Most bacteria have the ability to form communities, biofilms, that adhere to a wide variety of surfaces and are difficult to remove. This can lead to major problems, for example in hospitals or in the food industry.
A research team has studied a model system for biofilms at the synchrotron radiation facilities BESSY II at HZB and the ESRF and found out what role the structures within the biofilm play in the distribution of nutrients and water.
Bacterial biofilms can thrive on almost all types of surfaces: We find them on rocks and plants, on teeth and mucous membranes, but also on contact lenses, medical implants or catheters, in the hoses of the dairy industry or drinking water pipes, where they can pose a serious threat to human health. Some biofilms are also useful, for example, in the production of cheese, where specific types of biofilms not only produce the many tiny holes, but also provide its delicious taste.
Together, the bacteria within a biofilm form a protective layer of carbohydrates and proteins, the so-called extracellular matrix. This matrix protects the bacteria from disinfectants, UV radiation or desiccation and ensures that biofilms are really difficult to remove mechanically or eradicate chemically. However, the matrix is not a homogeneous sludge:
As samples, the scientists used biofilms from Bacillus subtilis, a harmless bacterium that thrives on plant roots and forms a useful symbiosis with them: it stores water so that the plant can possibly take moisture from the biofilm during drought and they also protect the roots from pathogens. In return, the cells in the biofilm feeds on root exudates. Nevertheless, Bacillus subtilis bacteria can serve as a model system for many other bacterial biofilms.
The scientists were able to spatially resolve the structures within the biofilm and distinguish well between matrix components, bacterial cells, spores and water using X-ray fluorescence spectroscopy.
The evaluation shows that calcium ions preferentially accumulate in the matrix, while zinc, manganese and iron ions accumulate along the wrinkles, where they can possibly trigger the formation of spores, which are important for the dispersion of the bacteria.
The results show that the structures in the matrix not only play an important role in the distribution of nutrients and water, but also actively influence the bacteria's ability to behave as a multicellular organism. "This could help us to better deal with biofilms overall, with the beneficial ones as well as the harmful ones," says Liraz Chai.
David N. Azulay, Oliver Spaeker, Mnar Ghrayeb, et al. Multiscale X-ray study of Bacillus subtilis biofilms reveals interlinked structural hierarchy and elemental heterogeneity. Proceedings of the National Academy of Sciences, 2022; 119 (4): e2118107119 DOI: 10.1073/pnas.2118107119
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)
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