Fungal Growth Rates on Three ISS Dust Samples, by Relative Humidity and Exposure Duration
| RH level | Duration (hours/day) | Fungal growth rate (generations/day) |
|---|---|---|
| 85% | 12 | 1.293 |
| 100% | 18 | 2.066 |
| 100% | 24 | 2.3545 |
Just like household dust on Earth, dust on the International Space Station (ISS) harbors hundreds of common microorganisms—Aspergillus sydowii and other fungi, along with bacteria, such as Corynebacterium kroppenstedtii. According to experiments conducted using samples of ISS dust of initially similar compositions, changes in both relative humidity (RH) and duration of humidity exposure elicited changes in growth for both fungal and bacterial species. However, when overall fungal growth increased, it was mainly due to an increase in growth of A. sydowii, whereas bacterial growth was widely distributed across species in the samples.