Sulfur tuft and turkey tail: biosynthesis and biodegradation of organohalogens by Basidiomycetes

Air-surface exchange of halomethoxybenzenes in a Swedish subarctic catchment

Halomethoxybenzenes (HMBs) and related halomethoxyphenols are produced naturally in the marine and terrestrial environment and some also have anthropogenic origins. They are relatively volatile and water soluble and undergo atmospheric exchange with water bodies and soil. Here we report air-surface exchange of HMB compounds brominated anisoles and chlorinated dimethoxybenzenes in a Subarctic lake and catchment in Sweden during September 2022. HMBs were isolated from water on solid-phase extraction cartridges and from ground litter/soil by solvent extraction and determined by capillary gas chromatography - quadrupole mass spectrometry. Identified compounds in lake and stream water in the 10-100 pg L-1 range were 1,2,4,5-tetrachloro-3,6-dimethoxybenzene (DAME) > 2,4-dibromoanisole (DiBA) ≥ 2,4,6-tribromoanisole (TriBA) > 1,2,3,4-tetrachloro-5,6-dimethoxybenzene (tetrachloroveratrole, TeCV). DAME and the related compound 2,3,5,6-tetrachloro-4-methoxyphenol (DA) are reported in Subarctic litter/soil in the range 0.005-1.1 mg kg-1 dry weight (dw), whereas DiBA and TriBA were not detected in any litter/soil sample and TeCV in only one. Exchanges were assessed from concentrations in water and soil, air concentrations from a monitoring station at Pallas, Finland, and the physicochemical properties of the HMBs. Fluxes to and from the lake were estimated using the two-film gas exchange model. Net loadings (deposition minus volatilization) for the month of September were - 23, -15 and - 68 g for DiBA, TriBA and DAME, respectively, which amounted to about 4-7 % of the estimated lake inventory. An exchange assessment for DAME from litter/soil showed significant net volatilization at five sites, net deposition at one site and near-equilibrium at one site. The Torneträsk catchment appeared close to steady state with respect to HMB exchange during September 2022. The situation could be different during the warmer and colder seasons, and extending the study to cover these periods is a suggested next step.

Mold Odor from Wood Treated with Chlorophenols despite Mold Growth That Can Only Be Seen Using a Microscope

We previously reported that indoor odorous chloroanisoles (CAs) are still being emitted due to microbial methylation of hazardous chlorophenols (CPs) present in legacy wood preservatives. Meanwhile, Swedish researchers reported that this malodor, described since the early 1970s, is caused by hazardous mold. Here, we examined to what extent CP-treated wood contains mold and if mold correlates with perceived odor. We found no studies in PubMed or Web of Science addressing this question. Further, we investigated two schools built in the 1960s with odor originating from crawlspaces. No visible mold was evident in the crawlspaces or on the surfaces of treated wood samples. Using a microscope, varying amounts of mold growth were detected on the samples, all containing both CP(s) and CA(s). Some samples smelled, and the odor correlated with the amount of mold growth. We conclude that superficial microscopic mold on treated wood suffices produced the odor. Further, we argue that CPs rather than mold could explain the health effects reported in epidemiological studies that use mold odor as an indicator of hazardous exposure.

Drosophilin A methyl ether (DAME) and other chlorinated dimethoxybenzenes in fungi and forest litter from Sweden

Fungi and substrates undergoing fungal decomposition were collected from forests in northern and southern Sweden and analyzed for chlorinated dimethoxybenzenes (DMBs). Specimens were fungi fruiting bodies, rotting wood, forest litter and underlying humus. Targeted compounds were DAME (1,2,4,5-tetrachloro-3,6-DMB) and related fungal secondary metabolites. A screening procedure was developed which involved soaking the specimens in ethyl acetate followed by analysis by capillary gas chromatography - mass spectrometry with mass selective detection (GC-MSD). DAME was the most frequently found (62% of 47 specimens) and often the most abundant target compound, with range and mean ± SD concentrations of <0.0017-3.81 and 0.21 ± 0.63 mg kg-1 ww. Based on log-log correlations of partition coefficients of hydrophobic compounds between fungal biomass/water (KD) and octanol/water (KOW), five species of fungi are suggested to produce DAME de novo versus bioaccumulation from forest runoff water. Full-scan mass spectra of some high-concentration specimens indicated the presence of a Cl2DMB and a Cl3DMB, which could not be identified further due to lack of standards, and drosophilin A (DA = 2,3,5,6-tetrachloro-4-methoxyphenol), the precursor to DAME. Tetrachloroveratrole (TeCV = 1,2,3,4-tetrachloro-5,6-DMB) was found in only a few specimens. This study supports our hypothesis of fungi as a source of DAME in terrestrial runoff and indicates that other chlorinated secondary metabolites are present. DAME is widely distributed globally, and it would be good to have a better understanding of its sources and pathways as a marker of terrestrial organochlorines and their availability for bioaccumulation.

A comprehensive review of chlorophenols: Fate, toxicology and its treatment

Chlorophenols represent one of the most abundant families of toxic pollutants emerging from various industrial manufacturing units. The toxicity of these chloroderivatives is proportional to the number and position of chlorine atoms on the benzene ring. In the aquatic environment, these pollutants accumulate in the tissues of living organisms, primarily in fishes, inducing mortality at an early embryonic stage. Contemplating the behaviour of such xenobiotics and their prevalence in different environmental components, it is crucial to understand the methods used to remove/degrade the chlorophenol from contaminated environment. The current review describes the different treatment methods and their mechanism towards the degradation of these pollutants. Both abiotic and biotic methods are investigated for the removal of chlorophenols. Chlorophenols are either degraded through photochemical reactions in the natural environment, or microbes, the most diverse communities on earth, perform various metabolic functions to detoxify the environment. Biological treatment is a slow process because of the more complex and stable structure of pollutants. Advanced Oxidation Processes are effective in degrading such organics with enhanced rate and efficiency. Based on their ability to generate hydroxyl radicals, source of energy, catalyst type, etc., different processes such as sonication, ozonation, photocatalysis, and Fenton's process are discussed for the treatment or remediation efficiency towards the degradation of chlorophenols. The review entails both advantages and limitations of treatment methods. The study also focuses on reclamation of chlorophenol-contaminated sites. Different remediation methods are discussed to restore the degraded ecosystem back in its natural condition.

Modeling the microbial pretreatment of camelina straw and switchgrass by Trametes versicolor and Phanerochaete chrysosporium via solid-state fermentation process: A growth kinetic sub-model in the context of biomass-based biorefineries

Advancing microbial pretreatment of lignocellulose has the potential not only to reduce the carbon footprint and environmental impacts of the pretreatment processes from cradle-to-grave, but also increase biomass valorization, support agricultural growers, and boost the bioeconomy. Mathematical modeling of microbial pretreatment of lignocellulose provides insights into the metabolic activities of the microorganisms as responses to substrate and environment and provides baseline targets for the design, development, and optimization of solid-state-fermentation (SSF) bioreactors, including substrate concentrations, heat and mass transfer. In this study, the growth of Trametes versicolor 52J (TV52J), Trametes versicolor m4D (TVm4D), and Phanerochaete chrysosporium (PC) on camelina straw (CS) and switchgrass (SG) during an SSF process was examined. While TV52J illustrated the highest specific growth rate and maximum cell concentration, a mutant strain deficient in cellulose catabolism, TVm4D, performed best in terms of holocellulose preservation and delignification. The hybrid logistic-Monod equation along with holocellulose consumption and delignification models described well the growth kinetics. The oxygen uptake rate and carbon dioxide production rate were directly correlated to the fungal biomass concentration; however, a more sophisticated non-linear relationship might explain those correlations better than a linear model. This study provides an informative baseline for developing SSF systems to integrate fungal pretreatment into a large-scale, on-farm, wet-storage process for the utilization of agricultural residues as feedstocks for biofuel production.

Halomethoxybenzenes in air of the Nordic region

Halomethoxybenzenes (HMBs) are a group of compounds with natural and anthropogenic origins. Here we extend a 2002-2015 survey of bromoanisoles (BAs) in the air and precipitation at Råö on the Swedish west coast and Pallas in Subarctic Finland. New BAs data are reported for 2018 and 2019 and chlorinated HMBs are included for these and some previous years: drosophilin A methyl ether (DAME: 1,2,4,5-tetrachloro-3,6-dimethoxybenzene), tetrachloroveratrole (TeCV: 1,2,3,4-tetrachloro-5,6-dimethoxybenzene), and pentachloroanisole (PeCA). The order of abundance of HMBs at Råö was ΣBAs > DAME > TeCV > PeCA, whereas at Pallas the order of abundance was DAME > ΣBAs > TeCA > PeCA. The lower abundance of BAs at Pallas reflects its inland location, away from direct marine influence. Clausius-Clapeyron (CC) plots of log partial pressure (P_air)/Pa versus 1/T suggested distant transport at both sites for PeCA and local exchange for DAME and TeCV. BAs were dominated by distant transport at Pallas and by both local and distant sources at Råö. Relationships between air and precipitation concentrations were examined by scavenging ratios, SR = (ng m^-3)_precip/(ng m^-3)_air. SRs were higher at Pallas than Råö due to greater Henry's law partitioning of gaseous compounds into precipitation at colder temperatures. DAME is produced by terrestrial fungi. We screened 19 fungal species from Swedish forests and found seven of them contained 0.01-3.8 mg DAME per kg fresh weight. We suggest that the volatilization of DAME from fungi and forest litter containing fungal mycelia may contribute to atmospheric levels at both sites.

The biogeochemical cycling of chlorine

Chlorine has important roles in the Earth's systems. In different forms, it helps balance the charge and osmotic potential of cells, provides energy for microorganisms, mobilizes metals in geologic fluids, alters the salinity of waters, and degrades atmospheric ozone. Despite this importance, there has not been a comprehensive summary of chlorine's geobiology. Here, we unite different areas of recent research to describe a biogeochemical cycle for chlorine. Chlorine enters the biosphere through volcanism and weathering of rocks and is sequestered by subduction and the formation of evaporite sediments from inland seas. In the biosphere, chlorine is converted between solid, dissolved, and gaseous states and in oxidation states ranging from -1 to +7, with the soluble, reduced chloride ion as its most common form. Living organisms and chemical reactions change chlorine's form through oxidation and reduction and the addition and removal of chlorine from organic molecules. Chlorine can be transported through the atmosphere, and the highest oxidation states of chlorine are produced by reactions between sunlight and trace chlorine gases. Partial oxidation of chlorine occurs across the biosphere and creates reactive chlorine species that contribute to the oxidative stress experienced by living cells. A unified view of this chlorine cycle demonstrates connections between chlorine biology, chemistry, and geology that affect life on the Earth.

Further Biochemical Profiling of Hypholoma fasciculare Metabolome Reveals Its Chemogenetic Diversity

Natural products with novel chemistry are urgently needed to battle the continued increase in microbial drug resistance. Mushroom-forming fungi are underutilized as a source of novel antibiotics in the literature due to their challenging culture preparation and genetic intractability. However, modern fungal molecular and synthetic biology tools have renewed interest in exploring mushroom fungi for novel therapeutic agents. The aims of this study were to investigate the secondary metabolites of nine basidiomycetes, screen their biological and chemical properties, and then investigate the genetic pathways associated with their production. Of the nine fungi selected, Hypholoma fasciculare was revealed to be a highly active antagonistic species, with antimicrobial activity against three different microorganisms: Bacillus subtilis, Escherichia coli, and Saccharomyces cerevisiae. Genomic comparisons and chromatographic studies were employed to characterize more than 15 biosynthetic gene clusters and resulted in the identification of 3,5-dichloromethoxy benzoic acid as a potential antibacterial compound. The biosynthetic gene cluster for this product is also predicted. This study reinforces the potential of mushroom-forming fungi as an underexplored reservoir of bioactive natural products. Access to genomic data, and chemical-based frameworks, will assist the development and application of novel molecules with applications in both the pharmaceutical and agrochemical industries.

Microbial Synthesis and Transformation of Inorganic and Organic Chlorine Compounds

Organic and inorganic chlorine compounds are formed by a broad range of natural geochemical, photochemical and biological processes. In addition, chlorine compounds are produced in large quantities for industrial, agricultural and pharmaceutical purposes, which has led to widespread environmental pollution. Abiotic transformations and microbial metabolism of inorganic and organic chlorine compounds combined with human activities constitute the chlorine cycle on Earth. Naturally occurring organochlorines compounds are synthesized and transformed by diverse groups of (micro)organisms in the presence or absence of oxygen. In turn, anthropogenic chlorine contaminants may be degraded under natural or stimulated conditions. Here, we review phylogeny, biochemistry and ecology of microorganisms mediating chlorination and dechlorination processes. In addition, the co-occurrence and potential interdependency of catabolic and anabolic transformations of natural and synthetic chlorine compounds are discussed for selected microorganisms and particular ecosystems.

Archaeaare prominent members of the prokaryotic communities colonizing common forest mushrooms

In this study, the abundance and composition of prokaryotic communities associated with the inner tissue of fruiting bodies of Suillus bovinus, Boletus pinophilus, Cantharellus cibarius, Agaricus arvensis, Lycoperdon perlatum, and Piptoporus betulinus were analyzed using culture-independent methods. Our findings indicate that archaea and bacteria colonize the internal tissues of all investigated specimens and that archaea are prominent members of the prokaryotic community. The ratio of archaeal 16S rRNA gene copy numbers to those of bacteria was >1 in the fruiting bodies of four out of six fungal species included in the study. The largest proportion of archaeal 16S rRNA gene sequences belonged to thaumarchaeotal classes Terrestrial group, Miscellaneous Crenarchaeotic Group (MCG), and Thermoplasmata. Bacterial communities showed characteristic compositions in each fungal species. Bacterial classes Gammaproteobacteria, Actinobacteria, Bacilli, and Clostridia were prominent among communities in fruiting body tissues. Bacterial populations in each fungal species had different characteristics. The results of this study imply that fruiting body tissues are an important habitat for abundant and diverse populations of archaea and bacteria.

Organohalide respiration in pristine environments: implications for the natural halogen cycle

Halogenated organic compounds, also termed organohalogens, were initially considered to be of almost exclusively anthropogenic origin. However, over 5000 naturally synthesized organohalogens are known today. This has also fuelled the hypothesis that the natural and ancient origin of organohalogens could have primed development of metabolic machineries for their degradation, especially in microorganisms. Among these, a special group of anaerobic microorganisms was discovered that could conserve energy by reducing organohalogens as terminal electron acceptor in a process termed organohalide respiration. Originally discovered in a quest for biodegradation of anthropogenic organohalogens, these organohalide-respiring bacteria (OHRB) were soon found to reside in pristine environments, such as the deep subseafloor and Arctic tundra soil with limited/no connections to anthropogenic activities. As such, accumulating evidence suggests an important role of OHRB in local natural halogen cycles, presumably taking advantage of natural organohalogens. In this minireview, we integrate current knowledge regarding the natural origin and occurrence of industrially important organohalogens and the evolution and spread of OHRB, and describe potential implications for natural halogen and carbon cycles.

Metagenome-derived haloalkane dehalogenases with novel catalytic properties

Haloalkane dehalogenases (HLDs) are environmentally relevant enzymes cleaving a carbon-halogen bond in a wide range of halogenated pollutants. PCR with degenerate primers and genome-walking was used for the retrieval of four HLD-encoding genes from groundwater-derived environmental DNA. Using specific primers and the environmental DNA as a template, we succeeded in generating additional amplicons, resulting altogether in three clusters of sequences with each cluster comprising 8-13 closely related putative HLD-encoding genes. A phylogenetic analysis of the translated genes revealed that three HLDs are members of the HLD-I subfamily, whereas one gene encodes an enzyme from the subfamily HLD-II. Two metagenome-derived HLDs, eHLD-B and eHLD-C, each from a different subfamily, were heterologously produced in active form, purified and characterized in terms of their thermostability, pH and temperature optimum, quaternary structure, substrate specificity towards 30 halogenated compounds, and enantioselectivity. eHLD-B and eHLD-C showed striking differences in their activities, substrate preferences, and tolerance to temperature. Profound differences were also determined in the enantiopreference and enantioselectivity of these enzymes towards selected substrates. Comparing our data with those of known HLDs revealed that eHLD-C exhibits a unique combination of high thermostability, high activity, and an unusually broad pH optimum, which covers the entire range of pH 5.5-8.9. Moreover, a so far unreported high thermostability for HLDs was determined for this enzyme at pH values lower than 6.0. Thus, eHLD-C represents an attractive and novel biocatalyst for biotechnological applications.

Novel pollutants in the Moscow atmosphere in winter period: Gas chromatography-high resolution time-of-flight mass spectrometry study

The most common mass spectrometry approach analyzing contamination of the environment deals with targeted analysis, i.e. detection and quantification of the selected (priority) pollutants. However non-targeted analysis is becoming more often the method of choice for environmental chemists. It involves implementation of modern analytical instrumentation allowing for comprehensive detection and identification of the wide variety of compounds of the environmental interest present in the sample, such as pharmaceuticals and their metabolites, musks, nanomaterials, perfluorinated compounds, hormones, disinfection by-products, flame retardants, personal care products, and many others emerging contaminants. The paper presents the results of detection and identification of previously unreported organic compounds in snow samples collected in Moscow in March 2016. The snow analysis allows evaluation of long-term air pollution in the winter period. Gas chromatography coupled to a high resolution time-of-flight mass spectrometer has enabled us with capability to detect and identify such novel analytes as iodinated compounds, polychlorinated anisoles and even Ni-containing organic complex, which are unexpected in environmental samples. Some considerations concerning the possible sources of origin of these compounds in the environment are discussed.

Understanding fungal functional biodiversity during the mitigation of environmentally dispersed pentachlorophenol in cork oak forest soils

Pentachlorophenol (PCP) is globally dispersed and contamination of soil with this biocide adversely affects its functional biodiversity, particularly of fungi - key colonizers. Their functional role as a community is poorly understood, although a few pathways have been already elucidated in pure cultures. This constitutes here our main challenge - elucidate how fungi influence the pollutant mitigation processes in forest soils. Circumstantial evidence exists that cork oak forests in N. W. Tunisia - economically critical managed forests are likely to be contaminated with PCP, but the scientific evidence has previously been lacking. Our data illustrate significant forest contamination through the detection of undefined active sources of PCP. By solving the taxonomic diversity and the PCP-derived metabolomes of both the cultivable fungi and the fungal community, we demonstrate here that most strains (predominantly penicillia) participate in the pollutant biotic degradation. They form an array of degradation intermediates and by-products, including several hydroquinone, resorcinol and catechol derivatives, either chlorinated or not. The degradation pathway of the fungal community includes uncharacterized derivatives, e.g. tetrachloroguaiacol isomers. Our study highlights fungi key role in the mineralization and short lifetime of PCP in forest soils and provide novel tools to monitor its degradation in other fungi dominated food webs.

Experimental evidence of large changes in terrestrial chlorine cycling following altered tree species composition

Organochlorine molecules (Clorg) are surprisingly abundant in soils and frequently exceed chloride (Cl(-)) levels. Despite the widespread abundance of Clorg and the common ability of microorganisms to produce Clorg, we lack fundamental knowledge about how overall chlorine cycling is regulated in forested ecosystems. Here we present data from a long-term reforestation experiment where native forest was cleared and replaced with five different tree species. Our results show that the abundance and residence times of Cl(-) and Clorg after 30 years were highly dependent on which tree species were planted on the nearby plots. Average Cl(-) and Clorg content in soil humus were higher, at experimental plots with coniferous trees than in those with deciduous trees. Plots with Norway spruce had the highest net accumulation of Cl(-) and Clorg over the experiment period, and showed a 10 and 4 times higher Cl(-) and Clorg storage (kg ha(-1)) in the biomass, respectively, and 7 and 9 times higher storage of Cl(-) and Clorg in the soil humus layer, compared to plots with oak. The results can explain why local soil chlorine levels are frequently independent of atmospheric deposition, and provide opportunities for improved modeling of chlorine distribution and cycling in terrestrial ecosystems.

Assessment of organochlorine pesticides residues in higher plants from oil exploration areas of Niger Delta, Nigeria

The concentrations and distributions of organochlorine pesticides (OCPs) in some higher plant samples collected from oil exploration areas of the Niger Delta, Nigeria were examined. The concentrations of Σ(25)OCP ranged from 82 to 424, 44 to 200 , 34 to 358, 33 to 106 and 16 to 75 ng/g in Olomoro, Oginni, Uzere, Irri and Calabar plants, respectively. The compositional profiles of the analysed OCPs in most of the plants showed no fresh inputs in the area. The OCPs detected in the samples could have resulted from pesticide usage for intense farming activities cum the use of pesticides to control household pests and insects in the area. Drilling fluids and corrosion inhibitors used in petroleum explorations also have chlorinated compounds as additives thereby serving as potential sources of OCPs. Among the studied plants, elephant grass showed high bioaccumulation and phytoremediation potentials of OCPs. The ΣHCH concentrations exceeded the allowable daily intake limit thereby serving as potential threat to humans.

The Evolutionary Innovation of Nutritional Symbioses in Leaf-Cutter Ants

Fungus-growing ants gain access to nutrients stored in plant biomass through their association with a mutualistic fungus they grow for food. This 50 million-year-old obligate mutualism likely facilitated some of these species becoming dominant Neotropical herbivores that can achieve immense colony sizes. Recent culture-independent investigations have shed light on the conversion of plant biomass into nutrients within ant fungus gardens, revealing that this process involves both the fungal cultivar and a symbiotic community of bacteria including Enterobacter, Klebsiella, and Pantoea species. Moreover, the genome sequences of the leaf-cutter ants Atta cephalotes and Acromyrmex echinatior have provided key insights into how this symbiosis has shaped the evolution of these ants at a genetic level. Here we summarize the findings of recent research on the microbial community dynamics within fungus-growing ant fungus gardens and discuss their implications for this ancient symbiosis.

Acidicapsa borealis gen. nov., sp. nov. and Acidicapsa ligni sp. nov., subdivision 1 Acidobacteria from Sphagnum peat and decaying wood

Two strains of subdivision 1 Acidobacteria, a pink-pigmented bacterium KA1(T) and a colourless isolate WH120(T), were obtained from acidic Sphagnum peat and wood under decay by the white-rot fungus Hyploma fasciculare, respectively. Cells of these isolates were Gram-negative-staining, non-motile, short rods, which were covered by large polysaccharide capsules and occurred singly, in pairs, or in short chains. Strains KA1(T) and WH120(T) were strictly aerobic mesophiles that grew between 10 and 33 °C, with an optimum at 22-28 °C. Both isolates developed under acidic conditions, but strain WH120(T) was more acidophilic (pH growth range 3.5-6.4; optimum, 4.0-4.5) than strain KA1(T) (pH growth range 3.5-7.3; optimum , 5.0-5.5). The preferred growth substrates were sugars. In addition, the wood-derived isolate WH120(T) grew on oxalate, lactate and xylan, while the peat-inhabiting acidobacterium strain KA1(T) utilized galacturonate, glucuronate and pectin. The major fatty acids were iso-C(15:0) and iso-C(17:1)ω8c; the cells also contained significant amounts of 13,16-dimethyl octacosanedioic acid. The quinone was MK-8. The DNA G+C contents of strains KA1(T) and WH120(T) were 54.1 and 51.7 mol%, respectively. Strains KA1(T) and WH120(T) displayed 97.8% 16S rRNA gene sequence similarity to each other. The closest recognized relatives were Acidobacterium capsulatum and Telmatobacter bradus (93.4-94.3% 16S rRNA gene sequence similarity). These species differed from strains KA1(T) and WH120(T) by their ability to grow under anoxic conditions, the absence of capsules, presence of cell motility and differing fatty acid composition. Based on these differences, the two new isolates are proposed as representing a novel genus, Acidicapsa gen. nov., and two novel species. Acidicapsa borealis gen. nov., sp. nov. is the type species for the new genus with strain KA1(T) (=DSM 23886(T)=LMG 25897(T)=VKM B-2678(T)) as the type strain. The name Acidicapsa ligni sp. nov. is proposed for strain WH120(T) (=LMG 26244(T)=VKM B-2677(T)=NCCB 100371(T)).

Identification of a fungi-derived terrestrial halogenated natural product in wild boar (Sus scrofa)

In this study, we identified and quantitated a tetrachlorinated compound found at high concentrations in some samples of the meat of free-ranging wild boar (Sus scrofa) from Southern Germany. Mass spectrometric analysis indicated that the compound was a tetrachloromethoxyphenol isomer, and the subsequently synthesized tetrachloro-p-methoxyphenol was identical with the unknown compound in wild boar. Tetrachloro-p-methoxyphenol is a known secondary metabolite of basidiomycetous fungi, which in turn are regular feed items of the wild boar. It is extremely likely that the wild boar have accumulated tetrachloro-p-methoxyphenol by exploiting basidiomycetes. The highest concentration in the samples (n = 22) was ~1 mg/kg lipids tetrachloro-p-methoxyphenol. This concentration was higher than that of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in any of the samples. Some samples did not contain tetrachloro-p-methoxyphenol, which indicates varied preferences in fungi by wild boars. Our data suggest that during their entire evolution, humans have been in contact with the natural product tetrachloro-p-methoxyphenol by consuming wild boars.

Mechanism of antibacterial activity of the white-rot fungus Hypholoma fasciculare colonizing wood

In a previous study it was shown that the number of wood-inhabiting bacteria was drastically reduced after colonization of beech ( Fagus sylvatica ) wood blocks by the white-rot fungus Hypholoma fasciculare , or sulfur tuft ( Folman et al. 2008 ). Here we report on the mechanisms of this fungal-induced antibacterial activity. Hypholoma fasciculare was allowed to invade beech and pine ( Pinus sylvestris ) wood blocks that had been precolonized by microorganisms from forest soil. The changes in the number of bacteria, fungal biomass, and fungal-related wood properties were followed for 23 weeks. Colonization by the fungus resulted in a rapid and large reduction in the number of bacteria (colony-forming units), which was already apparent after 4 weeks of incubation. The reduction in the number of bacteria coincided with fungal-induced acidification in both beech and pine wood blocks. No evidence was found for the involvement of toxic secondary metabolites or reactive oxygen species in the reduction of the number of bacteria. Additional experiments showed that the dominant bacteria present in the wood blocks were not able to grow under the acidic conditions (pH 3.5) created by the fungus. Hence our research pointed at rapid acidification as the major factor causing reduction of wood-inhabiting bacteria upon colonization of wood by H. fasciculare.

Kinetic and chemical characterization of aldehyde oxidation by fungal aryl-alcohol oxidase

Fungal AAO (aryl-alcohol oxidase) provides H2O2 for lignin biodegradation. AAO is active on benzyl alcohols that are oxidized to aldehydes. However, during oxidation of some alcohols, AAO forms more than a stoichiometric number of H2O2 molecules with respect to the amount of aldehyde detected due to a double reaction that involves aryl-aldehyde oxidase activity. The latter reaction was investigated using different benzylic aldehydes, whose oxidation to acids was demonstrated by GC-MS. The steady- and presteady state kinetic constants, together with the chromatographic results, revealed that the presence of substrate electron-withdrawing or electron-donating substituents had a strong influence on activity; the highest activity was with p-nitrobenzaldehyde and halogenated aldehydes and the lowest with methoxylated aldehydes. Moreover, activity was correlated to the aldehyde hydration rates estimated by 1H-NMR. These findings, together with the absence in the AAO active site of a residue able to drive oxidation via an aldehyde thiohemiacetal, suggested that oxidation mainly proceeds via the gem-diol species. The reaction mechanism (with a solvent isotope effect, 2H2Okred, of approx. 1.5) would be analogous to that described for alcohols, the reductive half-reaction involving concerted hydride transfer from the alpha-carbon and proton abstraction from one of the gem-diol hydroxy groups by a base. The existence of two steps of opposite polar requirements (hydration and hydride transfer) explains some aspects of aldehyde oxidation by AAO. Site-directed mutagenesis identified two histidine residues strongly involved in gem-diol oxidation and, unexpectedly, suggested that an active-site tyrosine residue could facilitate the oxidation of some aldehydes that show no detectable hydration. Double alcohol and aldehyde oxidase activities of AAO would contribute to H2O2 supply by the enzyme.

Microbial chlorination of organic matter in forest soil: investigation using 36Cl-chloride and its methodology

Chloride, which comes into the forest ecosystem largely from the sea as aerosol (and has been in the past assumed to be inert), causes chlorination of soil organic matter. Studies of the chlorination showed that the content of organically bound chlorine in temperate forest soils is higher than that of chloride, and various chlorinated compounds are produced. Our study of chlorination of organic matter in the fermentation horizon of forest soil using radioisotope 36Cl and tracer techniques shows that microbial chlorination clearly prevails over abiotic, chlorination of soil organic matter being enzymatically mediated and proportional to chloride content and time. Long-term (>100 days) chlorination leads to more stable chlorinated substances contained in the organic layer of forest soil (overtime; chlorine is bound progressively more firmly in humic acids) and volatile organochlorines are formed. Penetration of chloride into microorganisms can be documented by the freezing/thawing technique. Chloride absorption in microorganisms in soil and in litter residues in the fermentation horizon complicates the analysis of 36Cl-chlorinated soil. The results show that the analytical procedure used should be tested for every soil type under study.

Possible role of reactive chlorine in microbial antagonism and organic matter chlorination in terrestrial environments

Several studies have demonstrated that extensive formation of organically bound chlorine occurs both in soil and in decaying plant material. Previous studies suggest that enzymatic formation of reactive chlorine outside cells is a major source. However, the ecological role of microbial-induced extracellular chlorination processes remains unclear. In the present paper, we assess whether or not the literature supports the hypothesis that extracellular chlorination is involved in direct antagonism against competitors for the same resources. Our review shows that it is by no means rare that biotic processes create conditions that render biocidal concentrations of reactive chlorine compounds, which suggest that extracellular production of reactive chlorine may have an important role in antagonistic microbial interactions. To test the validity, we searched the UniprotPK database for microorganisms that are known to produce haloperoxidases. It appeared that many of the identified haloperoxidases from terrestrial environments are originating from organisms that are associated with living plants or decomposing plant material. The results of the in silico screening were supported by various field and laboratory studies on natural chlorination. Hence, the ability to produce reactive chlorine seems to be especially common in environments that are known for antibiotic-mediated competition for resources (interference competition). Yet, the ability to produce haloperoxidases is also recorded, for example, for plant endosymbionts and parasites, and there is little or no empirical evidence that suggests that these organisms are antagonistic.

The formation and fate of chlorinated organic substances in temperate and boreal forest soils

BACKGROUND, AIM AND SCOPE

Chlorine is an abundant element, commonly occurring in nature either as chloride ions or as chlorinated organic compounds (OCls). Chlorinated organic substances were long considered purely anthropogenic products; however, they are, in addition, a commonly occurring and important part of natural ecosystems. Formation of OCls may affect the degradation of soil organic matter (SOM) and thus the carbon cycle with implications for the ability of forest soils to sequester carbon, whilst the occurrence of potentially toxic OCls in groundwater aquifers is of concern with regard to water quality. It is thus important to understand the biogeochemical cycle of chlorine, both inorganic and organic, to get information about the relevant processes in the forest ecosystem and the effects on these from human activities, including forestry practices. A survey is given of processes in the soil of temperate and boreal forests, predominantly in Europe, including the participation of chlorine, and gaps in knowledge and the need for further work are discussed.

RESULTS

Chlorine is present as chloride ion and/or OCls in all compartments of temperate and boreal forest ecosystems. It contributes to the degradation of SOM, thus also affecting carbon sequestration in the forest soil. The most important source of chloride to coastal forest ecosystems is sea salt deposition, and volcanoes and coal burning can also be important sources. Locally, de-icing salt can be an important chloride input near major roads. In addition, anthropogenic sources of OCls are manifold. However, results also indicate the formation of chlorinated organics by microorganisms as an important source, together with natural abiotic formation. In fact, the soil pool of OCls seems to be a result of the balance between chlorination and degradation processes. Ecologically, organochlorines may function as antibiotics, signal substances and energy equivalents, in descending order of significance. Forest management practices can affect the chlorine cycle, although little is at present known about how.

DISCUSSION

The present data on the apparently considerable size of the pool of OCls indicate its importance for the functioning of the forest soil system and its stability, but factors controlling their formation, degradation and transport are not clearly understood. It would be useful to estimate the significance and rates of key processes to be able to judge the importance of OCls in SOM and litter degradation. Effects of forest management processes affecting SOM and chloride deposition are likely to affect OCls as well. Further standardisation and harmonisation of sampling and analytical procedures is necessary.

CONCLUSIONS AND PERSPECTIVES

More work is necessary in order to understand and, if necessary, develop strategies for mitigating the environmental impact of OCls in temperate and boreal forest soils. This includes both intensified research, especially to understand the key processes of formation and degradation of chlorinated compounds, and monitoring of the substances in question in forest ecosystems. It is also important to understand the effect of various forest management techniques on OCls, as management can be used to produce desired effects.

Fungal Diversity and Use in Decomposition of Environmental Pollutants

This article presents a critical review of the actual state of fungal activities on environmental pollutants, fungal diversity, the use of fungi in the degradation of chemical pollutants, enzyme degrading systems and perspectives on the use of fungi in bioremediation and unexplored research. The ability of fungi to transform or metabolize chemical pollutants has received much attention due to environmental persistence and chemical toxicity. The fungal degradation of xenobiotics is looked upon as an effective method of removing these pollutants from the environment by a process which is currently known as bioremediation. This review summarizes information from fundamental works that have revealed that a wide variety of fungi are capable of degrading an equally wide range of toxical chemical. The capacity of non-ligninolytic and ligninolytic fungi in the bioremediation of polycyclic aromatic hydrocarbon (PAHs), benzene-toluene-ethylbenzene-xylene (BTEX), chlorophenols, polychlorinated biphenyl, munitions waste and pesticides have been discussed. Besides this, several extracellular enzymes are involved in the metabolism of xenobiotic compounds as well as other factors related to these processes.

Environmental significance of O-demethylation of chloroanisoles by soil bacterial isolates as a mechanism that improves the overall biodegradation of chlorophenols

The biodegradation rate of chlorophenols in the environment seems to be limited by a competitive mechanism of O-methylation which produces chloroanisoles with a high potential of being bioconcentrated in living organisms. In this work we report for the first time the isolation of three soil bacterial strains able to efficiently degrade 2,4,6-trichloroanisole (2,4,6-TCA). These strains were identified as Xanthomonas retroflexus INBB4, Pseudomonas putida INBP1 and Acinetobacter radioresistens INBS1. In these isolates 2,4,6-TCA was efficiently metabolized in a minimal medium containing methanol and 2,4,6-TCA as the only carbon sources, with a concomitant release of 3 mol of chloride ion from 1 mol of 2,4,6-TCA, indicating complete dehalogenation of 2,4,6-TCA. 2,4,6-trichlorophenol (2,4,6-TCP) was identified as a degradative intermediate, indicating that 2,4,6-TCA underwent O-demethylation as the first step in the biodegradation process. 2,4,6-TCP was further transformed into 2,6-dichloro-para-hydroquinone (2,6-DCHQ) and subsequently mineralized. The degradation of chloroanisoles could improve the overall biodegradation of chlorophenols in the environment, because those chlorophenols previously biomethylated might also be later biodegraded. Xanthomonas retroflexus INBB4 has two O-demethylation systems: one is an oxygenase-type demethylase, and the other is a tetrahydrofolate (THF)-dependent O-demethylase. On the contrary O-demethylation of 2,4,6-TCA in P. putida INBP1 is just catalysed by an oxygenase-type NADH/NADPH-dependent O-demethylase, whereas in A. radioresistens INBS1 a THF-dependent O-demethylase activity was detected.

Expression of reductive dehalogenase genes in Dehalococcoides ethenogenes strain 195 growing on tetrachloroethene, trichloroethene, or 2,3-dichlorophenol

Reductive dehalogenase (RD) gene transcript levels in Dehalococcoides ethenogenes strain 195 were investigated using reverse transcriptase quantitative PCR during growth and reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), or 2,3-dichlorophenol (2,3-DCP). Cells grown with PCE or TCE had high transcript levels (greater than that for rpoB) for tceA, which encodes the TCE RD, pceA, which encodes the PCE RD, and DET0162, which contains a predicted stop codon and is considered nonfunctional. In cells grown with 2,3-DCP, tceA mRNA was less than 1% of that for rpoB, indicating that its transcription was regulated. pceA and DET0162 were the only RD genes with high transcript levels in cells grown with 2,3-DCP. Proteomic analysis of PCE-grown cells detected both PceA and TceA with high peptide coverage but not DET0162, and analysis of 2,3-DCP-grown cells detected PceA with high coverage but not TceA, DET0162, or any other potential RD. Cells grown with PCE or 2,3-DCP were tested for the ability to dechlorinate PCE, TCE, or 2,3-DCP with H2 as the electron donor. 2,3-DCP-grown cells were unable to dechlorinate TCE but dechlorinated PCE to TCE without a lag, and PCE-grown cells dechlorinated 2,3-DCP without a lag. These results show that 2,3-DCP-grown cells do not produce TceA and that DET0162 is transcribed but its translation product is not detectable in cells and are consistent with PceA's being bifunctional, also serving as the 2,3-DCP RD. Chlorophenols naturally occur in soils and are good candidates for the original substrates for PceA.

Growth of Dehalococcoides strains with chlorophenols as electron acceptors

Dehalococcoides strains reductively dechlorinate a wide variety of halogenated compounds including chlorinated benzenes, biphenyls, naphthalenes, dioxins, and ethenes. Recent genome sequencing of the two Dehalococcoides strains CBDB1 and 195 revealed the presence of 32 and 18 reductive dehalogenase homologous genes, respectively, and therefore suggested an even higher dechlorinating potential than previously anticipated. Here, we demonstrate reductive dehalogenation of chlorophenol congeners by Dehalococcoides strains CBDB1 and 195. Strain CBDB1 completely converted 2,3-dichlorophenol, all six trichlorophenols, all three tetrachlorophenols, and pentachlorophenol to lower chlorinated phenols. Observed dechlorination rates in batch cultures with cell numbers of 10(7) mL(-1) amounted up to 35 microM day(-1). Chlorophenols were preferentially dechlorinated in the ortho position, but also doubly flanked and singly flanked meta- or para-chlorine substituents were removed. We used a newly designed computer-assisted direct cell counting protocol and quantitative PCR to demonstrate that strain CBDB1 uses chlorophenols as electron acceptors for respiratory growth. The growth yield of strain CBDB1 with 2,3-dichlorophenol was 7.6 x 10(13) cells per mol of Cl- released, and the growth rate was 0.41 day(-1). For strain 195, fast ortho dechlorination of 2,3-dichlorophenol, 2,3,4-trichlorophenol, and 2,3,6-trichlorophenol was detected, with only the ortho chlorine removed. Because chlorinated phenolic compounds are widely distributed as natural components in anaerobic environments, our results reveal one mode in which the Dehalococcoides species could have survived through earth history.

Heme-thiolate haloperoxidases: versatile biocatalysts with biotechnological and environmental significance

Heme-thiolate haloperoxidases are undoubtedly the most versatile biocatalysts of the hemeprotein family and share catalytic properties with at least three further classes of heme-containing oxidoreductases, namely, classic plant and fungal peroxidases, cytochrome P450 monooxygenases, and catalases. For a long time, only one enzyme of this type--the chloroperoxidase (CPO) of the ascomycete Caldariomyces fumago--has been known. The enzyme is commercially available as a fine chemical and catalyzes the unspecific chlorination, bromination, and iodation (but no fluorination) of a variety of electrophilic organic substrates via hypohalous acid as actual halogenating agent. In the absence of halide, CPO resembles cytochrome P450s and epoxidizes and hydroxylates activated substrates such as organic sulfides and olefins; aromatic rings, however, are not susceptible to CPO-catalyzed oxygen-transfer. Recently, a second fungal haloperoxidase of the heme-thiolate type has been discovered in the agaric mushroom Agrocybe aegerita. The UV-Vis adsorption spectrum of the isolated enzyme shows little similarity to that of CPO but is almost identical to a resting-state P450. The Agrocybe aegerita peroxidase (AaP) has strong brominating as well as weak chlorinating and iodating activities, and catalyzes both benzylic and aromatic hydroxylations (e.g., of toluene and naphthalene). AaP and related fungal peroxidases could become promising biocatalysts in biotechnological applications because they seemingly fill the gap between CPO and P450 enzymes and act as "self-sufficient" peroxygenases. From the environmental point of view, the existence of a halogenating mushroom enzyme is interesting because it could be linked to the multitude of halogenated compounds known from these organisms.

Degradation of dioxins by cyclic ether degrading fungus,Cordyceps sinensis

Use of the cyclic ether degrading fungus, Cordyceps sinensis strain A to degrade dibenzo-p-dioxin (DD), 2,3,7-trichlorodibenzo-p-dioxin (2,3,7-triCDD) and octachlorodibenzo-p-dioxin (octaCDD) has revealed a new degradation pathway for dioxins. Catechols and other possible degradation products were synthesized to facilitate the identification, detection and quantification of these products, and phenylboronate was used for the derivatization and analysis of dihydroxylated degradation products. Degradation of DD yielded catechol, which was further metabolized to cis,cis-muconate. 2,3,7-triCDD yielded mono- and dichloro-catechol as well as catechol itself; and the cis,cis-muconates were also detected. octaCDD gave mono- to trichloro-catechol as well as catechol, and the cis,cis-muconates were also found. For all tested dioxin samples dechlorination resulted in replacement of chlorine with hydrogen, and no hydroxylation was observed. It appeared that dechlorination may occur in the degradation of octaCDD to catechols and possibly in the subsequent degradation of chlorinated catechols and/or chlorinated cis,cis-muconates to further breakdown products.

Novel Analgesic Triglycerides from Cultures of Agaricus macrosporus and Other Basidiomycetes as Selective Inhibitors of Neurolysin

The agaricoglycerides are a new class of fungal secondary metabolites that constitute esters of chlorinated 4-hydroxy benzoic acid and glycerol. They are produced in cultures of the edible mushroom, Agaricus macrosporus, and several other basidiomycetes of the genera Agaricus, Hypholoma, Psathyrella and Stropharia. The main active principle, agaricoglyceride A, showed strong activities against neurolysin, a protease involved in the regulation of dynorphin and neurotensin metabolism (IC50 = 200 nM), and even exhibited moderate analgesic in vivo activities in an in vivo model. Agaricoglyceride monoacetates (IC50 = 50 nM) showed even stronger in vitro activities. Several further co-metabolites with weaker or lacking bioactivities were also obtained and characterized. Among those were further agaricoglyceride derivatives, as well as further chlorinated phenol derivatives such as the new compound, agaricic ester. The characteristics of the producer organisms, the isolation of bioactive metabolites from cultures of A. macrosporus, their biological activities, and preliminary results on their occurrence in basidiomycetes, are described.

Novel haloperoxidase from the agaric basidiomycete Agrocybe aegerita oxidizes aryl alcohols and aldehydes

Agrocybe aegerita, a bark mulch- and wood-colonizing basidiomycete, was found to produce a peroxidase (AaP) that oxidizes aryl alcohols, such as veratryl and benzyl alcohols, into the corresponding aldehydes and then into benzoic acids. The enzyme also catalyzed the oxidation of typical peroxidase substrates, such as 2,6-dimethoxyphenol (DMP) or 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS). A. aegerita peroxidase production depended on the concentration of organic nitrogen in the medium, and highest enzyme levels were detected in the presence of soybean meal. Two fractions of the enzyme, AaP I and AaP II, which had identical molecular masses (46 kDa) and isoelectric points of 4.6 to 5.4 and 4.9 to 5.6, respectively (corresponding to six different isoforms), were identified after several steps of purification, including anion- and cation-exchange chromatography. The optimum pH for the oxidation of aryl alcohols was found to be around 7, and the enzyme required relatively high concentrations of H(2)O(2) (2 mM) for optimum activity. The apparent K(m) values for ABTS, DMP, benzyl alcohol, veratryl alcohol, and H(2)O(2) were 37, 298, 1,001, 2,367 and 1,313 microM, respectively. The N-terminal amino acid sequences of the main AaP II spots blotted after two-dimensional gel electrophoresis were almost identical and exhibited almost no homology to the sequences of other peroxidases from basidiomycetes, but they shared the first three amino acids, as well as two additional amino acids, with the heme chloroperoxidase (CPO) from the ascomycete Caldariomyces fumago. This finding is consistent with the fact that AaP halogenates monochlorodimedone, the specific substrate of CPO. The existence of haloperoxidases in basidiomycetous fungi may be of general significance for the natural formation of chlorinated organic compounds in forest soils.

Chlorophenol production by anaerobic microorganisms: transformation of a biogenic chlorinated hydroquinone metabolite

Chlorinated hydroquinones of biological origin are fully dechlorinated to 1,4-dihydroquinone by anaerobic bacteria such as Desulfitobacterium spp. (C. E. Milliken, G. P. Meier, J. E. M. Watts, K. R. Sowers, and H. D. May, Appl. Environ. Microbiol. 70:385-392, 2004). In the present study, mixed microbial communities from Baltimore Harbor sediment and a pure culture of Desulfitobacterium sp. strain PCE1 were discovered to demethylate, reductively dehydroxylate, and dechlorinate chlorinated hydroquinones into chlorophenols. Mixed microbial cultures from a freshwater source and several other desulfitobacteria in pure culture did not perform these reactions. Desulfitobacterium sp. strain PCE1 degraded 2,3,5,6-tetrachloro-4-methoxyphenol, a metabolite of basidiomycete fungi, to 2,3,5,6-tetrachlorophenol and 2,3,5-trichlorophenol, recalcitrant compounds that are primarily synthesized anthropogenically.

Chlorobenzoate-degrading bacteria in similar pristine soils exhibit different community structures and population dynamics in response to anthropogenic 2-, 3-, and 4-chlorobenzoate levels

A study was conducted to determine the diversity of 2-, 3-, and 4-chlorobenzoate (CB) degraders in two pristine soils with similar physical and chemical characteristics. Surface soils were collected from forested sites and amended with 500 microg of 2-, 3-, or 4-CB g(-1) soil. The CB levels and degrader numbers were monitored throughout the study. Degraders were isolated, grouped by DNA fingerprints, identified via 16S rDNA sequences, and screened for plasmids. The CB genes in selected degraders were isolated and/or sequenced. In the Madera soil, 2-CB and 4-CB degraded within 11 and 42 d, respectively, but 3-CB did not degrade. In contrast, 3-CB and 4-CB degraded in the Oversite soil within 14 and 28 d, respectively, while 2-CB did not degrade. Approximately 10(7) CFU g(-1) of degraders were detected in the Madera soil with 2-CB, and the Oversite soil with 3- and 4-CB. No degraders were detected in the Madera soil with 4-CB even though the 4-CB degraded. Nearly all of the 2-CB degraders isolated from the Madera soil were identified as a Burkholderia sp. containing chromosomally encoded degradative genes. In contrast, several different 3- and 4-CB degraders were isolated from the Oversite soil, and their populations changed as CB degradation progressed. Most of these 3-CB degraders were identified as Burkholderia spp. while the majority of 4-CB degraders were identified as Bradyrhizobium spp. Several of the 3-CB degraders contained the degradative genes on large plasmids, and there was variation between the plasmids in different isolates. When a fresh sample of Madera soil was amended with 50, 100, or 200 microg 3-CB g(-1), 3-CB degradation occurred, suggesting that 500 microg 3-CB g(-1) was toxic to the degraders. Also, different 3-CB degraders were isolated from the Madera soil at each of the three lower levels of 3-CB. No 2-CB degradation was detected in the Oversite soil even at lower 2-CB levels. These results indicate that the development of 2-, 3-, and 4-CB degrader populations is site-specific and that 2-, 3-, and 4-CB are degraded by different bacterial populations in pristine soils. These results also imply that the microbial ecology of two soils that develop under similar biotic and abiotic environments can be quite different.

Trichloroacetic acid cycling in Sitka spruce saplings and effects on sapling health following long term exposure

Trichloroacetic acid (TCA, CCl(3)COOH) has been associated with forest damage but the source of TCA to trees is poorly characterised. To investigate the routes and effects of TCA uptake in conifers, 120 Sitka spruce (Picea sitchensis (Bong.) Carr) saplings were exposed to control, 10 or 100 microg l(-1) solutions of TCA applied twice weekly to foliage only or soil only over two consecutive 5-month growing seasons. At the end of each growing season similar elevated TCA concentrations (approximate range 200-300 ng g(-1) dwt) were detected in both foliage and soil-dosed saplings exposed to 100 microg l(-1) TCA solutions showing that TCA uptake can occur from both exposure routes. Higher TCA concentrations in branchwood of foliage-dosed saplings suggest that atmospheric TCA in solution is taken up indirectly into conifer needles via branch and stemwood. TCA concentrations in needles declined slowly by only 25-30% over 6 months of winter without dosing. No effect of TCA exposure on sapling growth was measured during the experiment. However at the end of the first growing season needles of saplings exposed to 10 or 100 microg l(-1) foliage-applied TCA showed significantly more visible damage, higher activities of some detoxifying enzymes, lower protein contents and poorer water control than needles of saplings dosed with the same TCA concentrations to the soil. At the end of each growing season the combined TCA storage in needles, stemwood, branchwood and soil of each sapling was <6% of TCA applied. Even with an estimated half-life of tens of days for within-sapling elimination of TCA during the growing season, this indicates that TCA is eliminated rapidly before uptake or accumulates in another compartment. Although TCA stored in sapling needles accounted for only a small proportion of TCA stored in the sapling/soil system it appears to significantly affect some measures of sapling health.

Halometabolites and cellular dehalogenase systems: an evolutionary perspective

We review the role of iodothyronine deiodinases (IDs) in the evolution of vertebrate thyroidal systems within the larger context of biological metabolism of halogens. Since the beginning of life, the ubiquity of organohalogens in the biosphere has provided a major selective pressure for the evolution and conservation of cellular mechanisms specialized in halogen metabolism. Among naturally available halogens, iodine emerged as a critical component of unique developmental and metabolic messengers. Metabolism of iodinated compounds occurs in the three major domains of life, and invertebrate deuterostomes possess several biochemical traits and molecular homologs of vertebrate thyroidal systems, including ancestral homologs of IDs identified in urochordates. The finely tuned cellular regulation of iodometabolite uptake and disposal is a remarkable event in evolution and might have been decisive for the explosive diversification of ontogenetic strategies in vertebrates.

Microbial anaerobic demethylation and dechlorination of chlorinated hydroquinone metabolites synthesized by basidiomycete fungi

The synthesis and degradation of anthropogenic and natural organohalides are the basis of a global halogen cycle. Chlorinated hydroquinone metabolites (CHMs) synthesized by basidiomycete fungi and present in wetland and forest soil are constituents of that cycle. Anaerobic dehalogenating bacteria coexist with basidiomycete fungi in soils and sediments, but little is known about the fate of these halogenated fungal compounds. In sediment microcosms, the CHMs 2,3,5,6-tetrachloro-1,4-dimethoxybenzene and 2,3,5,6-tetrachloro-4-methoxyphenol (TCMP) were anaerobically demethylated to tetrachlorohydroquinone (TCHQ). Subsequently, TCHQ was converted to trichlorohydroquinone and 2,5-dichlorohydroquinone (2,5-DCHQ) in freshwater and estuarine enrichment cultures. Screening of several dehalogenating bacteria revealed that Desulfitobacterium hafniense strains DCB2 and PCP1, Desulfitobacterium chlororespirans strain Co23, and Desulfitobacterium dehalogenans JW/DU1 sequentially dechlorinate TCMP to 2,3,5-trichloro-4-methoxyphenol and 3,5-dichloro-4-methoxyphenol (3,5-DCMP). After a lag, these strains demethylate 3,5-DCMP to 2,6-DCHQ, which is then completely dechlorinated to 1,4-dihydroquinone (HQ). 2,5-DCHQ accumulated as an intermediate during the dechlorination of TCHQ to HQ by the TCMP-degrading desulfitobacteria. HQ accumulation following TCMP or TCHQ dechlorination was transient and became undetectable after 14 days, which suggests mineralization of the fungal compounds. This is the first report on the anaerobic degradation of fungal CHMs, and it establishes a fundamental role for microbial reductive degradation of natural organochlorides in the global halogen cycle.

Stereoselective biosynthesis of chloroarylpropane diols by the basidiomyceteBjerkandera adusta: exploring the roles of amino acids, pyruvate, glycerol and phenyl acetyl carbinol

Bjerkandera adusta produces many chlorometabolites including chlorinated anisyl metabolites (CAMs) and 1-arylpropane-1,2-diols (1, 2, 3, 4) as idiophasic metabolic products of L-phenylalanine. These diols are stereoselectively biosynthesized from a C7-unit (benzylic, from L-phenylalanine) and a C2-unit, of unknown origin, as predominantly erythro (1R,2S) enantiomers. Of the labeled amino acids tested as possible C2-units, at the 4-10 mM level, none were found to efficiently label the 2,3-propane carbons of the diols. However, glycine (2-13C), L-serine (2,3,3-d3) and L-methionine (methyl-d3) entered the biomethylation pathway. Neither pyruvate (2,3-13C2), acetate (1,2-13C2), acetaldehyde (d4) nor ethanol (ethyl-d5) labeled the 2,3-propane carbons of the diols at the 4-10 mM level. Pyruvate (2,3-13C2) and L-serine (2,3,3-d3) (which also entered the biomethylation pathway) did, however, effectively label the 2,3-propane carbons of the alpha-ketols and diols at the 40 mM level as evidenced by mass spectrometry. Glycerol (1,1,2,3,3-d5) also appeared to label one of the 2,3-propane carbons (ca. 5% as 2H2 in the C3 side chain) as suggested by mass spectrometric data and also entered the biomethylation pathway, likely via amino acid synthesis. Glycerol (through pyruvate), therefore, likely supplies C2 and C3 of the propane side chain with arylpropane diol biosynthesis. Incubation of B. adusta with synthetic [2-2H1, 2-18O]-glycerol showed that neither 2H nor 18O were incorporated in the alpha-ketols or diols. The oxygen atom on the C2 of the ketols/diols, therefore, does not appear to come from the oxygen atom on the C2 of glycerol. Glycerol, however, can readily form L-serine (which can then form pyruvate via PLP/serine dehydratase and involve transamination washing out the 18O label and providing the oxygen from water), and can then go on to label the C2-unit. Labeled alpha-ketol, phenyl acetyl carbinol (5) (PAC; ring-d(5), 2,3-13C2 propane) cultured with B. adusta leads to stereospecific reduction to the (1R,2S)-diol (6) (ring-d5 and 2,3-13C2); in all other metabolites produced, the 2,3-13C2) label is washed out. Incubation of the fungus with 4-fluorobenzaldehyde (13) produces a pooling of predominantly erythro (1R,2S) 1-(4'-fluorophenyl)-1,2-propane diol (18 as diacetate) (through the corresponding alpha-ketols 16, 17). Blocking the para-position with fluorine thus appears to prevent ring oxygenation and also chlorination, forcing the conclusion that para-ring oxygenation precedes meta-chlorination.

Stereoselective biosynthesis of chloroarylpropane diols by the basidiomycete Bjerkandera adusta

Previously we have shown that 1-arylpropane-1,2-diols are catabolic products of L-phenylalanine during idiophasic metabolism of B. adusta that are stereoselectively biosynthesized from a C(7)-unit (ring+benzylic carbon) and a C(2)-unit as predominantly erythro 1R, 2S enantiomers.In order to probe the mechanism of 1-arylpropane-1,2-diol formation, the products of the incubation of isotopically labelled aromatic aldehydes as substrates with Bjerkandera adusta (DAOM 215869) have been characterized. The aromatic aldehydes were benzaldehyde (ring D(5)) and 4-methoxy- and 4-hydroxybenzaldehydes (ring 13C(6)). These aldehydes were all stereoselectively incorporated into the corresponding 1-arylpropane-1,2-diols, including the chloro analogues, as well as into the corresponding alpha-ketols (phenyl acetyl carbinols (PAC's) and 2-hydroxy propiophenones (2-HPP's)) the presumed precursors of the diols. Benzoic acid (ring D(5)) was likewise incorporated into the diols, chlorodiols and alpha-ketols. These results lead us to conclude that the aromatic aldehydes benzaldehyde, 4-hydroxybenzaldehyde and 4-methoxybenzaldehyde are likely C(7)-unit precursors in the carboligation reaction(s) that leads to 1-arylpropane-1,2-diol biosynthesis. The metabolic role of the diols remains to be elucidated but they may be important intermediates in CAM (chlorinated anisyl metabolite) aldehyde-alcohol cycling and also act as substrates for the chlorination/hydroxylation enzymes yet to be identified in white rot fungi.

Characterization of the 4-hydroxybenzoyl-coenzyme A thioesterase from Arthrobacter sp. strain SU

The Arthrobacter sp. strain SU 4-chlorobenzoate (4-CBA) dehalogenation pathway converts 4-CBA to 4-hydroxybenzoate (4-HBA). The pathway operon contains the genes fcbA, fcbB, and fcbC (A. Schmitz, K. H. Gartemann, J. Fiedler, E. Grund, and R. Eichenlaub, Appl. Environ. Microbiol. 58:4068-4071, 1992). Genes fcbA and fcbB encode 4-CBA-coenzyme A (CoA) ligase and 4-CBA-CoA dehalogenase, respectively, whereas the function of fcbC is not known. We subcloned fcbC and expressed it in Escherichia coli, and we purified and characterized the FcbC protein. A substrate activity screen identified benzoyl-CoA thioesters as the most active substrates. Catalysis of 4-HBA-CoA hydrolysis to 4-HBA and CoA occurred with a k(cat) of 6.7 s(-1) and a K(m) of 1.2 micro M. The k(cat) pH rate profile for 4-HBA-CoA hydrolysis indicated optimal activity over a pH range of 6 to 10. The amino acid sequence of the FcbC protein was compared to other sequences contained in the protein sequence data banks. A large number of sequence homologues of unknown function were identified. On the other hand, the 4-HBA-CoA thioesterases isolated from 4-CBA-degrading Pseudomonas strains did not share significant sequence identity with the FcbC protein, indicating early divergence of the thioesterase-encoding genes.