Seasonal differences in trace metal concentrations in the major rivers of the hyper-arid southwestern Andes basins of Peru.

The southern rivers of Peru originate in the Andes Mountains and flow in a southwestern direction to the Pacific Ocean through one of the most hyper-arid regions of the world. During each sub-equatorial summer from December to February, rains and snow melt in the Andes increase the streamflow in these rivers, even as they pass through the 100 km arid zone to the ocean. This study quantified seasonal dynamics of 34 trace metal elements (TM) and other constituent concentrations in four southern river basins of Peru (Chili-Quilca, Tambo, Camana-Majes-Colca, and Ocoña) during 2019-2020. Consistent with previous studies, we observed that: (1) the river water in the southern basins had relatively high concentrations of B, As, Fe, Al, Mn, P, Pb and Ni, with As the most ubiquitous toxic TM in all the basins, often detected at concentrations surpassing Peruvian and USEPA regulated concentrations; and (2) basins with the most to least toxic TM contamination were the Tambo > Chili-Quilca > Camana-Majes-Colca > Ocoña. Seasonal streamflow strongly influenced the concentrations of twenty TM, with 15 TM (Al, Au, Ba, Cd, Co, Cu, Fe, Gd, Mn, Ni, P, Pb, Ti, Yb and Zr) consistently higher in the wet season, and with As, B, Ge, Li, and Pd higher in the dry season. Our results improve the understanding of seasonal variability and vulnerability in western Andes superficial water sources, which are highly influenced by both local geogenic and anthropogenic conditions. A Spanish translation of this paper is available in the online Supplementary Material.

Litter quality, dispersal and invasion drive earthworm community dynamics and forest soil development.

In temperate deciduous forests of eastern USA, most earthworm communities are dominated by invasive species. Their structure and functional group composition have critical impacts on ecological properties and processes. However, the factors determining their community structure are still poorly understood, and little is known regarding their dynamics during forest succession and the mechanisms leading to these changes. Earthworm communities are usually assumed to be stable and driven by vegetation. In contrast, the importance of dispersal and ecological drift is seldom acknowledged. By analyzing a 19-year dataset collected from forest stands in eastern USA, we demonstrated that on a decadal timescale, earthworm community dynamics are shaped by the interplay of selection, dispersal, and ecological drift. We highlighted that forests at different successional stages have distinct earthworm species and functional groups as a result of environmental filtering through leaf litter quality. Specifically, young forests are characterized by soil-feeding species that rely on relatively fresh soil organic matter derived from fast-decomposing litter, whereas old forests are characterized by those feeding on highly processed soil organic matter derived from slow-decomposing litter. In addition, year-to-year species gains and losses are primarily driven by dispersal from regional to local species pools, and by local extinction resulted from competition and ecological drift. We concluded that with continued dispersal of European species and the recent "second wave" of earthworm invasion by Asian species from the surrounding landscape, earthworms at the investigated forests are well-established, and will remain as the major drivers of soil development for the foreseeable future.

Degradation and Microbial Uptake of C60 Fullerols in Contrasting Agricultural Soils.

The environmental fate of functionalized carbon nanomaterials (CNM) remains poorly understood. Using 13C-labeled nanomaterial we present the results of a study investigating the mineralization and microbial uptake of surface-functionalized C60 (fullerols) in agricultural soils with contrasting properties. Soil microcosms rapidly mineralized fullerol C, as determined by 13C-content in the respired CO2, with higher fullerol mineralization in an organic, clay-rich soil versus a silty, low C soil (∼56.3% vs ∼30.9% fullerol C mineralized over 65 days). By tracking the enriched 13C from fullerol into microbial phospholipid fatty acids (PLFA) we also report, for the first time, the incorporation of nanomaterial-derived C into soil microbial biomass, primarily by fungi and Gram-negative bacteria. While more fullerol C was incorporated into PLFA in the organic C-rich soil (0.77% vs 0.19% of PLFA C), this soil incorporated fullerol C into biomass less efficiently than the silty, low C soil (0.13% and 0.84% of assimilated fullerol C, respectively). These results demonstrate that, in contrast to pristine C60, surface functionalized C60 are unlikely to accumulate in surface soils and are readily mineralized by a range of soil microorganisms.

Belowground competition among invading detritivores.

The factors regulating soil animal communities are poorly understood. Current theory favors niche complementarity and facilitation over competition as the primary forms of non-trophic interspecific interaction in soil fauna; however, competition has frequently been suggested as an important community-structuring factor in earthworms, ecosystem engineers that influence belowground processes. To date, direct evidence of competition in earthworms is lacking due to the difficulty inherent in identifying a limiting resource for saprophagous animals. In the present study, we offer the first direct evidence of interspecific competition for food in this dominant soil detritivore group by combining field observations with laboratory mesocosm experiments using 13C and 15N double-enriched leaf litter to track consumption patterns. In our experiments, the Asian invasive species Amynthas hilgendorfi was a dominant competitor for leaf litter against two European species currently invading the temperate deciduous forests in North America. This competitive advantage may account for recent invasion success of A. hilgendorfi in forests with established populations of European species, and we hypothesize that specific phenological differences play an important role in determining the outcome of the belowground competition. In contrast, Eisenoides lonnbergi, a common native species in the Eastern United States, occupied a unique trophic position with limited interactions with other species, which may contribute to its persistence in habitats dominated by invasive species. Furthermore, our results supported neither the hypothesis that facilitation occurs between species of different functional groups nor the hypothesis that species in the same group exhibit functional equivalency in C and N translocation in the soil. We propose that species identity is a more powerful approach to understand earthworm invasion and its impacts on belowground processes.

Weathering of pyrogenic organic matter induces fungal oxidative enzyme response in single culture inoculation experiments.

The addition of pyrogenic organic matter (PyOM), the aromatic carbon-rich product of the incomplete combustion of plant biomass or fossil fuels, to soil can influence the rate of microbial metabolism of native soil carbon. The interaction of soil heterotrophs with PyOM may be governed by the surficial chemical and physical properties of PyOM that evolve with environmental exposure. We present results of a 36-day laboratory incubation investigating the interaction of a common white-rot fungus, Trametes versicolor, with three forms of 13C-enriched (2.08 atom% 13C) PyOM derived from Pinus ponderosa (450 °C): one freshly produced, and two artificially weathered (254 nm, UV light-water treatment and water-leaching alone). Analysis (FTIR, XPS) of the UV-weathered PyOM showed increased aliphatic C-H content and oxidation of aromatic carbon relative to both the original and water-leached PyOM. The addition of both weathered forms of PyOM stimulated (positively primed) fungal respiration of the growth media, while the unaltered PyOM mildly inhibited (negatively primed) respiration. Artificial weathering resulted in higher oxidative (laccase and peroxidase) enzyme activity than unaltered PyOM, possibly the result of a diminished capacity to bind reactive substrates and extracellular enzymes after weathering. However, and contrary to expectations, simple water-leached weathering resulted in a relatively higher enzyme activity and respiration than that of UV-weathering. The 13C content of respired CO2 indicated negligible fungal oxidation of PyOM for all treatments, demonstrating the overall low microbial reactivity of this high temperature PyOM. The increased enzymatic and positive priming response of T. versicolor to weathered PyOM highlights the importance of weathering-induced chemistry in controlling PyOM-microbe-soil carbon interactions.

Effects of elevated CO2 on the extractable amino acids of leaf litter and fine roots.

Elevated atmospheric CO2 concentrations can change chemistry and input rate of plant tissue to soil, potentially influencing above- and below-ground biogeochemical cycles. Given the important role played by leaf and root litter chemistry in controlling ecosystem function and vulnerability to environmental stresses, we investigated the hydrolyzable amino acid distribution and concentration in leaf and fine root litter among control and elevated CO2 treatments at the Rhinelander free air CO2 enrichment (FACE) experiment (WI, USA). We extracted hydrolyzable amino acids from leaf litter and fine (< 2 mm) roots at three depths for both control and elevated CO2 plots. We found that elevated CO2 decreased the proportion of total leaf amino acid carbon (C), but had no effect on total leaf amino acid nitrogen (N). There was no treatment effect for total root amino acid N or amino acid C for any depth. The decrease in leaf amino acids is probably a result of the shift of protein compounds to more structural compounds. Despite the decrease in leaf amino acid C concentrations, the overall increase in annual plant production under elevated CO2 would result in an increase in plant amino acids to the soil.

Invasive Japanese beetle (Popillia japonica Newman) larvae alter structure and carbon distribution in infested surface soil.

Invasive macrofauna influence the biophysical state and function of soil, helping to drive ecological changes over time. Many soil-dwelling invertebrates affect soil stability by facilitating or hindering the soil aggregation process, changing the availability of plant and soil organic matter (SOM) for aggregate incorporation, and shifting the predominant mechanisms by which carbon is incorporated into soil aggregates. Using mass fractionation and stable carbon isotope techniques, this 17-month experimental study examined silt-clay-loam mesocosms either infested or not infested with soil-dwelling larvae of the invasive Japanese beetle, Popillia japonica Newman (JB). We hypothesized that larval root-herbivory would promote a pathway of large aggregate formation that features the mixing of digested root tissue with mineral soil and subsequent fecal deposition. These newly deposited, large soil aggregates will then grow by agglomeration of particles, thereby occluding a larger pool of fresh organic carbon, or be broken apart, exposing fresh organic inputs to microbial activity and mineralization processes, depending on soil conditions. Findings show a proportional increase of larger soil size fractions (2- 8 mm) in the rhizosphere of infested soil after 1½ life cycles of the beetle, but a decrease in the smaller soil size fractions (0.053-2 mm). In infested bulk surface soil (0-2.5 cm) carbon increased, primarily due to greater carbon content in the largest size fractions. Carbon also increased in all size fractions, although the proportion of total carbon in fractions was greater only in the largest fractions due to their greater relative abundance. There may also be an increase of microbially derived carbon in the largest size fractions, possibly indicating significant priming effects associated with JB larval herbivory. The implications of these findings for relative stabilization of the bulk surface soil carbon pool in JB-infested soil likely depends on the residence time of, and stable microaggregate formation within these large size fractions.

Storm pulse responses of fluvial organic carbon to seasonal source supply and transport controls in a midwestern agricultural watershed.

Storm events are the primary mechanisms of delivering fluvial organic carbon (OC) in both dissolved (DOC) and particulate (POC) forms but their sources and flow pathways can vary with seasonal land use and weather. Within the low relief and poorly drained landscapes of a predominantly agricultural watershed in Eastern Iowa, six storm events were monitored for DOC and POC concentrations over a two hydrological year period in order to investigate the export mechanisms, landscape connectivity, and hydro-climatological controls of fluvial OC under representative events and associated management practices. Event-driven dynamics favored POC over DOC, where POC accounted for 54-94 % of total OC export during events, highlighting a sampling-driven bias against POC in the absence of event monitoring. The disparity between POC and DOC export exhibited a seasonal effect, where the POC:DOC export ratio was low (1.3-1.7) for October events while June/July events yielded a much higher value (up to a value of 14.7). The relationships between event DOC and POC export, Normalized Difference Vegetation Index of landscapes, and antecedent wetness conditions suggest a strong interaction or competing influences between vegetation coverage and runoff-generation threshold. While we recognize the low statistical power of the limited data set (n = 6), the storm events could be binned into two clusters: a "bare soil" period and a crop "rapid growth" period. Specifically, intra-storm variations in OC concentration and concentration-discharge (C-Q) hysteresis patterns demonstrated a seasonally-dependent access to contributing OC sources, which can be viewed as the rapid liberation of DOC during the "bare soil" period, and a progressive leaching of terrestrial DOC during the "rapid growth" period. Although high resolution event monitoring of fluvial carbon is rare this work highlights the importance of such efforts to predict C sourcing and transformation in inland water systems under variable land use and across seasons.

Lignocellulosic polysaccharides and lignin degradation by wood decay fungi: the relevance of nonenzymatic Fenton-based reactions.

The brown rot fungus Wolfiporia cocos and the selective white rot fungus Perenniporia medulla-panis produce peptides and phenolate-derivative compounds as low molecular weight Fe³+-reductants. Phenolates were the major compounds with Fe³+-reducing activity in both fungi and displayed Fe³+-reducing activity at pH 2.0 and 4.5 in the absence and presence of oxalic acid. The chemical structures of these compounds were identified. Together with Fe³+ and H2O2 (mediated Fenton reaction) they produced oxygen radicals that oxidized lignocellulosic polysaccharides and lignin extensively in vitro under conditions similar to those found in vivo. These results indicate that, in addition to the extensively studied Gloeophyllum trabeum--a model brown rot fungus--other brown rot fungi as well as selective white rot fungi, possess the means to promote Fenton chemistry to degrade cellulose and hemicellulose, and to modify lignin. Moreover, new information is provided, particularly regarding how lignin is attacked, and either repolymerized or solubilized depending on the type of fungal attack, and suggests a new pathway for selective white rot degradation of wood. The importance of Fenton reactions mediated by phenolates operating separately or synergistically with carbohydrate-degrading enzymes in brown rot fungi, and lignin-modifying enzymes in white rot fungi is discussed. This research improves our understanding of natural processes in carbon cycling in the environment, which may enable the exploration of novel methods for bioconversion of lignocellulose in the production of biofuels or polymers, in addition to the development of new and better ways to protect wood from degradation by microorganisms.

Lignin degradation in wood-feeding insects.

The aromatic polymer lignin protects plants from most forms of microbial attack. Despite the fact that a significant fraction of all lignocellulose degraded passes through arthropod guts, the fate of lignin in these systems is not known. Using tetramethylammonium hydroxide thermochemolysis, we show lignin degradation by two insect species, the Asian longhorned beetle (Anoplophora glabripennis) and the Pacific dampwood termite (Zootermopsis angusticollis). In both the beetle and termite, significant levels of propyl side-chain oxidation (depolymerization) and demethylation of ring methoxyl groups is detected; for the termite, ring hydroxylation is also observed. In addition, culture-independent fungal gut community analysis of A. glabripennis identified a single species of fungus in the Fusarium solani/Nectria haematococca species complex. This is a soft-rot fungus that may be contributing to wood degradation. These results transform our understanding of lignin degradation by wood-feeding insects.

Biomimetic oxidative treatment of spruce wood studied by pyrolysis-molecular beam mass spectrometry coupled with multivariate analysis and 13C-labeled tetramethylammonium hydroxide thermochemolysis: implications for fungal degradation of wood.

In this work, pyrolysis-molecular beam mass spectrometry analysis coupled with principal components analysis and (13)C-labeled tetramethylammonium hydroxide thermochemolysis were used to study lignin oxidation, depolymerization, and demethylation of spruce wood treated by biomimetic oxidative systems. Neat Fenton and chelator-mediated Fenton reaction (CMFR) systems as well as cellulosic enzyme treatments were used to mimic the nonenzymatic process involved in wood brown-rot biodegradation. The results suggest that compared with enzymatic processes, Fenton-based treatment more readily opens the structure of the lignocellulosic matrix, freeing cellulose fibrils from the matrix. The results demonstrate that, under the current treatment conditions, Fenton and CMFR treatment cause limited demethoxylation of lignin in the insoluble wood residue. However, analysis of a water-extractable fraction revealed considerable soluble lignin residue structures that had undergone side chain oxidation as well as demethoxylation upon CMFR treatment. This research has implications for our understanding of nonenzymatic degradation of wood and the diffusion of CMFR agents in the wood cell wall during fungal degradation processes.

Quantitative analysis of diverse sporomorph-derived sporopollenins.

Over the years studies on sporopollenin have reported a wide variety of structures. However, the methods and techniques used to elucidate sporopollenin structures are highly diverse so that much is still unclear with respect to the nature and structural diversity of sporopollenins. In order to investigate the structural diversity in sporopollenin between different taxa, extant sporomorphs of ten different species ranging from a mushroom to a cycad were examined using a relatively simple and fast analytical procedure. Sporomorphs, before and after saponification, were analysed for sporopollenin composition by Thermally assisted Hydrolysis and Methylation (THM) using [13C]tetramethylammonium hydroxide ([13C]TMAH). The sporomorp chemical composition differed markedly between the groups of organisms analysed. Moreover, we not only identified the nature and relative quantities of the well-known sporopollenin constituents p-coumaric acid and ferulic acid but also many other phenolic moieties, such as caffeic acid, which appeared to be the most abundant phenolic constituent in spores of Equisetum palustre, Salvinia molesta, Cyrtomium falcatum and Anemia phyllitidis. Within the two Equisetum species analysed as well as in the closely related Azolla and Salvinia species the same suite of phenolic constituents were observed, but their relative distribution varied largely. We thus demonstrate the existence of a high structural diversity, both qualitatively and quantitatively in sporopollenins enabling future studies related to the evolution, phylogeny and (palaeo)environment of sporopollenin-producing organisms. Furthermore, a better knowledge of sporopollenin and its structural variety is of relevance to the rapidly growing application of spores and pollen as a drug delivery agent in medicine.

Gut anatomical properties and microbial functional assembly promote lignocellulose deconstruction and colony subsistence of a wood-feeding beetle.

Beneficial microbial associations enhance the fitness of most living organisms, and wood-feeding insects offer some of the most striking examples of this. Odontotaenius disjunctus is a wood-feeding beetle that possesses a digestive tract with four main compartments, each of which contains well-differentiated microbial populations, suggesting that anatomical properties and separation of these compartments may enhance energy extraction from woody biomass. Here, using integrated chemical analyses, we demonstrate that lignocellulose deconstruction and fermentation occur sequentially across compartments, and that selection for microbial groups and their metabolic pathways is facilitated by gut anatomical features. Metaproteogenomics showed that higher oxygen concentration in the midgut drives lignocellulose depolymerization, while a thicker gut wall in the anterior hindgut reduces oxygen diffusion and favours hydrogen accumulation, facilitating fermentation, homoacetogenesis and nitrogen fixation. We demonstrate that depolymerization continues in the posterior hindgut, and that the beetle excretes an energy- and nutrient-rich product on which its offspring subsist and develop. Our results show that the establishment of beneficial microbial partners within a host requires both the acquisition of the microorganisms and the formation of specific habitats within the host to promote key microbial metabolic functions. Together, gut anatomical properties and microbial functional assembly enable lignocellulose deconstruction and colony subsistence on an extremely nutrient-poor diet.

Applicability of a "Multi-Stage Pulse Labeling" 15N Approach to Phenotype N Dynamics in Maize Plant Components during the Growing Season.

Highlights This work utilizes "multi-stage pulse labeling" 15N applications, primarily during reproductive growth stages, as a phenotyping strategy to identify maize hybrids with superior N use efficiency (NUE) under low N conditions. Research using labeled isotopic N (15N) can precisely quantify fertilizer nitrogen (N) uptake and organ-specific N allocation in field crops such as maize (Zea mays L.). The overall research objective was to study plant N uptake patterns potentially correlated with N use efficiency (NUE) in field-grown maize hybrids using a "multi-stage pulse labeling" 15N phenotyping strategy with an emphasis on the reproductive period. Five hybrids varying in NUE were compared under zero N fertilizer application (0N) plus a moderate rate of 112 kg N ha-1 (112N) in 2013 (2 locations) and 2014 growing seasons. The equivalent of 3.2 (2013) to 2.1 (2014) kg of 15N ha-1, as labeled Ca(15NO3)2, was injected into soil on both sides of consecutive plants at multiple stages between V14 and R5. Aboveground plant biomass was primarily collected in short-term intervals (4-6 days after each 15N application) in both years, and following a single long-term interval (at R6 after 15N injection at R1) in 2014. Averaged across hybrids and site-years, the moderate N rate (112N) increased absolute 15N uptake at all stages; however, plants in the 0N treatment allocated proportionally more 15N to reproductive organs. Before flowering, short-term recovery of 15N (15Nrec) totaled ~0.30 or 0.40 kg kg-1 of the 15N applied, and ~50% of that accumulated 15Nu was found in leaves and 40% in stems. After flowering, plant 15Nrec totaled ~0.30 kg kg-1 of 15N applied, and an average 30% of accumulated 15Nu was present in leaves, 17% in stems, and the remainder-usually the majority-in ears. At the R5 stage, despite a declining overall rate of 15N uptake per GDD thermal unit, plant 15Nrec represented ~0.25 kg kg-1 of 15N applied, of which ~65% was allocated to kernels. Overall long-term 15Nrec during grain filling was ~0.45 and 0.70 kg kg-1 of total 15N applied at R1 with 0 and 112N, respectively, and most (~77%) 15N uptake was found in kernels. The "multi-stage pulse labeling" technique proved to be a robust phenotyping strategy to differentiate reproductive-stage N uptake/allocation patterns to plant organs and maize efficiencies with newly available fertilizer N.

Birnessite mediated debromination of decabromodiphenyl ether.

Decabromodiphenyl ether (BDE-209) is a major component of a commercial flame retardant formulation; however, there is limited information on the fate of BDE-209 in the environment, including metal oxide mediated degradation. Laboratory experiments were conducted to investigate the birnessite (delta-MnO(2))-promoted debromination of BDE-209 in tetrahydrofuran (THF)-water systems as well as catechol solutions. Up to 100% (0.1044 micromol initial charge) of BDE-209 disappeared upon reaction with birnessite in THF/H(2)O (4:6-9:1). The formation of aqueous Br(-) from BDE-209 reduction was determined and up to 16 mole% of initial bromine was released over the course of the reaction indicating approximately 1.7 Br-C bonds were reduced per BDE-209 molecule. The distribution of debrominated congeners, however, indicated a much greater extent of debromination for some products than what was inferred from an average bromine mass balance. The produced congeners varied from tetra- to nona-bromodiphenyl ether, including BDE-47 and -99, during the 24 h reaction. Experiments with deuterated water indicated that water was not the major hydrogen donor in the reduction but rather THF provided the reducing power. This conclusion was supported by the presence of succinic acid, which was produced from oxidation of THF. The reactions with aqueous catechol, rather than THF-water mixtures, were performed to assess the possible role that compounds found in natural environments, such a tannin-like phenols, might have on the chemistry. These experiments indicated that birnessite mediated debromination of BDE-209 might occur in natural settings.

Changes in northeast African hydrology and vegetation associated with Pliocene-Pleistocene sapropel cycles.

East African climate change since the Late Miocene consisted of persistent shorter-term, orbital-scale wet-dry cycles superimposed upon a long-term trend towards more open, grassy landscapes. Either or both of these modes of palaeoclimate variability may have influenced East African mammalian evolution, yet the interrelationship between these secular and orbital palaeoclimate signals remains poorly understood. Here, we explore whether the long-term secular climate change was also accompanied by significant changes at the orbital-scale. We develop northeast African hydroclimate and vegetation proxy data for two 100 kyr-duration windows near 3.05 and 1.75 Ma at ODP Site 967 in the eastern Mediterranean basin, where sedimentation is dominated by eastern Sahara dust input and Nile River run-off. These two windows were selected because they have comparable orbital configurations and bracket an important increase in East African C4 grasslands. We conducted high-resolution (2.5 kyr sampling) multiproxy biomarker, H- and C-isotopic analyses of plant waxes and lignin phenols to document orbital-scale changes in hydrology, vegetation and woody cover for these two intervals. Both intervals are dominated by large-amplitude, precession-scale (approx. 20 kyr) changes in northeast African vegetation and rainfall/run-off. The δ(13)Cwax values and lignin phenol composition record a variable but consistently C4 grass-dominated ecosystem for both intervals (50-80% C4). Precessional δDwax cycles were approximately 20-30‰ in peak-to-peak amplitude, comparable with other δDwax records of the Early Holocene African Humid Period. There were no significant differences in the means or variances of the δDwax or δ(13)Cwax data for the 3.05 and 1.75 Ma intervals studied, suggesting that the palaeohydrology and palaeovegetation responses to precessional forcing were similar for these two periods. Data for these two windows suggest that the eastern Sahara did not experience the significant increase in C4 vegetation that has been observed in East Africa over this time period. This observation would be consistent with a proposed mechanism whereby East African precipitation is reduced, and drier conditions established, in response to the emergence of modern zonal sea surface temperature gradients in the tropical oceans between 3 and 2 Ma.This article is part of the themed issue 'Major transitions in human evolution'.

Soil microbial response to photo-degraded C60 fullerenes.

Recent studies indicate that while unfunctionalized carbon nanomaterials (CNMs) exhibit very low decomposition rates in soils, even minor surface functionalization (e.g., as a result of photochemical weathering) may accelerate microbial decay. We present results from a C60 fullerene-soil incubation study designed to investigate the potential links between photochemical and microbial degradation of photo-irradiated C60. Irradiating aqueous (13)C-labeled C60 with solar-wavelength light resulted in a complex mixture of intermediate products with decreased aromaticity. Although addition of irradiated C60 to soil microcosms had little effect on net soil respiration, excess (13)C in the respired CO2 demonstrates that photo-irradiating C60 enhanced its degradation in soil, with ∼ 0.78% of 60 day photo-irradiated C60 mineralized. Community analysis by DGGE found that soil microbial community structure was altered and depended on the photo-treatment duration. These findings demonstrate how abiotic and biotic transformation processes can couple to influence degradation of CNMs in the natural environment.

Oxidative enzymatic response of white-rot fungi to single-walled carbon nanotubes.

Although carbon nanomaterials such as single-walled carbon nanotubes (SWCNT) are becoming increasingly prevalent in manufacturing, there is little knowledge on the environmental fate of these materials. Environmental degradation of SWCNT is hindered by their highly condensed aromatic structure as well as the size and aspect ratio, which prevents intracellular degradation and limits microbial decomposition to extracellular processes such as those catalyzed by oxidative enzymes. This study investigates the peroxidase and laccase enzymatic response of the saprotrophic white-rot fungi Trametes versicolor and Phlebia tremellosa when exposed to SWCNTs of different purity and surface chemistry under different growth conditions. Both unpurified, metal catalyst-rich SWCNT and purified, carboxylated SWCNTs promoted significant changes in the oxidative enzyme activity of the fungi while pristine SWCNT did not. These results suggest that functionalization of purified SWCNT is essential to up regulate enzymes that may be capable of decomposing CNT in the environment.

Lignocellulose modifications by brown rot fungi and their effects, as pretreatments, on cellulolysis.

Brown rot fungi Gloeophyllum trabeum and Postia placenta were used to degrade aspen, spruce, or corn stover over 16 weeks. Decayed residues were saccharified using commercial cellulases or brown rot fungal extracts, loaded at equal but low endoglucanase titers. Saccharification was then repeated for high-yield samples using full strength commercial cellulases. Overall, brown rot pretreatments enhanced yields up to threefold when using either cellulase preparation. In the best case, aspen degraded 2 weeks by G. trabeum yielded 72% glucose-from-cellulose, a 51% yield relative to original glucan. A follow-up trial with more frequent harvests showed similar patterns and demonstrated interplay between tissue modifications and saccharification. Hemicellulose and vanillic acid (G6) or vanillin (G4) lignin residues were good predictors of saccharification potential, the latter notable given lignin's potential active role in brown rot. Results show basic relationships over a brown rot time course and lend targets for controlling an applied bioconversion process.

White-rot basidiomycete-mediated decomposition of C60 fullerol.

Industrially produced carbon-based nanomaterials (CNM), including fullerenes and nanotubes, will be introduced into the environment in increasing amounts in the next decades. One likely environmental chemical transformation of C60 is oxidation to C60 fullerol through both abiotic- and biotic-mediated means. Unfortunately, knowledge of the environmental fate of oxidized CNM is lacking. This study used bulk and compound-specific 13C stable isotope ratio mass spectrometry techniques and spectroradiometry analysis to examine the ability of two white rot basidiomycete fungi (Phlebia tremellosa and Trametes versicolor) to metabolize and degrade an oxygenated CNM, C60 fullerol. After 32 weeks of decay, both fungi were able to bleach and oxidize fullerol to CO2. Additionally, the fungi incorporated minor amounts of the fullerol carbon into lipid biomass. These findings are significant in that they represent the first report of direct biodegradation and utilization of any fullerene derivative and provide valuable information about the possible environmental fates of other CNM.