Allele specific synthetic lethality between priC and dnaA(ts )alleles at the permissive temperature of 30°C in E. coli K-12

BACKGROUND: DnaA is an essential protein in the regulation and initiation of DNA replication in many bacteria. It forms a protein-DNA complex at oriC to which DnaC loads DnaB. DNA replication forks initiated at oriC by DnaA can collapse on route to the terminus for a variety of reasons. PriA, PriB, PriC, DnaT, Rep and DnaC form multiple pathways to restart repaired replication forks. DnaC809 and dnaC809,820 are suppressors of priA2::kan mutant phenotypes. The former requires PriC and Rep while the latter is independent of them. RnhA339::cat mutations allow DnaA-independent initiation of DNA replication. RESULTS: It is shown herein that a priC303::kan mutation is synthetically lethal with either a dnaA46 or dnaA508 temperature sensitive mutation at the permissive temperature of 30°C. The priC-dnaA lethality is specific for the dnaA allele. The priC303::kan mutant was viable when placed in combination with either dnaA5, dnaA167, dnaA204 or dnaA602. The priC-dnaA508 and priC-dnaA46 lethality could be suppressed by rnhA339::cat. The priC-dnaA508 lethality could be suppressed by a dnaC809,820 mutation, but not dnaC809. Neither of the dnaC mutations could suppress the priC-dnaA46 lethality. CONCLUSIONS: A hitherto unknown function for either DnaA in replication restart or PriC in initiation of DNA replication that occurs in certain dnaA temperature sensitive mutant strains at the permissive temperature of 30°C has been documented. Models considering roles for PriC during initiation of DNA replication and roles for DnaA in replication restart were tested and found not to decisively explain the data. Other roles of dnaA in transcription and nucleoid structure are additionally considered

Stress-Induced Reorganization of the Mycobacterial Membrane Domain

Cell elongation occurs primarily at the mycobacterial cell poles, but the molecular mechanisms governing this spatial regulation remain elusive. We recently reported the presence of an intracellular membrane domain (IMD) that was spatially segregated from the conventional plasma membrane in Mycobacterium smegmatis. The IMD is enriched in the polar region of actively elongating cells and houses many essential enzymes involved in envelope biosynthesis, suggesting its role in spatially restricted elongation at the cell poles. Here, we examined reorganization of the IMD when the cells are no longer elongating. To monitor the IMD, we used a previously established reporter strain expressing fluorescent IMD markers and grew it to the stationary growth phase or exposed the cells to nutrient starvation. In both cases, the IMD was delocalized from the cell pole and distributed along the sidewall. Importantly, the IMD could still be isolated biochemically by density gradient fractionation, indicating its maintenance as a membrane domain. Chemical and genetic inhibition of peptidoglycan biosynthesis led to the delocalization of the IMD, suggesting the suppression of peptidoglycan biosynthesis as a trigger of spatial IMD rearrangement. Starved cells with a delocalized IMD can resume growth upon nutrient repletion, and polar enrichment of the IMD coincides with the initiation of cell elongation. These data reveal that the IMD is a membrane domain with the unprecedented capability of subcellular repositioning in response to the physiological conditions of the mycobacterial cell. IMPORTANCE Mycobacteria include medically important species, such as the human tuberculosis pathogen Mycobacterium tuberculosis. The highly impermeable cell envelope is a hallmark of these microbes, and its biosynthesis is a proven chemotherapeutic target. Despite the accumulating knowledge regarding the biosynthesis of individual envelope components, the regulatory mechanisms behind the coordinated synthesis of the complex cell envelope remain elusive. We previously reported the presence of a metabolically active membrane domain enriched in the elongating poles of actively growing mycobacteria. However, the spatiotemporal dynamics of the membrane domain in response to stress have not been examined. Here, we show that the membrane domain is spatially reorganized when growth is inhibited in the stationary growth phase, under nutrient starvation, or in response to perturbation of peptidoglycan biosynthesis. Our results suggest that mycobacteria have a mechanism to spatiotemporally coordinate the membrane domain in response to metabolic needs under different growth conditions

Reduction in diarrhoeal rates through interventions that prevent unnecessary antibiotic exposure early in life in an observational birth cohort

Antibiotic treatment early in life is often not needed and has been associated with increased rates of subsequent diarrhea. We estimated the impact of realistic interventions, which would prevent unnecessary antibiotic exposures before 6 months of age, on reducing childhood diarrheal rates

The management aspect of psychotherapy with aggressive children

Psychotherapy with an aggressive child may require the imposition of rather firm limitations over aspects of the patient's aggressive behavior. The nature of this management strategy is determined by the individual child's psychopathology. The management aspects of the psychotherapy with two aggressive boys are illustrated in detail. In one case, stringent limitations were imposed when it was discovered that the boy's behavior was regressive and represented an effort to sadistically control people in his environment. In the other case, the behavior was initially left almost unchallenged; this boy's aggressive and delinquent behavior reflected an effort to achieve a sense of order in an inconsistent external and potentially chaotic internal environment.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43969/1/10578_2005_Article_BF01463450.pd

Sex-differences in oral anticoagulation therapy in patients hospitalized with atrial fibrillation:a nationwide cohort study

Background Important disparities in the treatment and outcomes of women and men with atrial fibrillation (AF) are well recognized. Whether introduction of direct oral anticoagulants has reduced disparities in treatment is uncertain. Methods and Results All patients who had an incident hospitalization from 2010 to 2019 with nonvalvular AF in Scotland were included in the present cohort study. Community drug dispensing data were used to determine prescribed oral anticoagulation therapy and comorbidity status. Logistic regression modeling was used to evaluate patient factors associated with treatment with vitamin K antagonists and direct oral anticoagulants. A total of 172 989 patients (48% women [82 833 of 172 989]) had an incident hospitalization with nonvalvular AF in Scotland between 2010 and 2019. By 2019, factor Xa inhibitors accounted for 83.6% of all oral anticoagulants prescribed, while treatment with vitamin K antagonists and direct thrombin inhibitors declined to 15.9% and 0.6%, respectively. Women were less likely to be prescribed any oral anticoagulation therapy compared with men (adjusted odds ratio [aOR], 0.68 [95% CI, 0.67–0.70]). This disparity was mainly attributed to vitamin K antagonists (aOR, 0.68 [95% CI, 0.66–0.70]), while there was less disparity in the use of factor Xa inhibitors between women and men (aOR, 0.92 [95% CI, 0.90–0.95]). Conclusions Women with nonvalvular AF were significantly less likely to be prescribed vitamin K antagonists compared with men. Most patients admitted to the hospital in Scotland with incident nonvalvular AF are now treated with factor Xa inhibitors and this is associated with fewer treatment disparities between women and men

Mu Insertions Are Repaired by the Double-Strand Break Repair Pathway of Escherichia coli

Mu is both a transposable element and a temperate bacteriophage. During lytic growth, it amplifies its genome by replicative transposition. During infection, it integrates into the Escherichia coli chromosome through a mechanism not requiring extensive DNA replication. In the latter pathway, the transposition intermediate is repaired by transposase-mediated resecting of the 5′ flaps attached to the ends of the incoming Mu genome, followed by filling the remaining 5 bp gaps at each end of the Mu insertion. It is widely assumed that the gaps are repaired by a gap-filling host polymerase. Using the E. coli Keio Collection to screen for mutants defective in recovery of stable Mu insertions, we show in this study that the gaps are repaired by the machinery responsible for the repair of double-strand breaks in E. coli—the replication restart proteins PriA-DnaT and homologous recombination proteins RecABC. We discuss alternate models for recombinational repair of the Mu gaps

Antibiotic treatment of diarrhoea is associated with decreased time to the next diarrhoea episode among young children in Vellore, India

Background Antibiotics are commonly given for the treatment of childhood diarrhoea, but are not indicated in most cases. Antibiotics modify the gastrointestinal microbiota, which may have unanticipated effects on the risk of subsequent diarrhoea

Differential Requirements of Two recA Mutants for Constitutive SOS Expression in Escherichia coli K-12

Background Repairing DNA damage begins with its detection and is often followed by elicitation of a cellular response. In E. coli, RecA polymerizes on ssDNA produced after DNA damage and induces the SOS Response. The RecA-DNA filament is an allosteric effector of LexA auto-proteolysis. LexA is the repressor of the SOS Response. Not all RecA-DNA filaments, however, lead to an SOS Response. Certain recA mutants express the SOS Response (recAC) in the absence of external DNA damage in log phase cells. Methodology/Principal Findings Genetic analysis of two recAC mutants was used to determine the mechanism of constitutive SOS (SOSC) expression in a population of log phase cells using fluorescence of single cells carrying an SOS reporter system (sulAp-gfp). SOSC expression in recA4142 mutants was dependent on its initial level of transcription, recBCD, recFOR, recX, dinI, xthA and the type of medium in which the cells were grown. SOSC expression in recA730 mutants was affected by none of the mutations or conditions tested above. Conclusions/Significance It is concluded that not all recAC alleles cause SOSC expression by the same mechanism. It is hypothesized that RecA4142 is loaded on to a double-strand end of DNA and that the RecA filament is stabilized by the presence of DinI and destabilized by RecX. RecFOR regulate the activity of RecX to destabilize the RecA filament. RecA730 causes SOSC expression by binding to ssDNA in a mechanism yet to be determined

Nongenetic Determinants of Risk for Early-Onset Colorectal Cancer

Background: Incidence of early-onset (younger than 50 years of age) colorectal cancer (CRC) is increasing in many countries. Thus, elucidating the role of traditional CRC risk factors in early-onset CRC is a high priority. We sought to determine whether risk factors associated with late-onset CRC were also linked to early-onset CRC and whether association patterns differed by anatomic subsite. Methods: Using data pooled from 13 population-based studies, we studied 3767 CRC cases and 4049 controls aged younger than 50 years and 23 437 CRC cases and 35 311 controls aged 50 years and older. Using multivariable and multinomial logistic regression, we estimated odds ratios (ORs) and 95% confidence intervals (CIs) to assess the association between risk factors and early-onset CRC and by anatomic subsite. Results: Early-onset CRC was associated with not regularly using nonsteroidal anti-inflammatory drugs (OR = 1.43, 95% CI = 1.21 to 1.68), greater red meat intake (OR = 1.10, 95% CI = 1.04 to 1.16), lower educational attainment (OR = 1.10, 95% CI = 1.04 to 1.16), alcohol abstinence (OR = 1.23, 95% CI = 1.08 to 1.39), and heavier alcohol use (OR = 1.25, 95% CI = 1.04 to 1.50). No factors exhibited a greater excess in early-onset compared with late-onset CRC. Evaluating risks by anatomic subsite, we found that lower total fiber intake was linked more strongly to rectal (OR = 1.30, 95% CI = 1.14 to 1.48) than colon cancer (OR = 1.14, 95% CI = 1.02 to 1.27; P = .04). Conclusion: In this large study, we identified several nongenetic risk factors associated with early-onset CRC, providing a basis for targeted identification of those most at risk, which is imperative in mitigating the rising burden of this disease

Cumulative Burden of Colorectal Cancer-Associated Genetic Variants Is More Strongly Associated With Early-Onset vs Late-Onset Cancer.

BACKGROUND & AIMS: Early-onset colorectal cancer (CRC, in persons younger than 50 years old) is increasing in incidence; yet, in the absence of a family history of CRC, this population lacks harmonized recommendations for prevention. We aimed to determine whether a polygenic risk score (PRS) developed from 95 CRC-associated common genetic risk variants was associated with risk for early-onset CRC. METHODS: We studied risk for CRC associated with a weighted PRS in 12,197 participants younger than 50 years old vs 95,865 participants 50 years or older. PRS was calculated based on single nucleotide polymorphisms associated with CRC in a large-scale genome-wide association study as of January 2019. Participants were pooled from 3 large consortia that provided clinical and genotyping data: the Colon Cancer Family Registry, the Colorectal Transdisciplinary Study, and the Genetics and Epidemiology of Colorectal Cancer Consortium and were all of genetically defined European descent. Findings were replicated in an independent cohort of 72,573 participants. RESULTS: Overall associations with CRC per standard deviation of PRS were significant for early-onset cancer, and were stronger compared with late-onset cancer (P for interaction = .01); when we compared the highest PRS quartile with the lowest, risk increased 3.7-fold for early-onset CRC (95% CI 3.28-4.24) vs 2.9-fold for late-onset CRC (95% CI 2.80-3.04). This association was strongest for participants without a first-degree family history of CRC (P for interaction = 5.61 × 10-5). When we compared the highest with the lowest quartiles in this group, risk increased 4.3-fold for early-onset CRC (95% CI 3.61-5.01) vs 2.9-fold for late-onset CRC (95% CI 2.70-3.00). Sensitivity analyses were consistent with these findings. CONCLUSIONS: In an analysis of associations with CRC per standard deviation of PRS, we found the cumulative burden of CRC-associated common genetic variants to associate with early-onset cancer, and to be more strongly associated with early-onset than late-onset cancer, particularly in the absence of CRC family history. Analyses of PRS, along with environmental and lifestyle risk factors, might identify younger individuals who would benefit from preventive measures