Collective condensation and auto-aggregation of Escherichia coli in uniform acidic environments.

Chemotaxis-the movement of cells along chemical gradients-leads to collective behaviors when cells coordinate their movements. Here, using Escherichia coli as a model, we demonstrate a distinct type of bacterial collective response in acidic environments containing organic acids. Bacterial populations immersed in such environments collectively condensed into millimeter-sized focal points.

Signal integration in chemoreceptor complexes.

Motile bacteria use large receptor arrays to detect chemical and physical stimuli in their environment, process this complex information, and accordingly bias their swimming in a direction they deem favorable. The chemoreceptor molecules form tripod-like trimers of receptor dimers through direct contacts between their cytoplasmic tips. A pair of trimers, together with a dedicated kinase enzyme, form a core signaling complex.

Long-term positioning and polar preference of chemoreceptor clusters in E. coli.

The bacterial chemosensory arrays are a notable model for studying the basic principles of receptor clustering and cellular organization. Here, we provide a new perspective regarding the long-term dynamics of these clusters in growing E. coli cells.

Dynamic Clustering of the Bacterial Sensory Kinase BaeS.

Several bacterial sensory-kinase receptors form clusters on the cell membrane. However, the dynamics of sensory-kinase clustering are largely unclear. Using measurements of fluorescence anisotropy and time-lapse imaging of Escherichia coli cells, we demonstrate that copper ions trigger self-association of BaeS receptors and lead to rapid formation of clusters, which can be reversibly dispersed by a metal chelator.

The role of motility and chemotaxis in the bacterial colonization of protected surfaces.

Internal epithelial surfaces in humans are both oxygenated and physically protected by a few hundred microns thick hydrogel mucosal layer, conditions that might support bacterial aerotaxis. However, the potential role of aerotaxis in crossing such a thin hydrogel layer is not clear. Here, we used a new setup to study the potential role of motility and chemotaxis in the bacterial colonization of surfaces covered by a thin hydrogel layer and subjected to a vertical oxygen gradient.

The sensory histidine kinases TorS and EvgS tend to form clusters in Escherichia coli cells.

Microorganisms use multiple two-component sensory systems to detect changes in their environment and elicit physiological responses. Despite their wide spread and importance, the intracellular organization of two-component sensory proteins in bacteria remains little investigated. A notable exception is the well-studied clustering of the chemoreceptor-kinase complexes that mediate chemotaxis behaviour.

The physical and functional thermal sensitivity of bacterial chemoreceptors.

The bacterium Escherichia coli exhibits chemotactic behavior at temperatures ranging from approximately 20 °C to at least 42 °C. This behavior is controlled by clusters of transmembrane chemoreceptors made from trimers of dimers that are linked together by cross-binding to cytoplasmic components. By detecting fluorescence energy transfer between various components of this system, we studied the underlying molecular behavior of these receptors in vivo and throughout their operating temperature range.

Disrupted gene pattern in patients with repeated in vitro fertilization (IVF) failure.

Background: Repeated implantation failure (RIF) is a severe obstacle in human assisted reproduction treatment.

Methods: Aiming to identify global gene profile in RIF patients, gene-array analyses were performed on endometrial samples collected on day 21 of the cycle from fertile women (n = 12) and from RIF patients (n = 20). Validation of cyclin E2, Slug, dickkopf homolog 1 (DKK1), lymphoid enhancer-binding factor 1 (LEF1) and secreted frizzled-related protein 1 (SFRP1) was carried out by real-time PCR.

Transcription of steroidogenic acute regulatory protein in the rodent ovary and placenta: alternative modes of cyclic adenosine 3', 5'-monophosphate dependent and independent regulation.

Steroid hormone synthesis is a vital function of the adrenal cortex, serves a critical role in gonadal function, and maintains pregnancy if normally executed in the placenta. The substrate for the synthesis of all steroid hormones is cholesterol, and its conversion to the first steroid, pregnenolone, by the cholesterol side-chain cleavage cytochrome P450 (CYP11A1) enzyme complex takes place in the inner mitochondrial membranes. Steroidogenic acute regulatory protein (STAR) facilitates the rate-limiting transfer of cholesterol from the outer mitochondrial membrane to CYP11A1 located in the inner organelle membranes.

Changing etiology of tubal pregnancy following IVF.

Background: Tubal pregnancy (TP) is twice as common following IVF when compared with natural conception. This is surprising, since embryo transfer is aimed for an accurate area in the uterine cavity. We thus hypothesized that either the embryo or the Fallopian tube actively participates in a pathological process leading to implantation outside the uterine cavity.

Heparanase improves mouse embryo implantation.

Objective: To improve mouse embryonic implantation by recombinant heparanase supplementation. Heparanase, an endoglycosidase-degrading heparan sulfate proteoglycan, may have a role in embryonic implantation because of its enzymatic, angiogenic, and adhesive properties. Increasing endometrial receptivity could improve one of the most difficult pathologies in human fertility.

Mouse embryos generated from frozen-thawed oocytes can successfully survive a second cryopreservation.

Background: To determine whether mouse embryos generated from frozen-thawed oocytes can successfully survive a second cryopreservation.

Methods: Immature C57BL6*BALB/c female mice underwent superovulation and the collected oocytes were divided into three groups. Group A oocytes (n = 107) underwent IVF.

Transcription of cholesterol side-chain cleavage cytochrome P450 in the placenta: activating protein-2 assumes the role of steroidogenic factor-1 by binding to an overlapping promoter element.

Progesterone is essential to the sustenance of pregnancy in humans and other mammals. From the second trimester on, the human placenta is the sole origin of de novo synthesized steroid hormones. In mice, placentation at midgestation is accompanied by a temporal rise of steroid hormone synthesis commencing in the giant cells of the mouse trophoblast.

Uterine and placental expression of steroidogenic genes during rodent pregnancy.

The ontogeny and functional role of steroidogenesis during mammalian gestation is poorly understood. This review provides a summary of our recent findings on the spatio-temporal expression of key steroidogenic genes controlling progesterone synthesis in the uterus during mouse pregnancy. We have shown that onset of cholesterol side chain cleavage cytochrome P450 (P450scc) and a newly identified isoform of murine 3beta-hydroxysteroid dehydrogenase/isomerase type VI (3betaHSD VI) expression occurs upon decidualization of the uterine wall induced by implantation.