What is it about?
Space travel might result in mutations in bacteria, that are undesirable, thereby helping them to band together and survive. This paper reports the longest study yet of bacteria in simulated microgravity. Adaptations to simulated microgravity, remained even when attempts were made to erase them. A major concern for long-duration space flight is how the microorganisms who hitch a ride with us will adapt to the loss of gravity. Astronauts’ immune systems change in space, potentially making them more susceptible to infection, so if these bacteria become more virulent or antibiotic-resistant, they could pose a risk. To assess that risk, E. coli was grown in a rotating vessel designed to simulate microgravity, for over 1,000 bacterial generations, much longer than in previous studies. The microgravity adapted cells were combined with another strain of E. coli that hadn’t been subjected to microgravity, allowing them to grow together. The adapted cells grew about three times as many colonies as the others. Even after the cells were taken out of microgravity for up to 30 generations before being combined with the control strain, they maintained 72 per cent of their adaptive advantage, pointing to permanent mutations in the genes rather than merely a temporary adjustment. Genome sequencing revealed 16 mutations in the E. coli after microgravity exposure. Some of the mutations occur on genes related to the ability to form biofilms, colonies of cells embedded in protective slime. Biofilms have been shown to make bacteria hardier in many situations, which may present a problem if one were to form, say, on a spaceship’s life support system.
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Why is it important?
Monitoring microbial response to real time space conditions over extended periods is constrained by operational difficulty as well as costs, and thus, simulated microgravity offers a cheaper prototype analog of space conditions. The difference in cost between performing such studies on Earth as against the same done in space, can be significantly huge. E. coli is relatively innocuous, but the infection risk for astronauts on long missions could skyrocket if microgravity also makes pathogenic bacteria, such as Salmonella, adapted to space conditions.
Perspectives
“Nothing in Biology Makes Sense except in the Light of Evolution” Theodosius Dobzhansky Complex dynamics are often involved in long-term evolution of genomes. Given the complexity of the phenomenon of evolution, it is difficult to predict. One can never know how many generations it would take for adaptations to become irreversible. It can be expected that organisms on the space station or other long term missions would continue adapting indefinitely as has been observed in long-term studies of E. coli. This process would possibly be accelerated by the elevated radiation levels experienced in space. During such true long-term adaptation, neutral mutations would likely become more common. This kind of work only reiterates the importance of understanding adaptation and evolution of microbial systems. Understanding these phenomena at the fundamental level will augment our knowledge of the dynamics of biofilm formation, and microbial colonization. Such knowledge can be extended towards microbial growth and adaptation dynamics in closed environments as found in hospitals, the food industry etc.
Madhan R Tirumalai
Read the Original
This page is a summary of: The adaptation of Escherichia coli cells grown in simulated microgravity for an extended period is both phenotypic and genomic, npj Microgravity, May 2017, Springer Science + Business Media,
DOI: 10.1038/s41526-017-0020-1.
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