The concentration of the cell division proteins FtsZ, FtsA, and ZipA and their assembly into a division ring during theEscherichia coliB/r K cell cycle have been measured in synchronous cultures obtained by the membrane elution technique. Immunostaining of the three proteins revealed no organized structure in newly born cells. In a culture with a doubling time of 49 min, assembly of the Z ring started around minute 25 and was detected first as a two-dot structure that became a sharp band before cell constriction. FtsA and ZipA localized into a division ring following the same pattern and time course as FtsZ. The concentration (amount relative to total mass) of the three proteins remained constant during one complete cell cycle, showing that assembly of a division ring is not driven by changes in the concentration of these proteins. Maintenance of the Z ring during the process of septation is a dynamic energy-dependent event, as evidenced by its disappearance in cells treated with sodium azide.

Background: Since the confirmation of the first patient infected with SARS-CoV-2 in Spain in January 2020, the epidemic has grown rapidly, with the greatest impact on the region of Madrid. This article describes the first 2226 adult patients with COVID-19, consecutively admitted to La Paz University Hospital in Madrid. Methods: Our cohort included all patients consecutively hospitalized who had a final outcome (death or discharge) in a 1286-bed hospital of Madrid (Spain) from 25 February (first case admitted) to 19 April 2020. The data were manually entered into an electronic case report form, which was monitored prior to the analysis. Results: We consecutively included 2226 adult patients admitted to the hospital who either died (460) or were discharged (1766). The patients’ median age was 61 years, and 51.8% were women. The most common comorbidity was arterial hypertension (41.3%), and the most common symptom on admission was fever (71.2%). The median time from disease onset to hospital admission was 6 days. The overall mortality was 20.7% and was higher in men (26.6% vs. 15.1%). Seventy-five patients with a final outcome were transferred to the intensive care unit (ICU) (3.4%). Most patients admitted to the ICU were men, and the median age was 64 years. Baseline laboratory values on admission were consistent with an impaired immune-inflammatory profile. Conclusions: We provide a description of the first large cohort of hospitalized patients with COVID-19 in Europe. Advanced age, male sex, the presence of comorbidities and abnormal laboratory values were more common among the patients with fatal outcomes.

Experimental conditions that simulate the crowded bacterial cytoplasmic environment have been used to study the assembly of the essential cell division protein FtsZ from Escherichia coli. In solutions containing a suitable concentration of physiological osmolytes, macromolecular crowding promotes the GTP-dependent assembly of FtsZ into dynamic two-dimensional polymers that disassemble upon GTP depletion. Atomic force microscopy reveals that these FtsZ polymers adopt the shape of ribbons that are one subunit thick. When compared with the FtsZ filaments observed in vitro in the absence of crowding, the ribbons show a lag in the GTPase activity and a decrease in the GTPase rate and in the rate of GTP exchange within the polymer. We propose that, in the crowded bacterial cytoplasm under assembly-promoting conditions, the FtsZ filaments tend to align forming dynamic ribbon polymers. In vivo these ribbons would fit into the Z-ring even in the absence of other interactions. Therefore, the presence of mechanisms to prevent the spontaneous assembly of the Z-ring in non-dividing cells must be invoked.

FtsZ, the prokaryotic homologue of tubulin, is an essential cell division protein. In the cell, it localizes at the center, forming a ring that constricts during division. In vitro, it binds and hydrolyzes GTP and polymerizes in a GTP-dependent manner. We have used atomic force microscopy to study the structure and dynamics of FtsZ polymer assembly on a mica surface under buffer solution. The polymers were highly dynamic and flexible, and they continuously rearranged over the surface. End-to-end joining of filaments and depolymerization from internal zones were observed, suggesting that fragmentation and reannealing may contribute significantly to the dynamics of FtsZ assembly. The shape evolution of the restructured polymers manifested a strong inherent tendency to curve. Polymers formed in the presence of non-hydrolyzable nucleotide analogues or in the presence of GDP and AlF₃ were structurally similar but showed a slower dynamic behavior. These results provide experimental evidence supporting the model of single-strand polymerization plus cyclization recently proposed to explain the hydrodynamic behavior of the polymers in solution.