Will humans inevitably cause microbial colonization of space?

One area of concern in space exploration is forward and backward contamination – bringing life forms from Earth to other places or vice versa. There are protocols in place to prevent such “contamination”. But is microbial colonization inevitable? We as humans host entire communities of microbes without which we would die. As we travel off-planet, these microscopic lifeforms will inevitably join us. To learn more about microbial colonization of space, we spoke to Jose Victor Lopez, a professor of natural sciences and oceanography at Nova Southeastern University. He recently co-authored a paper describing how microbial colonization of space is “inevitable”. He spoke about the paper and his interest in this subject.

Why do you suggest that humans’ introducing microbes to space is inevitable?

Most plants and animals, including humans, live in intimate partnerships (called “symbiosis”) with unseen microorganisms. These are often bacteria, and they can number in the hundreds to thousands of different species (and trillions of bacterial cells) per person. These “symbionts” live unseen on our skin, mouth, intestines, genitals, etc. – basically from head to toe. Often these microbes cause people no harm. Sometimes we can smell them, but other than that, these symbiotic bacteria are often indispensable and beneficial to our lives. For example, some “good” symbionts can outcompete or destroy pathogens (harmful microbes, which can always be present but at lower frequencies than typically thought). “Good” symbionts can also release enzymes or native antibiotics that destroy extracellular viruses or help us digest nutrients that would otherwise pass through us. 

In this context, wherever people go in this solar system or the universe, our microbial symbionts will automatically travel with us, whether we like it or not. We cannot 100% sterilize our bodies, even if we wanted to.

What are the implications of this inevitability for space exploration philosophy and planetary protection policy?

Our paper was meant to be a gift to fellow microbiologists, as well as a way of introducing each other to the space-exploring world of astronauts, engineers, and planners. 

We think that once microbial presence and inevitability is accepted by the community of present and future space explorers and “colonists”, there will be more focused research programs on what earthly microbes can do as extraterrestrial pioneers, alongside human beings. Space programs need to include microbiological parameters and experiments for future colonization plans. Microbes provide useful functions such as photosynthesis, decomposition, and recycling of elements. They will thus be needed to shape and regulate ecosystems that we want to have with us on extraterrestrial habitats. A holistic view of space exploration should address the nature of microbial activity. This can practically affect budgets and experiments.

How did you come to be interested in this area of study?

I am not formally trained as a microbiologist but rather consider myself more of an evolutionary geneticist. The latter always leads me to think of origins and the relationships between diverse organisms, like on an evolutionary tree. However, I have thought about symbioses for a long time. Furthermore, my lab has been intensely studying the dynamics of microbial communities (“microbiomes”) within many different types of holobionts (= host + their microbial symbionts) such as corals, sponges, humans, and even sharks. 

Then there was a convergence of events in 2015. Firstly, we had a visit by a Nova Southeastern University alumnus who worked at NASA and presented the agency’s future plans for Mars exploration. At the same time, frozen water was recently discovered on the Red Planet, and then the Hollywood movie “The Martian” was released, which I watched. With all of this activity, I noticed that microorganisms were rarely mentioned. Even the presentation of plants being fictitiously grown in Martian soil did not mention essential microbial plant symbionts. (These typically live in tandem with plant roots and help obtain nitrogen in the atmosphere.)

Lastly, our labs have focused on marine habitats like the deep sea and coral reefs. I still view these as “alien”-like habitats, because people cannot easily or routinely visit these unique places. Furthermore, the wide diversity of relatively unknown organisms that live under the waves, unseen and relatively inaccessible, make the oceans a great place for exploration, just like space. The main difference is that the oceans are in our collective backyards, teeming with life but deteriorating quickly. Thus, alien marine habitats need our help and protection. Drawing contrasts with space is meant to increase overall appreciation for our planet’s resources.