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Biomedical biofilm research

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Rapid advances in biomedical research on biofilms have recently been made thanks to the Unisense range of microsensors.

Biofilms are colonies of micro-organisms, including bacteria and fungi, that are found just about everywhere including on your teeth, in the bathroom, and in sewers and drains. While many biofilms are benign, or even beneficial, there are biofilms that can have serious health implications.

In this blog, two case studies are presented on recent biomedical biofilm research Pseudomonas aeruginosa and lung infections. These case studies were originally posted on the Unisense website (http://www.unisense.com/selected_applications).

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 supportsPseudomonas aeruginosa biofilm growth and virulence. eLife, 6: e30205

O2 and N2O microprofiles in sputum samples from cystic fibrosis patients with chronic Pseudomonas aeruginosa lung infection

With the Unisense microsensors and the Unisense MicroProfiling System you can complete microprofiles in biofilms with extreme positioning accuracy (precision < 10 μm) and high spatial resolution to obtain valuable information about the microenvironment.

Kolpen et al. (2014) used the Unisense O2 and N2O microsensors to measure microprofiles in sputum samples from cystic fibrosis patients with chronic Pseudomonas aeruginosa infection. P. aeruginosa is the major cause of chronic lung infection of cystic fibrosis patients where the bacteria live as biofilm aggregates in the lungs. The biofilms can persist for years in the airways of the patient despite an active immune response and antibiotic therapy. The measurements in the paper by Kolpen et al. provided new insights about the microenvironment and growth of the P. aeruginosa biofilm which may lead to new treatment strategies.

Based on the O2 and N2O microsensor profiling measurements, the authors demonstrated that sputum samples from patients with chronic P. aeruginosa infection consist of an upper oxygenated zone and a lower anoxic zone below around 3 mm from the sputum surface (Figure 2). N2O production from the bacteria was mainly confined to the lower anoxic part and a maximum median concentration of 41.8 μM N2O was found. Significantly less N2O was found in control sputum samples from cystic fibrosis patients without infection. N2O is an intermediate in the denitrification pathway and the data indicated that P. aeruginosa may acquire energy for growth from denitrification when O2 is absent. Using the Unisense microsensors to obtain O2 and N2O concentration gradients with high spatial resolution, the authors could explore the microenvironment in the sputum and they demonstrated N2O production in clinical samples from infected cystic fibrosis patients for the first time.

Please read the full application note. The results are published in Kolpen et al. (2014) Nitrous oxide production in sputum from cystic fibrosis patients with chronic pseudomonas aeruginosa lung