Wherever you find people you find microorganisms and life onboard the International Space Station is no exception. Do these organism behave differently and do any differences pose a threat to astronauts?
These are some of the questions that scientists have been grappling with as part of the studies into extended stays in space and in preparation for deep space missions, such as the planned trip to Mars.
In terms of major pathogen threats the risks are generally lower on the International Space Station than on Earth, which reflects the overall cleaner environment and the manufacture of space craft and equipment on Earth inside controlled environments called cleanrooms. In such environments the level of airborne particulates, and hence microorganisms, is controlled together with an enhanced cleaning and disinfection regime.
In addition to these practices, it is standard procedure for astronauts assigned to the space station to spend 10 days in pre-flight quarantine. This is to assess, for instance, whether an astronauts has the flu. An influenza outbreak in space would be disastrous since it could incapacitate the throe crew.
Another reason for trying to minimize pathogens in space is because microgravity appears to weaken the immune system, so NASA need to be careful to reduce the chances of spaceflyers catching nasty bugs before they lift off. This happens because a protein called osteopontin, which is a stress hormone connected with bone loss in space, appears to be linked with a condition that leads to the wasting of the spleen and thymus organs. These organs create white bloods cells that battle infections, and the condition leads to a general weakening of the immune system.
This also means that microbiological monitoring needs to be take place onboard the space station. This is to help assess astronaut health; it is also experimental, to see whether common-Earth bound microorganisms undergo significant alternations in space.
According to Dr. Mark Ott, who is a microbiologist at Johnson Space Center. Roscosmos (the Russian space agency): "Once every three months, we sample from two locations in each module of the U.S. segment of the station."
Ott explains that samples are collected from surfaces and from the air. These are cultured using classic microbiological culture-based growth techniques where plates containing a growth medium with agar are used. It is common to use one medium to target bacteria and a different medium for fungi. There's a flaw here in that only those organisms that are culturable on the agars selected and under the incubation parameters used will be recoverable.
The plates are preserved and then returned to the ground with astronaut exchanges. Back on Earth the plates are assessed and, where microbial growth occurs, microbiologists perform identification.
With the types of microbes Recovered these are not dissimilar from the types recovered on Earth. The results of environmental monitoring show very few isolates are of the type that would make people sick. If any of medical importance are recovered, a special cleaning protocol is imitated. Sometimes the issue is segregation, as Ott explains: "It may be something typically found in a bathroom, for example, but that you wouldn't want in an office space," the researcher contextualizes.
A further microbiological issue on the space station is with the treatment and control of drinking water. On the space station, as it would be on Earth, drinking water is chemically treated to ensure that it is safe to drink. Water also needs to be controlled so that bacterial proliferation is prevented once water has been treated, while it is stored.
With any of the monitoring if something atypical is recovered then instead of standard cultural techniques and conventional identifications (which look at the microbial phenotype), the organisms are sent for genotypic testing. Here microbial DNA is used for the identification. This allows closely related species to be differentiated. The types of organisms more often subjected to this analysis are spore forming organisms of the genera Bacillus.
In terms of on-going analysis what the scientists are keen to establish are the most common types of organisms likely to survive on-board the space station and whether these would pose any problems for extended stays or for future deep space missions. Of particular interest is the impact of space upon an astronaut's own microbiome and how this affects the human immune system.
This forms part of a wider international study called the "Study of the Impact of Long-Term Space Travel on the Astronauts' Microbiome." Work to support this initiative, which has been on-going since 2013, includes, taking regular samples from different parts of the astronauts' bodies. As part of this study, the likelihood and consequences of alterations in the microbiome due to extreme environments, and the related human health risk, will be assessed.
In April 2017, five post-doctoral fellowships were awarded by NASA to help review and characterize the microbes recovered from the space station and from the bodies of astronauts. Such research will be of continuing importance since it is unavoidable that every time humans venture into space, so microorganisms come with us.
Posted by Dr. Tim Sandle