A microbial survey of the most extreme built environment, the International Space Station (ISS)

Jenna M. Lang (jennomics@gmail.com). Genome Center, University of California, Davis, CA, USA
David A. Coil (coil.david@gmail.com). Genome Center, University of California, Davis, CA, USA
Russell Y. Neches (russell@vort.org). Genome Center, University of California, Davis, CA, USA
Wendy E. Brown (thewendybrown@gmail.com). Science Cheerleader, Genome Center, University of California, Davis, CA, USA
Darlene Cavalier (darcav1@gmail.com). Science Cheerleader, SciStarter.org
Mark Severance (scicheerspaceguy@scistarter.org). Science Cheerleader, SciStarter.org
Jarrad Marcell (jhampton-marcell@anl.gov). Argonne National Laboratory, University of Chicago, Lemont, IL, USA
Jack A. Gilbert (gilbert.jack@gmail.com). Argonne National Laboratory, University of Chicago, Lemont, IL, USA
Jonathan A. Eisen (jaeisen@ucdavis.edu). Genome Center, Evolution and Ecology, Medical Microbiology and Immunology, University of California, Davis, Davis, CA, USA




Modern advances in sequencing technology have enabled the census of microbial members of many natural ecosystems. Recently, attention is increasingly being paid to the microbial residents of human-made, built ecosystems, both private (homes) and very public (subways, office buildings, and hospitals). Here, we report results of the characterization of the microbial ecology of a singular built environment, the International Space Station. This sampling involved the collection and microbial analysis (via 16S rDNA PCR) of 15 samples swabbed from surfaces onboard the International Space Station. This sampling is a component of Project MERCCURI (Microbial Ecology Research Combining Citizen and University Researchers on ISS) - a collaborative effort of the "microbiology of the Built Environment network" (microBE.net) project, Science Cheerleaders, NanoRacks, Space Florida, and Scistarter.com. Learning more about the microbial inhabitants of the "buildings" in which we travel through space will take on increasing importance, as plans for human exploration and colonization of the solar system come to fruition.


Sterile swabs were used to sample 15 surfaces onboard the International Space Station. The sites sampled were designed to be analogous to samples collected for 1) the Wildlife of Our Homes project and 2) a study of cell phones and shoes that were concurrently being collected for another component of Project MERCCURI. Sequencing of the 16S rRNA genes amplified from DNA extracted from each swab was used to produce a "census" of the microbes present on each surface sampled. We compared the microbes found on the ISS swabs to those from both the Earth homes and the Human Microbiome Project.


While significantly different from homes on Earth and the Human Microbiome Project samples analyzed here, the microbial community composition on the International Space Station was more similar to home surfaces than to the human microbiome samples. The International Space Station surfaces are species-rich with 1036-4294 operational taxonomic units per sample. There was no discernible biogeography of microbes on the 15 surfaces, although this may be a reflection of the small sample size we were able to obtain.


There is a growing appreciation of the importance of microbial communities found in diverse environments from the oceans, to soil, to the insides and outsides of plants and animals. Recently, there has been an expanding focus on the microbial ecology of the "built environment" - human constructed entities like buildings, cars, and trains - places where humans spend a large fraction of their time. One relatively unexplored type of built environment is that found in space. As humans expand their reach into the solar system, with more and more plans for space travel, and with the possibility of the colonization of other planets and moons, it is of critical importance to understand the microbial ecology of the built environments being utilized for such endeavors.

Interest in the microbial occupants of spacecraft long precedes the launch of the International Space Station (ISS) (Trexler 1964)(Silverman 1971). Early work primarily focused on ensuring that the surfaces of spacecraft were free of microbial contaminants in an effort to avoid inadvertent panspermia (seeding other planets with microbes from Earth) (Pierson 2007). Work on human-occupied spacecraft such as Mir, Space Shuttles, and Skylab focused more on microbes with possible human health effects. With the launch of the ISS, it was understood that this new built environment would be permanently housing microbes as well as humans. Calls were made for a better understanding of microbial ecology and human-microbe interactions during extended stays in space (Pierson 2007) (Roberts 2004) (Ott 2004). Efforts were made to establish a baseline microbial census. For example, Novikova et al