During development, organisms acquire three-dimensional 3D shapes with important physiol. While basic mechanisms underlying morphogenesis are known in eukaryotes, it is often difficult to manipulate them in vivo. To circumvent this issue, here we present a study of developing Vibrio cholerae biofilms grown on agar substrates in which the spatiotemporal morphol.
Expanding biofilms are initially flat but later undergo a mech. Our model shows quant. Our results, which establish that nonuniform growth and friction are fundamental determinants of stress anisotropy and hence biofilm morphol. We discuss the implications of forming undulated biofilm morphologies, which may enhance the availability of nutrients and signaling mols.
A three-dimensional phase diagram of growth-induced surface instabilities. Probing phenotypic growth in expanding Bacillus subtilis biofilms. Wang, Xiaoling; Koehler, Stephan A. We develop an optical imaging technique for spatially and temporally tracking biofilm growth and the distribution of the main phenotypes of a Bacillus subtilis strain with a triple-fluorescent reporter for motility, matrix prodn.
We develop a calibration procedure for detg. To obtain the phenotype distribution, we assume a linear relationship between the no. Based on this anal. We take advantage of the circular growth to make kymograph plots of all three phenotypes and the dominant phenotype in terms of radial distance and time. To visualize the nonlocal character of biofilm growth, we also make kymographs using the local colonization time. Our technique is suitable for real-time, noninvasive, quant. Nutrient depletion in Bacillus subtilis biofilms triggers matrix production.
New J. Extracellular-matrix-mediated osmotic pressure drives Vibrio cholerae biofilm expansion and cheater exclusion. Nature communications , 8 1 , ISSN:. Biofilms, surface-attached communities of bacteria encased in an extracellular matrix, are a major mode of bacterial life. How the material properties of the matrix contribute to biofilm growth and robustness is largely unexplored, in particular in response to environmental perturbations such as changes in osmotic pressure.
Here, using Vibrio cholerae as our model organism, we show that during active cell growth, matrix production enables biofilm-dwelling bacterial cells to establish an osmotic pressure difference between the biofilm and the external environment.
This pressure difference promotes biofilm expansion on nutritious surfaces by physically swelling the colony, which enhances nutrient uptake, and enables matrix-producing cells to outcompete non-matrix-producing cheaters via physical exclusion. Osmotic pressure together with crosslinking of the matrix also controls the growth of submerged biofilms and their susceptibility to invasion by planktonic cells.
As the basic physicochemical principles of matrix crosslinking and osmotic swelling are universal, our findings may have implications for other biofilm-forming bacterial species. Most bacteria live in biofilms, surface-attached communities encased in an extracellular matrix. Here, Yan et al. Osmotic spreading of Bacillus subtilis biofilms driven by an extracellular matrix.
Seminara, Agnese; Angelini, Thomas E. Bacterial biofilms are organized communities of cells living in assocn. The hallmark of biofilm formation is the secretion of a polymeric matrix rich in sugars and proteins in the extracellular space.
In Bacillus subtilis, secretion of the exopolysaccharide EPS component of the extracellular matrix is genetically coupled to the inhibition of flagella-mediated motility. The onset of this switch results in slow expansion of the biofilm on a substrate. Different strains have radically different capabilities in surface colonization. Flagella-null strains spread at the same rate as wild type, while both are dramatically faster than EPS mutants. Multiple functions have been attributed to the EPS, but none of these provides a phys.
The authors propose that the secretion of EPS drives surface motility by generating osmotic pressure gradients in the extracellular space. A simple math. The authors discuss the implications of this osmotically driven type of surface motility for nutrient uptake that may elucidate the reduced fitness of the matrix-deficient mutant strains. Liquid transport facilitated by channels in Bacillus subtilis biofilms. Wilking, James N. Many bacteria on Earth exist in surface-attached communities known as biofilms.
These films are responsible for manifold problems, including hospital-acquired infections and biofouling, but they can also be beneficial.
Biofilm growth depends on the transport of nutrients and waste, for which diffusion is thought to be the main source of transport. However, diffusion is ineffective for transport over large distances and thus should limit growth. Nevertheless, biofilms can grow to be very large. Here, the authors report the presence of a remarkable network of well defined channels that form in wild-type Bacillus subtilis biofilms and provide a system for enhanced transport.
They observe that these channels have high permeability to liq. These channels offer a remarkably simple system for liq. Elastic and viscoelastic characterization of agar. Elsevier B. Agar is a biol. In this study, nanoindentation was used to characterize both the time-independent and time-dependent response of agar samples having various concns. Quasi-static indentation was performed at different loads and depths using both open- and closed-loop controls.
Reduced modulus Er values change with agar concn. Dynamic indentation was performed to assess the effects of load, dynamic frequency and amplitude.
Storage modulus values ranged from approx. Loss modulus remained consistently less than 30 kPa at all conditions, indicating a diminished damping response in agar. Influence of agar content on the growth parameters of Bacillus cereus. Food Microbiol. Surface-attached bacterial communities called biofilms display a diversity of morphologies. Although structural and regulatory components required for biofilm formation are known, it is not understood how these essential constituents promote biofilm surface morphol.
Here, using Vibrio cholerae as our model system, we combine mech. We also identify interfacial energy as a key driving force for mechanomorphogenesis because it dictates the generation of new and the annihilation of existing interfaces. Finally, we discover feedback between mechanomorphogenesis and biofilm expansion, which shapes the overall biofilm contour. The morphogenesis principles that we discover in bacterial biofilms, which rely on mech.
Phosphoethanolamine cellulose: A naturally produced chemically modified cellulose. Science , , — , DOI: Thongsomboon, Wiriya; Serra, Diego O. American Association for the Advancement of Science.
Cellulose is a major contributor to the chem. We find that Escherichia coli produces chem. Solid-state NMR spectroscopy of the intact and insol. Installation of the phosphoethanolamine group requires BcsG, a proposed phosphoethanolamine transferase, with biofilm-promoting cyclic diguanylate monophosphate input through a BcsE-BcsF-BcsG transmembrane signaling pathway.
The bcsEFG operon is present in many bacteria, including Salmonella species, that also produce the modified cellulose. The discovery of phosphoethanolamine cellulose and the genetic and mol. Vertical stratification of matrix production is essential for physical integrity and architecture of macrocolony biofilms of Escherichia coli.
Bacterial macrocolony biofilms grow into intricate three-dimensional structures that depend on self-produced extracellular polymers conferring protection, cohesion and elasticity to the biofilm.
In Escherichia coli, synthesis of this matrix - consisting of amyloid curli fibers and cellulose - requires CsgD, a transcription factor regulated by the stationary phase sigma factor RpoS, and occurs in the nutrient-deprived cells of the upper layer of macrocolonies. Is this asym. This re-wiring of csgD led to CsgD and matrix prodn. As a result, the two strata broke apart followed by desiccation and exfoliation of the top layer. By contrast, matrix-free cells at the bottom of wild-type macrocolonies maintain colony contact with the humid agar support by flexibly filling the space that opens up under buckling areas of the macrocolony.
Precisely regulated stratification in matrix-free and matrix-producing cell layers is thus essential for the phys.
Variation in the ratio of curli and phosphoethanolamine cellulose associated with biofilm architecture and properties.
Biopolymers , , 1 — 11 , DOI: A multiphase theory for spreading microbial swarms and films. Stress responses go three dimensional - The spatial order of physiological differentiation in bacterial macrocolony biofilms. Summary : In natural habitats, bacteria often occur in multicellular communities characterized by a robust extracellular matrix of proteins, amyloid fibers, exopolysaccharides and extracellular DNA. These biofilms show pronounced stress resistance including a resilience against antibiotics that causes serious medical and tech.
This review summarizes recent studies that have revealed clear spatial physiol. By responding to gradients of nutrients, oxygen, waste products and signalling compds.
As a consequence, biofilms differentiate into at least two distinct layers of vegetatively growing and stationary phase cells that exhibit very different cellular physiol.
This includes a stratification of matrix prodn. Using Escherichia coli as a model system, this review also describes our detailed current knowledge about the underlying mol. Elsevier Ltd. The extracellular matrix in macrocolony biofilms of Escherichia coli is arranged in a complex large-scale architecture, with homogenic matrix prodn. Combining genetics, cryosectioning and fluorescence microscopy of macrocolony biofilms, we demonstrate in situ that this local matrix heterogeneity is generated by a c-di-GMP-dependent mol.
In this switch, the trigger phosphodiesterase PdeR is the key component for establishing local heterogeneity in the activation of the transcription factor MlrA, which in turn activates expression of the major matrix regulator CsgD. Upon its release of direct inhibition by PdeR, the 2nd switch component, the diguanylate cyclase DgcM, activates MlrA by direct interaction. Antagonistically acting PdeH and DgcE provide for a PdeR-sensed c-di-GMP input into this switch and-via their spatially differentially controlled expression-generate the long-range vertical asymmetry of the matrix architecture.
Using flow cytometry, we show heterogeneity of CsgD expression to also occur in spatially unstructured planktonic cultures, where it is controlled by the same c-di-GMP circuitry as in macrocolony biofilms.
Quantification by flow cytometry also showed CsgDON subpopulations with distinct CsgD expression levels and revealed an addnl. Finally, local heterogeneity of matrix prodn. Functional bacterial amyloid increases Pseudomonas biofilm hydrophobicity and stiffness.
Bacterial collective motion near the contact line of an evaporating sessile drop. Fluids , 26 , , DOI: American Institute of Physics. The near-contact-line dynamics of evapg. The evapn. Our expts.
Based on a phys. Interfaces , 8 , , DOI: Ryzhkov, Nikolay V. Because bacteria-surface interactions play a decisive role in bacteria adhesion and biofilm spreading, it is essential to understand how biofilms respond to surface properties to develop effective strategies to combat them. Polyelectrolyte coating is a simple and efficient way of controlling surface charge and energy. Using polyelectrolytes of various types, with different mol. Here, the formation of Escherichia coli biofilms at a solid-air interface is explored, whereby charge and interfacial energy are tuned using polyelectrolyte coatings on the surface.
Cationic coatings are obsd. Interestingly, biofilm surface densities are higher on polycationic surfaces despite their well-studied bactericidal properties. Furthermore, the degree of polyelectrolyte protonation also appears to have an influence on biofilm spreading on polycation-coated substrates. Finally, altering the interplay between biomass prodn. Thereby, it is demonstrated that biofilm growth and spreading on a hydrogel substrate can be tuned from confined to expanded, simply by coating the surface using available polyelectrolytes.
Cellulose in Bacterial Biofilms. Bacillus subtilis biofilms characterized as hydrogels. Insights on water uptake and water binding in biofilms. Soft Matter , 16 , — , DOI: Biofilms are aggregates of cells that form on surfaces or at the air-water interface. Cells in a biofilm are encased in a self-secreted extracellular matrix ECM that provides them with mech. From a soft matter perspective, biofilms are regarded as colloidal hydrogels, with the cells playing the role of colloids and the ECM compared with a cross-linked hydrogel.
Here, we examd. We characterized the morphol. Our study revealed that Bacillus subtilis biofilms resemble cross-linked hydrogels in their morphol. Strikingly, we discovered that all the water in biofilms was bound water and there was no free water in the biofilms.
Water binding was mostly related with the presence of solutes and much less so with the major ECM components, the protein TasA and the polysaccharide EPS. This study sheds light on water uptake and water binding in biofilms and it is therefore important for the understanding of solute transport and enzymic function inside biofilms.
Biofilms as complex fluids. MRS Bull. Materials Research Society. Bacterial biofilms are interface-assocd. Selected Video Laryngoscopes. Summary Laryngoscopy is the primary means for placing a endotracheal tube during airway management in a variety of clinical settings. The author has disclosed no conflicts of interest. References 1. A short history of laryngoscopy. Logoped Phoniatr Vocol ; 21 : — OpenUrl PubMed. Green H Green H.
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Br J Anaesth ; 91 3 : — Alternative management techniques for the difficult airway: optical stylets. Curr Opin Anaesthesiol ; 17 6 : — Double lumen tube placement with the Bullard laryngoscope. Can J Anaesth ; 46 3 : — A comparison of the Bullard laryngoscope versus the flexible fiberoptic bronchoscope during intubation in patients afforded inline stabilization. J Clin Anesth ; 13 3 : — Comparison of the Bullard and Macintosh laryngoscopes for endotracheal intubation of patients with a potential cervical spine injury.
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Did the system actually catch that button press or was it busy with something else and it ignored it? Did the item get added to cart? Did the request go through? However, even when the happy day of bug-free technology arrives, people will still wonder if they really clicked or tapped correctly. Appropriate feedback for a user action is perhaps the most basic guideline of user-interface design. It serves to keep users informed of the current status and to allow them to steer the interaction in the right direction, without wasting effort.
Such feedback can be as simple as a change of color once the user has clicked on a button, or a progress indicator when a process needs a little longer to finish. In this video clip from our mobile eyetracking study, the user has clicked on a button and is unsure whether a new page is actually loading because there is no feedback. The hollow red circle shows where the user is fixating on the screen. We can see that she looks back and forth between the button and the top of the screen, where a progress indicator for the page load typically appears, to assess whether anything is happening.
In most browsers, hover over the video to display the controls if they're not already visible. Providing immediate feedback for interactive events allows users to quickly identify the source of errors and fix them as soon as they were made. In fact, immediate feedback is one of the main benefits of direct manipulation , an interaction style in which users can act directly upon different UI objects.
In contrast to direct-manipulation UIs, command-line interfaces do not display the current state of the system, nor do they give immediate feedback. Programmers know how difficult it can be to locate the source of an error in an interface which lacks immediate feedback; they often have to resort to tools such as breakpoints and stepping to understand how the state of the system changes with each action specified in their code.
The real difference between these ancient command-line UIs and modern GUI designs is not the presence of colorful icons. Even when users cannot see the effect of an action because the system does not have a screen like is the case for voice-only devices such as Amazon Echo and Google Home , a minimum feedback that the command was heard is essential.
Modern systems are often complex, and it is unreasonable to assume that all the variables that describe the state of a system can be communicated to the user. Many backstage components , such as what JavaScript files are downloading and executing to make a site work, are of little interest to users. Yet, occasionally backstage aspects can actually play an important role frontstage. Take, for instance, the case of inventory size.
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