SEARCH · bioRxiv Science

Results for “Physiology”

Search indexed bioRxiv preprints in genomics, neuroscience, cell biology and bioinformatics. Read source abstracts and check manuscript versions; preprints are not peer reviewed.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,225 records · Page 68Linked to original sources

bioRxiv2017

Low-Level Carbon Monoxide Exposure Affects BOLD FMRI

Blood Oxygen Level Dependent (BOLD) FMRI is a common technique for measuring brain activation that could be affected by low-level carbon monoxide (CO) exposure from e.g. smoking. This study aimed to probe the vulnerability of BOLD FMRI to CO and determine whether it constitutes a significant confound in neuroimaging and clinical trials. Low-level (6ppm exhaled) CO effects on BOLD signal were assessed in 12 healthy never-smokers on two separate experimental days (CO and air control). FMRI tasks were breath-holds (hypercapnia), visual stimulation and fingertapping. CO significantly dampened global BOLD FMRI signal during hypercapnia and visual cortex activation during visual stimulation. During fingertapping, CO reduced visual cortex activation but increased premotor cortex activation. Behavioural and physiological measures remained unchanged. We conclude that BOLD FMRI is vulnerable to CO, possibly through baseline increases in CBF, and suggest exercising caution when imaging populations exposed to elevated CO levels, e.g. with high smoking prevalence.

neuroscience↗

bioRxiv2017

Disruption Of Ankyrin B And Caveolin-1 Interaction Sites Alters Na+,K+-ATPase Lateral Diffusion In HEK293 Cell Plasma Membranes

The Na+,K+-ATPase is a plasma membrane ion transporter of high physiological importance for ion homeostasis and cellular excitability in electrically active tissues. Mutations in the genes coding for Na+,K+-ATPase -subunit isoforms lead to severe human pathologies including Familial Hemiplegic Migraine type 2 (FHM2), Alternating Hemiplegia of Childhood (AHC), Rapid Dystonia Parkinsonism (RDP) or epilepsy. Many of the reported mutations lead to change- or loss-of-function effects, whereas others do not alter the functional properties, but lead to e.g. reduced protein stability, reduced protein expression or defective plasma membrane targeting. Na+,K+-ATPase frequently assembles with other membrane transporters or cellular matrix proteins in specialized plasma membrane microdomains, but the effects of these interactions on targeting or protein mobility are elusive so far. Mutational disruption of established interaction motifs of the Na+,K+-ATPase with ankyrin B and caveolin-1 are expected to result in changes in plasma membrane targeting, changes of the localization pattern, and of the diffusion behavior of the enzyme. We studied the consequences of mutations in these binding sites by monitoring diffusion of eGFP-labeled Na+,K+-ATPase constructs in the plasma membrane of living HEK293T cells by fluorescence correlation spectroscopy (FCS) as well as fluorescence recovery after photobleaching (FRAP) or photoswitching (FRAS) and observed significant differences compared to the wild-type enzyme, with synergistic effects for combinations of interaction site mutations. These measurements expand the possibilities to study the consequences of Na+,K+-ATPase mutations and provide information about the interaction of Na+,K+-ATPase 2-isoform with cellular matrix proteins, the cytoskeleton or other membrane protein complexes.

biophysics↗

bioRxiv2017

Extended Synaptotagmin Is A Presynaptic ER Ca2+ Sensor That Promotes Neurotransmission And Synaptic Growth In Drosophila

The endoplasmic reticulum (ER) is an extensive presynaptic organelle, exerting important influences at synapses by responding to Ca2+ and modulating transmission, growth, lipid metabolism, and membrane trafficking. Despite intriguing evidence for these crucial functions, how presynaptic ER influences synaptic physiology remains enigmatic. To gain insight into this question, we have generated and characterized mutations in the single Extended Synaptotagmin (Esyt) ortholog in Drosophila. Esyts are evolutionarily conserved ER proteins with Ca2+ sensing domains that have recently been shown to orchestrate membrane tethering and lipid exchange between the ER and plasma membrane. We first demonstrate that Esyt localizes to an extensive ER structure that invades presynaptic terminals at the neuromuscular junction. Next, we show that synaptic growth, structure, function, and plasticity are surprisingly unperturbed at synapses lacking Esyt expression. However, presynaptic overexpression of Esyt leads to enhanced synaptic growth, neurotransmission, and sustainment of the vesicle pool during intense levels of activity, suggesting that elevated Esyt at the ER promotes constitutive membrane trafficking or lipid exchange with the plasma membrane. Finally, we find that Esyt mutants fail to maintain basal neurotransmission and short term plasticity at elevated extracellular Ca2+, consistent with Esyt functioning as an ER Ca2+ sensor that modulates synaptic activity. Thus, we identify Esyt as a presynaptic ER Ca2+ sensor that can promote neurotransmission and synaptic growth, revealing the first in vivo neuronal functions of this conserved gene family.

neuroscience↗

bioRxiv2017

Drosophila CaV2 Channels Harboring Human Migraine Mutations Cause Synapse Hyperexcitability That Can Be Suppressed By Inhibition Of A Ca2+ Store Release Pathway

Gain-of-function mutations in the human CaV2.1 gene CACNA1A cause familial hemiplegic migraine type 1 (FHM1). To characterize cellular problems potentially triggered by CaV2.1 gains of function, we engineered mutations encoding FHM1 amino-acid substitutions S218L (SL) and R192Q (RQ) into transgenes of Drosophila melanogaster CaV2/cacophony. We expressed the transgenes pan-neuronally. Phenotypes were mild for RQ-expressing animals. By contrast, single mutant SL- and complex allele RQ,SL-expressing animals showed overt phenotypes, including sharply decreased viability. By electrophysiology, SL- and RQ,SL-expressing neuromuscular junctions (NMJs) exhibited enhanced evoked discharges, supernumerary discharges, and an increase in the amplitudes and frequencies of spontaneous events. Some spontaneous events were gigantic (10-40 mV), multi-quantal events. Gigantic spontaneous events were eliminated by application of TTX - or by lowered or chelated Ca2+ - suggesting that gigantic events were elicited by spontaneous nerve firing. A follow-up genetic approach revealed that some neuronal hyperexcitability phenotypes were reversed after knockdown or mutation of Drosophila homologs of phospholipase C{beta} (PLC{beta}), IP3 receptor, or ryanodine receptor (RyR) - all factors known to mediate Ca2+ release from intracellular stores. Pharmacological inhibitors of intracellular Ca2+ store release produced similar effects. Interestingly, however, the decreased viability phenotype was not reversed by genetic impairment of intracellular Ca2+ release factors. On a cellular level, our data suggest inhibition of signaling that triggers intracellular Ca2+ release could counteract hyperexcitability induced by gains of CaV2.1 function.\n\nAUTHOR SUMMARYPrior research has demonstrated that gain-of-function mutations in a gene important for neurotransmission (CACNA1A) are known to cause migraine in humans. We attempted to mimic some of those gain-of-function mutations in a simple genetic model organism and to examine neurotransmission by electrophysiology. Our findings yield potential clues as to how particular migraine-causing mutations may impact neurophysiology on a cellular level. We used the fruit fly Drosophila melanogaster and its model synapse, the neuromuscular junction (NMJ) to perform our studies. We document three main advances: 1) characterization of fruit fly models harboring gain-of-function calcium channel alterations known to cause human familial hemiplegic migraine type 1 (FHM1); 2) characterization of hyperactive neurotransmission caused by one of these alterations; and 3) an ability to quell hyperactive neurotransmission by impairing intracellular Ca2+ store release, through both genetic and pharmacological means. Our work contributes to a broader understanding of how pathological mutations could impact cellular physiology. More generally, the utilization of genetic model organisms promises to uncover potential ways to reverse those impacts.

neuroscience↗

bioRxiv2017

Rob And MarA Alter Susceptibility Of Escherichia coli To Antibiotics In Presence Of Salicylate

When exposed to stress, bacterial cells launch a diverse response to enhance their chances of survival. This response involves modulation of expression of a large number of proteins which help the cell counter stress. This modulation is facilitated by several transcription factors in bacteria and in E. coli three homologous regulators, MarA, Sox, and Rob are known to launch a coordinated response to combat various stress environments. MarA and SoxS are known to control multiple antibiotic resistance and superoxide regulon respectively. Rob has been observed to control similar downstream targets as MarA and SoxS. However, physiological relevance of Rob in not understood. We show that Rob along with MarA, in presence of inducer salicylate, can help cell survive in presence of lethal concentration of wide range of antibiotics.

microbiology↗

bioRxiv2017

Sequential Eviction Of Crowded Nucleoprotein Complexes By The RecBCD Molecular Motor

In physiological settings, all nucleic acids motor proteins must travel along substrates that are crowded with other proteins. However, the physical basis for how motor proteins behave in these highly crowded environments remains unknown. Here we use real-time single molecule imaging, kinetic Monte Carlo simulations, and Molecular dynamics simulations to determine how the ATP-dependent translocase RecBCD travels along DNA occupied by tandem arrays of high affinity DNA-binding proteins. We demonstrate that RecBCD forces each protein into its nearest adjacent neighbor, causing rapid disruption of the underlying protein-nucleic acid interface. This mechanism is not simply the same way that RecBCD disrupts isolated nucleoprotein complexes on otherwise naked DNA. Instead, molecular crowding itself completely alters the mechanism by which RecBCD removes tightly bound protein obstacles from DNA.\n\nSignificance statementChromosomes are crowded places, and any nucleic acid motor proteins that act upon DNA must function within these crowded environments. How crowded environments affect motor protein behaviors remains largely unexplored. Here, we use single molecule fluorescence microscopy visualize the ATP-dependent motor protein RecBCD as it travels along crowded DNA molecules bearing long tandem arrays of DNA-binding proteins. Our findings show that RecBCD can push through highly crowded protein arrays while evicting the proteins from DNA. Molecular dynamics simulations suggest that RecBCD forces the proteins into once another, causing rapid disruption of the protein-DNA interface. These findings may provide insights into how other types of motor proteins travel along crowded nucleic acids.

biophysics↗

bioRxiv2017

Olfactory Receptors Are Required For Social Behavior And Neural Plasticity In Ants, As Evidenced By CRISPR-Mediated Gene Knockout

The chemosensory system is key to establishing and maintaining social structure in eusocial insects. Ants exhibit cooperative colonial behaviors reflective of an advanced form of sociality with an extensive dependency on communication. Cuticular hydrocarbons (CHCs) serve as pheromones and cues that regulate multiple aspects of social interactions and behaviors in ants. The perception of CHCs entails odorant receptor neurons (ORNs) that express specific odorant receptors (ORs) encoded by a dramatically expanded Or gene family in ants. Until recently, studies of the biological functions of ORs in eusocial insects were stymied by the lack of genetic tools. In most eusocial insect species, only one or a few queens in a colony can transmit the genetic information to their progeny. In contrast, any worker in the ant Harpegnathos saltator can be converted into a gamergate (pseudo-queen), and used as a foundress to engender an entire new colony and be crossed for genetic experiments. This feature facilitated CRISPR-Cas9 gene targeting to generate a germline mutation in the orco gene that encodes the obligate co-receptor whose mutation should significantly impact ant olfaction. Our results show that Orco exhibits a conserved role in the perception of general odorants but also a role in reproductive physiology and social behavior plasticity in ants. Surprisingly, and in contrast to other insect systems, the loss of OR functionality also dramatically reduces the development of the ant antennal lobe where ORNs project. Taken together, these findings open the possibility of studying the genetics of eusociality and provide inroads towards understanding the function of the expanded ORs family in eusocial insects in regulating caste determination, social communication and neuronal plasticity.

neuroscience↗

bioRxiv2017

Wireless Implantable Sensor For Non-Invasive, Longitudinal Quantification Of Axial Strain Across Rodent Long Bone Defects

Bone development, maintenance, and regeneration are remarkably sensitive to mechanical cues. Consequently, mechanical stimulation has long been sought as a putative target to promote endogenous healing after fracture. Given the transient nature of bone repair, tissue-level mechanical cues evolve rapidly over time after injury and are challenging to measure non-invasively. The objective of this work was to develop and characterize an implantable strain sensor for non-invasive monitoring of axial strain across a rodent femoral defect during functional activity. Herein, we present the design, characterization, and in vivo demonstration of the devices capabilities for quantitatively interrogating physiological dynamic strains during bone regeneration. Ex vivo experimental characterization of the device showed that it exceeded the technical requirements for sensitivity, signal resolution, and electromechanical stability. The digital telemetry minimized power consumption, enabling long-term intermittent data collection. Devices were implanted in a rat 6 mm femoral segmental defect model and after three days, data were acquired wirelessly during ambulation and synchronized to corresponding radiographic videos, validating the ability of the sensor to non-invasively measure strain in real-time. Lastly, in vivo strain measurements were utilized in a finite element model to estimate the strain distribution within the defect region. Together, these data indicate the sensor is a promising technology to quantify local tissue mechanics in a specimen specific manner, facilitating more detailed investigations into the role of the mechanical environment in dynamic skeletal healing and remodeling.

bioengineering↗

bioRxiv2017

Polycystic Ovary Syndrome As An Endogenous Alcoholic Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is a growing worldwide public health problem that affects millions of women in their reproductive age. Despite being a very common disorder among women, there are still gaps regarding knowledge of disease mechanisms. In this respect, it was recently reported that acetaldehyde (ACD) is endogenously formed during normal ovarian steroidogenesis. The researchers demonstrated that in physiological concentrations ACD caused no detrimental effect on ovarian tissue. Contrariwise, in supraphysiological levels, ACD impairs granulosa cell differentiation, reduces ovulation, and decreases oocyte quality. Gut microbiota of patients with nonalcoholic fatty liver disease (NAFLD) produces significant quantities of endogenous ethanol (EE) and ACD. Because PCOS is closely linked to NAFLD, an ethanol-producing disorder, we hypothesize that it can be an endogenous alcoholic polycystic ovary syndrome (EAPCOS). The main findings of this study were that (i) the odds ratio of having polycystic ovaries is 30-fold greater in alcohol-exposed women than among unexposed controls; (ii) NAFLD/PCOS patients produce gonadotoxic quantities of EE; (iii) NAFLD/PCOS and alcoholic hepatitis individuals share similar liver expression levels of genes regulating high-km ethanol-metabolizing enzymes; (iv) NAFLD/PCOS and alcohol-tolerant drinkers share similar high-capacity to metabolize ethanol in the gut-liver axis; and (v) low blood alcohol concentration (BAC) in NAFLD/PCOS and alcohol-tolerant individuals stem from extensive alcohol degradation in gut-liver axis and significant fecal loss of ethanol. In summary, we provide mechanistic insights supporting the hypothesis that PCOS can be indeed an EAPCOS.

molecular biology↗

bioRxiv2017

Local Signal Processing In Mouse Horizontal Cell Dendrites

The mouse retina contains a single type of horizontal cell, a GABAergic interneuron that samples from all cone photoreceptors within reach and modulates their glutamatergic output via parallel feedback mechanisms. Because horizontal cells form an electrically-coupled network, they have been implicated in global signal processing, such as large scale contrast enhancement. Recently, it has been proposed that horizontal cells can also act locally at the level of individual cone photoreceptors. To test this possibility physiologically, we used two-photon microscopy to record light stimulus-evoked Ca2+ signals in cone axon terminals and horizontal cell dendrites as well as glutamate release in the outer plexiform layer. By selectively stimulating the two mouse cone opsins with green and UV light, we assessed whether signals from individual cones remain \"isolated\" within horizontal cell dendritic tips, or whether they spread across the dendritic arbour. Consistent with the mouse s opsin expression gradient, we found that the Ca2+ signals recorded from dendrites of dorsal horizontal cells were dominated by M- and those of ventral horizontal cells by S-opsin activation. The signals measured in neighbouring horizontal cell dendritic tips varied markedly in their chromatic preference, arguing against global processing. Rather, our experimental data and results from biophysically realistic modelling support the idea that horizontal cells can process cone input locally, extending the \"classical\" view of horizontal cells function. Pharmacologically removing horizontal cells from the circuitry reduced the sensitivity of the cone signal to low frequencies, suggesting that local horizontal cell feedback shapes the temporal properties of cone output.\n\nHighlightsO_LILight-evoked Ca2+ signals in horizontal cell dendrites reflect opsin gradient\nC_LIO_LIChromatic preferences in neighbouring dendritic tips vary markedly\nC_LIO_LIMouse horizontal cells process cone photoreceptor input locally\nC_LIO_LILocal horizontal cell feedback shapes the temporal properties of cone output\nC_LI\n\neTOC BlurbChapot et al. show that local light responses in mouse horizontal cell dendrites inherit properties, including chromatic preference, from the presynaptic cone photoreceptor, suggesting that their dendrites can provide \"private\" feedback to cones, for instance, to shape the temporal filtering properties of the cone synapse.

neuroscience↗

bioRxiv2017

Coupling Of Tactile LFP Signals Between Mouse Cortex And Olfactory Bulb

Local field potentials are an important measure of brain activity and have been used to address various mechanistic and behavioral questions. We revealed a prominent whisker evoked local field potential signal in the olfactory bulb and investigated its physiology. This signal, dependent on barrel cortex activation and highly correlated with its local activity, represented a pure volume conductance signal that was sourced back to the activity in the ventro-lateral orbitofrontal cortex, located a few millimeters away. Thus, we suggest that special care should be taken when acquiring and interpreting LFP data.

neuroscience↗

bioRxiv2018

Different alleles of the same gene vary in pleiotropy, often mediated through currency metabolite production

A major obstacle to the mapping of genotype-phenotype relationships is pleiotropy, the tendency of mutations to affect seemingly unrelated traits. Pleiotropy has major implications for evolution, development, ageing, and disease. Except for disease data, pleiotropy is almost exclusively estimated from full gene knockouts. However, most deleterious alleles segregating in natural populations do not fully abolish gene function, and the degree to which a polymorphism reduces protein function may influence the number of traits it affects. Utilizing genome-scale metabolic models for Escherichia coli and the bakers yeast Saccharomyces cerevisiae, we show that most fitness-reducing full gene knockouts of metabolic genes have pleiotropic effects, i.e., they compromise the production of multiple biomass components. Alleles of the same gene with increasingly reduced enzyme function typically affect an increasing number of biomass components. This increasing pleiotropy is often mediated through effects on the generation of currency metabolites such as ATP or NADPH. We conclude that the physiological effects observed in full gene knockouts will in most cases not be representative for alleles with only partially reduced enzyme capacity or expression level.

systems biology↗

bioRxiv2017

Genome-Enabled Insights Into The Ecophysiology Of The Comammox Bacterium Candidatus Nitrospira nitrosa

The recently discovered comammox bacteria have the potential to completely oxidize ammonia to nitrate. These microorganisms are part of the Nitrospira genus and are present in a variety of environments, including Biological Nutrient Removal (BNR) systems. However, the physiological traits within and between comammox- and nitrite oxidizing bacteria (NOB)-like Nitrospira species have not been analyzed in these ecosystems. In this study, we identified Nitrospira strains dominating the nitrifying community of a sequencing batch reactor (SBR) performing BNR under micro-aerobic conditions. We recovered metagenomes-derived draft genomes from two Nitrospira strains: (1) Nitrospira sp. UW-LDO-01, a comammox-like organism classified as Candidatus Nitrospira nitrosa, and (2) Nitrospira sp. UW-LDO-02, a nitrite oxidizing strain belonging to the Nitrospira defluvii species. A comparative genomic analysis of these strains with other Nitrospira-like genomes identified genomic differences in Ca. Nitrospira nitrosa mainly attributed to each strains niche adaptation. Traits associated with energy metabolism also differentiate comammox from NOB-like genomes. We also identified several transcriptionally regulated adaptive traits, including stress tolerance, biofilm formation and micro-aerobic metabolism, which might explain survival of Nitrospira under multiple environmental conditions. Overall, our analysis expanded our understanding of the genetic functional features of Ca. Nitrospira nitrosa, and identified genomic traits that further illuminate the phylogenetic diversity and metabolic plasticity of the Nitrospira genus.

microbiology↗

bioRxiv2017

Contextual Tumor Suppressor Function Of T Cell Death-Associated Gene 8 (TDAG8) In Hematological Malignancies

Key points1. TDAG8 (GPR65) gene expression is down-regulated in hematological malignancies.\n\n2. Restoration of TDAG8 gene expression in blood cancer cells suppresses tumor growth and metastasis.\n\nAbstractExtracellular acidosis is a condition found within the tumor microenvironment due to inadequate blood perfusion, hypoxia, and altered tumor cell metabolism. Acidosis has pleiotropic effects on malignant progression; therefore it is essential to understand how acidosis exerts its diverse effects. In this study a bioinformatics analysis revealed the expression of the proton sensing G-protein-coupled receptor TDAG8 is significantly reduced in human blood cancers in comparison to normal blood cells. To understand how TDAG8 functions in hematological malignancies, TDAG8 expression was restored in U937 acute myeloid leukemia cells and other blood cancer cells. It was discovered that severe acidosis, pH 6.4, inhibited U937 cell proliferation while mild acidosis, pH 6.9, stimulated cell proliferation. However, restoring TDAG8 gene expression modulated the U937 cell response to mild extracellular acidosis and physiological pH by reducing cell proliferation. Tumor xenograft experiments further revealed that restoring TDAG8 expression in U937 and Ramos cancer cells reduced tumor growth. It was also shown U937 cells with restored TDAG8 expression attached less to Matrigel, migrated slower toward a chemoattractant, and metastasized less in severe combined immunodeficient mice. These effects correlated with a reduction in c-myc oncogene expression. The mechanistic investigation indicated that G13/RhoA signaling arbitrated the TDAG8-mediated c-myc oncogene repression in response to acidosis. Overall, this study provides compelling data to support the concept that TDAG8 functions as a contextual tumor suppressor in hematological malignancies and sensitizes blood cancer cells to acidotic stress.

cancer biology↗

bioRxiv2017

Classifying Drosophila Olfactory Projection Neuron Subtypes by Single-cell RNA Sequencing

How a neuronal cell type is defined and how this relates to its transcriptome are still open questions. The Drosophila olfactory projection neurons (PNs) are among the best-characterized neuronal types: Different PN classes target dendrites to distinct olfactory glomeruli and PNs of the same class exhibit indistinguishable anatomical and physiological properties. Using single-cell RNA-sequencing, we comprehensively characterized the transcriptomes of 40 PN classes and unequivocally identified transcriptomes for 6 classes. We found a new lineage-specific transcription factor that instructs PN dendrite targeting. Transcriptomes of closely-related PN classes exhibit the largest difference during circuit assembly, but become indistinguishable in adults, suggesting that neuronal subtype diversity peaks during development. Genes encoding transcription factors and cell-surface molecules are the most differentially expressed, indicating their central roles in specifying neuronal identity. Finally, we show that PNs use highly redundant combinatorial molecular codes to distinguish subtypes, enabling robust specification of cell identity and circuit assembly.

genomics↗

bioRxiv2017

Genetically modified human type II collagen for N- and C-terminal covalent tagging

Collagen is the predominant structural protein in vertebrates, where it contributes to connective tissues and the extracellular matrix; it is also widely used in biomaterials and tissue engineering. Dysfunction of this protein and its processing can lead to a wide variety of developmental disorders and connective tissue diseases. Recombinantly engineering the protein is challenging due to posttranslational modifications generally required for its stability and secretion from cells. Introducing end labels into the protein is problematic, because the N- and C-termini of the physiologically relevant tropocollagen lie internal to the initially flanking N- and C-propeptide sequences. Here, we introduce mutations into human type II procollagen in a manner that address these concerns, and purify the recombinant protein from a stably transfected HT1080 human fibrosarcoma cell line. Our approach introduces chemically addressable groups into the N- and Ctelopeptide termini of tropocollagen. Simultaneous overexpression of formylglycine generating enzyme (FGE) allows the endogenous production of an aldehyde tag in a defined, substituted sequence in the N-terminus of the mutated collagen, while the C-terminus of each chain presents a sulfhydryl group from an introduced cysteine. These modifications are designed to enable specific covalent end-labelling of collagen. We find that the doubly-mutated protein folds and is secreted from cells, while higher-order assembly into well-ordered collagen fibrils is demonstrated through transmission electron microscopy. Chemical tagging of thiols is successful, however background from endogenous aldehydes present in wildtype collagen has thus far obscured the desired specific N-terminal labelling. Strategies to overcome this challenge are proposed.

biochemistry↗

bioRxiv2017

Bacterial lipopolysaccharide reduces the stability of avian and human influenza viruses

Commensal bacteria can promote or reduce the severity of viral infection and disease progression in their hosts depending on the specific viral pathogen1. Influenza A virus (IAV) has a broad host-range, comprises many subtypes, and utilizes different routes of transmission including the fecal-oral route in wild birds2. It has been previously demonstrated that commensal bacteria can interact with the hosts immune system to protect against IAV pathogenesis3,4. However, it is unclear whether bacteria and their products may be interacting directly with IAV to impact virion stability. Herein we show that gastrointestinal (GI) tract bacterial isolates in an in vitro system significantly reduce the thermal stability of IAV. Moreover, bacterial lipopolysaccharide (LPS), found on the exterior surfaces of bacteria, was sufficient to significantly decrease the stability of both human and avian viral strains at the physiological temperatures of their respective hosts, as well as in the aquatic environment. Subtype and host-origin of the viruses were shown to affect the extent to which IAV was susceptible to LPS. Furthermore, using a receptor-binding assay and transmission electron microscopy, we observed that LPS binds to and affects the morphology of influenza virions.

microbiology↗

bioRxiv2017

Cooling Induced by Uphill Energy Transport in Plant Photosystems

The uphill energy transfer in photosystems implies input energy at higher wavelength leading to energy output at lower wavelength. Briefly, energy is uphill transported from photosystem I (PSI) to photosystem II (PSII), the latter having a lower wavelength emission. This uphill energy transport involves absorption of thermal energy from the surroundings. While such cooling effects have been reported in laser systems we report for the first time a white light driven cooling in thylakoid suspension. The cooling of the surrounding medium by appropriate illumination was illustrated using thermal measurements. Again cooling is inhibited by agents like 3-(3,4-Dichlorophenyl)-1,1-dimethylurea,that block the linear electron flow between the photocenters, implying a dependence of the cooling on interplay between such centers. Furthermore, it is possible to modulate the cooling pattern by addition of external agents like nanopaticles, some favoring further cooling (e.g., Ag nanoparticle) and some like Au or chlorophyll nanoparticles, showing insignificant or even reverse trends. Interestingly, the cooling is invariably associated with the 77K spectra of the thylakoid suspension. With reference to the dark control, an agent causing cooling always increases PSII to PSI ratio and vice versa i.e.,the uphill energy transport. Importantly, the cooling effect, apart from its import role in plant physiology can be exploited artificially for energy saving in post-harvest or food preservation.

bioengineering↗