Regulation of transcription in a reduced bacterial genome: nutrient-provisioning genes of the obligate symbiont Buchnera aphidicola.

Buchnera aphidicola, the obligate symbiont of aphids, has an extremely reduced genome, of which about 10% is devoted to the biosynthesis of essential amino acids needed by its hosts. Most regulatory genes for these pathways are absent, raising the question of whether and how transcription of these genes responds to the major shifts in dietary amino acid content encountered by aphids. Using full-genome microarrays for B.

Evolutionary relationships of three new species of Enterobacteriaceae living as symbionts of aphids and other insects.

Ecological studies on three bacterial lineages symbiotic in aphids have shown that they impose a variety of effects on their hosts, including resistance to parasitoids and tolerance to heat stress. Phylogenetic analyses of partial sequences of gyrB and recA are consistent with previous analyses limited to 16S rRNA gene sequences and yield improved confidence of the evolutionary relationships of these symbionts. All three symbionts are in the Enterobacteriaceae.

Extremely rapid recovery of human cone circulating current at the extinction of bleaching exposures.

We used a conductive fibre electrode placed in the lower conjunctival sac to record the a-wave of the human photopic electroretinogram elicited by bright white flashes, delivered during, or at different times after, exposure of the eye to bright white illumination that bleached a large fraction (approximately 90%) of the cone photopigment. During steady-state exposures of this intensity, the amplitude of the bright-flash response declined to approximately 50% of its dark-adapted level. After the intense background was turned off, the amplitude of the bright-flash response recovered substantially, for flashes presented within 20 ms of background extinction, and fully, for flashes presented 100 ms after extinction.

Evolutionary origins of genomic repertoires in bacteria.

Explaining the diversity of gene repertoires has been a major problem in modern evolutionary biology. In eukaryotes, this diversity is believed to result mainly from gene duplication and loss, but in prokaryotes, lateral gene transfer (LGT) can also contribute substantially to genome contents. To determine the histories of gene inventories, we conducted an exhaustive analysis of gene phylogenies for all gene families in a widely sampled group, the gamma-Proteobacteria.

Aroma release and retronasal perception during and after consumption of flavored whey protein gels with different textures. 1. in vivo release analysis.

The influence of gel texture on retronasal aroma release during mastication was followed by means of real-time proton-transfer reaction mass spectrometry and compared to sensory perception of overall aroma intensity. A clear correlation was found between individual-specific consumption patterns and the respective physicochemical release patterns in vivo. A modified data analysis approach was used to monitor the aroma changes during the mastication process.

Genomic changes following host restriction in bacteria.

Many genomic sequences have been recently published for bacteria that can replicate only within eukaryotic hosts. Comparisons of genomic features with those of closely related bacteria retaining free-living stages indicate that rapid evolutionary change often occurs immediately after host restriction. Typical changes include a large increase in the frequency of mobile elements in the genome, chromosomal rearrangements mediated by recombination among these elements, pseudogene formation, and deletions of varying size.

Application of proteomics to the study of platelet regulatory mechanisms.

Newly developed proteomic technologies now permit the routine identification of hundreds or even thousands of proteins in a single experiment. However, the global study of any proteome has unique challenges that set it apart from comprehensive studies of genes and transcripts. The detection of low-abundance, biologically relevant proteins poses a particular challenge, especially given that the dynamic range of proteins in cells is estimated to be > or =10(6).

A heterodifunctionalised ferrocene derivative that self-assembles in solution through complementary hydrogen-bonding interactions.

A heterodifunctionalised ferrocene, containing a carboxylic acid and an amidopyridine unit, self-assembles in organic solvents through complementary hydrogen bonds.

Dynamic changes in the osmotic water permeability of protoplast plasma membrane.

The osmotic water permeability coefficient (P(f)) of plasma membrane of maize (Zea mays) Black Mexican Sweet protoplasts changed dynamically during a hypoosmotic challenge, as revealed using a model-based computational approach. The best-fitting model had three free parameters: initial P(f), P(f) rate-of-change (slope(P(f))), and a delay, which were hypothesized to reflect changes in the number and/or activity of aquaporins in the plasma membrane. Remarkably, the swelling response was delayed 2 to 11 s after start of the noninstantaneous (but accounted for) bath flush.

Epilepsy in the United Kingdom: seizure frequency and severity, anti-epileptic drug utilization and impact on life in 1652 people with epilepsy.

Objectives: To describe the clinical characteristics of epilepsy in a representative sample of the UK population, including seizure frequency and severity; overall severity of epilepsy; patterns of anti-epileptic drug (AED) use; and the impact of epilepsy on patients' lives. Secondly, to determine if these characteristics differ according to age.

Method: A large, geographically comprehensive survey of people with epilepsy by means of a postal questionnaire distributed by general practitioners to 3455 unselected patients receiving AEDs for epilepsy, regardless of age or type of epilepsy and including all regions of the UK.

Novel integrin-specific targets for anti-platelet therapies.

Extensive study in integrin research has seen the platelet specific receptor alpha(IIb)beta(3) (Glycoprotein GPIIb/IIIa) under much scrutiny, and provided vast information as to the workings of this integrin within the blood. Glanzmann's thrombasthenia, a rare autosomal recessive bleeding disorder, highlights the vital role played by this receptor in platelet function. Glanzmann's thrombasthenic platelets fail to aggregate due to a lack of surface expression of functional alpha(IIb) or beta(3) on the platelet surface.

ICln, a novel integrin alphaIIbbeta3-associated protein, functionally regulates platelet activation.

A critical role for the conserved alpha-integrin cytoplasmic motif, KVGFFKR, is recognized in the regulation of activation of the platelet integrin alpha(IIb)beta(3). To understand the molecular mechanisms of this regulation, we sought to determine the nature of the protein interactions with this cytoplasmic motif. We used a tagged synthetic peptide, biotin-KVGFFKR, to probe a high density protein expression array (37,200 recombinant human proteins) for high affinity interactions.

The evolutionary history of quorum-sensing systems in bacteria.

Communication among bacterial cells through quorum-sensing (QS) systems is used to regulate ecologically and medically important traits, including virulence to hosts. QS is widespread in bacteria; it has been demonstrated experimentally in diverse phylogenetic groups, and homologs to the implicated genes have been discovered in a large proportion of sequenced bacterial genomes. The widespread distribution of the underlying gene families (LuxI/R and LuxS) raises the questions of how often QS genes have been transferred among bacterial lineages and the extent to which genes in the same QS system exchange partners or coevolve.

A nodule-specific dicarboxylate transporter from alder is a member of the peptide transporter family.

Alder (Alnus glutinosa) and more than 200 angiosperms that encompass 24 genera are collectively called actinorhizal plants. These plants form a symbiotic relationship with the nitrogen-fixing actinomycete Frankia strain HFPArI3. The plants provide the bacteria with carbon sources in exchange for fixed nitrogen, but this metabolite exchange in actinorhizal nodules has not been well defined.

Calreticulin-independent regulation of the platelet integrin alphaIIbbeta3 by the KVGFFKR alphaIIb-cytoplasmic motif.

The platelet integrin alphaIIbbeta3 alters conformation in response to platelet activation and ligand binding, although the molecular mechanisms involved are not known. We previously showed that a lipid modified peptide, corresponding to the membrane proximal 989KVGFFKR995 portion of the alphaIIb cytoplasmic tail, independently activates platelet alphaIIbbeta3. Calreticulin (CRT) is a potential integrin regulatory protein based on its interaction with the highly conserved alpha-integrin sequence KxGFFKR.

Redox modulation of integrin [correction of integin] alpha IIb beta 3 involves a novel allosteric regulation of its thiol isomerase activity.

The molecular mechanisms involved in regulating the activation-dependent conformational switch in integrins are not known although recent evidence suggests that integrins are a direct target for redox modulation. We have identified an endogenous integrin thiol isomerase activity that may be responsible for regulating integrin activation states. The purpose of this study was to examine the effects of redox conditions elicited by nitric oxide and glutathione on the thiol isomerase activity of the platelet integrin alphaIIbbeta3 and also on the activation status of this integrin in intact platelets.

A palmitylated peptide derived from the glycoprotein Ib beta cytoplasmic tail inhibits platelet activation.

The platelet receptor GPIb/IX/V mediates a crucial role in hemostasis, yet the signaling mechanisms involved are incompletely understood. The complex consists of four polypeptides GPIb alpha, GPIb beta, GPIX and GPV. We identified an amino acid sequence in the cytoplasmic tail of the GPIb beta subunit between residues R151 and A161 that is highly conserved across species and hypothesized that it has functional importance.

Tracing the evolution of gene loss in obligate bacterial symbionts.

The gamma-proteobacterial symbionts of insects are a model group for comparative studies of genome reduction. The phylogenetic proximity of these reduced genomes to the larger genomes of well-studied free-living bacteria has enabled reconstructions of the process by which genes and DNA are lost. Three genome sequences are now available for Buchnera aphidicola.

From gene trees to organismal phylogeny in prokaryotes: the case of the gamma-Proteobacteria.

The rapid increase in published genomic sequences for bacteria presents the first opportunity to reconstruct evolutionary events on the scale of entire genomes. However, extensive lateral gene transfer (LGT) may thwart this goal by preventing the establishment of organismal relationships based on individual gene phylogenies. The group for which cases of LGT are most frequently documented and for which the greatest density of complete genome sequences is available is the gamma-Proteobacteria, an ecologically diverse and ancient group including free-living species as well as pathogens and intracellular symbionts of plants and animals.

Phylogenetics and the cohesion of bacterial genomes.

Gene acquisition is an ongoing process in many bacterial genomes, contributing to adaptation and ecological diversification. Lateral gene transfer is considered the primary explanation for discordance among gene phylogenies and as an obstacle to reconstructing the tree of life. We measured the extent of phylogenetic conflict and alien-gene acquisition within quartets of sequenced genomes.

Consequences of reductive evolution for gene expression in an obligate endosymbiont.

The smallest cellular genomes are found in obligate symbiotic and pathogenic bacteria living within eukaryotic hosts. In comparison with large genomes of free-living relatives, these reduced genomes are rearranged and have lost most regulatory elements. To test whether reduced bacterial genomes incur reduced regulatory capacities, we used full-genome microarrays to evaluate transcriptional response to environmental stress in Buchnera aphidicola, the obligate endosymbiont of aphids.

Loss of DNA recombinational repair enzymes in the initial stages of genome degeneration.

Many obligate intracellular pathogens and symbionts undergo genome degeneration during long-term association with eukaryotic hosts; however, very little is known about genome changes that occur in the initial stages of such intracellular associations. By focusing on a clade of bacteria that have recently established symbiotic associations with insect hosts, we have identified events that may contribute to the reduction and degeneration of symbiont genomes. Unlike virtually all other bacteria, the obligate symbionts of maize and rice weevils each display substantial sequence divergence between multiple copies of their rDNA genes, resulting from a reduction in the efficacy of recombinational gene conversion, coincident with the inactivation of the recombinational repair gene recF in the common ancestor of both symbionts.