Oxidative stress in wild European rabbits naturally infected with myxoma virus and rabbit haemorrhagic disease virus

The European rabbit (Oryctolagus cuniculus) is one of the most important vertebrate species in the Mediterranean Basin ecosystem. Over the last 60 years, the arrival of two viral diseases, myxomatosis and rabbit haemorrhagic disease, have led to dramatic declines in wild rabbit populations across the Iberian Peninsula. These diseases are currently endemic. Periodic outbreaks occur and have significant impacts on wild populations. Both infection types have diverse physiological effects on their hosts that are rooted in aerobic metabolic processes. To fight off these viruses, rabbits activate their immune systems. However, the production of immune defences generates reactive oxygen species that may consequently damage host tissues. Hypothesising that immune responses increase oxidative stress, we examined whether wild rabbits naturally infected with myxoma virus (MV) and rabbit haemorrhagic disease virus (RHDV) had high oxidative stress. Using blood samples, we measured anti-MV and anti-RHDV antibody concentrations and different oxidative stress markers (i.e., glutathione peroxidase, glutathione reductase, superoxide dismutase, catalase, and malondialdehyde). Our results show that rabbits that were seropositive for both MV and RHDV had high concentrations of malondialdehyde. Age and body condition were also positively related to dual seropositivity. No significant relationships were observed between serostatus and the concentrations of the other oxidative stress markers. Although we expected infection with MV and RHDV to be correlated with oxidative stress, the influence of external sources of oxidative stress (e.g., climatic conditions) likely made it more difficult to detect such relationships in wild rabbits.     

Pyrodiversity interacts with rainfall to increase bird and mammal richness in African savannas

Fire is a fundamental process in savannas and is widely used for management. Pyrodiversity, variation in local fire characteristics, has been proposed as a driver of biodiversity although empirical evidence is equivocal. Using a new measure of pyrodiversity (Hempson et al.), we undertook the first continent‐wide assessment of how pyrodiversity affects biodiversity in protected areas across African savannas. The influence of pyrodiversity on bird and mammal species richness varied with rainfall: strongest support for a positive effect occurred in wet savannas (> 650 mm/year), where species richness increased by 27% for mammals and 40% for birds in the most pyrodiverse regions. Range‐restricted birds were most increased by pyrodiversity, suggesting the diversity of fire regimes increases the availability of rare niches. Our findings are significant because they explain the conflicting results found in previous studies of savannas. We argue that managing savanna landscapes to increase pyrodiversity is especially important in wet savannas.     

Biodiversity effects on ecosystem functioning respond unimodally to environmental stress

Understanding how biodiversity (B) affects ecosystem functioning (EF) is essential for assessing the consequences of ongoing biodiversity changes. An increasing number of studies, however, show that environmental conditions affect the shape of BEF relationships. Here, we first use a game‐theoretic community model to reveal that a unimodal response of the BEF slope can be expected along environmental stress gradients, but also how the ecological mechanisms underlying this response may vary depending on how stress affects species interactions. Next, we analysed a global dataset of 44 experiments that crossed biodiversity with environmental conditions. Confirming our main model prediction, the effect of biodiversity on ecosystem functioning tends to be greater at intermediate levels of environmental stress, but varies among studies corresponding to differences in stress‐effects on species interactions. Together, these results suggest that increases in stress from ongoing global environmental changes may amplify the consequences of biodiversity changes.     

Spatial heterogeneity in species composition constrains plant community responses to herbivory and fertilisation

Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change – fertilisation and herbivore loss – are affected by species pool size and spatial compositional heterogeneity. Fertilisation led to higher rates of local extinction, whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.     

Save your host,save yourself? Caste‐ratio adjustment in a parasite with division of labor and snail host survival following shell damage

Shell damage and parasitic infections are frequent in gastropods, influencing key snail host life‐history traits such as survival, growth, and reproduction. However, their interactions and potential effects on hosts and parasites have never been tested. Host–parasite interactions are particularly interesting in the context of the recently discovered division of labor in trematodes infecting marine snails. Some species have colonies consisting of two different castes present at varying ratios; reproductive members and nonreproductive soldiers specialized in defending the colony. We assessed snail host survival, growth, and shell regeneration in interaction with infections by two trematode species, Philophthalmus sp. and Maritrema novaezealandense, following damage to the shell in the New Zealand mud snail Zeacumantus subcarinatus. We concomitantly assessed caste‐ratio adjustment between nonreproductive soldiers and reproductive members in colonies of the trematode Philophthalmus sp. in response to interspecific competition and shell damage to its snail host. Shell damage, but not parasitic infection, significantly increased snail mortality, likely due to secondary infections by pathogens. However, trematode infection and shell damage did not negatively affect shell regeneration or growth in Z. subcarinatus; infected snails actually produced more new shell than their uninfected counterparts. Both interspecific competition and shell damage to the snail host induced caste‐ratio adjustment in Philophthalmus sp. colonies. The proportion of nonreproductive soldiers increased in response to interspecific competition and host shell damage, likely to defend the parasite colony and potentially the snail host against increasing threats. These results indicate that secondary infections by pathogens following shell damage to snails both significantly increased snail mortality and induced caste‐ratio adjustments in parasites. This is the first evidence that parasites with a division of labor may be able to produce nonreproductive soldiers according to environmental factors other than interspecific competition with other parasites.     

Guano exposed: Impact of aerobic conditions on bat fecal microbiota

Bats and their associated guano microbiota provide important terrestrial and subterranean ecosystem services and serve as a reservoir for a wide range of epizootic and zoonotic diseases. Unfortunately, large‐scale studies of bats and their guano microbiotas are limited by the time and cost of sample collection, which requires specially trained individuals to work at night to capture bats when they are most active. Indirectly surveying bat gut microbiota through guano deposits could be a more cost‐effective alternative, but it must first be established whether the postdefecation exposure to an aerobic environment has a large impact on the guano microbial community. A number of recent studies on mammalian feces have shown that the impact of aerobic exposure is highly species specific; therefore, it is difficult to predict how exposure will affect the bat guano microbiota without empirical data. In our study, we collected fresh guano samples from 24 individuals of 10 bat species that are common throughout the arid environments of the American southwest and subjected the samples to 0, 1, and 12 hr of exposure. The biodiversity decreased rapidly after the shift from an anaerobic to an aerobic environment—much faster than previously reported in mammalian species. However, the relative composition of the core guano microbiota remained stable and, using highly sensitive targeted PCR methods, we found that pathogens present in the original, non‐exposed samples could still be recovered after 12 hr of exposure. These results suggest that with careful sample analysis protocols, a more efficient passive collection strategy is feasible; for example, guano could be collected on tarps placed near the roost entrance. Such passive collection methods would greatly reduce the cost of sample collection by allowing more sites or roosts to be surveyed with a fraction of trained personnel, time, and effort investments needed.     

KIBRA (WWC1) Is a Metastasis Suppressor Gene Affected by Chromosome 5q Loss in Triple-Negative Breast Cancer

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Guiding cellular activity with polarized light

Actin, cytoskeleton protein forming microfilaments, play a crucial role in cellular motility. Here we show that exposure to very low levels of polarized light guide their orientation in‐vivo within the live cell. Using a simple model to describe the role of actin‐filament orientation in directional cellular motion, we demonstrate that the actin polymerization/depolymerization mechanism develops primarily along this direction and, under certain conditions, can lead to guidance of the cell movement. Our results also show a dose dependent increase in actin activity in direct correspondence to the level of laser irradiance. We found that total expression of Tau protein, which stabilize microtubules, was decreased by the irradiance, indicating that exposure to the light may change the activity of kinase, leading to increased cell activity.

     

Release factor RF3 in E.coli accelerates the dissociation of release factors RF1 and RF2 from the ribosome in a GTP-dependent manner.

Ribosomes complexed with synthetic mRNA and peptidyl-tRNA, ready for peptide release, were purified by gel filtration and used to study the function of release factor RF3 and guanine nucleotides in the termination of protein synthesis. The peptide-releasing activity of RF1 and RF2 in limiting concentrations was stimulated by the addition of RF3 and GTP, stimulated, though to a lesser extent, by RF3 and a non-hydrolysable GTP analogue, and inhibited by RF3 and GDP or RF3 without guanine nucleotide. With short incubation times allowing only a single catalytic cycle of RF1 or RF2, peptide release activity was independent of RF3 and guanine nucleotide. RF3 hydrolysis of GTP to GDP + P(i) was dependent only on ribosomes and not on RF1 or RF2. RF3 affected neither the rate of association of RF1 and RF2 with the ribosome nor the catalytic rate of peptide release. A model is proposed which explains how RF3 recycles RF1 and RF2 by displacing the factors from the ribosome after the release of peptide.