Previous research on a fungus called Ulocladium chartarum -- a species harmless to healthy humans -- underwent a variety of changes when grown in space compared to on Earth. The appearance of hyphae (the protrusive part of fungal cells involved in absorption of nutrients) was less dense, and hyphae were significantly shorter. The colour of the colony also changed, with a yellowish appearance instead of a colourless colony.
A recent study published in the PLoS ONE journal describes the effect of space-flight on Candida albicans. Similarly to Aspergillus, Candida species can cause a variety of infections, from mucosal infection (thrush) to systemic and often fatal infections called candidiasis. Since astronauts are considered at risk in terms of immune function, and because systemic C. albicans infections occur more commonly in those with a reduced immune function, the aim of this study was to determine any genetic and physical changes to the fungus which could lead to an impact on human health in space.
Overall, 452 genes were found to be expressed differently by C. albicans in space compared to when the same strain is grown in normal gravity conditions. The genes involved had a variety of functions, from helping the yeast cells stick together to influencing resistance to antifungal drugs. Whether this translates to a more resistant organism, though, has yet to be determined by laboratory testing.
Nevertheless, the study presents interesting variations on the C. albicans strain testing and it is the first example of a common human fungal pathogen (and commensal organism) being studied under a microgravity scenario. Crucially, the study also opens the way for further testing of fungal species including the common mould Aspergillus fumigatus.