Force generation in dividing E. coli cells: A handles-on approach using optical tweezers

In bacteria, what __drives__ the process of cell division is unknown. Possibly, forces generated by an internal protein ring (termed __the Z-ring__) are responsible for the division process, but direct evidence is lacking. Here we describe the development of a method to measure forces in a single dividing bacterium. Using optical tweezers, forces can be measured on optically trapped micron-sized beads. To attach such a bead to a living bacterium, one of its outer membrane proteins is engineered to present a binding epitope on the cell surface. We show that it is possible to attach a bead to this __molecular handle__ via a DNA-molecule, and characterize the strength of this molecular construct. Finally, we show that genetic fusion of the surface exposed protein domain to an internal domain with mid-cell affinity can alter the localization pattern of the exposed domain. Our findings suggest that it is possible to create a fusion protein that exposes a binding epitope and localizes specifically to the division site.UBL - phd migration 201

Absence of long-range diffusion of OmpA in E. coli is not caused by its peptidoglycan binding domain.

BACKGROUND: It is widely believed that integral outer membrane (OM) proteins in bacteria are able to diffuse laterally in the OM. However, stable, immobile proteins have been identified in the OM of Escherichia coli. In explaining the observations, a hypothesized interaction of the immobilized OM proteins with the underlying peptidoglycan (PG) cell wall played a prominent role. RESULTS: OmpA is an abundant outer membrane protein in E. coli containing a PG-binding domain. We use FRAP to investigate whether OmpA is able to diffuse laterally over long-range (> ~100 nm) distances in the OM. First, we show that OmpA, containing a PG binding domain, does not exhibit long-range lateral diffusion in the OM. Then, to test whether PG interaction was required for this immobilization, we genetically removed the PG binding domain and repeated the FRAP experiment. To our surprise, this did not increase the mobility of the protein in the OM. CONCLUSIONS: OmpA exhibits an absence of long-range (> ~100 nm) diffusion in the OM that is not caused by its PG binding domain. Therefore, other mechanisms are needed to explain this observation, such as the presence of physical barriers in the OM, or strong interactions with other elements in the cell envelope

Model calculations of superlubricity of graphite

Quantum Matter and Optic

Financiële gevolgen Regeerakkoord en Meerjarig Financieel Kader van de EU voor de land- en tuinbouw; Een vergelijking met andere mkb-sectoren

Naar aanleiding van het debat over de regeringsverklaring (14 november 2012) heeft het kabinet aangegeven om de effecten van het Regeerakkoord voor de primaire land- en tuinbouw door te laten rekenen. Hierop heeft het ministerie van EZ aan een samenwerkingsverband van LEI Wageningen UR en Panteia de opdracht verstrekt om de gevolgen voor de land- en tuinbouw door te rekenen en te vergelijken met die voor enkele andere mkb-sectoren. In aanvulling hierop heeft het ministerie gevraagd om ook de gevolgen van het nieuwe Meerjarig Finan-cieel Kader (2014-2020) van de Europese Unie mee te nemen. Het akkoord dat de lidstaten hierover begin februari 2013 hebben bereikt, houdt een korting in van het budget voor het Gemeenschappelijk Landbouwbeleid (GLB)

The PHENIX Experiment at RHIC

The physics emphases of the PHENIX collaboration and the design and current status of the PHENIX detector are discussed. The plan of the collaboration for making the most effective use of the available luminosity in the first years of RHIC operation is also presented.Comment: 5 pages, 1 figure. Further details of the PHENIX physics program available at http://www.rhic.bnl.gov/phenix

Recovery of dialysis patients with COVID-19 : health outcomes 3 months after diagnosis in ERACODA

Background. Coronavirus disease 2019 (COVID-19)-related short-term mortality is high in dialysis patients, but longer-term outcomes are largely unknown. We therefore assessed patient recovery in a large cohort of dialysis patients 3 months after their COVID-19 diagnosis. Methods. We analyzed data on dialysis patients diagnosed with COVID-19 from 1 February 2020 to 31 March 2021 from the European Renal Association COVID-19 Database (ERACODA). The outcomes studied were patient survival, residence and functional and mental health status (estimated by their treating physician) 3 months after COVID-19 diagnosis. Complete follow-up data were available for 854 surviving patients. Patient characteristics associated with recovery were analyzed using logistic regression. Results. In 2449 hemodialysis patients (mean ± SD age 67.5 ± 14.4 years, 62% male), survival probabilities at 3 months after COVID-19 diagnosis were 90% for nonhospitalized patients (n = 1087), 73% for patients admitted to the hospital but not to an intensive care unit (ICU) (n = 1165) and 40% for those admitted to an ICU (n = 197). Patient survival hardly decreased between 28 days and 3 months after COVID-19 diagnosis. At 3 months, 87% functioned at their pre-existent functional and 94% at their pre-existent mental level. Only few of the surviving patients were still admitted to the hospital (0.8-6.3%) or a nursing home (∼5%). A higher age and frailty score at presentation and ICU admission were associated with worse functional outcome. Conclusions. Mortality between 28 days and 3 months after COVID-19 diagnosis was low and the majority of patients who survived COVID-19 recovered to their pre-existent functional and mental health level at 3 months after diagnosis

Differential bacterial surface display of peptides by the transmembrane domain of OmpA

Peptide libraries or antigenic determinants can be displayed on the surface of bacteria through insertion in a suitable outer membrane scaffold protein. Here, we inserted the well-known antibody epitopes 3xFLAG and 2xmyc in exterior loops of the transmembrane (TM) domain of OmpA. Although these highly charged epitopes were successfully displayed on the cell surface, their levels were 10-fold reduced due to degradation. We verified that the degradation was not caused by the absence of the C-terminal domain of OmpA. In contrast, a peptide that was only moderately charged (SA-1) appeared to be stably incorporated in the outer membrane at normal protein levels. Together, these results suggest that the display efficiency is sensitive to the charge of the inserted epitopes. In addition, the high-level expression of OmpA variants with surface-displayed epitopes adversely affected growth in a strain dependent, transient manner. In a MC4100 derived strain growth was affected, whereas in MC1061 derived strains growth was unaffected. Finally, results obtained using a gel-shift assay to monitor β-barrel folding in vivo show that the insertion of small epitopes can change the heat modifiability of the OmpA TM domain from ‘aberrant’ to normal, and predict that some β-barrels will not display any significant heat-modifiability at all