Microbial analysis in space: Modular device for biological experiments in microgravity

Biological experiments on bacteria in extra-terrestrial environments have recently gained increased importance in the context of space exploration and the human space programme. Here, we demonstrate a modular self-contained device, based on the lab-on-a-chip (LoC) paradigm, for performing miniaturized biological experiments in microgravity or outer space environments. The device is designed to incubate microscopic organisms; in the present work it was employed to incubate bacteria via a suitable actuation mechanism and measure bacterial activity over long term by periodic querying, sensing and data transmission/storage. Growth is measured using optical density measurements using an on-board LED/photo-diode pair. The modular design enables several simultaneous experimental runs arranged in individual cartridges, each containing multiple experiments in separate cassettes. This allows for statistical significance and in-built redundancy in case of remote failure. We use this system to study the growth pattern of Sporosarcina pasteurii, a spore-forming bacteria widely explored for its capability to induce calcite precipitation. Growth in the device was confirmed by continuous monitoring of optical density (OD), as well as post log-phase optical and scanning electron microscopy (SEM). Additionally, the performance of the device was evaluated at multiple temperatures, pressures and under different device orientations, and found to be unchanged within experimental error. Given its modular structure, the proposed platform can be easily adapted as a biological payload for self-contained LoC based studies of other microorganisms in microgravity environments.