The Enigma of the Respiratory Chain Supercomplex

Respiratory chain dysfunction plays an important role in human disease and aging. It is now well established that the individual respiratory complexes can be organized into supercomplexes, and structures for these macromolecular assemblies, determined by electron cryo-microscopy, have been described recently. Nevertheless, the reason why supercomplexes exist remains an enigma. The widely held view that they enhance catalysis by channeling substrates is challenged by both structural and biophysical information. Here, we evaluate and discuss data and hypotheses on the structures, roles, and assembly of respiratory-chain supercomplexes and propose a future research agenda to address unanswered questions.N.G.L. receives support from the Max Planck Society, the Swedish Research Council (2015-00418), and the Knut and Alice Wallenberg foundation. J.H. and J.N.B. are supported by The Medical Research Council (U105663141 to J.H.)

Figure 2. Number of damaged seeds and total seed number per capitulum in treatments with No insect (N), Wasp-only (W), Tephritid (T), and Tephritid and Wasp (TW) in Saussurea nigrescens

The Minimum,first quantile,median,third quantile, Maximum, and mean are provided for each treatment in the controlled field experiment

Figure 1. The effect of Tephritid flies and Wasps on seed damage in five Asteraceae host species

The Minimum,first quantile,median,third quantile, Maximum, and mean are provided for each treatment in the observational study

Stability of community productivity as affected by bacterial genotypic and functional diversity.

<p>Effects of bacterial genotypic (a, b) and functional diversity (c, d) on the stability of community productivity in varied resource environments (1/coefficient of variation of 14 resource treatments) (a, c) and invader treatments (no invader, <i>Pseudomonas putida</i> and <i>Serratia liquefaciens</i> as model invaders) (b, d). Each circle represents the stability of productivity of a given bacterial community in varied abiotic (a, c) or biotic environments (b, d).</p

Bacterial Diversity Stabilizes Community Productivity

<div><h3>Background</h3><p>Stability is a crucial ecosystem feature gaining particular importance in face of increasing anthropogenic stressors. Biodiversity is considered to be a driving biotic force maintaining stability, and in this study we investigate how different indices of biodiversity affect the stability of communities in varied abiotic (composition of available resources) and biotic (invasion) contexts.</p> <h3>Methodology/Principal Findings</h3><p>We set up microbial microcosms to study the effects of genotypic diversity on the reliability of community productivity, defined as the inverse of the coefficient of variation of across-treatment productivity, in different environmental contexts. We established a bacterial diversity gradient ranging from 1 to 8 <em>Pseudomonas fluorescens</em> genotypes and grew the communities in different resource environments or in the presence of model invasive species. Biodiversity significantly stabilized community productivity across treatments in both experiments. Path analyses revealed that different aspects of diversity determined stability: genotypic richness stabilized community productivity across resource environments, whereas functional diversity determined stability when subjected to invasion.</p> <h3>Conclusions/Significance</h3><p>Biodiversity increases the stability of microbial communities against both biotic and abiotic environmental perturbations. Depending on stressor type, varying aspects of biodiversity contribute to the stability of ecosystem functions. The results suggest that both genetic and functional diversity need to be preserved to ensure buffering of communities against abiotic and biotic stresses.</p> </div

Relative importance of genotypic richness and functional diversity effects.

<p>Path analyses of direct and indirect (through increasing functional diversity) bacterial genotypic richness effects on stability of bacterial community productivity in the varied resource experiment (VRE) (a) and varied invader experiment (VIE) (b). While no <i>χ</i>²-value could be calculated for the initial model for VRE (<i>AIC</i> 12.00), removing the arrow between functional diversity and stability resulted in a model with good fit to the data (<i>χ²_1,5</i> = 0.05, <i>p</i> = 0.83, <i>AIC</i> 10.05). Similarly, no <i>χ²</i>-value could be calculated for the initial model for VIE (<i>AIC</i> 12.00), however, removing the non-significant path between genotypic richness and stability resulted in a model with good fit to the data (<i>χ²_1,5</i> = 0.38, <i>p</i> = 0.54, <i>AIC</i> 10.38). The width of the arrows indicates the strength of the causal influence: bold arrows indicate significant standardized path coefficients (<i>P</i><0.01; unstandardized path coefficients in brackets), whereas thin arrows indicate non-significant relationships (<i>P</i>>0.05). Exogenous variables are highlighted with grey rectangles, while endogenous variables are given in white. Values at the top corner of white rectangles are the variance of the respective variable explained by the model.</p

Appendix A. Tables showing number of replicates per diversity level, design of the experiment, and final ANOVA models, as well as figures showing the unstandardizard path coefficients in structural equation models 1 and 2.

Tables showing number of replicates per diversity level, design of the experiment, and final ANOVA models, as well as figures showing the unstandardizard path coefficients in structural equation models 1 and 2

Plant soil feedbacks (PSF) as affected by soil microarthropods

<div>Kuťáková, E.; Cesarz, S.; Münzberová, Z. & Eisenhauer, N. 2018. Soil microarthropods alter the outcome of plant-soil feedback experiments. Scientific Reports <i>in press</i>. DOI: 10.1038/s41598-018-30340-w</div><div><br></div>See the reference (Materials and Methods) for a detailed description of the PSF experiment and the individual measured variables.<div>Plant data measured in the feedback phase refer to the mean values of plant individuals in each microcosm.</div><div>Nematode counts refer to the numbers of individuals per gram soil dry weight (the actual numbers of determined nematodes being extrapolated to the total nematode counts in the respective sample).</div

Experimental Evaluation of Herbivory on Live Plant Seedlings by the Earthworm <i>Lumbricus terrestris</i> L. in the Presence and Absence of Soil Surface Litter

<div><p>Background</p><p>Recent studies suggested that the earthworm <i>Lumbricus terrestris</i> might act as a seedling predator by ingesting emerging seedlings, and individuals were observed damaging fresh leaves of various plant species in the field. To evaluate the significance of herbivore behavior of <i>L</i>. <i>terrestris</i> for plant and earthworm performance we exposed 23- to 33-days-old seedlings of six plant species to earthworms in two microcosm experiments. Plants belonged to the three functional groups grasses, non-leguminous herbs, and legumes. Leaf damage, leaf mortality, the number of leaves as well as mortality and growth of seedlings were followed over a period of up to 26 days. In a subset of replicates 0.1 g of soil surface litter of each of the six plant species was provided and consumption was estimated regularly to determine potential feeding preferences of earthworms.</p><p>Results</p><p>There was no difference in seedling growth, the number of live seedlings and dead leaves between treatments with or without worms. Fresh leaves were damaged eight times during the experiment, most likely by <i>L</i>. <i>terrestris</i>, with two direct observations of earthworms tearing off leaf parts. Another nine leaves were partly pulled into earthworm burrows. <i>Lumbricus terrestris</i> preferred to consume legume litter over litter of the other plant functional groups. Earthworms that consumed litter lost less weight than individuals that were provided with soil and live plants only, indicating that live plants are not a suitable substitute for litter in earthworm nutrition.</p><p>Conclusion</p><p>Our results demonstrate that <i>L</i>. <i>terrestris</i> damages live plants; however, this behavior occurs only rarely. Pulling live plants into earthworm burrows might induce microbial decomposition of leaves to make them suitable for later consumption. Herbivory on plants beyond the initial seedling stage may only play a minor role in earthworm nutrition and has limited potential to influence plant growth.</p></div

ANOVA table for the analysis of the number of leaves and plant height in the herbivory experiment.

<p>ANOVA table of degrees of freedom (DF), F- and P-values for comparisons of the number of leaves per seedling and plant height according to treatment (earthworm present or not), the days since the start of the experiment, the three plant functional groups legumes ('plant species' <i>Medicago x varia</i>, <i>Trifolium repens</i>), non-leguminous herbs (<i>Bellis perennis</i>, <i>Plantago lanceolata</i>) and grasses (<i>Phleum pratense</i>, <i>Poa trivialis</i>) and with the initial number of leaves or initial plant height at the beginning of the experiment included as a covariate.</p><p>Significant effects (P<0.05) are given in bold.</p><p>ANOVA table for the analysis of the number of leaves and plant height in the herbivory experiment.</p