Verticalization of bacterial biofilms

Biofilms are communities of bacteria adhered to surfaces. Recently, biofilms of rod-shaped bacteria were observed at single-cell resolution and shown to develop from a disordered, two-dimensional layer of founder cells into a three-dimensional structure with a vertically-aligned core. Here, we elucidate the physical mechanism underpinning this transition using a combination of agent-based and continuum modeling. We find that verticalization proceeds through a series of localized mechanical instabilities on the cellular scale. For short cells, these instabilities are primarily triggered by cell division, whereas long cells are more likely to be peeled off the surface by nearby vertical cells, creating an "inverse domino effect". The interplay between cell growth and cell verticalization gives rise to an exotic mechanical state in which the effective surface pressure becomes constant throughout the growing core of the biofilm surface layer. This dynamical isobaricity determines the expansion speed of a biofilm cluster and thereby governs how cells access the third dimension. In particular, theory predicts that a longer average cell length yields more rapidly expanding, flatter biofilms. We experimentally show that such changes in biofilm development occur by exploiting chemicals that modulate cell length.Comment: Main text 10 pages, 4 figures; Supplementary Information 35 pages, 15 figure

Thinking the unthinkable: Imagining an ‘un-American,’ Girl-friendly, Women- and Trans-Inclusive Alternative for Baseball

The purpose of this article is twofold: to capture the injustice inherent in the gendered bifurcation of baseball and softball via the prism of critical feminist sport studies; and to begin to imagine a girl-friendly/women-and trans-inclusive future for baseball that is less fertile for cooptation into post-911 United States security state discourses. In this article I link the "unthinkability" of the occupational segregation of baseball in North America to the dominance of the ideology of the two sex system and European disasporic morality. To illustrate the extent of this occupational segregation via the gendered bifurcation of baseball and softball, I draw on feminist sport studies to examine the exemplars or "texts" of three Canadian brother/sister baseball softball duos: Jason Bay and Lauren Bay Regula; Brett and Danielle Lawrie; and Mathew and Katie Reyes

Interinstitutional variations in mode of birth after a previous caesarean section : a cross-sectional study in six German hospitals

Aims: Regional and interinstitutional variations have been recognized in the increasing incidence of caesarean section. Modes of birth after previous caesarean section vary widely, ranging from elective repeat caesarean section (ERCS) and unplanned repeat caesarean section (URCS) after trial of labour to vaginal birth after caesarean section (VBAC). This study describes interinstitutional variations in mode of birth after previous caesarean section in relation to regional indicators in Germany. Material and methods: A cross-sectional study using the birth registers of six maternity units (n=12,060) in five different German states (n=370,209). Indicators were tested by χ2 and relative deviations from regional values were expressed as relative risks and 95% confidence intervals. Results: The percentages of women in the six units with previous caesarean section ranged from 11.9% to 15.9% (P=0.002). VBAC was planned for 36.0% to 49.8% (P=0.003) of these women, but actually completed in only 26.2% to 32.8% (P=0.66). Depending on the indicator, the units studied deviated from the regional data by up to 32% [relative risk 0.68 (0.47–0.97)] in respect of completed VBAC among all initiated VBAC. Conclusions: There is substantial interinstitutional variation in mode of birth following previous caesarean section. This variation is in addition to regional patterns

Spatiotemporal Correlations between Blood-Brain Barrier Permeability and Apparent Diffusion Coefficient in a Rat Model of Ischemic Stroke

Variations in apparent diffusion coefficient of water (ADC) and blood-brain barrier (BBB) permeability after ischemia have been suggested, though the correlation between ADC alterations and BBB opening remains to be studied. We hypothesized that there are correlations between the alteration of ADC and BBB permeability. Rats were subjected to 2 h of transient middle cerebral artery occlusion and studied at 3 and 48 h of reperfusion, which are crucial times of BBB opening. BBB permeability and ADC values were measured by dynamic contrast-enhanced MRI and diffusion-weighted imaging, respectively. Temporal and spatial analyses of the evolution of BBB permeability and ADC alteration in cortical and subcortical regions were conducted along with the correlation between ADC and BBB permeability data. We found significant increases in BBB leakage and reduction in ADC values between 3 and 48 h of reperfusion. We identified three MR tissue signature models: high Ki and low ADC, high Ki and normal ADC, and normal Ki and low ADC. Over time, areas with normal Ki and low ADC transformed into areas with high Ki. We observed a pattern of lesion evolution where the extent of initial ischemic injury reflected by ADC abnormalities determines vascular integrity. Our results suggest that regions with vasogenic edema alone are not likely to develop low ADC by 48 h and may undergo recovery

Burkholderia Type VI Secretion Systems Have Distinct Roles in Eukaryotic and Bacterial Cell Interactions

Bacteria that live in the environment have evolved pathways specialized to defend against eukaryotic organisms or other bacteria. In this manuscript, we systematically examined the role of the five type VI secretion systems (T6SSs) of Burkholderia thailandensis (B. thai) in eukaryotic and bacterial cell interactions. Consistent with phylogenetic analyses comparing the distribution of the B. thai T6SSs with well-characterized bacterial and eukaryotic cell-targeting T6SSs, we found that T6SS-5 plays a critical role in the virulence of the organism in a murine melioidosis model, while a strain lacking the other four T6SSs remained as virulent as the wild-type. The function of T6SS-5 appeared to be specialized to the host and not related to an in vivo growth defect, as ΔT6SS-5 was fully virulent in mice lacking MyD88. Next we probed the role of the five systems in interbacterial interactions. From a group of 31 diverse bacteria, we identified several organisms that competed less effectively against wild-type B. thai than a strain lacking T6SS-1 function. Inactivation of T6SS-1 renders B. thai greatly more susceptible to cell contact-induced stasis by Pseudomonas putida, Pseudomonas fluorescens and Serratia proteamaculans—leaving it 100- to 1000-fold less fit than the wild-type in competition experiments with these organisms. Flow cell biofilm assays showed that T6S-dependent interbacterial interactions are likely relevant in the environment. B. thai cells lacking T6SS-1 were rapidly displaced in mixed biofilms with P. putida, whereas wild-type cells persisted and overran the competitor. Our data show that T6SSs within a single organism can have distinct functions in eukaryotic versus bacterial cell interactions. These systems are likely to be a decisive factor in the survival of bacterial cells of one species in intimate association with those of another, such as in polymicrobial communities present both in the environment and in many infections

Untersuchungen zur sensorischen Qualitaet und zur Vitaminwertigkeit von UHT-Milch und pasteurisierter Milch

Available from: Zentralstelle fuer Agrardokumentation und -information (ZADI), Villichgasse 17, D-53177 Bonn / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman