Differences in ingestive behavior between grazing goats and sheep at the bite scale.

This study aimed to clarify the differences in ingestive behavior between goats and sheep at the bite scale. Animals were allowed to graze a feeding station of bahiagrass (Paspalum notatum Flügge) with two sward heights (short and tall) to two levels of bite depletion (20 and 40 bites). Ingestive behavior variables, which represent the rate and mass of bites and chews, intake rate, bite dimensions, and bite placement characteristics, were quantified. The interspecies difference in ingestive behavior became obvious at the short sward. Goats reduced the inter-bite distance and maintained bite overlapping but took deeper bites than sheep at the short sward, resulting in slightly greater bite mass. These behavioral changes with efficient chewing may be helpful to maintain the intake rate at the short sward. Sheep maintained their inter-bite distance regardless of the sward height and decreased overlapping bites at the short sward. These behavioral characteristics in sheep in response to sward height may partly compensate for the decrease in the bite mass at the short sward, although it may not always maintain the intake rate. Thus, the present study suggests that goats and sheep implement different bite scale ingestive behaviors, including bite placement, when they eat short swards.

A 75-year history of microplastic fragment accumulation rates in a semi-enclosed hypoxic basin.

Plastic budgets in the marine environment and their long-term trends are yet to be fully understood. Measuring the accumulation rates in bottom sediments is crucial to solving the riddle of missing ocean plastics. Previous studies based on coastal sediment cores have found that accumulation rates have increased with increases in plastic production and/or regional populations. However, the correlations between the rates and bioactivities or ocean dynamics, which are crucial for modeling the microplastic sinking process, have not been examined. We revealed a 75-year microplastic fragment (0.3-5.0 mm) accumulation rate history in a hypoxic basin, Beppu Bay, Japan, based on multi-core analysis and 210Pb dating of the sediment which was cross-checked by time control with 137Cs radioactivity peaks. We found that a long-term linear increasing trend with an approximately 20-year variation overlapped with significant peaks around 1990 and 2014 with the first polypropylene microplastic fragment detected from a 1958.8-1961.0 CE sediment layer. The maximum rate was 203 pieces m-2 y-1 with an abundance of 86 pieces kg-1-dry in 2014. Smaller fragments in the size range of 0.3-2.0 mm have been consistently dominant in terms of the accumulation rate throughout the 1955-2015 period, accounting for 85.3 % of the total accumulation rate. The three major polymers (polyethylene, polypropylene, and polystyrene) accounted for 96.6 % of the total rate. The rate was highly and positively correlated with the chlorophyll-a accumulation rate and concentration in the sediment. Based on the microplastic accumulation rates and concentration in the seawater, the mean sinking velocity of microplastics was estimated to be in the order of 101 m d-1. Our results will contribute to significant progress in modeling the microplastic sinking process by offering the first field measurement-based mean sinking velocity and significant correlations between the rate and bioactivity-related signals.

Effect of particle size on the colonization of biofilms and the potential of biofilm-covered microplastics as metal carriers.

Upon release into the aquatic environment, the surface of microplastics (MPs) can be readily colonized by biofilms, which may enhance the adsorption of contaminants. In this study, industrial-grade polystyrene (PS) of about 4 mm in size (MP4000-1), food-grade PS of about 4 mm in size (MP4000-2), and Powder PS of about 75 µm in size (MP75) were co-cultured with a model freshwater fungus, namely Acremonium strictum strain KR21-2, for seven days to form biofilms on their surface. We also determined the changes in surface physicochemical properties of the biofilm-covered MPs (BMPs) and the heavy metal adsorption capacity of the original MPs and BMPs. The results revealed that the biofilms improve the adsorption of heavy metals on MPs, and the particle size of MPs plays a crucial role in biofilm colonization and adsorption of heavy metals by BMPs. MP75 can carry more biofilm on its surface than that of the two MP4000s and form heteroaggregates with biofilms. In addition, there were more functional groups on the surface of BMP75 than on the surface of the two BMP4000s, which could promote the electrostatic interaction and chemical association of heavy metals. Moreover, BMP75 exhibited a higher capacity to adsorb Cu and reduce Cr (VI), which may be related to the functional groups in its biofilm. Overall, this study showed that after biofilms colonization, BMPs of smaller size have more significant potential as a metal vector, and the particle size deserves more scientific attention during the risk assessment.

Removal of heavy metal cations by biogenic magnetite nanoparticles produced in Fe(III)-reducing microbial enrichment cultures.

The biogenic magnetite nanoparticles presented here had a high capacity of adsorbing metal cations, which was approximately 30- to 40-fold greater than commercially available magnetite. These results suggest the potential application of microbial magnetite formation in the removal of toxic metal cations from water.

Sedimentary records of metal deposition in Japanese alpine lakes for the last 250 years: recent enrichment of airborne Sb and In in East Asia.

Concentrations of 18 elements, including Sb, In, Sn, and Bi, were measured in sediment cores from two pristine alpine lakes on Mount Hachimantai, northern Japan, representing the past 250 years. Vertical variations in concentrations are better explained by atmospheric metal deposition than by diagenetic redistribution of Fe and Mn hydroxide and organic matter. Anthropogenic metal fluxes were estimated from (210)Pb-derived accumulation rates and metal concentrations in excess of the Al-normalized mean background concentration before 1850. Anthropogenic fluxes of Sb and In showed gradual increases starting around 1900 in both lakes, and marked increases after 1980. Comparison of Sb/Pb and Pb stable isotope ratios in sediments with those in aerosols of China or northern Japan and Japanese source materials (recent traffic- and incinerator-derived dust) suggest that the markedly elevated Sb flux after 1980 resulted primarily from enhanced long-range transport in aerosols containing Sb and Pb from coal combustion on the Asian continent. The fluxes of In, Sn, and Bi which are present in Chinese coal showed increasing trends similar to Sb for both study lakes. This suggests that the same source although incinerators in Japan may not be ruled out as sources of In. The sedimentary records for the last 250 years indicate that atmospheric pollution of Sb and In in East Asia have intensified during recent decades.

Fungal mn oxides supporting Mn(II) oxidase activity as effective Mn(II) sequestering materials.

We examined the Mn(II)-oxidizing ability of the biogenic Mn oxide (BMO) formed in cultures ofa Mn(II)-oxidizing fungus, Acremonium strictum strain KR21-2. The newly formed BMO effectively sequestered dissolved Mn(II) mainly by oxidizing Mn(II) to insoluble Mn under air-equilibrated conditions, and this ability lasted for at least 8 days. Deaerating the BMOs, poisoning them with NaN3, or heating them all readily weakened their Mn(II) oxidation ability, indicating the involvement of enzymatic Mn(II) oxidation. There was no Mn(II)-oxidizing ability observed for mycelia cultivated without Mn(II) or for residual mycelia after the BMO phase was dissolved, suggesting the need for the oxide phase. A sodium dodecyl sulphate-polyacrylamide gel electrophoresis assay demonstrated that the oxide phase embeds the Mn(II) oxidase and thereby maintains the enzymatic activity in BMOs. Freezing at -80 degrees C preserved the Mn(II)-oxidizing ability in BMOs for at least 4 weeks, while lyophilization caused a complete loss of this ability. Based on these results, we propose that fungal Mn oxides supporting Mn(II) oxidase activity are an effective Mn(II)-sequestering material capable of oxidizing Mn(II) continuously from solutions containing no additional nutrients to maintain biological activity.

UVB-exposed chlorinated bisphenol A generates phosphorylated histone H2AX in human skin cells.

Bisphenol A (BPA) and chlorinated bisphenol A (ClBPAs) were detected in wastewater from waste paper recycling plants. Previously, we showed that exposure to UV augmented the toxicity of ClBPAs [Mutou (2006) Environ. Toxicol. Pharmacol. 21, 283- 289 and Mutou (2008) Toxicol. in Vitro 22, 864- 872]. BPA and ClBPAs are exposed to sunlight in the environment; however, research concerning the change of toxicity during their photodegradation is scarce, especially for ClBPAs. In this study using human keratinocytes and skin fibroblasts, we found that 3,3'-dichlorobisphenol A (3,3'-diClBPA) exposed to UVB induces phosphorylation of histone H2AX, the event considered to be a marker of formation of DNA double strand breaks. The cells treated with the UVB-exposed 3,3'-diClBPA formed clear foci of phosphorylated histone H2AX in the nucleus. Unchlorinated BPA caused no phosphorylation of histone H2AX even when exposed to high doses of UVB (approximately 200 J/cm(2)). HPLC analysis clarified that several compounds with increased hydrophilicity were produced from 3,3'-diClBPA by UVB irradiation, not from BPA, suggesting the chlorinated chemical structure to be important for the degradation and generation of products related to the phosphorylation of histone H2AX. In separated peaks of 3,3'-diClBPA exposed to UVB, peak fluctuation of 3-hydroxybisphenol A (3-OHBPA) was consistent with the UVB dose-dependent appearance of phosphorylated histone H2AX. We suspected that some oxidized BPA involving 3-OHBPA produced by UVB irradiation contributed to the phosphorylation. Considering that the phosphorylation of histone H2AX is required for maintaining the genome's stability and the repair of DNA, attention to photoproducts from chlorinated compounds is important for the risk evaluation of chemicals.

Organic pollutants in paper-recycling process water discharge areas: first detection and emission in aquatic environment.

In this study, eight compounds have been identified and quantified from the samples collected from paper-recycling process water discharge areas. In particular, five aryl hydrocarbons, including a novel chlorinated aryl ether, were identified for the first time as environmental pollutants. In the effluent stream, concentration levels of up to 1600 microg L(-1) and 190 microg g(-1) were detected in the surface water and surface sediment, respectively. The results of this study have raised concerns regarding the organic chemicals used in thermal paper and the environmental consequences of their release.

Microbial manganese oxide formation and interaction with toxic metal ions.

Diverse bacteria and fungi oxidize Mn(II) enzymatically and produce insoluble Mn(III, IV) oxides, and these organisms are considered to be the primal agents for the occurrence of natural Mn oxide phases in most environments. Biogenic Mn oxides have a high sorption capacity for metal cations and an ability to oxidize numerous inorganic and organic compounds, owing to their structural and redox features. Thus, the microbial process is of significance in both biogeochemical and biotechnological contexts. In this article we summarize the enzymatic Mn(II) oxidation and interactions of biogenic Mn oxides with toxic metal and metalloid ions. Although Mn oxide formation by fungi has not been fully characterized yet, recent researches with ascomycetes emphasize the similarity between the bacterial and fungal Mn(II) oxidation with respect to the involved catalyst (i.e., multicopper oxidase-type enzymes) and the reaction product [i.e., layer-type Mn(IV) oxides]. Laboratory cultures of bacterial and fungal Mn oxidizers are expected to provide fundamental knowledge in their potential use for remediation of environments and effluents contaminated with toxic metal(loid) ions.

Production of biogenic manganese oxides by repeated-batch cultures of laboratory microcosms.

We investigated the production of manganese (Mn) oxides using repeated-batch bioreactors maintained over long periods under laboratory conditions. Freshwater epilithic biofilms were used as the initial inocula. The bioreactors yielded suspended solids that could remove 0.1 mM dissolved Mn(II) within a few days. Chemical titration, X-ray absorption near-edge structure spectroscopy, and X-ray diffraction analysis revealed that the Mn(II) had been converted to poorly crystallized layer-type Mn(IV) oxides, which were similar to known biogenic Mn oxides from pure bacterial cultures. Spherical or rod-shaped Mn microconcretions occurred in the suspended solids; transmission electron microscopy showed that these structures likely resulted from the microbial activity but not represent living cells. Instead, the presence of encapsulated, sheathed, and hyphal budding cells in the suspended solids indicated that a range of Mn-depositing bacteria contributed to the Mn oxide formation. To our knowledge, our data represent the first observation of production of such Mn oxides in a laboratory microcosm wherein a range of Mn-depositing bacteria coexist. The fact that sorption of trace Zn(II) and Ni(II) ions onto the suspended solids co-occurred with the removal of dissolved Mn(II) emphasizes the important role of Mn-oxidizing microorganisms in the fates of trace or contaminant metals in the aquatic environment.

Manganese(IV) oxide production by Acremonium sp. strain KR21-2 and extracellular Mn(II) oxidase activity.

Ascomycetes that can deposit Mn(III, IV) oxides are widespread in aquatic and soil environments, yet the mechanism(s) involved in Mn oxide deposition remains unclear. A Mn(II)-oxidizing ascomycete, Acremonium sp. strain KR21-2, produced a Mn oxide phase with filamentous nanostructures. X-ray absorption near-edge structure (XANES) spectroscopy showed that the Mn phase was primarily Mn(IV). We purified to homogeneity a laccase-like enzyme with Mn(II) oxidase activity from cultures of strain KR21-2. The purified enzyme oxidized Mn(II) to yield suspended Mn particles; XANES spectra indicated that Mn(II) had been converted to Mn(IV). The pH optimum for Mn(II) oxidation was 7.0, and the apparent half-saturation constant was 0.20 mM. The enzyme oxidized ABTS [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] (pH optimum, 5.5; Km, 1.2 mM) and contained two copper atoms per molecule. Moreover, the N-terminal amino acid sequence (residues 3 to 25) was 61% identical with the corresponding sequence of an Acremonium polyphenol oxidase and 57% identical with that of a Myrothecium bilirubin oxidase. These results provide the first evidence that a fungal multicopper oxidase can convert Mn(II) to Mn(IV) oxide. The present study reinforces the notion of the contribution of multicopper oxidase to microbially mediated precipitation of Mn oxides and suggests that Acremonium sp. strain KR21-2 is a good model for understanding the oxidation of Mn in diverse ascomycetes.

Evaluation of the Ishikawa cell line bioassay for the detection of estrogenic substances from sediment extracts.

This study examines the application of Ishikawa human endometrial adenocarcinoma cells to measure the estrogenic activity of fractionated extracts of sediments from Tokyo Bay, Japan. Estrogen stimulates alkaline phosphatase activity in this cell line. The results of these assays were compared with those of a yeast estrogen screen (YES) assay. The Ishikawa cell line bioassay showed higher sensitivity to 17beta-estradiol (median effective concentration [EC50], 10.7 pM) than did the YES assay (EC50, 480 pM). Fractionation of sediment extracts (all samples collected from 5 sites) showed that the nonpolar fraction was poisonous to yeast cells; the estrogenic activity of this fraction, therefore, could not be measured by YES. However, the nonpolar fraction did not kill the Ishikawa cells. The 17beta-estradiol-equivalent values of 15 extracts (3 fractions from each of 5 sediment samples) ranged from 5.7 to 697 pg/g dry weight according to the Ishikawa cell line bioassay. Chemical analysis using gas chromatography-mass spectrometry revealed that the highest concentrations of endocrine-disrupting chemicals were observed at the sampling station near the sewage treatment plant. The results support that the Ishikawa cell line bioassay is suitable for measuring the estrogenic activity of sediment samples.

Sorption of Co(II), Ni(II), and Zn(II) on biogenic manganese oxides produced by a Mn-oxidizing fungus, strain KR21-2.

The characteristics of Co(II), Ni(II), and Zn(II) sorption on freshly produced biogenic Mn oxides by a Mn-oxidizing fungus, strain KR21-2, were investigated. The biogenic Mn oxides showed about 10-fold higher efficiencies for sorbing the metal ions than a synthetic Mn oxide (gamma-MnO2) on the basis of unit weight and unit surface area. The order of sorption efficiency on the biogenic Mn oxides was Co(II) > Zn(II) > Ni(II), while that on the synthetic Mn oxide was Zn(II) > Co(II) > Ni(II). These sorption selectivities were confirmed by both sorption isotherms and competitive sorption experiments. Two-step extraction, using 10mM CuSO4 solution for exchangeable sorbed ions and 10-20mM hydroxylamine hydrochloride for ions bound to reducible Mn oxide phase, showed higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides while Zn(II) sorption was mostly reversible (Cu(II)-exchangeable). Sorptions of Co(II), Ni(II), and Zn(II) on the synthetic Mn oxide were, however, found to be mostly reversible. Higher irreversibility of Co(II) and Ni(II) sorption on the biogenic Mn oxides may partly explain higher accumulation of these metal ions in Mn oxide phases in natural environments. The results obtained in this study raise the possibility to applying the biogenic Mn oxide formation to treatment of water contaminated with toxic metal ions.

Interaction of inorganic arsenic with biogenic manganese oxide produced by a Mn-oxidizing fungus, strain KR21-2.

In batch culture experiments we examined oxidation of As(III) and adsorption of As(III/V) by biogenic manganese oxide formed by a manganese oxide-depositing fungus, strain KR21-2. We expected to gain insight into the applicability of Mn-depositing microorganisms for biological treatment of As-contaminated waters. In cultures containing Mn2+ and As(V), the solid Mn phase was rich in bound Mn2+ (molar ratio, approximately 30%) and showed a transiently high accumulation of As(V) during the early stage of manganese oxide formation. As manganese oxide formation progressed, a large proportion of adsorbed As(V) was subsequently released. The high proportion of bound Mn2+ may suppress a charge repulsion between As(V) and the manganese oxide surface, which has structural negative charges, promoting complex formation. In cultures containing Mn2+ and As(III), As(III) started to be oxidized to As(V) after manganese oxide formation was mostly completed. In suspensions of the biogenic manganese oxides with dissolved Mn2+, As(III) oxidation rates decreased with increasing dissolved Mn2+. These results indicate that biogenic manganese oxide with a high proportion of bound Mn2+ oxidizes As(III) less effectively than with a low proportion of bound Mn2+. Coexisting Zn2+, Ni2+, and Co2+ also showed similar effects to different extents. The present study demonstrates characteristic features of oxidation and adsorption of As by biogenic manganese oxides and suggests possibilities of developing a microbial treatment system for water contaminated with As that is suited to the actual situation of contamination.

Enzymatic formation of manganese oxides by an Acremonium-like hyphomycete fungus, strain KR21-2.

A Mn-depositing fungus, Acremonium-like hyphomycete strain KR21-2, was isolated from a Mn deposit occurring on the wall of a storage bottle containing Mn(III, IV) oxide-coated streambed pebbles and stream water. 18S rRNA gene sequence analysis revealed that strain KR21-2 was phylogenetically related to members of the order Hypocreales within the class Ascomycetes. The spent culture medium at the stationary phase of fungal growth contained a 54-kDa protein capable of depositing Mn oxides. The enzymatic activity was inhibited by azide and o-phenanthroline. The Mn(II)-oxidizing protein possessed a laccase activity, as indicated by direct oxidation of p-phenylenediamine and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid). These results are consistent with the role assumed for laccase-like multicopper oxidase, which is proposed to be involved in the Mn(II)-oxidizing factors from some bacteria. Unlike laccases of basidiomycete fungi, however, the protein of strain KR21-2 did not produce soluble Mn(III) species in the presence of either of the Mn chelators pyrophosphate and malonate. This is the first report on the possible involvement of laccase and/or multicopper oxidase in Mn oxide deposition by ascomycetes (including their anamorphs) ubiquitous in natural environments.