1,628 research outputs found
The Response of the Honey Bee Gut Microbiota to Nosema ceranae Is Modulated by the Probiotic Pediococcus acidilactici and the Neonicotinoid Thiamethoxam.
The honey bee Apis mellifera is exposed to a variety of biotic and abiotic stressors, such as the highly prevalent microsporidian parasite Nosema (Vairimorpha) ceranae and neonicotinoid insecticides. Both can affect honey bee physiology and microbial gut communities, eventually reducing its lifespan. They can also have a combined effect on the insect's survival. The use of bacterial probiotics has been proposed to improve honey bee health, but their beneficial effect remains an open question. In the present study, western honey bees were experimentally infected with N. ceranae spores, chronically exposed to the neonicotinoid thiamethoxam, and/or supplied daily with the homofermentative bacterium Pediococcus acidilactici MA18/5M thought to improve the honey bees' tolerance to the parasite. Deep shotgun metagenomic sequencing allowed the response of the gut microbiota to be investigated with a taxonomic resolution at the species level. All treatments induced significant changes in honey bee gut bacterial communities. Nosema ceranae infection increased the abundance of Proteus mirabilis, Frischella perrara, and Gilliamella apicola and reduced the abundance of Bifidobacterium asteroides, Fructobacillus fructosus, and Lactobacillus spp. Supplementation with P. acidilactici overturned some of these alterations, bringing back the abundance of some altered species close to the relative abundance found in the controls. Surprisingly, the exposure to thiamethoxam also restored the relative abundance of some species modulated by N. ceranae. This study shows that stressors and probiotics may have an antagonistic impact on honey bee gut bacterial communities and that P. acidilactici may have a protective effect against the dysbiosis induced by an infection with N. ceranae
Modeling Bacterial DNA: Simulation of Self-avoiding Supercoiled Worm-Like Chains Including Structural Transitions of the Helix
Under supercoiling constraints, naked DNA, such as a large part of bacterial
DNA, folds into braided structures called plectonemes. The double-helix can
also undergo local structural transitions, leading to the formation of
denaturation bubbles and other alternative structures. Various polymer models
have been developed to capture these properties, with Monte-Carlo (MC)
approaches dedicated to the inference of thermodynamic properties. In this
chapter, we explain how to perform such Monte-Carlo simulations, following two
objectives. On one hand, we present the self-avoiding supercoiled Worm-Like
Chain (ssWLC) model, which is known to capture the folding properties of
supercoiled DNA, and provide a detailed explanation of a standard MC simulation
method. On the other hand, we explain how to extend this ssWLC model to include
structural transitions of the helix.Comment: Book chapter to appear in The Bacterial Nucleoid, Methods and
Protocols, Springer serie
Patterns of subnet usage reveal distinct scales of regulation in the transcriptional regulatory network of Escherichia coli
The set of regulatory interactions between genes, mediated by transcription
factors, forms a species' transcriptional regulatory network (TRN). By
comparing this network with measured gene expression data one can identify
functional properties of the TRN and gain general insight into transcriptional
control. We define the subnet of a node as the subgraph consisting of all nodes
topologically downstream of the node, including itself. Using a large set of
microarray expression data of the bacterium Escherichia coli, we find that the
gene expression in different subnets exhibits a structured pattern in response
to environmental changes and genotypic mutation. Subnets with less changes in
their expression pattern have a higher fraction of feed-forward loop motifs and
a lower fraction of small RNA targets within them. Our study implies that the
TRN consists of several scales of regulatory organization: 1) subnets with more
varying gene expression controlled by both transcription factors and
post-transcriptional RNA regulation, and 2) subnets with less varying gene
expression having more feed-forward loops and less post-transcriptional RNA
regulation.Comment: 14 pages, 8 figures, to be published in PLoS Computational Biolog
PHIL photoinjector test line
LAL is now equiped with its own platform for photoinjectors tests and
Research and Developement, named PHIL (PHotoInjectors at LAL). This facility
has two main purposes: push the limits of the photoinjectors performances
working on both the design and the associated technology and provide a low
energy (MeV) short pulses (ps) electron beam for the interested users. Another
very important goal of this machine will be to provide an opportunity to form
accelerator physics students, working in a high technology environment. To
achieve this goal a test line was realised equipped with an RF source, magnets
and beam diagnostics. In this article we will desrcibe the PHIL beamline and
its characteristics together with the description of the first two
photoinjector realised in LAL and tested: the ALPHAX and the PHIN RF Guns
Low Energy Beam Measurements Using PHIL Accelerator at LAL, Comparison with PARMELA Simulations
http://accelconf.web.cern.ch/AccelConf/PAC2011/papers/wep210.pdfInternational audiencePHIL ("PHoÂto-InÂjecÂtor at LAL") is a new elecÂtron beam acÂcelÂerÂaÂtor at LAL. This acÂcelÂerÂaÂtor is dedÂiÂcatÂed to test and charÂacÂterÂize elecÂtron RF-guns and to deÂlivÂer elecÂtron beam to users. This maÂchine has been deÂsigned to proÂduce and charÂacÂterise low enÂerÂgy (E<10 MeV), small emitÂtance (e<10 p.âmm.âmrad), high brilÂliance elecÂtrons bunch at low repÂeÂtiÂtion freÂquenÂcy (n<10Hz). The first beam has been obÂtained on the 4th of NovemÂber 2009. The curÂrent RF-gun testÂed on PHIL is the AlÂphaX gun, a 2.5 cell S-band cavÂiÂty deÂsigned by LAL for the plasÂma acÂcelÂerÂaÂtor studÂies perÂformed at the StrathÂclyde uniÂverÂsiÂty. This paper will preÂsent the first AlÂphaX RF-gun charÂacÂterÂiÂzaÂtions perÂformed at LAL on PHIL acÂcelÂerÂaÂtor, and will show comÂparÂisons beÂtween meaÂsureÂments and PARMELA simÂuÂlaÂtions
Chondroprotective Potential of Fruit Extracts of Phyllanthus emblica in Osteoarthritis
There is a need for effective nutraceuticals for osteoarthritis care. The fruit of Phyllanthus emblica is used as a powerful rejuvenator in Ayurvedic medicine. This study measured the chondroprotective potential of P. emblica (âAmalakiâ) fruits in vitro. We used aqueous extracts of unprocessed P. emblica fruit powder (powder A), and the powder obtained after hot water extraction and drying of powder A (powder B). Chondroprotection was measured in three different assay systems. First, we tested the effects of both fruit powders on the activities of the enzymes hyaluronidase and collagenase type 2. Second, an in vitro model of cartilage degradation was set-up with explant cultures of articular knee cartilage from osteoarthritis patients. Cartilage damage was assayed by measuring glycosaminoglycan release from explants treated with/without P. emblica fruit powders. Aqueous extracts of both fruit powders significantly inhibited the activities of hyaluronidase and collagenase type 2 in vitro. Third, in the explant model of cartilage matrix damage, extracts of glucosamine sulphate and powder B (0.05 mg/ml) exhibited statistically significant, long-term chondroprotective activity in cartilage explants from 50% of the patients tested. This result is important since glucosamine sulphate is the leading nutraceutical for osteoarthritis. Powder A induced a statistically significant, short-term chondroprotective activity in cartilage explants from all of the patients tested. This is the first study to identify and quantitate new chondroprotective activities of P. emblica fruits. These data provide pilot pre-clinical evidence for the use of P. emblica fruits as a chondroprotective agent in osteoarthritis therapy
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