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Biofilm - Oxygen and redox potential in P. aeruginosa

Oxygen and redox potential in Pseudomonas aeruginosa colony biofilms

Associate Professor Lars Dietrich and his research group at Columbia University routinely use Unisense oxygen microsensors and redox microelectrodes to characterize the chemical gradients that form in bacterial colony biofilms.

The Dietrich lab focuses mainly on Pseudomonas aeruginosa PA14 which is a gram-negative pathogen involved in e.g. lung infections. They use the Unisense microsensors together with the Unisense Microprofiling System to obtain valuable information about the biofilm microenvironment and redox metabolism. In this study, the reduction of phenazines, which are antibiotics produced by P. aeruginosa, was investigated.

The figure shows the oxygen concentration and redox potential as a function of depth in the wild-type P. aeruginosa colony biofilm and a phenazinenull mutant (no phenazine production). The oxygen gradient in the wildtype and mutant biofilms decreased similarly from the surface and down into the biofilm. The redox potential in the wild-type biofilm decreased with depth whereas the redox potential in the mutant remained the same throughout the biofilm. The decrease of redox potential in the wild type indicated reduction of the phenazines. The decline in oxygen concentration was seen right from the surface of the wild-type biofilm whereas the decline in redox potential was mostly pronounced at around 50 μm depth.

The data suggested that the use of oxygen and phenazines as electron acceptors by the bacteria is depending on the depth in the biofilm and that oxygen is preferred. The reduction of phenazines in the hypoxic zones of the biofilm could contribute to survival of the bacteria and may be an important finding for the development of new treatment strategies.

For further reading please see the full application note and the article: Jo et al. (2017) An orphan cbb3-type cytochrome oxidase subunit supports Pseudomonas aeruginosa biofilm growth and virulence. eLife, 6: e30205


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