Bacterial infections are especially resilient to treatment when individual bacteria group together and form what is known as a biofilm. Biofilm formation can now be studied as it happens using chemicals that fluoresce at different wavelengths as their conformation changes.
Understanding of the dynamics of biofilm formation was previously hindered by the lack of suitable research tools.
Until now there were no methods specific for detecting biofilm. Today, researchers can use microscopes to see individual bacteria but not the extracellular slime. The dyes currently used bind non-specifically to charged molecules, including bacterial protein and DNA which quickly leads to cell death.
The molecular chameleons that have been developed in the current study provide an optical fingerprint, depending on what they bind to. A portion of the molecule has the ability to emit light, while the second portion can bind specifically to a target molecule, in this case the biofilm. When bound to the bacterial extracellular slime, the molecular chameleons changes colour.
"The molecules we have developed are unique in that they can send out different colors, depending on how they twist and bend. We usually call them molecular chameleons, because they change color according to the environment," says Professor Peter Nilsson, Linköping University, whose research team synthesised the tracking molecules.
"This is the first method that specifically dyes the biofilm components. This means that researchers who want to study the mechanisms behind how bacteria form biofilms now have a new tool to understand the process," says Professor Agneta Richter-Dahlfors at Karolinska Institutet, who led the study.
In the study, the researchers demonstrate how the method can be used to study Salmonella bacteria, both in culture dishes and in infected tissue. Researchers hope that this method will eventually be of use in both the healthcare and food industries where biofilms cause waste and serious illness. However, there are also situations where the ability of bacteria to form biofilms is positive, for example when the bacteria are used to produce biogas for fuel.
"We are very excited to be able to provide this new tool for microbial researchers to be able to use and we are looking forward to seeing new results in the near future", says Professor Agneta Richter-Dahlfors.
The research was funded with support from the Swedish Foundation for Strategic Research, Erling-Persson Family Foundation,Carl Bennet AB the Swedish Research Council. Some of the researchers behind the study is part owner of a company that could commercialize molecules for use in medicine and industry.
"Real-time opto-tracing of curli and cellulose into live Salmonella biofilms using luminescent oligothiophenes"
Ferdinand X. Choong, Marcus Brooks, Sara Fahlén, BG Leif Johansson, Keira Melican, Michael Rhine, K. Peter R Nilsson, Agneta Richter Dahlfors
Nature Journal Biofilms and Microbiomes, published online 23 October 2016, doi: 10.1038/npjbiofilms.2016.24