How do astronauts stay healthy in space? When thinking about this important question it is essential to always remember that the astronauts are not alone as they travel to and work in space. There is a cacophony of microbial voices communicating with their bodies, which together comprise the astronaut’s microbiome. Understanding how spaceflight alters the astronaut’s microbiome is a critical hurdle to overcome for long-duration missions in space.
As it is a very difficult task to study humans and their microbiome in a space environment, model systems are needed. In this paper, we simulated the microgravity environment using High Aspect Ratio Vessels (see image below). We examined the effects of the simulated microgravity on the beneficial luminescent bacterium Vibrio fischeri, which is known to form a symbiotic association with the bobtail squid Euprymna scolopes.
In our study, we examined changes in V. fischeri transcriptome, which are all the genes expressed at a given moment in time, under both gravity and modeled microgravity conditions. We examined the V. fischeri transcriptomes over time to see if the modeled microgravity had a different effect that was dependent on the growth phase of the bacterium. Interestingly, the modeled microgravity had no significant impact on the beneficial microbe’s transcriptome suggesting that the molecular machinery that the bacterium uses to grow and interface with the host won’t be negatively impacted during actual microgravity conditions.
To delve deeper into how microbes behave at a molecular level in simulated microgravity we also examined a mutant of V. fischeri defective in the gene hfq, which encodes for a protein that is a critical regulator of stress responses, including microgravity, in some microbes. In our experiment, the absence of the hfq gene in modeled microgravity hampered the ability of V. fischeri to remove certain RNA products associated with various stress responses and metabolic activities, such as motility and respiration. Our results suggest that hfq may be a critical gene for helping the beneficial V. fischeri respond to the stress of microgravity.
Through this study, we have expanded our understanding of how beneficial microbes are affected by modeled microgravity and laid the groundwork for future spaceflight experiments. The next steps will be to not only replicate this work under natural microgravity conditions but also to examine the changes that spaceflight has on beneficial microbes in the presence of their hosts. Through these efforts, we can begin to delineate the effects of spaceflight on host microbiomes at the molecular level to help ensure the health of those working and living in the space environment.
Images depict an adult bobtail squid (upper left) and the beneficial V. fischeri (upper right) that colonizes the host animal. The High Aspect Ratio Vessels (bottom image) were used to cultivate the microbes and simulate the microgravity environment.
This post was a collaboration between Alexandrea Duscher and Jamie Foster. The complete article can be found in the journal of npj Microgravity: https://www.nature.com/articles/s41526-018-0060-1