Fungal biofilm structure and its indications in invasive aspergillosis

Example of increased furrowing and white, non-sporing edges at lower oxygen levels (Kowalski et al., 2019)

Microorganisms can group together on a surface to form collections of cells called biofilms; one example of this is dental plaque. Grouping together as a community protects these cells from environments which they may not be able to survive alone, such as the wrong pH or a lack of water or oxygen. Biofilms may be made up of many different species of microorganism and these species may be varied further by strain. In a recent paper, Caitlin Kowalski and colleagues at the Geisel School of Medicine at Dartmouth, USA, studied the ability of Aspergillus fumigatus biofilms to grow in low oxygen environments and cause invasive aspergillosis in mice.  

Kowalski and colleagues exposed A. fumigatus to low levels of oxygen, which reflect the levels found in the lesions where the fungus grows in the lung, in order to identify genes and mechanisms involved in allowing the pathogen to grow under these conditions. They then discovered a specific mutation which allowed the strain to both grow better in low oxygen, but also cause disease better under these conditions. It remains to be discovered how this particular mutation allows the strain to grow more successfully and be more virulent in low oxygen. However in other fungal biofilms, for example the yeast Candida albicans, the colony can form wrinkles which improve oxygen penetration. Understanding how the structure of biofilm colony growth reflects advantages in the ability of the fungus to cause disease may allow clinicians and scientists to better predict the progression of disease and improve patient care.

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