The role of biofilm matrix composition in controlling colony expansion and morphology.

Biofilms are biological viscoelastic gels composed of bacterial cells embedded in a self-secreted polymeric extracellular matrix (ECM). In environmental settings, such as in the rhizosphere and phyllosphere, biofilm colonization occurs at the solid-air interface. The biofilms' ability to colonize and expand over these surfaces depends on the formation of osmotic gradients and ECM viscoelastic properties.

Experimental challenges in determining the rheological properties of bacterial biofilms.

Bacterial biofilms are communities living in a matrix consisting of self-produced, hydrated extracellular polymeric substances. Most microorganisms adopt the biofilm lifestyle since it protects by conferring resistance to antibiotics and physico-chemical stress factors. Consequently, mechanical removal is often necessary but rendered difficult by the biofilm's complex, viscoelastic response, and adhesive properties.

The role of surface adhesion on the macroscopic wrinkling of biofilms.

Biofilms, bacterial communities of cells encased by a self-produced matrix, exhibit a variety of three-dimensional structures. Specifically, channel networks formed within the bulk of the biofilm have been identified to play an important role in the colonies' viability by promoting the transport of nutrients and chemicals. Here, we study channel formation and focus on the role of the adhesion of the biofilm matrix to the substrate in biofilms grown under constant flow in microfluidic channels.

Designer liquid-liquid interfaces made from transient double emulsions.

Current methods for generating liquid-liquid interfaces with either controlled composition or coverage often rely on adsorption equilibria which limits the freedom to design such multiphase materials, in particular when different components are used. Moreover, when interfaces become densely populated, slowing down of adsorption may impose additional constraints. Up to now, it is not possible to control surface coverage and composition of droplet interfaces at will.

Dying in yoghurt: the number of living bacteria in probiotic yoghurt decreases under exposure to room temperature.

Background/aims: While probiotic bacteria are successfully used in the treatment of ulcerative colitis, the effect of commercially available probiotic products is still controversial. Here, we study whether the number of living probiotic bacteria in yoghurts is altered by an interruption of the cold chain.

Methods: Three commonly available probiotic yoghurts were kept at 4°C or put at room temperature (RT) for 6 h or 24 h.