Zwitterionic surface chemistry enhances detachment of bacteria under shear.

The ubiquitous nature of microorganisms, especially of biofilm-forming bacteria, makes biofouling a prevalent challenge in many settings, including medical and industrial environments immersed in liquid and subjected to shear forces. Recent studies have shown that zwitterionic groups are effective in suppressing bacteria and protein adhesion as well as biofilm growth. However, the effect of zwitterionic groups on the removal of surface-bound bacteria has not been extensively studied.

The PSL Polysaccharide Is a Social but Noncheatable Trait in Biofilms.

Extracellular polysaccharides are compounds secreted by microorganisms into the surrounding environment, and they are important for surface attachment and maintaining structural integrity within biofilms. The social nature of many extracellular polysaccharides remains unclear, and it has been suggested that they could function as either cooperative public goods or as traits that provide a competitive advantage. Here, we empirically tested the cooperative nature of the PSL polysaccharide, which is crucial for the formation of biofilms in We show that (i) PSL is not metabolically costly to produce; (ii) PSL provides population-level benefits in biofilms, for both growth and antibiotic tolerance; (iii) the benefits of PSL production are social and are shared with other cells; (iv) the benefits of PSL production appear to be preferentially directed toward cells which produce PSL; (v) cells which do not produce PSL are unable to successfully exploit cells which produce PSL.

Role of Multicellular Aggregates in Biofilm Formation.

Unlabelled: In traditional models ofin vitrobiofilm development, individual bacterial cells seed a surface, multiply, and mature into multicellular, three-dimensional structures. Much research has been devoted to elucidating the mechanisms governing the initial attachment of single cells to surfaces. However, in natural environments and during infection, bacterial cells tend to clump as multicellular aggregates, and biofilms can also slough off aggregates as a part of the dispersal process.

Shaping the Growth Behaviour of Biofilms Initiated from Bacterial Aggregates.

Bacterial biofilms are usually assumed to originate from individual cells deposited on a surface. However, many biofilm-forming bacteria tend to aggregate in the planktonic phase so that it is possible that many natural and infectious biofilms originate wholly or partially from pre-formed cell aggregates. Here, we use agent-based computer simulations to investigate the role of pre-formed aggregates in biofilm development.

Osmotically-induced tension and the binding of N-BAR protein to lipid vesicles.

The binding affinity of a curvature-sensing protein domain (N-BAR) is measured as a function of applied osmotic stress while the membrane curvature is nearly constant. Varying the osmotic stress allows us to control membrane tension, which provides a probe of the mechanism of binding. We study the N-BAR domain of the Drosophila amphiphysin and monitor its binding on 50 nm-radius vesicles composed of 90 mol% DOPC and 10 mol% PIP.

Single-cell control of initial spatial structure in biofilm development using laser trapping.

Biofilms are sessile communities of microbes that are spatially structured by an embedding matrix. Biofilm infections are notoriously intractable. This arises, in part, from changes in the bacterial phenotype that result from spatial structure.

Change of line tension in phase-separated vesicles upon protein binding.

We measured the effect of a model membrane-binding protein on line tension and morphology of phase-separated lipid-bilayer vesicles. We studied giant unilamellar vesicles composed of a cholesterol/dioleoylphosphatidylcholine/palmitoylsphingomyelin mixture and a controlled mole fraction of a Ni-chelating lipid. These vesicles exhibited two coexisting fluid-phase domains at room temperature.