The human microbiome is essential to our health and deserves special consideration in the closed environments of space travel. The dynamics of host-microbe interactions will change if normal immune functions are altered during extended space travel. Opportunistic pathogens common in the human microbiome, including those in the genera Candida, Aspergillus, and Staphylococcus, could spread among crewmembers and put them at risk of serious disease. Not only will the microbiome be important to the maintenance of crew health, it will be critical in establishing a new healthy human population from the small group of founders. This imposed bottleneck on human evolution and the associated microbial communities offers incredible opportunities to eliminate common pathogens that put human health at risk.
Conversely, isolating a subset of the human population could exclude some organisms that confer a significant health advantage. The characterization of the human microbiome is a relatively recent area of investigation, and the full functionality of the vast microbiota living in and on the human body is not yet well understood. Data suggest microbial involvement in diverse areas of human health and further studies will likely yield novel strategies to maximize the benefits of individuals’ microbial communities in a particular environment. The ideal microbiome of space explorers should be developed alongside the spacecraft and dietary plans.
However, there are many ethical considerations associated with selecting participants for an interstellar program based on the composition of their microbiome, or significantly altering participants’ microbiome. Similar to genomic sequencing, there are aspects of an individual’s microbiota that could cause prejudice. Should the isolation of Staphylococcus aureus from a person’s nares prevent his or her participation in a brave new world? Developing a more complete understanding of the benefits and harms conferred by the fungi, viruses, archaea, and bacteria that exist in and on our bodies will guide our determination of what non-human organisms can and should be included on the ark.