Role of DiaA and SeqA homologues in the deep-sea adapted growth of photobacterium profundum SS9

The mechanism of high pressure-adapted growth in the deep-sea bacterium Photobacterium profundum SS9 is poorly understood. To gain further insights, two P. profundum SS9R mutants were investigated. FL23 (pbpra3229::m-Tn10) and FL28 (pbpra1039::m-Tn10) had been previously characterised as high pressuresensitive and pressure-enhanced, respectively. FL23 had a growth defect at atmospheric pressure but failed to show high pressure-adapted growth on solid agar. Pbpra3229 is 75 % identical to E. coli DiaA (stimulator of DNA replication and critical for the timely initiation of replication) and 45% identical to E. coli GmhA (essential for lipopolysaccharide core biosynthesis), which led to an investigation into whether either process was affected in FL23. However, the lipopolysaccharide of FL23 and its parent strain were identical, which suggests that Pbpra3229 is not a GmhA homologue. In contrast, the pbpra3229 and E. coli diaA genes were functionally interchangeable and both restored the timing of DNA replication in an E. coli diaA mutant. FL28 had growth and morphological defects at high pressure, but both phenotypes were exacerbated at atmospheric pressure. Pbpra1039 is 55% identical to E. coli SeqA, which is a negative regulator of DNA replication and also essential for timely initiation. Pbpra1039 was shown to be a functional homologue of E. coli SeqA, as pbpra1039 partially complemented the DNA replication defect of an E. coli seqA mutant. Combined, these findings provide evidence that Pbpra3229 is a DiaA homologue, whereas Pbpra1039 is a cold adapted SeqA homologue, and that both positive and negative regulation of initiation of DNA replication are essential for the ability of P. profundum SS9 to adapt to deep-sea conditions. A marine metagenomic library was also screened for clones that produced novel cell envelope polysaccharides and tools were developed to identify cell envelope polysaccharides in P. profundum SS9

Helicobacter pylori, persistent infection burden and structural brain imaging markers

Persistent infections, whether viral, bacterial or parasitic, including Helicobacter pylori infection, have been implicated in non-communicable diseases, including dementia and other neurodegenerative diseases. In this cross-sectional study, data on 635 cognitively normal participants from the UK Biobank study (2006–21, age range: 40–70 years) were used to examine whether H. pylori seropositivity (e.g. presence of antibodies), serointensities of five H. pylori antigens and a measure of total persistent infection burden were associated with selected brain volumetric structural MRI (total, white, grey matter, frontal grey matter (left/right), white matter hyperintensity as percent intracranial volume and bi-lateral sub-cortical volumes) and diffusion-weighted MRI measures (global and tract-specific bi-lateral fractional anisotropy and mean diffusivity), after an average 9–10 years of lag time. Persistent infection burden was calculated as a cumulative score of seropositivity for over 20 different pathogens. Multivariable-adjusted linear regression analyses were conducted, whereby selected potential confounders (all measures) and intracranial volume (sub-cortical volumes) were adjusted, with stratification by Alzheimer’s disease polygenic risk score tertile when exposures were H. pylori antigen serointensities. Type I error was adjusted to 0.007. We report little evidence of an association between H. pylori seropositivity and persistent infection burden with various volumetric outcomes (P > 0.007, from multivariable regression models), unlike previously reported in past research. However, H. pylori antigen serointensities, particularly immunoglobulin G against the vacuolating cytotoxin A, GroEL and outer membrane protein antigens, were associated with poorer tract-specific white matter integrity (P < 0.007), with outer membrane protein serointensity linked to worse outcomes in cognition-related tracts such as the external capsule, the anterior limb of the internal capsule and the cingulum, specifically at low Alzheimer’s disease polygenic risk. Vacuolating cytotoxin A serointensity was associated with greater white matter hyperintensity volume among individuals with mid-level Alzheimer’s disease polygenic risk, while among individuals with the highest Alzheimer’s disease polygenic risk, the urease serointensity was consistently associated with reduced bi-lateral caudate volumes and the vacuolating cytotoxin A serointensity was linked to reduced right putamen volume (P < 0.007). Outer membrane protein and urease were associated with larger sub-cortical volumes (e.g. left putamen and right nucleus accumbens) at middle Alzheimer’s disease polygenic risk levels (P < 0.007). Our results shed light on the relationship between H. pylori seropositivity, H. pylori antigen levels and persistent infection burden with brain volumetric structural measures. These data are important given the links between infectious agents and neurodegenerative diseases, including Alzheimer’s disease, and can be used for the development of drugs and preventive interventions that would reduce the burden of those diseases

Global injury morbidity and mortality from 1990 to 2017 : results from the Global Burden of Disease Study 2017

Correction:Background Past research in population health trends has shown that injuries form a substantial burden of population health loss. Regular updates to injury burden assessments are critical. We report Global Burden of Disease (GBD) 2017 Study estimates on morbidity and mortality for all injuries. Methods We reviewed results for injuries from the GBD 2017 study. GBD 2017 measured injury-specific mortality and years of life lost (YLLs) using the Cause of Death Ensemble model. To measure non-fatal injuries, GBD 2017 modelled injury-specific incidence and converted this to prevalence and years lived with disability (YLDs). YLLs and YLDs were summed to calculate disability-adjusted life years (DALYs). Findings In 1990, there were 4 260 493 (4 085 700 to 4 396 138) injury deaths, which increased to 4 484 722 (4 332 010 to 4 585 554) deaths in 2017, while age-standardised mortality decreased from 1079 (1073 to 1086) to 738 (730 to 745) per 100 000. In 1990, there were 354 064 302 (95% uncertainty interval: 338 174 876 to 371 610 802) new cases of injury globally, which increased to 520 710 288 (493 430 247 to 547 988 635) new cases in 2017. During this time, age-standardised incidence decreased non-significantly from 6824 (6534 to 7147) to 6763 (6412 to 7118) per 100 000. Between 1990 and 2017, age-standardised DALYs decreased from 4947 (4655 to 5233) per 100 000 to 3267 (3058 to 3505). Interpretation Injuries are an important cause of health loss globally, though mortality has declined between 1990 and 2017. Future research in injury burden should focus on prevention in high-burden populations, improving data collection and ensuring access to medical care.Peer reviewe

How much territory can a single E. coli cell control?

Bacteria have been traditionally classified in terms of size and shape and are best known for their very small size. E. coli cells in particular are small rods, each 1-2 microns. However the size varies with the medium, and faster growing cells are larger because they must have more ribosomes to make more protoplasm per unit time, and ribosomes take up space. Indeed, Maaloe's experiments on how E. coli establishes its size began with shifts between rich and poor media.Recently much larger bacteria have been described, including Epulopiscium fishelsoni at 700 μm and Thiomargarita namibiensisis at 750 μm. These are not only much longer than E. coli cells but also much wider, necessitating considerable intracellular organization. Epulopiscium cells for instance, at 80 μm wide, enclose a large enough volume of cytoplasm to present it with major transport problems.This review surveys E. coli cells much longer than those which grow in nature and in usual lab cultures. These include cells mutated in a single gene (metK) which are 2-4x longer than their nonmutated parent. This metK mutant stops dividing when slowly starved of S-adenosylmethionine but continues to elongate to 50 μm and more. FtsZ mutants have been routinely isolated as long cells which form during growth at 42°C. The SOS response is a well-characterized regulatory network that is activated in response to DNA damage and also results in cell elongation. Our champion elongated E. coli is a metK strain with a further, as yet unidentified mutation, which reaches 750 μm with no internal divisions and no increase in width

Role of DiaA and SeqA homologues in the deep-sea adapted growth of Photobacterium profundum SS9

The mechanism of high pressure-adapted growth in the deep-sea bacterium Photobacterium profundum SS9 is poorly understood. To gain further insights, two P. profundum SS9R mutants were investigated. FL23 (pbpra3229::m-Tn10) and FL28 (pbpra1039::m-Tn10) had been previously characterised as high pressuresensitive and pressure-enhanced, respectively. FL23 had a growth defect at atmospheric pressure but failed to show high pressure-adapted growth on solid agar. Pbpra3229 is 75 % identical to E. coli DiaA (stimulator of DNA replication and critical for the timely initiation of replication) and 45% identical to E. coli GmhA (essential for lipopolysaccharide core biosynthesis), which led to an investigation into whether either process was affected in FL23. However, the lipopolysaccharide of FL23 and its parent strain were identical, which suggests that Pbpra3229 is not a GmhA homologue. In contrast, the pbpra3229 and E. coli diaA genes were functionally interchangeable and both restored the timing of DNA replication in an E. coli diaA mutant. FL28 had growth and morphological defects at high pressure, but both phenotypes were exacerbated at atmospheric pressure. Pbpra1039 is 55% identical to E. coli SeqA, which is a negative regulator of DNA replication and also essential for timely initiation. Pbpra1039 was shown to be a functional homologue of E. coli SeqA, as pbpra1039 partially complemented the DNA replication defect of an E. coli seqA mutant. Combined, these findings provide evidence that Pbpra3229 is a DiaA homologue, whereas Pbpra1039 is a cold adapted SeqA homologue, and that both positive and negative regulation of initiation of DNA replication are essential for the ability of P. profundum SS9 to adapt to deep-sea conditions. A marine metagenomic library was also screened for clones that produced novel cell envelope polysaccharides and tools were developed to identify cell envelope polysaccharides in P. profundum SS9.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Deficiency in l-Serine Deaminase Interferes with One-Carbon Metabolism and Cell Wall Synthesis in Escherichia coli K-12▿

Escherichia coli K-12 provided with glucose and a mixture of amino acids depletes l-serine more quickly than any other amino acid even in the presence of ammonium sulfate. A mutant without three 4Fe4S l-serine deaminases (SdaA, SdaB, and TdcG) of E. coli K-12 is unable to do this. The high level of l-serine that accumulates when such a mutant is exposed to amino acid mixtures starves the cells for C1 units and interferes with cell wall synthesis. We suggest that at high concentrations, l-serine decreases synthesis of UDP-N-acetylmuramate-l-alanine by the murC-encoded ligase, weakening the cell wall and producing misshapen cells and lysis. The inhibition by high l-serine is overcome in several ways: by a large concentration of l-alanine, by overproducing MurC together with a low concentration of l-alanine, and by overproducing FtsW, thus promoting septal assembly and also by overexpression of the glycine cleavage operon. S-Adenosylmethionine reduces lysis and allows an extensive increase in biomass without improving cell division. This suggests that E. coli has a metabolic trigger for cell division. Without that reaction, if no other inhibition occurs, other metabolic functions can continue and cells can elongate and replicate their DNA, reaching at least 180 times their usual length, but cannot divide

Pathways explaining racial/ethnic disparities in incident all‐cause and Alzheimer's disease dementia among older US men and women

Abstract Introduction Racial disparities in Alzheimer's disease (AD) and all‐cause dementia (DEMENTIA) incidence may exist differentially among men and women, with unknown mechanisms. Methods A retrospective cohort study examining all‐cause and AD dementia incidence was conducted linking Third National Health and Nutrition Examination Survey (NHANES III) to Centers for Medicare & Medicaid Services Medicare data over ≤26 years of follow‐up (1988 to 2014). Cox regression and generalized structural equation models (GSEMs) were constructed among men and women ≥60 years of age at baseline (N = 4592). Outcomes included onset ages of all‐cause and AD dementia, whereas the main exposures were race/ethnicity contrasts (RACE_ETHN). Potential mediators) included socio‐economic status (SES), lifestyle factors (dietary quality [DIET] nutritional biomarkers [NUTR], physical activity [PA], social support [SS], alcohol [ALCOHOL], poor health [or HEALTH], poor cognitive performance [or COGN]. In addition to RACE_ETHN, the following were exogenous covariates in the GSEM and potential confounders in Cox models: age, sex, urban‐rural, household size, and marital status. Results Non‐Hispanic Black (NHB) women had a higher risk of DEMENTIA versus non‐Hispanic White (NHW) women in GSEM, consistent with Cox models (age‐adjusted model: hazard ratio [HR] = 1.34, 95% confidence interval [CI]: 1.10 to 1.61). The total effect of this RACE_ETHN contrast in women was explained by four main pathways: (1) RACE_ETHN→ poor cognitive performance (COGN, +) → DEMENTIA (+); (2) RACE_ETHN → SES (−) → COGN (−) → DEMENTIA (+); (3) RACE_ETHN → SES (−) → physical activity (PA, +) → COGN (−) → DEMENTIA (+); and (4) RACE_ETHN → SES (−) → DIET (+) → COGN (−) → DEMENTIA (+). A reduced AD risk in Mexican American (MA) women versus NHW women upon adjustment for SES and downstream factors (HR = 0.53, 95% CI: 0.35 to 0.80). For the non‐White versus NHW contrast in incident DEMENTIA, pathways involved lower SES, directly increasing cognitive deficits (or indirectly through lifestyle factors), which then directly increases DEMENTIA . Discussion Socioeconomic and lifestyle factors explaining disparities between NHB and NHW in dementia onset among women are important to consider for future observational and intervention studies

Importance of Proteins Controlling Initiation of DNA Replication in the Growth of the High-Pressure-Loving Bacterium Photobacterium profundum SS9▿

The molecular mechanism(s) by which deep-sea bacteria grow optimally under high hydrostatic pressure at low temperatures is poorly understood. To gain further insight into the mechanism(s), a previous study screened transposon mutant libraries of the deep-sea bacterium Photobacterium profundum SS9 and identified mutants which exhibited alterations in growth at high pressure relative to that of the parent strain. Two of these mutants, FL23 (PBPRA3229::mini-Tn10) and FL28 (PBPRA1039::mini-Tn10), were found to have high-pressure sensitivity and enhanced-growth phenotypes, respectively. The PBPRA3229 and PBPRA1039 genes encode proteins which are highly similar to Escherichia coli DiaA, a positive regulator, and SeqA, a negative regulator, respectively, of the initiation of DNA replication. In this study, we investigated the hypothesis that PBPRA3229 and PBPRA1039 encode DiaA and SeqA homologs, respectively. Consistent with this, we determined that the plasmid-carried PBPRA3229 and PBPRA1039 genes restored synchrony to the initiation of DNA replication in E. coli mutants lacking DiaA and SeqA, respectively. Additionally, PBPRA3229 restored the cold sensitivity phenotype of an E. coli dnaA(Cs) diaA double mutant whereas PBPRA1039 suppressed the cold sensitivity phenotype of an E. coli dnaA(Cs) single mutant. Taken together, these findings show that the genes disrupted in FL23 and FL28 encode DiaA and SeqA homologs, respectively. Consequently, our findings add support to a model whereby high pressure affects the initiation of DNA replication in P. profundum SS9 and either the presence of a positive regulator (DiaA) or the removal of a negative regulator (SeqA) promotes growth under these conditions

The role of phosphate in kidney disease

The importance of phosphate homeostasis in chronic kidney disease (CKD) has been recognized for decades, but novel insights-which are frequently relevant to everyday clinical practice-continue to emerge. Epidemiological data consistently indicate an association between hyperphosphataemia and poor clinical outcomes. Moreover, compelling evidence suggests direct toxicity of increased phosphate concentrations. Importantly, serum phosphate concentration has a circadian rhythm that must be considered when interpreting patient phosphate levels. Detailed understanding of dietary sources of phosphate, including food additives, can enable phosphate restriction without risking protein malnutrition. Dietary counselling provides an often underestimated opportunity to target the increasing exposure to dietary phosphate of both the general population and patients with CKD. In patients with secondary hyperparathyroidism, bone can be an important source of serum phosphate, and adequate appreciation of this fact should impact treatment. Dietary and pharmotherapeutic interventions are efficacious strategies to lower phosphate intake and serum concentration. However, strong evidence that targeting serum phosphate improves patient outcomes is currently lacking. Future studies are, therefore, required to investigate the effects of modern dietary and pharmacological interventions on clinically meaningful end points