Thylakoid attachment to the plasma membrane in Synechocystis sp. PCC 6803 requires the AncM protein.

Thylakoids are the highly specialized internal membrane systems that harbor the photosynthetic electron transport machinery in cyanobacteria and in chloroplasts. In Synechocystis sp. PCC 6803, thylakoid membranes (TMs) are arranged in peripheral sheets that occasionally converge on the plasma membrane (PM) to form thylakoid convergence membranes (TCMs). TCMs connect several thylakoid sheets and form local contact sites called thylapses between the two membrane systems, at which the early steps of photosystem II (PSII) assembly occur. The protein CurT is one of the main drivers of TCM formation known so far. Here, we identify, by whole-genome sequencing of a curT- suppressor strain, the protein anchor of convergence membranes (AncM) as a factor required for the attachment of thylakoids to the PM at thylapses. An ancM- mutant is shown to have a photosynthetic phenotype characterized by reductions in oxygen-evolution rate, PSII accumulation, and PS assembly. Moreover, the ancM- strain exhibits an altered thylakoid ultrastructure with additional sheets and TCMs detached from the PM. By combining biochemical studies with fluorescence and correlative light-electron microscopy-based approaches, we show that AncM is an integral membrane protein located in biogenic TCMs that form thylapses. These data suggest an antagonistic function of AncM and CurT in shaping TM ultrastructure.

Structural basis for VIPP1 oligomerization and maintenance of thylakoid membrane integrity.

Vesicle-inducing protein in plastids 1 (VIPP1) is essential for the biogenesis and maintenance of thylakoid membranes, which transform light into life. However, it is unknown how VIPP1 performs its vital membrane-remodeling functions. Here, we use cryo-electron microscopy to determine structures of cyanobacterial VIPP1 rings, revealing how VIPP1 monomers flex and interweave to form basket-like assemblies of different symmetries. Three VIPP1 monomers together coordinate a non-canonical nucleotide binding pocket on one end of the ring. Inside the ring's lumen, amphipathic helices from each monomer align to form large hydrophobic columns, enabling VIPP1 to bind and curve membranes. In vivo mutations in these hydrophobic surfaces cause extreme thylakoid swelling under high light, indicating an essential role of VIPP1 lipid binding in resisting stress-induced damage. Using cryo-correlative light and electron microscopy (cryo-CLEM), we observe oligomeric VIPP1 coats encapsulating membrane tubules within the Chlamydomonas chloroplast. Our work provides a structural foundation for understanding how VIPP1 directs thylakoid biogenesis and maintenance.

Pitfall prayer marks: Recognition and appropriate treatment: A case report and review of literature.

Prayer marks are asymptomatic callosities resulting from repeated, extended pressure, and friction exerted on bony prominences when praying on hard ground. A 41-year-old woman with ulcerative colitis treated with infliximab was referred to our clinic due to skin changes on her feet that were suspected to be drug eruptions. The patient presented several asymptomatic, hyperpigmented, and hyperkeratotic plaques over the lateral malleoli suggesting that the lesions had a mechanical cause. Further exploration revealed that the patient, a practicing Muslim, prays in a sitting position called "Julus" several times a day. After color marking, the lesions over the lateral feet left a precise imprint on the underlay when the patient was asked to imitate the praying posture-thus proving the origin of the skin lesions. We searched the database on July 31, 2019 using the terms «prayer marks¼ OR «prayer nodules¼ OR "prayer callosities." Only electronically available publications were reviewed. Recognition of prayer marks is important to avoid misdiagnosis, performance of unnecessary diagnostic procedures, and to enhance the intercultural competence of clinicians who practice in multicultural societies.

Biogenic regions of cyanobacterial thylakoids form contact sites with the plasma membrane.

Little is known about how the photosynthetic machinery is arranged in time and space during the biogenesis of thylakoid membranes. Using in situ cryo-electron tomography to image the three-dimensional architecture of the cyanobacterium Synechocystis, we observed that the tips of multiple thylakoids merge to form a substructure called the 'convergence membrane'. This high-curvature membrane comes into close contact with the plasma membrane at discrete sites. We generated subtomogram averages of 70S ribosomes and array-forming phycobilisomes, then mapped these structures onto the native membrane architecture as markers for protein synthesis and photosynthesis, respectively. This molecular localization identified two distinct biogenic regions in the thylakoid network: thylakoids facing the cytosolic interior of the cell that were associated with both marker complexes, and convergence membranes that were decorated by ribosomes but not phycobilisomes. We propose that the convergence membranes perform a specialized biogenic function, coupling the synthesis of thylakoid proteins with the integration of cofactors from the plasma membrane and the periplasmic space.

Hypersensitivity reaction with multi-organ failure following re-exposure to rifampicin: case report and review of the literature including WHO spontaneous safety reports.

BACKGROUND: True hypersensitivity reactions to rifampicin are relatively rare, nonetheless severe manifestations mostly involving a single organ have been documented. We report a case of acute multi-organ failure occurring after a medication error with re-exposure to rifampicin. CASE PRESENTATION: A 68-year old patient developed acute hypersensitivity pneumonitis, acute renal failure, acute liver failure and haemolytic anemia within hours after a second re-exposure to Rifampicin for the treatment of a hip prosthesis infection with Staphylococcus epidermidis. A recent rifampicin exposure 1 week earlier had resulted in a massive rise of CRP levels without organ manifestations. Nine years previously, the patient had developed a multi-organ hypersensitivity reaction 8 days after commencing treatment with rifampicin for pulmonary tuberculosis; and 23 years previously he had received rifampicin without problems. The organ-specific hypersensitivity reactions were largely reversible after withdrawal of rifampicin and treatment with steroids. A review of the literature and summary of WHO spontaneous safety reports is also given. CONCLUSIONS: Re-exposure to rifampicin in sensitised individuals may cause acute severe hypersensitivity reactions. Due to its indications in the management of mycobacterial and implant-associated infections, rifampicin is a drug which might be given decades apart, which poses a risk that information about previous intolerance is lost.

Thylakoid Membrane Architecture in Synechocystis Depends on CurT, a Homolog of the Granal CURVATURE THYLAKOID1 Proteins.

Photosynthesis occurs in thylakoids, a highly specialized membrane system. In the cyanobacterium Synechocystis sp PCC 6803 (hereafter Synechocystis 6803), the thylakoids are arranged parallel to the plasma membrane and occasionally converge toward it to form biogenesis centers. The initial steps in PSII assembly are thought to take place in these regions, which contain a membrane subcompartment harboring the early assembly factor PratA and are referred to as PratA-defined membranes (PDMs). Loss of CurT, the Synechocystis 6803 homolog of Arabidopsis thaliana grana-shaping proteins of the CURVATURE THYLAKOID1 family, results in disrupted thylakoid organization and the absence of biogenesis centers. As a consequence, PSII is less efficiently assembled and accumulates to only 50% of wild-type levels. CurT induces membrane curvature in vitro and is distributed all over the thylakoids, with local concentrations at biogenesis centers. There it forms a sophisticated tubular network at the cell periphery, as revealed by live-cell imaging. CurT is part of several high molecular mass complexes, and Blue Native/SDS-PAGE and isoelectric focusing demonstrated that different isoforms associate with PDMs and thylakoids. Moreover, CurT deficiency enhances sensitivity to osmotic stress, adding a level of complexity to CurT function. We propose that CurT is crucial for the differentiation of membrane architecture, including the formation of PSII-related biogenesis centers, in Synechocystis 6803.

The Role of Slr0151, a Tetratricopeptide Repeat Protein from Synechocystis sp. PCC 6803, during Photosystem II Assembly and Repair.

The assembly and repair of photosystem II (PSII) is facilitated by a variety of assembly factors. Among those, the tetratricopeptide repeat (TPR) protein Slr0151 from Synechocystis sp. PCC 6803 (hereafter Synechocystis) has previously been assigned a repair function under high light conditions (Yang et al., 2014). Here, we show that inactivation of slr0151 affects thylakoid membrane ultrastructure even under normal light conditions. Moreover, the level and localization of Slr0151 are affected in a variety of PSII-related mutants. In particular, the data suggest a close functional relationship between Slr0151 and Sll0933, which interacts with Ycf48 during PSII assembly and is homologous to PAM68 in Arabidopsis thaliana. Immunofluorescence analysis revealed a punctate distribution of Slr0151 within several different membrane types in Synechocystis cells.

Performance of the Manchester Triage System in Adult Medical Emergency Patients: A Prospective Cohort Study.

BACKGROUND: Accurate initial patient triage in the emergency department (ED) is pivotal in reducing time to effective treatment by the medical team and in expediting patient flow. The Manchester Triage System (MTS) is widely implemented for this purpose. Yet the overall effectiveness of its performance remains unclear. OBJECTIVES: We investigated the ability of MTS to accurately assess high treatment priority and to predict adverse clinical outcomes in a large unselected population of medical ED patients. METHODS: We prospectively followed consecutive medical patients seeking ED care for 30 days. Triage nurses implemented MTS upon arrival of patients admitted to the ED. The primary endpoint was high initial treatment priority adjudicated by two independent physicians. Secondary endpoints were 30-day all-cause mortality, admission to the intensive care unit (ICU), and length of stay. We used regression models with area under the receiver operating characteristic curve (AUC) as a measure of discrimination. RESULTS: Of the 2407 patients, 524 (21.8%) included patients (60.5 years, 55.7% males) who were classified as high treatment priority; 3.9% (n = 93) were transferred to the ICU; and 5.7% (n = 136) died. The initial MTS showed fair prognostic accuracy in predicting treatment priority (AUC 0.71) and ICU admission (AUC 0.68), but not in predicting mortality (AUC 0.55). Results were robust across most predefined subgroups, including patients diagnosed with infections, or cardiovascular or gastrointestinal diseases. In the subgroup of neurological symptoms and disorders, the MTS showed the best performance. CONCLUSION: The MTS showed fair performance in predicting high treatment priority and adverse clinical outcomes across different medical ED patient populations. Future research should focus on further refinement of the MTS so that its performance can be improved. TRIAL REGISTRATION: Clinicaltrials.gov: NCT01768494.

Can We Reduce Negative Blood Cultures With Clinical Scores and Blood Markers? Results From an Observational Cohort Study.

Only a small proportion of blood cultures routinely performed in emergency department (ED) patients is positive. Multiple clinical scores and biomarkers have previously been examined for their ability to predict bacteremia. Conclusive clinical validation of these scores and biomarkers is essential.This observational cohort study included patients with suspected infection who had blood culture sampling at ED admission. We assessed 5 clinical scores and admission concentrations of procalcitonin (PCT), C-reactive protein (CRP), lymphocyte and white blood cell counts, the neutrophil-lymphocyte count ratio (NLCR), and the red blood cell distribution width (RDW). Two independent physicians assessed true blood culture positivity. We used logistic regression models with area under the curve (AUC) analysis.Of 1083 patients, 104 (9.6%) had positive blood cultures. Of the clinical scores, the Shapiro score performed best (AUC 0.729). The best biomarkers were PCT (AUC 0.803) and NLCR (AUC 0.700). Combining the Shapiro score with PCT levels significantly increased the AUC to 0.827. Limiting blood cultures only to patients with either a Shapiro score of ≥4 or PCT > 0.1 µg/L would reduce negative sampling by 20.2% while still identifying 100% of positive cultures. Similarly, a Shapiro score ≥3 or PCT >0.25 µg/L would reduce cultures by 41.7% and still identify 96.1% of positive blood cultures.Combination of the Shapiro score with admission levels of PCT can help reduce unnecessary blood cultures with minimal false negative rates.The study was registered on January 9, 2013 at the 'ClinicalTrials.gov' registration web site (NCT01768494).

Association of nutritional risk and adverse medical outcomes across different medical inpatient populations.

OBJECTIVE: The aim of this study was to examine the prevalence of nutritional risk and its association with multiple adverse clinical outcomes in a large cohort of acutely ill medical inpatients from a Swiss tertiary care hospital. METHODS: We prospectively followed consecutive adult medical inpatients for 30 d. Multivariate regression models were used to investigate the association of the initial Nutritional Risk Score (NRS 2002) with mortality, impairment in activities of daily living (Barthel Index <95 points), hospital length of stay, hospital readmission rates, and quality of life (QoL; adapted from EQ5 D); all parameters were measured at 30 d. RESULTS: Of 3186 patients (mean age 71 y, 44.7% women), 887 (27.8%) were at risk for malnutrition with an NRS ≥3 points. We found strong associations (odds ratio/hazard ratio [OR/HR], 95% confidence interval [CI]) between nutritional risk and mortality (OR/HR, 7.82; 95% CI, 6.04-10.12), impaired Barthel Index (OR/HR, 2.56; 95% CI, 2.12-3.09), time to hospital discharge (OR/HR, 0.48; 95% CI, 0.43-0.52), hospital readmission (OR/HR, 1.46; 95% CI, 1.08-1.97), and all five dimensions of QoL measures. Associations remained significant after adjustment for sociodemographic characteristics, comorbidities, and medical diagnoses. Results were robust in subgroup analysis with evidence of effect modification (P for interaction < 0.05) based on age and main diagnosis groups. CONCLUSION: Nutritional risk is significant in acutely ill medical inpatients and is associated with increased medical resource use, adverse clinical outcomes, and impairments in functional ability and QoL. Randomized trials are needed to evaluate evidence-based preventive and treatment strategies focusing on nutritional factors to improve outcomes in these high-risk patients.

Procalcitonin and pyuria-based algorithm reduces antibiotic use in urinary tract infections: a randomized controlled trial.

BACKGROUND: Urinary tract infections (UTIs) are common drivers of antibiotic use. The minimal effective duration of antibiotic therapy for UTIs is unknown, but any reduction is important to diminish selection pressure for antibiotic resistance, costs, and drug-related side-effects. The aim of this study was to investigate whether an algorithm based on procalcitonin (PCT) and quantitative pyuria reduces antibiotic exposure. METHODS: From April 2012 to March 2014, we conducted a factorial design randomized controlled open-label trial. Immunocompetent adults with community-acquired non-catheter-related UTI were enrolled in the emergency department of a tertiary-care 600-bed hospital in northwestern Switzerland. Clinical presentation was used to guide initiation and duration of antibiotic therapy according to current guidelines (control group) or with a PCT-pyuria-based algorithm (PCT-pyuria group). The primary endpoint was overall antibiotic exposure within 90 days. Secondary endpoints included duration of the initial antibiotic therapy, persistent infection 7 days after end of therapy and 30 days after enrollment, recurrence and rehospitalizations within 90 days. RESULTS: Overall, 394 patients were screened, 228 met predefined exclusion criteria, 30 declined to participate, and 11 were not eligible. Of these, 125 (76% women) were enrolled in the intention-to-treat (ITT) analysis and 96 patients with microbiologically confirmed UTI constituted the per protocol group; 84 of 125 (67%) patients had a febrile UTI, 28 (22%) had bacteremia, 5 (4%) died, and 3 (2%) were lost to follow-up. Overall antibiotic exposure within 90 days was shorter in the PCT-pyuria group than in the control group (median 7.0 [IQR, 5.0-14.0] vs. 10.0 [IQR, 7.0-16.0] days, P = 0.011) in the ITT analysis. Mortality, rates of persistent infections, recurrences, and rehospitalizations were not different. CONCLUSIONS: A PCT-pyuria-based algorithm reduced antibiotic exposure by 30% when compared to current guidelines without apparent negative effects on clinical outcomes.

Use of procalcitonin, C-reactive protein and white blood cell count to distinguish between lower limb erysipelas and deep vein thrombosis in the emergency department: A prospective observational study.

Early differentiation of erysipelas from deep vein thrombosis (DVT) based solely on clinical signs and symptoms is challenging. There is a lack of data regarding the usefulness of the inflammatory biomarkers procalcitonin (PCT), C-reactive protein (CRP) and white blood cell (WBC) count in the diagnosis of localized cutaneous infections. Herein, we investigated the diagnostic value of inflammatory markers in a prospective at-risk patient population. This is an observational quality control study including consecutive patients presenting with a final diagnosis of either erysipelas or DVT. The association of PCT (µg/L) and CRP (mg/L) levels and WBC counts (g/L) with the primary outcome was assessed using logistic regression models with area under the receiver-operator curve. Forty-eight patients (erysipelas, n = 31; DVT, n = 17) were included. Compared with patients with DVT, those with erysipelas had significantly higher PCT concentrations. No significant differences in CRP concentrations and WBC counts were found between the two groups. At a PCT threshold of 0.1 µg/L or more, specificity and positive predictive values (PPV) for erysipelas were 82.4% and 85.7%, respectively, and increased to 100% and 100% at a threshold of more than 0.25 µg/L. Levels of PCT also correlated with the severity of erysipelas, with a stepwise increase according to systemic inflammatory response syndrome criteria. We found a high discriminatory value of PCT for differentiation between erysipelas and DVT, in contrast to other commonly used inflammatory biomarkers. Whether the use of PCT levels for early differentiation of erysipelas from DVT reduces unnecessary antibiotic exposure needs to be assessed in an interventional trial.

Procalcitonin improves the Glasgow Prognostic Score for outcome prediction in emergency patients with cancer: a cohort study.

The Glasgow Prognostic Score (GPS) is useful for predicting long-term mortality in cancer patients. Our aim was to validate the GPS in ED patients with different cancer-related urgency and investigate whether biomarkers would improve its accuracy. We followed consecutive medical patients presenting with a cancer-related medical urgency to a tertiary care hospital in Switzerland. Upon admission, we measured procalcitonin (PCT), white blood cell count, urea, 25-hydroxyvitamin D, corrected calcium, C-reactive protein, and albumin and calculated the GPS. Of 341 included patients (median age 68 years, 61% males), 81 (23.8%) died within 30 days after admission. The GPS showed moderate prognostic accuracy (AUC 0.67) for mortality. Among the different biomarkers, PCT provided the highest prognostic accuracy (odds ratio 1.6 (95% confidence interval 1.3 to 1.9), P < 0.001, AUC 0.69) and significantly improved the GPS to a combined AUC of 0.74 (P = 0.007). Considering all investigated biomarkers, the AUC increased to 0.76 (P < 0.001). The GPS performance was significantly improved by the addition of PCT and other biomarkers for risk stratification in ED cancer patients. The benefit of early risk stratification by the GPS in combination with biomarkers from different pathways should be investigated in further interventional trials.

Biogenesis of thylakoid membranes.

Thylakoids mediate photosynthetic electron transfer and represent one of the most elaborate energy-transducing membrane systems. Despite our detailed knowledge of its structure and function, much remains to be learned about how the machinery is put together. The concerted synthesis and assembly of lipids, proteins and low-molecular-weight cofactors like pigments and transition metal ions require a high level of spatiotemporal coordination. While increasing numbers of assembly factors are being functionally characterized, the principles that govern how thylakoid membrane maturation is organized in space are just starting to emerge. In both cyanobacteria and chloroplasts, distinct production lines for the fabrication of photosynthetic complexes, in particular photosystem II, have been identified. This article is part of a Special Issue entitled: Chloroplast Biogenesis.