However, T. versicolor inoculation, which produced the highest hydrocarbon degradation in soil, also promoted autochthonous Gram-positive bacterial groups, such as Firmicutes and Actinobacteria. An acute toxicity test using Eisenia fetida confirmed the improvement in the quality of the soil after all biostimulation and bioaugmentation strategies.

Biosorption and biodegradation of phenanthrene and pyrene in sterilized and unsterilized soil slurry systems stimulated by Phanerochaete chrysosporium

To assess the "bioaccessible" pool of mycelia-bound polycyclic aromatic hydrocarbons (PAHs) and to quantify its biodegradation kinetics in soil, a soil-slurry system containing mycelial pellets of Phanerochaete chrysosporium as a separable biophase was set up. In sterilized and unsterilized soil-slurry, the distribution and dissipation of phenanthrene and pyrene in soil, fungal body of P. chrysosporium and water were independently quantified over the incubation periods. Biosorption and biodegradation contributions to bio-dissipation of dissolved- and sorbed-PAHs were identified. The biodegradation kinetics of PAHs by allochthonous P. chrysosporium and soil wild microorganisms was higher than those predicted by a coupled desorption-biodegradation model, suggesting both allochthonous and wild microorganisms could access sorbed-PAHs. The obvious hysteresis of PAHs in soil reduced their biodegradation, while the biosorbed-PAHs in P. chrysosporium body as an interim pool exhibited reversibly desorption and were almost exhausted via biodegradation. Both biosorption and direct biodegradation of PAHs in soil slurry were stimulated by allochthonous P. chrysosporium. After 90-day incubation, the respective biodegradation percentages for phenanthrene and pyrene were 63.8% and 51.9% in the unsterilized soil without allochthonous microorganisms, and then increased to 94.9% and 90.6% when amended with live P. chrysosporium. These indicate that allochthonous and wild microorganisms may synergistically attack sorbed-PAHs.

Mycelia promote active transport and spatial dispersion of polycyclic aromatic hydrocarbons

To cope with heterogeneous subsurface environments mycelial microorganisms have developed a unique ramified growth form. By extending hyphae, they can obtain nutrients from remote places and transport them even through air gaps and in small pore spaces, repectively. To date, studies have been focusing on the role that networks play in the distribution of nutrients. Here, we investigated the role of mycelia for the translocation of nonessential substances, using polycyclic aromatic hydrocarbons (PAHs) as model compounds. We show that the hyphae of the mycelial soil oomycete Pythium ultimum function as active translocation vectors for a wide range of PAHs. Visualization by two-photon excitation microscopy (TPEM) demonstrated the uptake and accumulation of phenanthrene (PHE) in lipid vesicles and its active transport by cytoplasmic streaming of the hyphae ('hyphal pipelines'). In mycelial networks, contaminants were translocated over larger distances than by diffusion. Given their transport capacity and ubiquity, hyphae may substantially distribute remote hydrophobic contaminants in soil, thereby improving their bioavailability to bacterial degradation. Hyphal contaminant dispersal may provide an untapped potential for future bioremediation approaches.

Two-phase olive mill waste composting: community dynamics and functional role of the resident microbiota

In this study, physico-chemical modifications and community dynamics and functional role of the resident microbiota during composting of humid husk from a two-phase extraction system (TPOMW) were investigated. High mineralization and humification of carbon, low loss of nitrogen and complete degradation of polyphenols led to the waste biotransformation into a high-quality compost. Viable cell counts and denaturing gradient gel electrophoresis (DGGE) profiling of the 16S rRNA genes showed that the thermophilic phase was characterized by the strongest variations of cell number, the highest biodiversity and the most variable community profiles. The isolation of tannin-degrading bacteria (e.g. Lysinibacillus fusiformis, Kocuria palustris, Tetrathiobacter kashmirensis and Rhodococcus rhodochrous) suggested a role of this enzymatic activity during the process. Taken together, the results indicated that the composting process, particularly the thermophilic phase, was characterized by a rapid succession of specialized bacterial populations with key roles in the organic matter biotransformation.

Influence of Pleurotus ostreatus inoculation on wood degradation and fungal colonization

The influence of Pleurotus ostreatus inoculation on wood degradation and on fungal community structure was studied. The experiments were performed on an organically poor fly ash deposit covered with a 10 cm layer of beech wood chips inoculated with P. ostreatus isolate ZIM76. Compared to non-inoculated wood chips, inoculation increased the temperatures and relative humidities and, in the first 6 months, accelerated Klason lignin degradation by 9% and also, after 17 months, increased iron translocation into wood chips by 30%. After 6 months, PCR-DGGE showed 22-28 and 13-21 fungal taxa in non-inoculated and P. ostreatus-inoculated beech chips, respectively. The differences in number of taxa and in the fungal community structure (based on Dice coefficient) between non-inoculated and inoculated wood chips diminished with time. The results indicate that the naturally occurring processes of wood degradation are as efficient as those occurring in sites inoculated with P. ostreatus.

Lentinus (Panus) tigrinus augmentation of a historically contaminated soil: matrix decontamination and structure and function of the resident bacterial community

The ability of Lentinus tigrinus to grow and to degrade persistent aromatic hydrocarbons in aged contaminated soil was assessed in this study. L. tigrinus extensively colonized the soil; its degradation activity after 60 d incubation at 28°C, however, was mostly limited to dichloroaniline isomers, polychlorinated benzenes and diphenyl ether while the fungus was unable to deplete 9,10-anthracenedione and 7-H-benz[DE]anthracene-7-one which were the major soil contaminants. Although clean-up levels were limited, both density of cultivable heterotrophic bacteria and richness of the resident bacterial community in L. tigrinus microcosms (LtM) increased over time to a significantly larger extent than the respective amended incubation controls (1.9×10(9) CFU g(-1) vs. 1.0×10(9) CFU g(-1) and 37 vs. 16, respectively). Naphthalene- and catechol 2,3-dioxygenase gene copy numbers, however, decreased over time at a higher rate in LtM than in incubation controls likely due to a higher stimulation on heterotrophs than xenobiotics-degrading community members.

A combination method to study microbial communities and activities in zinc contaminated soil

Zinc (Zn) plays a special role in soil ecology and fertility because it can support the growth of soil organisms or inhibit their growth depending on its concentrations. In this work, the effects of different concentrations of Zn on soil microbial communities and activities were analyzed by loading five different doses of Zn (160-6000 microg g(-1)) into a wheat surface soil. The microbial metabolic process revealed a significant bimodal pattern at high concentrations of Zn (>1920 microg g(-1)). This phenomenon suggested that soil microorganisms were very sensitive to zincous poisoning. A variety of soil quality properties were also measured and assessed. The results showed slower bacterial growth in soil cultures polluted with high levels of Zn. In addition, two kinds of fungi were identified by morphology and glomalin-related soil protein content in the Zn-contaminated soil. The growth of the first kind was inhibited with increase in Zn concentration. By contrast, the second kind could survive and continue to grow with increasing doses of Zn at 160-1920 microg g(-1) and its growth began to decline with further increase in Zn concentration. Finally, the fungus could not survive at very high (6000 microg g(-1)) Zn concentration. In this work, we conclude that soil microbial communities and activities can adapt to Zn pollution to a certain extent.

Microbiological polyphasic approach for soil health evaluation in an Italian polluted site

The use of microorganisms as bioindicators of soil health is quite a new feature, rarely considered for the soil health evaluation in chronically-polluted industrial sites, and still suffering of the bias related to the technique applied. In this work we applied a microbiological polyphasic approach, relying on soil indigenous microorganisms as bioindicators and combining culture-dependent and -independent methods, in order to evaluate soil health of four sites (1a, 1b, 2a and 2b) inside a chemical factory with a centenary activity. Functional as well as structural aspects were comprehensively considered. Results were related to the kind of pollutants found in each site. Heavy metal pollution was recorded in sites 1b and 2b, while both organic and inorganic substances were detected in sites 1a and 2a. Based on the chemical and physical properties of the four soils, site 1b and 2b grouped together, while 1a and 2a were separated from the others. The density of the culturable bacteria was very low in site 2a, where only gram-positive were found. According to the identification of culturable bacteria, site 2a showed the lowest similarity with the other sites. Microbial activity was detected only in sites 1b and 2b. PCR-DGGE (Denaturing Gradient Gel Electrophoresis), was performed on the culturable, total and active microbial communities. Consistently with the identification of culturable bacterial strains, the molecular profile of the culturable fraction of site 2a, was clearly separated from the molecular profiles of other sites in cluster analysis. Molecular fingerprintings of the whole and active bacterial communities differed among the sites, but clustered according to the pollutants present in each site. The presence of possible key species in each site has been discussed according to the whole and active species. Since the results obtained by microbiological analysis are consistent with the chemical data, we suggest that the use of this microbiological polyphasic approach and of microorganisms as intrinsic bioindicators, can be suitable for the evaluation of soil health.

Removal of spilled petroleum in industrial soils by spent compost of mushroom Pleurotus pulmonarius

Two batches of oil-contaminated soil collected from an industrial area and one pile of oil-contaminated soil in a power plant were treated by the spent compost of mushroom Pleurotus pulmonarius (SMC). SMC contained macronutrients for biostimulation, possessed 1.0-1.5 U mg(-1) laccase and 0.8-0.9 U mg(-1) manganese peroxidase for biodegradation and harboured (11+/-3)x10(7) cfu g(-1) bacteria and (56+/-9)x10(4) cfu g(-1) fungi for bioaugmentation. In off-site ex situ bioremediation, the industrial area soil was contaminated with organic 5.4-6.9 g kg(-1) total petroleum hydrocarbons (TPH), 14.5-19.0 g kg(-1) oil and grease and 95-99 mg kg(-1) di(2-ethylhexyl) phthalate (DEHP) and inorganic 104-136 mg kg(-1) Cu, 430-691 mg kg(-1) Pb and 477-578 mg kg(-1) Zn. The removal by 3% SMC amendment applied twice accounted for 56-64%, 31-33% and 51-54% disappearance of the TPH, oil and grease and DEHP contaminants, respectively. For the latter soil, one 0.3% SMC application removed 40-45% of the initial 1.2+/-0.2 g kg(-1) TPH and 4.0+/-0.6 g kg(-1) oil and grease in 22 d. Further using four bacteria and four fungi inoculated onto the sterilized soil samples, samples with greater removal of the pollutants bore larger microbial populations. Thus SMC simultaneously degrades petroleum residues and reduces toxicity in less than a month.

Fungal bioremediation of the creosote-contaminated soil: influence of Pleurotus ostreatus and Irpex lacteus on polycyclic aromatic hydrocarbons removal and soil microbial community composition in the laboratory-scale study

The aim of this study was to determine the efficacy of selected basidiomycetes in the removing of polycyclic aromatic hydrocarbons (PAH) from the creosote-contaminated soil. Fungi Pleurotus ostreatus and Irpex lacteus were supplemented with creosote-contaminated (50-200 mg kg(-1) PAH) soil originating from a wood-preserving plant and incubated at 15 °C for 120 d. Either fungus degraded PAH with 4-6 aromatic rings more efficiently than the microbial community present initially in the soil. PAH removal was higher in P. ostreatus treatments (55-67%) than in I. lacteus treatments (27-36%) in general. P. ostreatus (respectively, I. lacteus) removed 86-96% (47-59%) of 2-rings PAH, 63-72% (33-45%) of 3-rings PAH, 32-49% (9-14%) of 4-rings PAH and 31-38% (11-13%) of 5-6-rings PAH. MIS (Microbial Identification System) Sherlock analysis of the bacterial community determined the presence of dominant Gram-negative bacteria (G-) Pseudomonas in the inoculated soil before the application of fungi. Complex soil microbial community was characterized by phospholipid fatty acids analysis followed by GC-MS/MS. Either fungus induced the decrease of bacterial biomass (G- bacteria in particular), but the soil microbial community was influenced by P. ostreatus in a different way than by I. lacteus. The bacterial community was stressed more by the presence of I. lacteus than P. ostreatus (as proved by the ratio of the fungal/bacterial markers and by the ratio of trans/cis mono-unsaturated fatty acids). Moreover, P. ostreatus stimulated the growth of Gram-positive bacteria (G+), especially actinobacteria and these results indicate the potential of the positive synergistic interaction of this fungus and actinobacteria in creosote biodegradation.