Investigation into Space Effects on Biofilm Growth Using Simulated Microgravity

Bacterial growth in liquid media while under microgravity conditions is not well understood. Trends such as a shortened lag phase, longer log phase, slower growth rate, and a higher final population concentration have been noted but the underlying cause remains unclear. Ground-based spaceflight analogs, or simulated microgravity devices, are often employed to achieve different attributes of weightlessness to study effects on bacterial growth. Though these technologies could isolate gravity’s role in various biological processes, they cannot replicate all its effects and underlying mechanisms. Hence, results could be misleading even if they are similar to spaceflight. At the single cell level, it is predicted that bacteria are less gravity-sensitive than larger species. The effects on their immediate environment, including the cell settlement and slower mass transfer of nutrients, might help explain the trends seen in liquid media microgravity studies. Therefore, experimental design factors must be carefully considered when selecting a simulated microgravity device for proper underlying mechanisms and interpretation of results. To verify if the simulated microgravity devices simulate the relevant microgravity conditions for bacterial growth, including the changes in cell settlement and mass transfer of nutrients, a high aspect ratio vessel (HARV) was used with dyes of different density in various simulated microgravity setups. The results will help inform the selection of the proper simulated microgravity device as well as interpretation of subsequent biofilm growth results.