Sialic acid mediated transcriptional modulation of a highly conserved sialometabolism gene cluster in Haemophilus influenzae and its effect on virulence

Background. Sialic acid has been shown to be a major virulence determinant in the pathogenesis of otitis media caused by the bacterium Haemophilus influenzae. This study aimed to characterise the expression of genes required for the metabolism of sialic acid and to investigate the role of these genes in virulence. Results. Using qRT-PCR, we observed decreased transcriptional activity of genes within a cluster that are required for uptake and catabolism of 5-acetyl neuraminic acid (Neu5Ac), when bacteria were cultured in the presence of the sugar. We show that these uptake and catabolic genes, including a sialic acid regulatory gene (siaR), are highly conserved in the H. influenzae natural population. Mutant strains were constructed for seven of the nine genes and their influence upon LPS sialylation and resistance of the bacteria to the killing effect of normal human serum were assessed. Mutations in the Neu5Ac uptake (TRAP transporter) genes decreased virulence in the chinchilla model of otitis media, but the attenuation was strain dependent. In contrast, mutations in catabolism genes and genes regulating sialic acid metabolism (siaR and crp) did not attenuate virulence. Conclusion. The commensal and pathogenic behaviour of H. influenzae involves LPS sialylation that can be influenced by a complex regulatory interplay of sialometabolism genes. © 2010 Jenkins et al; licensee BioMed Central Ltd

Home food preparation practices, experiences and perceptions: A qualitative interview study with photo-elicitation

Food-related choices have an important impact on health. Food preparation methods may be linked to diet and health benefits. However, the factors influencing people’s food choices, and how they are shaped by food preparation experiences, are still not fully understood. We aimed to study home food preparation practices, experiences and perceptions amongst adults in North East England. A matrix was used to purposively sample participants with diverse socio-demographic characteristics. Participants developed photographic food diaries that were used as prompts during semi-structured interviews. Data were analysed using the Framework Method. Interviews were conducted with 18 adults (five men and 13 women), aged approximately 20 to 80 years, to reach data saturation. Participants’ practices varied widely, from reliance on pre-prepared foods, to preparing complex meals entirely from basic ingredients. Key themes emerged regarding the cook (identity), the task (process of cooking), and the context (situational drivers). Resources, in terms of time, money and facilities, were also underpinning influences on food preparation. Participants’ practices were determined by both personal motivations to cook, and the influence of others, and generally reflected compromises between varied competing demands and challenges in life. Most people appeared to be overall content with their food preparation behaviour, though ideally aspired to cook more frequently, using basic ingredients. This often seemed to be driven by social desirability. Home food preparation is complex, with heterogeneous practices, experiences and perceptions both between individuals and within the same individual over time, according to shifting priorities and circumstances. Generalisability of these findings may be limited by the regional participant sample; however the results support and build upon previous research. Focussing interventions on life transition points at which priorities and circumstances change, with careful targeting to stimulate personal motivation and social norms, may prove effective in encouraging home food preparation.This report is independent research arising from a Doctoral Research Fellowship Grant DRF-2014-07-020 for the lead author (SM), supported by the National Institute for Health Research. JA and MW received funding from the Centre for Diet and Activity Research (CEDAR), a UK Clinical Research Collaboration (UKCRC) Public Health Research Centre of Excellence. HB and SM are members of Fuse, also a UKCRC Public Health Research Centre of Excellence. Grant reference number is MR/K02325X/1. Funding for CEDAR and for Fuse from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research and the Wellcome Trust, under the auspices of the UKCRC, is gratefully acknowledged. The views expressed in this publication are those of the authors and not necessarily those of the National Health Service, the Department of Health, the funders or UKCRC. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Influence of -klen and mutations on the types of alterations occurring in 5′AGTC tetranucleotide repeat tracts

<p><b>Copyright information:</b></p><p>Taken from "Destabilization of tetranucleotide repeats in mutants lacking RnaseHI or the Klenow domain of PolI"</p><p>Nucleic Acids Research 2005;33(1):400-408.</p><p>Published online 14 Jan 2005</p><p>PMCID:PMC546164.</p><p>© 2005, the authors © </p> Repeat tracts from phase variants were amplified by PCR and either sequenced or sized by a gene scan protocol. Alterations were classified as insertions or deletions of 1, 2 or >2 repeat units and the number of each mutational type was then represented as a percentage of the total number of tracts analysed. The genotype of each strain is indicated below the columns (wt is strain Rd) and the direction of switching above the columns. The number of repeats in the parental strain is indicated in parentheses while the total number of tracts analysed is in curly brackets. Data for wt 17, wt 37 and wt 24/18 were published previously ()

Air-pasture transfer of PCBs.

A field experiment was conducted to study the air to pasture transfer of PCBs at a rural site in northwest England. Strong positive linear correlations were obtained between the log plant−air partition coefficients (m3 of air g-1 of plant dry weightdefined here as the scavenging coefficient) and log octanol−air (Koa) partition coefficients. Pasture typically retained amounts of PCB per g dry weight equivalent to that in 7 m3 of air for congener 18 and ranging up to 64 m3 for congener 170, regardless of whether the pasture growth (exposure) time had been 2, 6, or 12 weeks. This indicates that airborne PCBs partition onto freshly grown pasture and approach plant surface−air gas-phase equilibrium rather rapidly at this site, i.e., within 2 weeks of exposure. In late April−June, when grassland production is at a maximum, sequestering rates could approach 1.2 ng of PCB-18, 0.17 ng of PCB-170, and 12 ng of ∑PCB m-2 day-1. With 7 million ha of managed and rough grassland in the U.K., fresh pasture production in the spring and summer is estimated to remove an average of 0.8 kg of ∑PCB day-1 from the air during these times (80 kg of ∑PCB per growing season). Some buffering influence may be exerted on surface air concentrations during the most active periods of plant biomass production, while the incorporation of PCBs into pasture following air−pasture transfer processes controls the supply of PCBs to grazing animals and the human food chain

Growth rates and plating efficiencies of and mutants

<p><b>Copyright information:</b></p><p>Taken from "Destabilization of tetranucleotide repeats in mutants lacking RnaseHI or the Klenow domain of PolI"</p><p>Nucleic Acids Research 2005;33(1):400-408.</p><p>Published online 14 Jan 2005</p><p>PMCID:PMC546164.</p><p>© 2005, the authors © </p> Growth curves were performed with strains Rd, RdKlen and Rd using BHI-broth supplemented with NAD and haemin at 37°C. Four independent cultures were performed for each strain. () Optical density at 490 nm plotted against time. Average values and standard deviations are shown for each strain. () Samples were taken at different time points, serially diluted and plated on BHI-agar supplemented with Levinthal's supplement. The number of colony forming units (c.f.u.) per ml was then divided by the OD490 of the sample and these values were plotted on a log scale against OD490. The four independent experiments are shown separately as samples were taken at different optical density values in each experiment. (a and b) Filled shapes, Rd; open shapes, RdKlen; and alternative symbols, Rd

Passive air sampling for PCBs : field calculation of atmospheric sampling rates by Triolein containing semi-permeable membrane devices.

Triolein-containing standard U.S. Geological Survey (USGS) designed semipermeable membrane devices (SPMDs) were deployed in the field alongside conventional active air sampling equipment for durations of up to 3 months. A high degree of reproducibility between duplicate samples and linear uptake of polychlorinated biphenyls (PCBs) by the USGS SPMDs were observed. USGS SPMD air sampling rates were calculated for a range of PCBs. Sampling rates were found to be higher in winter than in summer and in general increased with increasing chlorination and decreased with increasing ortho-substitution. The sampling rate for the sum of the ICES congeners (IUPAC congeners 28, 52, 101, 118, 138, 153, and 180) was found to be 1.9 m3 day-1 SPMD-1 in summer (mean temperature 18 °C) and 7.6 m3 day-1 SPMD-1 in winter (mean temperature 4 °C). In a separate study USGS SPMDs were deployed for 2 months, and sequestered concentrations and the aforementioned sampling rates were used to calculate atmospheric concentrations. Excellent agreement was found between air concentrations calculated from the SPMDs and active samplers. The immense potential of these lipid-containing USGS SPMDs for time-integrated passive atmospheric monitoring of gas-phase persistent organic pollutants (POPs), for example, in remote areas or for spatial mapping near potential sources, is confirmed

Global distribution and budget of PCBs and HCB in background surface soils: implications for sources and environmental processes.

6 pages, 5 figures, 5 tables.-- PMID: 12636263 [PubMed].-- Printed version published Feb 15, 2003.-- Supporitng information available at: http://pubs.acs.org/doi/suppl/10.1021/es025809lThis paper presents data from a survey of polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) concentrations in 191 global background surface (0−5 cm) soils. Differences of up to 4 orders of magnitude were found between sites for PCBs. The lowest and highest PCB concentrations (26 and 97 000 pg/g dw) were found in samples from Greenland and mainland Europe (France, Germany, Poland), respectively. Background soil PCB concentrations were strongly influenced by proximity to source region and soil organic matter (SOM) content. Most (>80%) of the estimated soil PCB burden remains in the “global source region” of the Northern Hemisphere (NH) temperate latitudes (30−60° N) or in the OM-rich soils just north of that. %SOM correlated with PCB and HCB in the global data set, with the correlation coefficients being greater for HCB and the lighter PCBs than for heavier homologues. OM-rich soils in the NH consistently contained the highest burdens; such soils are a key global compartment for these compounds. Evidence for global fractionation of PCBs was found in the subset of soils from latitudes north of the global source region but was not discerned with the global data set. The full data set was used to estimate the burden for individual congeners/homologues in surface background soils and a global soil total PCB burden of 21 000 t. The significance of the inventory is briefly discussed in relation to the latest estimates of global production and atmospheric emission.Is grateful to Eurochlor for funding at Lancaster University for work on HCB and to the Dow Chemical Company Foundation for financially supporting research on the global cycling of POPs. K.B. acknowledges financial support from the European Chemical Industry Council (CEFIC-LRI).Peer reviewe

The global re-cycling of persistent organic pollutants is strongly retarded by soils.

Persistent organic pollutants’ (POPs) are semi-volatile, mobile in the environment and bioaccumulate. Their toxicity and propensity for long-range atmospheric transport (LRAT) has led to international bans/restrictions on their use/release. LRAT of POPs may occur by a ‘single hop’ or repeated temperature-driven air–surface exchange. It has been hypothesised that this will result in global fractionation and distillation—with condensation and accumulation in polar regions. Polychlorinated biphenyls (PCBs)—industrial chemicals banned/restricted in the 1970s—provide a classic illustration of POP behaviour. A latitudinally-segmented global PCB inventory has been produced, which shows that 86% of the 1.3×106 tonnes produced was used in the temperate industrial zone of the northern hemisphere. A global survey of background surface soils gives evidence for ‘fractionation’ of PCBs. More significantly, however, very little of the total inventory has ‘made the journey’ via primary emission and/or air–surface exchange and LRAT out of the heavily populated source regions, in the 70 years since PCBs were first produced. Soils generally occlude PCBs, especially soils with dynamic turnover of C/bioturbation/burial mechanisms. This limits the fraction of PCBs available for repeated air–soil exchange. The forested soils of the northern hemisphere, and other C-rich soils, appear to be playing an important role in ‘protecting’ the Arctic from the advective supply of POPs. Whilst investigations on POPs in remote environments are important, it is imperative that researchers also seek to better understand their release from sources, persistence in source regions, and the significant loss mechanisms/global sinks of these compounds, if they wish to predict future trends