Researchers at the Indian Institute of Technology Madras and NASA's Jet Propulsion Laboratory (JPL) have studied microbial interactions on the International Space Station (ISS) to devise disinfection strategies on orbital outposts. It is important to disinfect space stations because microbial growth could be detrimental to the health of astronauts.
Microgravity affects the health of astronauts, causing them to have altered immunity. Moreover, people living on the space station have limited access to terrestrial medical facilities. There are several risks associated with space travel on astronaut health due to the presence of microbes on the space station.
The new study describing strategies to disinfect the space station was published in the journal Microbiome.
While recent studies have provided insights into the persistence of microbes aboard the ISS, the interactions between the various microbes and how they shape the microbiome remain to be clearly understood. The researchers demonstrated several key interactions in the ISS microbiome as part of the study. They found significant information about the metabolic interactions and dependencies present among various microbes in a community.
Klebsiella pneumoniae is dominant on the ISS
Previous studies found the bacterium Klebsiella pneumoniae was found to be dominant on the surfaces of the space station. The bacterium causes pneumonia and other nosocomial infections, or healthcare-associated infections, which are diseases acquired during the time of healthcare. The researchers' interest in understanding how the bacterium affects the growth of other microbes on the space station motivated them to conduct the study.
Which organism is Klebsiella pneumoniae beneficial to?
After analysing the microbial sample data taken across three space flights at seven locations on the ISS, the researchers found that Klebsiella pneumoniae is beneficial to various other microbes present on the ISS, especially the bacteria belonging to the Pantoea genus.
The study found that species belonging to the Enterobacteriaceae family are often the most beneficial for the survival of other microorganisms in the ISS microbiome.
Antifungal activity exhibited by Klebsiella pneumoniae on the ISS
Surprisingly, the presence of Klebsiella pneumoniae was computationally observed to hamper the growth of the fungus Aspergillus. The researchers further tested the observation through laboratory experiments, and found that the presence of Klebsiella pneumoniae was indeed detrimental to the growth of Aspergillus.
Klebsiella pneumoniae exhibited parasitic behaviour with Aspergillus species and amensalistic (relating to an association between two organisms in which one is harmed while the other is unaffected) behaviour with Penicillium species.
This means that when Klebsiella pneumoniae and Aspergillus interact with each other, the former is benefitted, while the latter is harmed. Meanwhile, interactions between Klebsiella pneumoniae and Penicillium harm the latter while the former remains unaffected.
The researchers co-cultured Klebsiella pneumoniae and Aspergillus fumigatus under normal and simulated microgravity, and observed that the Klebsiella pneumoniae cells showed parasitic characteristics to the fungus.
The presence of Klebsiella pneumoniae compromised the morphology of fungal conidia and degenerated its biofilm-forming structures, the electron micrographs revealed. In other words, Klebsiella pneumoniae damages the key morphological features of the pathogenic fungus Aspergillus.
Which are the most beneficial microbes on the ISS?
Bacteria such as E. coli and Salmonella were found to be some of the most beneficial microbes on the ISS.
These microbes reach the ISS because they are present in the bodies of humans who live there.
While the microbial strains found by the researchers pose no threat to the space station astronauts, the new study highlights why it is important to monitor the microbiome on the ISS. Also, it is important to carefully monitor the microbes on the ISS and learn their mechanisms of adapting to microgravity in order to protect astronaut health.
Significance of the study
The authors conclude that the study underscores the importance of Klebsiella pneumoniae on the ISS, and its positive and negative interactions with other microbes, including potential pathogens. The authors proposed an integrated modelling approach in the paper which, combined with experiments, demonstrates the potential for understanding the organisation of other such microbiomes. This will help unravel more organisms on the ISS and their interdependencies.
Klebsiella pneumoniae exhibits antifungal activity in the ISS microbiome. The findings of the study could be used to examine the organisation of other microbiomes to identify key microorganisms for interdependencies and development of strategies that kill harmful microbes.