Abstract
One of the physiological responses of bacteria to external stress is to assemble into a biofilm. The formation of a biofilm greatly increases a bacterial population's resistance to a hostile environment by shielding cells, for example, from antibiotics. In this paper, we describe the conditions necessary for the emergence of biofilms in natural environments and relate them to the emergence of biofilm formation inside microfluidic devices. We show that competing species of Escherichia coli bacteria form biofilms to spatially segregate themselves in response to starvation stress, and use in situ methods to characterize the physical properties of the biofilms. Finally, we develop a microfluidic platform to study the inter-species interactions and show how biofilm-mediated genetic interactions can improve a species’ resistance to external stress.
Highlights
A natural response of many species of bacteria to increasing levels of stress is the formation of biofilms, in which cells assemble together and produce large amounts of a polysaccharide-based exopolymer matrix [1]
Given what we have shown in the previous section, that biofilm development for E. coli is highly dependent on the planktonic cell density, one might expect that the more complex redistribution of cells found during competition experiments, especially those observed in rapidly alternating fitness landscapes, would translate into more complex biofilm developmental dynamics
First we showed that the Keller–Segel model, when applied to bacterial self-interactions via signaling molecules, provides the first step toward the formation of biofilms through a fundamental instability, which prompts bacterial populations to crowd into small volumes
Summary
A natural response of many species of bacteria to increasing levels of stress is the formation of biofilms, in which cells assemble together and produce large amounts of a polysaccharide-based exopolymer matrix [1]. Since the diffusion of metabolites and chemicals is greatly limited inside the matrix [4], the microenvironment created by a biofilm is highly heterogeneous and physiologically stressful [5]. It is, accompanied by a high level of specialization within the bacterial community. In humans with bacterial infections, antibiotic treatment is often ineffective because the limited diffusivity inside a biofilm decreases the actual dose that reaches the bacteria. These communities combine and recombine in a process called flocculation, and are ubiquitous from the laboratory to the ocean [11] These flocs are properly perceived as suspended pieces of biofilm. We will discuss how microfabricated structures can be used to study the formative dynamics of biofilms, and present some of the mysteries that arise from these devices that we still do not understand
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