Abstract
Microbes living in biofilms, dense assemblages of cells, experience limitation for resources such as oxygen when cellular consumption outpaces diffusion. The pathogenic bacterium Pseudomonas aeruginosa has strategies for coping with hypoxia that support cellular redox balancing in biofilms; these include (1) increasing access to oxygen by forming wrinkles in the biofilm surface and (2) electrochemically reducing endogenous compounds called phenazines, which can shuttle electrons to oxidants available at a distance. Phenazine-mediated extracellular electron transfer (EET) has been shown to support survival for P. aeruginosa cells in anoxic liquid cultures, but the physiological relevance of EET over a distance for P. aeruginosa biofilms has remained unconfirmed. Here, we use a custom-built electrochemistry setup to show that phenazine-mediated electron transfer at a distance inhibits wrinkle formation in P. aeruginosa biofilms. This result demonstrates that phenazine-dependent EET to a distal oxidant affects biofilm morphogenesis.
Highlights
Microbes commonly grow as biofilms, assemblages of cells that adhere to each other and to objects using a self-produced polysaccharide matrix
To allow us to test the effect of electron transfer over a distance on biofilm development, we designed an apparatus that mimics our standard biofilm growth conditions but that provides compatibility with external electrochemical stimulation (Fig. 1B)
A reticulated vitreous carbon (RVC) foam electrode was chosen as the working electrode for its large area to volume ratio and was fully submerged in the agar-solidified growth medium
Summary
Microbes commonly grow as biofilms, assemblages of cells that adhere to each other and to objects using a self-produced polysaccharide matrix. Microelectrode measurements of biofilms reveal that with increasing distance from the surface of the biofilm, O2 concentrations fall below the limit of detection (0.3 μM) and the extracellular phenazine pool becomes more reduced [9,12] Together, these observations suggest that oxidant availability is a cue that inhibits matrix production in the median biofilm subzone. These observations suggest that oxidant availability is a cue that inhibits matrix production in the median biofilm subzone Consistent with their favorable redox potentials and redox-cycling properties, phenazines promote survival in anaerobic P. aeruginosa cell suspensions when an electrode is provided to support phenazine oxidation [8]. We describe the use of this device to test whether P. aeruginosa biofilms catalyze phenazine-mediated electron transfer at a distance and whether this activity inhibits biofilm wrinkle formation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
