Relationship between soil microarthropod species diversity and plant growth does not change when the system is disturbed

Soil microarthropods influence vital ecosystem processes, such as decomposition and nutrient mineralisation. There is evidence, however, that proper functioning of ecosystems does not require the presence of all its constituent species, and therefore some species can be regarded as functionally redundant. It has been proposed that species redundancy can act as an insurance against unfavourable conditions, and that functionally redundant species may become important when a system has faced a disturbance (the “insurance hypothesis”).
We conducted a laboratory microcosm experiment with coniferous forest soil and a seedling of silver birch (Betula pendula). A gradient of microarthropod diversity (from one to tens of species of soil mites and Collembola) was created to the systems. We disturbed microcosms with drought to test whether systems with altering microarthropod species richness respond differently to perturbations. Primary production (birch biomass), uptake of nitrogen by the birch seedling, the system's ability to retain nutrients and the structure and biomass of the soil microbial community were analysed.
Primary production and nutrient uptake of the birch seedlings increased slightly with increasing microarthropod species richness but only at the species poor end of the diversity gradient. Loss of nutrients and the biomass and community structure of microbes were unaffected by the microarthropods. The effect of drought on the birch biomass production was independent of the species richness of microarthropods. During the disturbance the biomass of microarthropods declined in diverse systems but not in simple ones. These systems were, however, quite resilient; microarthropod communities recovered quickly after the disturbance. Our results suggest that soil microarthropod species are functionally redundant in respect to plant growth, and that the resistance of a system to and its recovery from a disturbance are only weakly related to the species richness of this fauna.     

Age-associated changes in skeletal muscles and their effect on mobility: an operational diagnosis of sarcopenia.

Sarcopenia, the reduction of muscle mass and strength that occurs with aging, is widely considered one of the major causes of disability in older persons. Surprisingly, criteria that may help a clinician to identify persons with impaired muscle function are still lacking. Using data from a large representative sample of the general population, we examined how muscle function and calf muscle area change with aging and affect mobility in men and women free of neurological conditions. We tested several putative indicators of sarcopenia, including knee extension isometric torque, handgrip, lower extremity muscle power, and calf muscle area. For each indicator, sarcopenia was considered to be present when the measure was >2 SDs below the mean. For all four measures, the prevalence of sarcopenia increased with age, both in men and women. The age-associated gradient in prevalence was maximum for muscle power and minimum for calf-muscle area. However, lower extremity muscle power was no better than knee-extension torque or handgrip in the early identification of poor mobility, defined either as walking speed <0.8 m/s or inability to walk at least 1 km without difficulty and without developing symptoms. Optimal cutoff values that can be used in the clinical practice to identify older persons with poor mobility were developed. The findings of the study lay the basis for a cost-effective, clinical marker of sarcopenia based on a measure of isometric handgrip strength. Our findings should be verified in a longitudinal study.     

Oxidative stress and photoinhibition can be separated in the cyanobacterium Synechocystis sp. PCC 6803

Roles of oxidative stress and photoinhibition in high light acclimation were studied using a regulatory mutant of the cyanobacterium Synechocystis sp. PCC 6803. The mutant strain ΔsigCDE contains the stress responsive SigB as the only functional group 2 σ factor. The ?sigCDE strain grew more slowly than the control strain in methyl-viologen-induced oxidative stress. Furthermore, a fluorescence dye detecting H₂O₂, hydroxyl and peroxyl radicals and peroxynitrite, produced a stronger signal in ?sigCDE than in the control strain, and immunological detection of carbonylated residues showed more protein oxidation in ?sigCDE than in the control strain. These results indicate that ?sigCDE suffers from oxidative stress in standard conditions. The oxidative stress may be explained by the findings that ?sigCDE had a low content of glutathione and low amount of Flv3 protein functioning in the Mehler-like reaction. Although ?sigCDE suffers from oxidative stress, up-regulation of photoprotective carotenoids and Flv4, Sll2018, Flv2 proteins protected PSII against light induced damage by quenching singlet oxygen more efficiently in ?sigCDE than in the control strain in visible and in UV-A/B light. However, in UV-C light singlet oxygen is not produced and PSII damage occurred similarly in the ?sigCDE and control strains. According to our results, resistance against the light-induced damage of PSII alone does not lead to high light tolerance of the cells, but in addition efficient protection against oxidative stress would be required.     

Thermotolerant and thermostable laccases

Laccases are phenol-oxidizing, usually four-copper containing metalloenzymes. For industrial and biotechnological purposes, laccases were among the first fungal oxidoreductases providing larger-scale applications such as removal of polyphenols in wine and beverages, conversion of toxic compounds and textile dyes in waste waters, and in bleaching and removal of lignin from wood and non-wood fibres. In order to facilitate novel and more efficient bio-catalytic process applications, there is a need for laccases with improved biochemical properties, such as thermostability and thermotolerance. This review gives a current overview on the sources and characteristics of such laccases, with particular emphasis on the fungal enzymes.     

Kinetics of prolonged photoinhibition revisited: photoinhibited Photosystem II centres do not protect the active ones against loss of oxygen evolution

Photoinhibition of Photosystem II (PSII) in lincomycin-treated leaves begins as a first-order reaction, but fluorescence measurements have suggested that after prolonged illumination, the number of active PSII centres stabilizes to 15–20% of control. The stabilization has been interpreted to indicate that photoinhibited PSII centres protect the remaining active centres against photoinhibition (Lee, Hong and Chow, Planta 212:332–342, 2001). In an attempt to study the mechanism of this protection, we measured the reaction kinetics of photoinhibition in lincomycin-treated pumpkin (Cucurbita pepo L.) and pepper (Capsicum annuum L.) leaves in vivo. The light-saturated rate of PSII oxygen evolution, assayed from thylakoids and isolated from the treated leaves, was used as a direct measure of the number of remaining active PSII centres, and the fluorescence parameters F _V/F _M and (F _V/F _M)/F ₀ (=1/F ₀ − 1/F _M) were measured for comparison. To our surprise, no stabilization of PSII activity was observed and photoinhibition followed first-order kinetics until PSII activity had virtually declined to zero. A series of in vitro experiments was carried out to see whether stabilization of PSII activity occurs if a particular combination of light intensity and wavelength range is applied, or if a specific PSII preparation is used as experimental material. The results of the in vitro experiments confirmed the in vivo result about persistent first-order kinetics. We conclude that photoinhibited PSII centres offer no measurable protection against photoinhibition.     

Site fertility and soil water-table level affect fungal biomass production and community composition in boreal peatland forests

A substantial amount of below-ground carbon (C) is suggested to be associated with fungi, which may significantly affect the soil C balance in forested ecosystems. Ergosterol from in-growth mesh bags and litterbags was used to estimate fungal biomass production and community composition in drained peatland forests with differing fertility. Extramatrical mycelia (EMM) biomass production was generally higher in the nutrient-poor site, increased with deeper water table level and decreased along the length of the recovery time. EMM biomass production was of the same magnitude as in mineral-soil forests. Saprotrophic fungal biomass production was higher in the nutrient-rich site. Both ectomycorrhizal (ECM) and saprotrophic fungal community composition changed according to site fertility and water table level. ECM fungal community composition with different exploration types may explain the differences in fungal biomass production between peatland forests. Melanin-rich Hyaloscypha may indicate decreased turnover of biomass in nutrient-rich young peatland forest. Genera Lactarius and Laccaria may be important in nutrient rich and Piloderma in the nutrient-poor conditions, respectively. Furthermore, Paxillus involutus and Cortinarius sp. may be important generalists in all sites and responsible for EMM biomass production during the first summer months. Saprotrophs showed a functionally more diverse fungal community in the nutrient-rich site.     

Metabolic regulation in progression to autoimmune diabetes

Recent evidence from serum metabolomics indicates that specific metabolic disturbances precede β-cell autoimmunity in humans and can be used to identify those children who subsequently progress to type 1 diabetes. The mechanisms behind these disturbances are unknown. Here we show the specificity of the pre-autoimmune metabolic changes, as indicated by their conservation in a murine model of type 1 diabetes. We performed a study in non-obese prediabetic (NOD) mice which recapitulated the design of the human study and derived the metabolic states from longitudinal lipidomics data. We show that female NOD mice who later progress to autoimmune diabetes exhibit the same lipidomic pattern as prediabetic children. These metabolic changes are accompanied by enhanced glucose-stimulated insulin secretion, normoglycemia, upregulation of insulinotropic amino acids in islets, elevated plasma leptin and adiponectin, and diminished gut microbial diversity of the Clostridium leptum group. Together, the findings indicate that autoimmune diabetes is preceded by a state of increased metabolic demands on the islets resulting in elevated insulin secretion and suggest alternative metabolic related pathways as therapeutic targets to prevent diabetes.     

The ectomycorrhizal fungus Tricholoma matsutake is a facultative saprotroph in vitro

Tricholoma matsutake is an economically important ectomycorrhizal fungus of coniferous woodlands. Mycologists suspect that this fungus is also capable of saprotrophic feeding. In order to evaluate this hypothesis, enzyme and chemical assays were performed in the field and laboratory. From a natural population of T. matsutake in southern Finland, samples of soil-mycelium aggregate (shiro) were taken from sites of sporocarp formation and nearby control (PCR-negative) spots. Soil organic carbon and activity rates of hemicellulolytic enzymes were measured. The productivity of T. matsutake was related to the amount of utilizable organic carbon in the shiro, where the activity of xylosidase was significantly higher than in the control sample. In the laboratory, sterile pieces of bark from the roots of Scots pine were inoculated with T. matsutake and the activity rates of two hemicellulolytic enzymes (xylosidase and glucuronidase) were assayed. Furthermore, a liquid culture system showed how T. matsutake can utilize hemicellulose as its sole carbon source. Results linked and quantified the general relationship between enzymes secreted by T. matsutake and the degradation of hemicellulose. Our findings suggest that T. matsutake lives mainly as an ectomycorrhizal symbiont but can also feed as a saprotroph. A flexible trophic ecology confers T. matsutake with a clear advantage in a heterogeneous environment and during sporocarp formation.