bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA Helicase Activity of PcrA Is Not Required for the Displacement of RecA Protein from DNA or Inhibition of RecA-Mediated Strand Exchange
Authors: Anand Syam P. , Zheng Haocheng , Bianco Piero R. , Leuba Sanford H. , Khan Saleem A. 
Published: April 2007

ABSTRACT

PcrA is a conserved DNA helicase present in all gram-positive bacteria. Bacteria lacking PcrA show high levels of recombination. Lethality induced by PcrA depletion can be overcome by suppressor mutations in the recombination genes
recFOR
. RecFOR proteins load RecA onto single-stranded DNA during recombination. Here we test whether an essential function of PcrA is to interfere with RecA-mediated DNA recombination in vitro. We demonstrate that PcrA can inhibit the RecA-mediated DNA strand exchange reaction in vitro. Furthermore, PcrA displaced RecA from RecA nucleoprotein filaments. Interestingly, helicase mutants of PcrA also displaced RecA from DNA and inhibited RecA-mediated DNA strand exchange. Employing a novel single-pair fluorescence resonance energy transfer-based assay, we demonstrate a lengthening of double-stranded DNA upon polymerization of RecA and show that PcrA and its helicase mutants can reverse this process. Our results show that the displacement of RecA from DNA by PcrA is not dependent on its translocase activity. Further, our results show that the helicase activity of PcrA, although not essential, might play a facilitatory role in the RecA displacement reaction.
pH-Dependent Association of Enolase and Glyceraldehyde-3-Phosphate Dehydrogenase ofLactobacillus crispatuswith the Cell Wall and Lipoteichoic Acids
Authors: Antikainen Jenni , Kupannen Veera , Lähteenmäki Kaarina , Korhonen Timo K. 
Published: April 2007

ABSTRACTThe plasminogen-binding proteins enolase and glyceraldehyde-3-phosphate dehydrogenase ofLactobacillus crispatuswere localized on the cell surface at pH 5 but released into the medium at an alkaline pH. These proteins bound to lipoteichoic acids at a pH below their isoelectric point. The results indicate that lactobacilli rapidly modify their surface properties in response to changes in pH.
Localization of PcsB of
Streptococcus pneumoniae
and Its Differential Expression in Response to Stress
Authors: Mills Megumi F. , Marquart Mary E. , McDaniel Larry S. 
Published: April 2007

ABSTRACT

PcsB of
Streptococcus pneumoniae
is an essential hydrolase involved in the separation of dividing cells. In this study, it was found that PcsB localizes to the plasma membrane and is released into the growth environment, yet it is detectable on the pneumococcal surface by flow cytometry analysis. High temperature and osmolarity led to upregulation of
pcsB
expression.
Translational Regulation of the
Escherichia coli
Stress Factor RpoS: a Role for SsrA and Lon
Authors: Ranquet Caroline , Gottesman Susan 
Published: April 2007

ABSTRACT

Escherichia coli
cell viability during starvation is strongly dependent on the expression of the
rpoS
gene, encoding the RpoS sigma subunit of RNA polymerase. RpoS abundance has been reported to be regulated at many levels, including transcription initiation, translation, and protein stability. The regulatory RNA SsrA (or tmRNA) has both tRNA and mRNA activities, relieving ribosome stalling and cotranslationally tagging proteins. We report here that SsrA is needed for the correct high-level translation of RpoS. The ATP-dependent protease Lon was also found to negatively affect RpoS translation, but only at low temperature. We suggest that SsrA may indirectly improve RpoS translation by limiting ribosome stalling and depletion of some component of the translation machinery.
Molecular Characterization and Subcellular Localization of Macrophage Infectivity Potentiator, aChlamydia trachomatisLipoprotein
Authors: Neff Laurence , Daher Sawsan , Muzzin Patrick , Spenato Ursula , Gülaçar Fazil , Gabay Cem , Bas Sylvette 
Published: April 2007

ABSTRACTMacrophage infectivity potentiator (MIP) was originally reported to be a chlamydial lipoprotein from experiments showing incorporation of radiolabeled palmitic acid into native and recombinant MIP; inhibition of posttranslational processing of recombinant MIP by globomycin, known to inhibit signal peptidase II; and solubility of native MIP in Triton X-114. However, the detailed structural characterization of the lipid moiety on MIP has never been fully elucidated. In this study, bioinformatics and mass spectrometry analysis, as well as radiolabeling and immunochemical experiments, were conducted to further characterize MIP structure and subcellular localization. In silico analysis showed that the amino acid sequence of MIP is conserved across chlamydial species. A potential signal sequence with a contained lipobox was identified, and a recombinant C20A variant was prepared by replacing the probable lipobox cysteine with an alanine. Both incorporation of U-14C-esterified glycerol and [U-14C]palmitic acid and posttranslational processing that was inhibitable by globomycin were observed for recombinant wild-type MIP but not for the recombinant C20A MIP variant. The fatty acid contents of native and recombinant MIP were analyzed by gas chromatography-mass spectrometry, and the presence of amide-linked fatty acids in recombinant MIP was investigated by alkaline methanolysis. These results demonstrated a lipid modification in MIP similar to that of other prokaryotic lipoproteins. In addition, MIP was detected in an outer membrane preparation ofChlamydia trachomatiselementary bodies and was shown to be present at the surfaces of elementary bodies by surface biotinylation and surface immunoprecipitation experiments.
Analysis of the First Genome of a Hyperthermophilic Marine Virus-Like Particle, PAV1, Isolated fromPyrococcus abyssi
Authors: Geslin C. , Gaillard M. , Flament D. , Rouault K. , Le Romancer M. , Prieur D. , Erauso G. 
Published: April 2007

ABSTRACTOnly one virus-like particle (VLP) has been reported from hyperthermophilicEuryarchaeotes. This VLP, named PAV1, is shaped like a lemon and was isolated from a strain of “Pyrococcus abyssi,” a deep-sea isolate. Its genome consists of a double-stranded circular DNA of 18 kb which is also present at a high copy number (60 per chromosome) free within the host cytoplasm but is not integrated into the host chromosome. Here, we report the results of complete analysis of the PAV1 genome. All the 25 predicted genes, except 3, are located on one DNA strand. A transcription map has been made by using a reverse transcription-PCR assay. All the identified open reading frames (ORFs) are transcribed. The most significant similarities relate to four ORFs. ORF 180a shows 31% identity with ORF 181 of the pRT1 plasmid isolated fromPyrococcussp. strain JT1. ORFs 676 and 678 present similarities with a concanavalin A-like lectin/glucanase domain, which could be involved in the process of host-virus recognition, and ORF 59 presents similarities with the transcriptional regulator CopG. The genome of PAV1 displays unique features at the nucleic and proteinic level, indicating that PAV1 should be attached at least to a novel genus or virus family.
Cryo-Electron Tomography Reveals the Comparative Three-Dimensional Architecture ofProchlorococcus, a Globally Important Marine Cyanobacterium
Authors: Ting Claire S. , Hsieh Chyongere , Sundararaman Sesh , Mannella Carmen , Marko Michael 
Published: April 2007

ABSTRACTIn an age of comparative microbial genomics, knowledge of the near-native architecture of microorganisms is essential for achieving an integrative understanding of physiology and function. We characterized and compared the three-dimensional architecture of the ecologically important cyanobacteriumProchlorococcusin a near-native state using cryo-electron tomography and found that closely related strains have diverged substantially in cellular organization and structure. By visualizing native, hydrated structures within cells, we discovered that the MED4 strain, which possesses one of the smallest genomes (1.66 Mbp) of any known photosynthetic organism, has evolved a comparatively streamlined cellular architecture. This strain possesses a smaller cell volume, an attenuated cell wall, and less extensive intracytoplasmic (photosynthetic) membrane system compared to the more deeply branched MIT9313 strain. Comparative genomic analyses indicate that differences have evolved in key structural genes, including those encoding enzymes involved in cell wall peptidoglycan biosynthesis. Although both strains possess carboxysomes that are polygonal and cluster in the central cytoplasm, the carboxysomes of MED4 are smaller. A streamlined cellular structure could be advantageous to microorganisms thriving in the low-nutrient conditions characteristic of large regions of the open ocean and thus have consequences for ecological niche differentiation. Through cryo-electron tomography we visualized, for the first time, the three-dimensional structure of the extensive network of photosynthetic lamellae withinProchlorococcusand the potential pathways for intracellular and intermembrane movement of molecules. Comparative information on the near-native structure of microorganisms is an important and necessary component of exploring microbial diversity and understanding its consequences for function and ecology.
PmrA(Con) Confers
pmrHFIJKL
-Dependent EGTA and Polymyxin Resistance on
msbB Salmonella
by Decorating Lipid A with Phosphoethanolamine
Authors: Murray Sean R. , Ernst Robert K. , Bermudes David , Miller Samuel I. , Low K. Brooks 
Published: April 2007

ABSTRACT

Mutations in
pmrA
were recombined into
Salmonella
strain ATCC 14028
msbB
to determine if
pmrA
-regulated modifications of lipopolysaccharide could suppress
msbB
growth defects. A mutation that functions to constitutively activate
pmrA
[
pmrA
(Con)] suppresses
msbB
growth defects on EGTA-containing media. Lipid A structural analysis showed that
Salmonella msbB pmrA
(Con) strains, compared to
Salmonella msbB
strains, have increased amounts of palmitate and phosphoethanolamine but no aminoarabinose addition, suggesting that aminoarabinose is not incorporated into
msbB
lipid A. Surprisingly, loss-of-function mutations in the aminoarabinose biosynthetic genes restored EGTA and polymyxin sensitivity to
Salmonella msbB pmrA
(Con) strains. These blocks in aminoarabinose biosynthesis also prevented lipid A phosphoethanolamine incorporation and reduced the levels of palmitate addition, indicating previously unknown roles for the aminoarabinose biosynthetic enzymes. Lipid A structural analysis of the EGTA- and polymyxin-resistant triple mutant
msbB pmrA
(Con)
pagP
::Tn
10
, which contains phosphoethanolamine but no palmitoylated lipid A, suggests that phosphoethanolamine addition is sufficient to confer EGTA and polymyxin resistance on
Salmonella msbB
strains. Additionally, palmitoylated lipid A was observed only in wild-type
Salmonella
grown in the presence of salt in rich media. Thus, we correlate EGTA resistance and polymyxin resistance with phosphoethanolamine-decorated lipid A and demonstrate that the aminoarabinose biosynthetic proteins play an essential role in lipid A phosphoethanolamine addition and affect lipid A palmitate addition in
Salmonella msbB
strains.
Association between plasma BPDE-Alb adduct concentrations and DNA damage of peripheral blood lymphocytes among coke oven workers
Authors: Wang Hong , Chen Weihong , Zheng Hongyan , Guo Liang , Liang Huashan , Yang Xiaobo , Bai Yun , Sun Jianya , Su Yougong , Chen Yongwen , Yuan Jing , Bi Yongyi , Wei Qingyi , Wu Tangchun 
Published: April 2007

Objectives:Coke oven emissions COE containing polycyclic aromatic hydrocarbons PAHs can induce both benzoapyrene-r-7, t-8, t-9,c-10-tetrahydotetrol-albumin BPDE-Alb adducts and DNA damage. However, the relation between these biomarkers for early biological effects is not well documented in coke oven workers.Methods:In this study, the authors recruited 207 male workers exposed to COE and 102 controls not exposed to COE in the same steel plant in northern China. They measured BPDE-Alb adduct concentrations in plasma with reverse-phase high performance liquid chromatography and DNA damage in peripheral blood lymphocytes with alkaline comet assay.Results:The results showed that the median concentration of BPDE-Alb adducts in the exposed group 34.36 fmol/mg albumin was significantly higher than that in the control group 21.90 fmol/mg albumin, p0.012. The mean Olive tail moment Olive TM of DNA damage in the exposed and control groups were 1.20 and 0.63, respectively p0.000. Multivariate logistic regression analysis revealed that the odds ratio OR for BPDE-Alb adduct and Olive TM associated with the exposure were 1.72 95 CI 1.06 to 2.81 and 1.96 95 CI 1.20 to 3.19, respectively. These results show significant correlations between the concentrations of BPDE-Alb adduct and Olive TM levels in exposed group r0.235, p0.001 but not in control group r0.093, p0.353.Conclusion:The results suggest that occupational exposure to COE may induce both BPDEAlb adducts and DNA damage in the lymphocytes of coke oven workers and that these two markers are useful for monitoring exposure to COE in the workplace.
3-Hydroxybenzo[a]pyrene in the urine of workers with occupational exposure to polycyclic aromatic hydrocarbons in different industries
Authors: Förster K , Preuss R , Roßbach B , Brüning T , Angerer J , Simon P 
Published: April 2007

Objectives:This study was conducted to assess external and internal exposure of workers to polycyclic aromatic hydrocarbons (PAHs). In this context, the analytical and diagnostical reliability of 3-hydroxybenzo[a]pyrene (3OH-BaP) as a biomarker of internal exposure to PAHs was established.Methods:Ambient and biological monitoring was carried out of 225 PAH-exposed employees of different industries. External exposure was determined by personal air sampling and analysis of 16 EPA-PAH. Internal exposure was examined by the urinary metabolites 3OH-BaP, 1-hydroxypyrene (OH-Pyr) and monohydroxylated phenanthrenes (OH-Phens).Results:Benzo[a]pyrene (BaP) was detected at all workplaces. Concentrations in the breathing zone of the workers ranged from below the limit of detection up to 44.3 μg/m3. In biological monitoring, urinary 3OH-BaP was found in median concentrations of 0.8 ng/g creatinine (crea) and the 95th percentile of 6.7 ng/g crea. The results ranged from the limit of detection up to 19.5 ng/g crea. Only 1% of the analysed samples showed concentrations below the limit of detection (0.05 ng/l). Regarding median concentrations, workers in coking plants showed lower 3OH-BaP concentrations (0.5 ng/g crea) than those employed in the production of fireproof material in refractories (1.1 ng/g crea), converter infeed (1.2 ng/g crea) and graphite electrode production (1.3 ng/g crea). Strong correlations of 3OH-BaP with OH-Pyr and the sum of OH-Phens were found for the workplaces converter infeed, coking plants and graphite electrode production (rPearsonranging from 0.618 to 0.867, p<0.001). The poor correlation of BaP in the air and 3OH-BaP in urine is most probably caused by routes of uptake other than via air—for example, dermal uptake.Conclusion:3OH-BaP as a metabolite of the carcinogenic BaP could be shown to be a diagnostically specific and sensitive biomarker for determining the internal exposure of workers in different industries. Using this method, the estimation of health risks for workers can be fundamentally improved, because the 3OH-BaP represents the group of carcinogenic PAHs. The procedure for analysing 3OH-BaP is complex, but it is robust and produces reliable results.
Association of blood lead and homocysteine levels among lead exposed subjects in Vietnam and Singapore
Authors: Chia Sin Eng , Ali Safiyya Mohamed , Lee Bee Lan , Lim Gek Hsiang , Jin Su , Dong Nguyen-Viet , Tu Nguyen Thi Hong , Ong Choon Nam , Chia Kee Seng 
Published: April 2007

Objectives:Lead and homocysteine are both linked to cardiovascular disease. With this in mind, the authors evaluated the relation between blood lead and homocysteine in people aged 19–66 years in two Asian populations.Methods:This cross-sectional study comprised 183 workers from a lead stabiliser factory in Singapore and 323 workers from a battery factory in Vietnam. Workers were occupationally exposed to lead. Blood lead was analysed using atomic absorption spectrophotometry while plasma homocysteine was measured using high performance liquid chromatography.Results:Chinese subjects had the lowest blood lead levels while the Indians had the highest. Controlling for age, sex and race, an increase of 1 μg/dl in blood lead was associated with an increase of 0.04 μmol/l of homocysteine on the log scale. Gender and ethnicity seemed to be strongly associated with the relation between lead and homocysteine. The positive relation between lead and homocysteine among the Vietnamese subjects was significant (Pearson’s r = 0.254, p<0.01). When blood lead levels were divided by quartiles, the correlation coefficient between blood lead levels in the 4th quartile and homocysteine among the Vietnamese was higher (r = 0.405, p<0.01). Overall, an increase of 1 μg/dl in blood lead in all the Vietnamese subjects was associated with an increase of 0.05 μmol/l increase in homocysteine on the log scale. However, in the 4th quartile, the same increase was associated with an increase of 0.41 μmol/l of homocysteine on the log scale.Conclusions:Blood lead was found to be associated with homocysteine levels in this Asian sample. Although we cannot determine causality from cross-sectional data, it is sensible to consider the probability that this relation could explain one of the mechanisms of the impact of lead on the cardiovascular system. More studies would be needed to confirm this inference.
Follow-up study of chrysotile textile workers: cohort mortality and exposure-response
Authors: Hein Misty J , Stayner Leslie T , Lehman Everett , Dement John M 
Published: April 2007

Objectives:This report provides an update of the mortality experience of a cohort of South Carolina asbestos textile workers.Methods:A cohort of 3072 workers exposed to chrysotile in a South Carolina asbestos textile plant (1916–77) was followed up for mortality through 2001. Standardised mortality ratios (SMRs) were computed using US and South Carolina mortality rates. A job exposure matrix provided calendar time dependent estimates of chrysotile exposure concentrations. Poisson regression models were fitted for lung cancer and asbestosis. Covariates considered included sex, race, age, calendar time, birth cohort and time since first exposure. Cumulative exposure lags of 5 and 10 years were considered by disregarding exposure in the most recent 5 and 10 years, respectively.Results:A majority of the cohort was deceased (64%) and 702 of the 1961 deaths occurred since the previous update. Mortality was elevated based on US referent rates for a priori causes of interest including all causes combined (SMR 1.33, 95% CI 1.28 to 1.39); all cancers (SMR 1.27, 95% CI 1.16 to 1.39); oesophageal cancer (SMR 1.87, 95% CI 1.09 to 2.99); lung cancer (SMR 1.95, 95% CI 1.68 to 2.24); ischaemic heart disease (SMR 1.20, 95% CI 1.10 to 1.32); and pneumoconiosis and other respiratory diseases (SMR 4.81, 95% CI 3.84 to 5.94). Mortality remained elevated for these causes when South Carolina referent rates were used. Three cases of mesothelioma were observed among cohort members. Exposure-response modelling for lung cancer, using a linear relative risk model, produced a slope coefficient of 0.0198 (fibre-years/ml) (standard error 0.00496), when cumulative exposure was lagged 10 years. Poisson regression modelling confirmed significant positive relations between estimated chrysotile exposure and lung cancer and asbestosis mortality observed in previous updates of this cohort.Conclusions:This study confirms the findings from previous investigations of excess mortality from lung cancer and asbestosis and a strong exposure-response relation between estimated exposure to chrysotile and mortality from lung cancer and asbestosis.
Reducing healthy worker survivor bias by restricting date of hire in a cohort study of Vermont granite workers
Authors: Applebaum Katie M , Malloy Elizabeth J , Eisen Ellen A 
Published: April 2007

Objective:To explore the healthy worker survivor effect (HWSE) in a study of Vermont granite workers by distinguishing “prevalent” from “incident” hires based on date of hire before or after the start of follow-up.Methods:Records of workers between 1950 and 1982 were obtained from a medical surveillance programme. Proportional hazards models were used to model the association between silica exposure and lung cancer mortality, with penalised splines used to smooth the exposure-response relationship. A sensitivity analysis compared results between the original cohort and subcohorts defined by restricting date of hire to include varying proportions of prevalent hires.Results:Restricting to incident hires reduced the 213 cases by 74% and decreased the exposure range. The maximum mortality rate ratio (MRR) was close to twofold in all subcohorts. However, the exposure at which the maximum MRR was achieved decreased from 4.0 to 0.6 mg-year/m3as the proportion of prevalent hires decreased from 50% in the original cohort to 0% in the subcohort of incident hires.Conclusion:Despite loss in power and restricted exposure range, decreasing the relative proportion of prevalent to incident hires reduced HWSE bias, resulting in stronger evidence for a dose-response between silica exposure and lung cancer mortality.
Projected mesothelioma incidence in men in New South Wales
Authors: Clements Mark , Berry Geoffrey , Shi Jill , Ware Sandra , Yates Deborah , Johnson Anthony 
Published: April 2007

Objectives:Based on observed numbers of incident mesotheliomas since 1972, to predict future numbers in men in New South Wales.Methods:The incidence of mesothelioma was modelled in two ways. First by using an age/birth cohort model, and second by using a model based on potential exposure to asbestos in terms of age and calendar year. The latter model included a term for clearance of asbestos fibres from the lungs, and a term for diagnostic fraction. The age and calendar year model was based on the model introduced by Hodgson and colleagues but replaced piecewise effects by smooth functions represented by cubic splines.Results:The number of mesotheliomas between 2004 and 2060 was predicted as 6690 with the age-cohort model and as 6779 by the age and calendar year model, with peak annual numbers of 187 in the year 2021 and 196 in the year 2014 with the two models respectively.Conclusions:The pattern of parameter estimates in the two models was in accord with the known use of amphibole asbestos in Australia. The predicted peak year of 201421 is 3035 years after the phasing out of amphibole use, and this period is in accord with predictions for the UK and the US; in the latter country the peak was 1015 years earlier corresponding to a marked decline of amphibole use in and following the 1960s.