49 research outputs found
Forager bees (Apis mellifera) highly express immune and detoxification genes in tissues associated with nectar processing.
Pollinators, including honey bees, routinely encounter potentially harmful microorganisms and phytochemicals during foraging. However, the mechanisms by which honey bees manage these potential threats are poorly understood. In this study, we examine the expression of antimicrobial, immune and detoxification genes in Apis mellifera and compare between forager and nurse bees using tissue-specific RNA-seq and qPCR. Our analysis revealed extensive tissue-specific expression of antimicrobial, immune signaling, and detoxification genes. Variation in gene expression between worker stages was pronounced in the mandibular and hypopharyngeal gland (HPG), where foragers were enriched in transcripts that encode antimicrobial peptides (AMPs) and immune response. Additionally, forager HPGs and mandibular glands were enriched in transcripts encoding detoxification enzymes, including some associated with xenobiotic metabolism. Using qPCR on an independent dataset, we verified differential expression of three AMP and three P450 genes between foragers and nurses. High expression of AMP genes in nectar-processing tissues suggests that these peptides may contribute to antimicrobial properties of honey or to honey bee defense against environmentally-acquired microorganisms. Together, these results suggest that worker role and tissue-specific expression of AMPs, and immune and detoxification enzymes may contribute to defense against microorganisms and xenobiotic compounds acquired while foraging
Zooming into the coexisting regime of ferromagnetism and superconductivity in ErRh4B4 single crystals
High resolution measurements of the dynamic magnetic susceptibility are
reported for ferromagnetic re-entrant superconductor, ErRhB.
Detailed investigation of the coexisting regime reveals unusual
temperature-asymmetric and magnetically anisotropic behavior. The
superconducting phase appears via a series of discontinuous steps upon warming
from the ferromagnetic normal phase, whereas the ferromagnetic phase develops
via a gradual transition. A model based on local field inhomogeneity is
proposed to explain the observations
Coexistence of Long-Range Magnetic Order and Superconductivity from Campbell Penetration Depth Measurements
Application of a tunnel-diode resonator (TDR) technique for studies of the
vortex response in magnetic superconductors is described. Operating at very
small excitation fields and sufficiently high frequency, TDR was used to probe
small-amplitude linear AC response in several types of single crystals where
long-range magnetic order coexists with bulk superconductivity. Full local -
moment ferromagnetism destroys superconductivity and can coexist with it only
in a narrow temperature range ( K). In contrast, weak ferromagnetic
as well as antiferromagnetic orders can coexist with bulk superconductivity and
may even lead to enhancements of vortex pinning. By analyzing the Campbell
penetration depth we find sharp increase of the true critical current in the
vicinity of the magnetic phase transitions. We conclude that critical magnetic
fluctuations are responsible for this enhancement
Unconventional London penetration depth in Ba(Fe0.93Co0.07)2As2 single crystals
The London penetration depth, , has been measured in several
single crystals of Ba(FeCo)As. Thermodynamic,
electromagnetic, and structural characterization measurements confirm that
these crystals are of excellent quality. The observed low temperature variation
of follows a power-law, with , indicating the existence of normal quasiparticles down to at least
. This is in contrast to recent penetration depth measurements on
single crystals of NdFeAsOF and SmFeAsOF, which
indicate an anisotropic but nodeless gap. We propose that a more
three-dimensional character in the electronic structure of
Ba(FeCo)As may lead to an anisotropic wave gap
with point nodes that would explain the observed .Comment: 4 page
Non-exponential London penetration depth in RFeAsOF (R=La,Nd) single crystals
The superconducting penetration depth, , has been measured in
RFeAsOF (R=La,Nd) single crystals (R-1111). In Nd-1111, we find
an upturn in upon cooling and attribute it to the paramagnetism of
the Nd ions, similar to the case of the electron-doped cuprate Nd-Ce-Cu-O.
After the correction for paramagnetism, the London penetration depth variation
is found to follow a power-law behavior, at
low temperatures. The same variation of was found in
non-magnetic La-1111 crystals. Analysis of the superfluid density and of
penetration depth anisotropy over the full temperature range is consistent with
two-gap superconductivity. Based on this and on our previous work, we conclude
that both the RFeAsO (1111) and BaFeAs (122) families of pnictide
superconductors exhibit unconventional two-gap superconductivity.Comment: v2 is the same as v1 - error in the arxiv submissio
Arbuscular Mycorrhizal Fungi and Plant Chemical Defence : Effects of Colonisation on Aboveground and Belowground Metabolomes
Arbuscular mycorrhizal fungal (AMF) colonisation of plant roots is one of the most ancient and widespread interactions in ecology, yet the systemic consequences for plant secondary chemistry remain unclear. We performed the first metabolomic investigation into the impact of AMF colonisation by Rhizophagus irregularis on the chemical defences, spanning above- and below-ground tissues, in its host-plant ragwort (Senecio jacobaea). We used a non-targeted metabolomics approach to profile, and where possible identify, compounds induced by AMF colonisation in both roots and shoots. Metabolomics analyses revealed that 33 compounds were significantly increased in the root tissue of AMF colonised plants, including seven blumenols, plant-derived compounds known to be associated with AMF colonisation. One of these was a novel structure conjugated with a malonyl-sugar and uronic acid moiety, hitherto an unreported combination. Such structural modifications of blumenols could be significant for their previously reported functional roles associated with the establishment and maintenance of AM colonisation. Pyrrolizidine alkaloids (PAs), key anti-herbivore defence compounds in ragwort, dominated the metabolomic profiles of root and shoot extracts. Analyses of the metabolomic profiles revealed an increase in four PAs in roots (but not shoots) of AMF colonised plants, with the potential to protect colonised plants from below-ground organisms
Is there a common water-activity limit for the three domains of life?
Archaea and Bacteria constitute a majority of life systems on Earth but have long been considered inferior to Eukarya in terms of solute tolerance. Whereas the most halophilic prokaryotes are known for an ability to multiply at saturated NaCl (water activity (a w) 0.755) some xerophilic fungi can germinate, usually at high-sugar concentrations, at values as low as 0.650-0.605 a w. Here, we present evidence that halophilic prokayotes can grow down to water activities of <0.755 for Halanaerobium lacusrosei (0.748), Halobacterium strain 004.1 (0.728), Halobacterium sp. NRC-1 and Halococcus morrhuae (0.717), Haloquadratum walsbyi (0.709), Halococcus salifodinae (0.693), Halobacterium noricense (0.687), Natrinema pallidum (0.681) and haloarchaeal strains GN-2 and GN-5 (0.635 a w). Furthermore, extrapolation of growth curves (prone to giving conservative estimates) indicated theoretical minima down to 0.611 a w for extreme, obligately halophilic Archaea and Bacteria. These were compared with minima for the most solute-tolerant Bacteria in high-sugar (or other non-saline) media (Mycobacterium spp., Tetragenococcus halophilus, Saccharibacter floricola, Staphylococcus aureus and so on) and eukaryotic microbes in saline (Wallemia spp., Basipetospora halophila, Dunaliella spp. and so on) and high-sugar substrates (for example, Xeromyces bisporus, Zygosaccharomyces rouxii, Aspergillus and Eurotium spp.). We also manipulated the balance of chaotropic and kosmotropic stressors for the extreme, xerophilic fungi Aspergillus penicilloides and X. bisporus and, via this approach, their established water-activity limits for mycelial growth (∼0.65) were reduced to 0.640. Furthermore, extrapolations indicated theoretical limits of 0.632 and 0.636 a w for A. penicilloides and X. bisporus, respectively. Collectively, these findings suggest that there is a common water-activity limit that is determined by physicochemical constraints for the three domains of life
Challenges in microbial ecology: building predictive understanding of community function and dynamics.
The importance of microbial communities (MCs) cannot be overstated. MCs underpin the biogeochemical cycles of the earth's soil, oceans and the atmosphere, and perform ecosystem functions that impact plants, animals and humans. Yet our ability to predict and manage the function of these highly complex, dynamically changing communities is limited. Building predictive models that link MC composition to function is a key emerging challenge in microbial ecology. Here, we argue that addressing this challenge requires close coordination of experimental data collection and method development with mathematical model building. We discuss specific examples where model-experiment integration has already resulted in important insights into MC function and structure. We also highlight key research questions that still demand better integration of experiments and models. We argue that such integration is needed to achieve significant progress in our understanding of MC dynamics and function, and we make specific practical suggestions as to how this could be achieved