16 research outputs found
Regulation of ribonucleotide synthesis by the Pseudomonas aeruginosa two-component system AlgR in response to oxidative stress
Ribonucleotide reductases (RNR) catalyze the last step of deoxyribonucleotide synthesis, and are therefore essential to DNA-based life. Three forms of RNR exist: classes I, II, and III. While eukaryotic cells use only class Ia RNR, bacteria can harbor any combination of classes, granting them adaptability. The opportunistic pathogen Pseudomonas aeruginosa surprisingly encodes all three classes, allowing it to thrive in different environments. Here we study an aspect of the complex RNR regulation whose molecular mechanism has never been elucidated, the well-described induction through oxidative stress, and link it to the AlgZR two-component system, the primary regulator of the mucoid phenotype. Through bioinformatics, we identify AlgR binding locations in RNR promoters, which we characterize functionally through EMSA and physically through AFM imaging. Gene reporter assays in different growth models are used to study the AlgZR-mediated control on the RNR network under various environmental conditions and physiological states. Thereby, we show that the two-component system AlgZR, which is crucial for bacterial conversion to the mucoid phenotype associated with chronic disease, controls the RNR network and directs how the DNA synthesis pathway is modulated in mucoid and non-mucoid biofilms, allowing it to respond to oxidative stress
Nanoscale dielectric microscopy of non-planar samples by lift-mode electrostatic force microscopy
Internal Hydration Properties of Single Bacterial Endospores Probed by Electrostatic Force Microscopy
Development and preliminary evaluation of the validity and reliability of a revised illness perception questionnaire for healthcare professionals
The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients
Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation
Nanoscale dielectric microscopy of non-planar samples by lift-mode electrostatic force microscopy
Nanoscale Electric Permittivity of Single Bacterial Cells at Gigahertz Frequencies by Scanning Microwave Microscopy
Romper las barreras entre la familia y la escuela. Experiencia de investigación-acción en los centros escolares para promover la relación con las familias
Internal Hydration Properties of Single Bacterial Endospores Probed by Electrostatic Force Microscopy
We
show that the internal hydration properties of single <i>Bacillus
cereus</i> endospores in air under different relative
humidity (RH) conditions can be determined through the measurement
of its electric permittivity by means of quantitative electrostatic
force microscopy (EFM). We show that an increase in the RH from 0%
to 80% induces a large increase in the equivalent homogeneous relative
electric permittivity of the bacterial endospores, from ∼4
up to ∼17, accompanied only by a small increase in the endospore
height, of just a few nanometers. These results correlate the increase
of the moisture content of the endospore with the corresponding increase
of environmental RH. Three-dimensional finite element numerical calculations,
which include the internal structure of the endospores, indicate that
the moisture is mainly accumulated in the external layers of the endospore,
hence preserving the core of the endospore at low hydration levels.
This mechanism is different from what we observe for vegetative bacterial
cells of the same species, in which the cell wall at high humid atmospheric
conditions is not able to preserve the cytoplasmic region at low hydration
levels. These results show the potential of quantitative EFM under
environmental humidity control to study the hygroscopic properties
of small-scale biological (and nonbiological) entities and to determine
its internal hydration state. A better understanding of nanohygroscopic
properties can be of relevance in the study of essential biological
processes and in the design of bionanotechnological applications