Identification of efflux substrates using a riboswitch-based reporter in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is intrinsically resistant to many classes of antibiotics, reflecting the restrictive nature of its outer membrane and the action of its numerous efflux systems. However, the dynamics of compound uptake, retention and efflux in this bacterium remain incompletely understood. Here, we exploited the sensor capabilities of a Z-nucleotide sensing riboswitch to create an experimental system able to identify physicochemical and structural properties of compounds that permeate the bacterial cell, avoid efflux, and perturb the folate cycle or de novo purine synthesis. In a first step, a collection of structurally diverse compounds enriched in antifolate drugs was screened for ZTP riboswitch reporter activity in efflux-deficient P. aeruginosa , allowing us to identify compounds that entered the cell and disrupted the folate pathway. These initial hits were then rescreened using isogenic efflux-proficient bacteria, allowing us to separate efflux substrates from efflux avoiders. We confirmed this categorization by measuring intracellular levels of select compounds in the efflux-deficient and - proficient strain using high resolution LC-MS. This simple yet powerful method, optimized for high throughput screening, enables the discovery of numerous permeable compounds that avoid efflux and paves the way for further refinement of the physicochemical and structural rules governing efflux in this multi-drug resistant Gram-negative pathogen. Importance: Treatment of Pseudomonas aeruginosa infections has become increasingly challenging. The development of novel antibiotics against this multi-drug resistant bacterium is a priority, but many drug candidates never achieve effective concentrations in the bacterial cell due due to its highly restrictive outer membrane and the action of multiple efflux pumps. Here, we develop a robust and simple reporter system in P. aeruginosa to screen chemical libraries and identify compounds that either enter the cell and remain inside, or enter the cell and are exported by efflux systems. This approach enables developing rules of compound uptake and retention in P. aeruginosa that will lead to more rational design of novel antibiotics.

Identification of Efflux Substrates Using a Riboswitch-Based Reporter in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is intrinsically resistant to many classes of antibiotics, reflecting the restrictive nature of its outer membrane and the action of its numerous efflux systems. However, the dynamics of compound uptake, retention, and efflux in this bacterium remain incompletely understood. Here, we exploited the sensor capabilities of a Z-nucleotide-sensing riboswitch to create an experimental system able to identify physicochemical and structural properties of compounds that permeate the bacterial cell, avoid efflux, and perturb the folate cycle or de novo purine synthesis. In the first step, a collection of structurally diverse compounds enriched in antifolate drugs was screened for ZTP (5-aminoimidazole-4-carboxamide riboside 5'-triphosphate) riboswitch reporter activity in efflux-deficient P. aeruginosa, allowing us to identify compounds that entered the cell and disrupted the folate pathway. These initial hits were then rescreened using isogenic efflux-proficient bacteria, allowing us to separate efflux substrates from efflux avoiders. We confirmed this categorization by measuring intracellular levels of select compounds in the efflux-deficient and -proficient strain using high-resolution liquid chromatography-mass spectrometry (LC-MS). This simple yet powerful method, optimized for high-throughput screening, enables the discovery of numerous permeable compounds that avoid efflux and paves the way for further refinement of the physicochemical and structural rules governing efflux in this multidrug-resistant Gram-negative pathogen. IMPORTANCE Treatment of Pseudomonas aeruginosa infections has become increasingly challenging. The development of novel antibiotics against this multidrug-resistant bacterium is a priority, but many drug candidates never achieve effective concentrations in the bacterial cell due to its highly restrictive outer membrane and the action of multiple efflux pumps. Here, we develop a robust and simple reporter system in P. aeruginosa to screen chemical libraries and identify compounds that either enter the cell and remain inside or enter the cell and are exported by efflux systems. This approach enables the development of rules of compound uptake and retention in P. aeruginosa that will lead to more rational design of novel antibiotics.

Side-impact collision: mechanics of obstacle negotiation in sidewinding snakes.

Snakes excel at moving through cluttered environments, and heterogeneities can be used as propulsive contacts for snakes performing lateral undulation. However, sidewinding, which is often associated with sandy deserts, cuts a broad path through its environment that may increase its vulnerability to obstacles. Our prior work demonstrated that sidewinding can be represented as a pair of orthogonal body waves (vertical and horizontal) that can be independently modulated to achieve high maneuverability and incline ascent, suggesting that sidewinders may also use template modulations to negotiate obstacles. To test this hypothesis, we recorded overhead video of four sidewinder rattlesnakes (Crotalus cerastes) crossing a line of vertical pegs placed in the substrate. Snakes used three methods to traverse the obstacles: a Propagate Through behavior in which the lifted moving portion of the snake was deformed around the peg and dragged through as the snake continued sidewinding (115/160 runs), Reversal turns that reorient the snake entirely (35/160), or switching to Concertina locomotion (10/160). The Propagate Through response was only used if the anterior-most region of static contact would propagate along a path anterior to the peg, or if a new region of static contact could be formed near the head to satisfy this condition; otherwise, snakes could only use Reversal turns or switch to Concertina locomotion. Reversal turns allowed the snake to re-orient and either escape without further peg contact or re-orient into a posture amenable to using the Propagate Through response. We developed an algorithm to reproduce the Propagate Through behavior in a robophysical model using a modulation of the two-wave template. This range of behavioral strategies provides sidewinders with a versatile range of options for effectively negotiating obstacles in their natural habitat, as well as provide insights into the design and control of robotic systems dealing with heterogeneous habitats.

La obesidad y su relación con otros factores de riesgo cardiovascular en una población de estudiantes universitarios del centro de Bogotá / Obesity and its relationship with other cardiovascular risk factors in a population of university students in downtown Bogotá

La obesidad y sus complicaciones constituyen una de las principales pandemias a nivel mundial, en especial la Diabetes tipo 2 que está asociada a la resistencia a la insulina. El propósito de este trabajo es describir la relación existente entre la obesidad y otros de factores de riesgo cardiovascular en una población de estudiantes universitarios del centro de Bogotá. Previo consentimiento informado, se procedió a la medición de la composición corporal, a través de la toma de: pliegue tricipital y supraescapular mediante adipometro, perímetro de cintura, índice de Masa Corporal, Masa Magra, Masa Grasa y porcentaje de grasa entre otras. También se realizaron tomas de muestras de sangre para determinar glucemia, colesterol total, triglicéridos y lipoproteínas, cuya relación permite el cálculo del índice aterogénico. De una muestra final de 76 estudiantes, el 15,5% presenta sobrepeso; el 76,5 % está dentro de rangos considerados normales; y el 8,0% presenta bajo peso. En lo referente a los datos por sexo, se encontró que un 5,5 % de hombres y un 19,0% de las mujeres presentaban sobrepeso y un 5,5% de los hombres y un 8,6 % de las mujeres presentaban bajo peso, en ningún caso hubo personas obesas. El perímetro de cintura varió entre 68 y 97 cm en hombres y entre 61 y 92 cm en mujeres, finalmente el porcentaje de grasa estuvo entre 27,6 a 30,7 en hombres y entre 11,0 a 36,9 en mujeres. Teniendo en cuenta los resultados obtenidos, es importante promover en nuestra población una cultura de hábitos saludables, caracterizada por una alimentación saludable y una mayor actividad física; también se recomienda, especialmente durante los primeros años de vida, ya que es en esta etapa donde se adquieren o instauran gran parte de los mismos y que en muchos casos permanecerán toda la vida.

Obesity and its complications are one of the major pandemics at the global level, especially type 2 diabetes that is associated with insulin resistance. The purpose of this paper is to describe the relationship between obesity and other cardiovascular risk factors of university students in downtown Bogota. After obtaining an informed consent, we proceeded to the measurement of the following body parts: triceps skinfold and suprascapular through adipometer, waist circumference, body mass index, lean mass, fat mass and fat glucose, total percentage among others. Blood samples were also taken to determine blood cholesterol, triglycerides, and lipoproteins, whose relationship allows the calculation of the atherogenic index. From a final sample of 76 students, 15.5 % was overweight; 76.5 % was considered within normal ranges; and the 8.0 % was underweight. In regard to the data by sex, it was found that a 5.5 % of men and 19.0 % of women were overweight and 5.5 % of men and 8.6 % of the women had low weight, there were no obese people in any case. The waist perimeter varied between 68 and 97 cm in men and between 61 and 92 cm in women, finally the fat percentage was between 27.6 and 30.7 in men and from 11.0 to 36.9 in women. Taking into account the results obtained, it is important to promote in our population a culture of healthy habits, characterized by a healthy diet and increased physical activity; it is also recommended, especially during the first years of life, as it is in this stage where the majority of these habits are acquired and will last for life.

Parámetros espirométricos y ciclo menstrual en mujeres jóvenes

Efectos mecano-ventilatorios de la función respiratoria han sido atribuidos a los esteroides sexuales, sin embargo son limitados los reportes del estado fisiológico de parámetros espirométricos en el ciclo menstrual. En 50 mujeres jóvenes (20+ -1.5 años), eumenorreicas (6 meses), no fumadoras y con normopeso (IMC: 23.1+ -0.8); se evalúo de forma automatizada (Spiroanalizer ST90 Futuremed): capacidad vital forzada (CVF), volumen espiratorio máximo medio (MMEF), flujo espiratorio forzado al 50 por ciento de CVF (FEF50), máxima ventilación voluntaria (MVV) y el cociente FEV1/CVF. Distribuidas las mujeres en 4 grupos: Fase folicular precoz (FP:O-5d, n=21), fase folicular tardía (FT: 6-10d, n=12), fase ovulatoria (FO: 11-16d, n=6) y fase lútea (FL:18-28d, n=21); se observó: CVF(1) y FEV1 (1) similar en los 4 grupos, MMEF (1/s) Y MVV (1/min) inferiores en la FT (0,03) y FP(0.01), respectivamente el 80 en los 4 grupos, siendo máximo en FL (0,01). Además, en todos los grupos, los parámetros analizados superan el 90 por ciento de los valores predictivos (por edad, sexo, talla), excepto la MVV que osciló entre 58-78. Los resultados demuestran que, en mujeres jóvenes, eumenorreicas, no fumadoras existen variaciones en el estado fisiológico de los índices espirométricos en las diferentes fases del ciclo menstrual; lo cual debe ser tomado en cuenta en la práctica clínica.