I have mentioned before that bacteria in spacecraft can develop into more virulent strains with antibiotic resistance. This adds to the biological problems that humans face when living in space beyond the atmosphere and gravity of the Earth. A recent experiment on the International Space Station provided additional detail on how these changes occur. The report was published in Frontiers of Microbiology.
E coli bacteria were the subject of an experiment in space which subjected the bacteria to different concentrations of the antibiotic gentamicin sulfate which is known to kill it on Earth. The bacteria in space increased its cell number by thirteen times and reduced its cell column size by seventy three percent.
The report reveals how bacteria act in space when they are not subject to gravity related effects such as buoyancy and sedimentation. The bacteria changes shape in order to survive in the new environment. This limits the way that bacteria can ingest nutrients or drugs to the process of natural diffusion. Because the surface area of the bacterial cells decreases when in space, the rate at which molecules of a drug around the cell can interact with the cell decreases. The cell membrane becomes thicker in space which also serves to protect the bacteria from the antibiotic. Bacterial cells also form clumps in space which might be a defensive process that would sacrifice cells on the surface of the cell clump in order to protect cells inside the clump.
During the experiment, some of the E coli cells were seen creating membrane vesicles. These are small capsules that form on the outside of bacterial cell walls. They serve as messengers that allow the E coli cells to communicate with each other. When a clump of E coli cells reaches a critical mass, they can synchronize to start infecting a host.
The lead author of the study, Luis Zea, said "We knew bacteria behave differently in space and that it takes higher concentrations of antibiotics to kill them. What's new is that we conducted a systematic analysis of the changing physical appearance of the bacteria during the experiments. Both the increase in cell envelope thickness and in the outer membrane vesicles may be indicative of drug resistance mechanisms being activated in the space flight samples. This experiment and others like it give us the opportunity to better understand how bacteria become resistant to antibiotics here on Earth."
Our understanding of biological processes in space has increased our understanding of just how hostile that environment is. Not only are there negative effects on human bones, muscles, eyes and hearts but these experiments with E coli show that other hostile organisms become even more dangerous in space. It will be necessary to conduct more experiments in order to understand just exactly how to treat astronauts infected with these more dangerous bacteria. This will be especially important in long term missions such as manned missions to the planet Mars and other remote astronomical bodies.
E coli bacteria:
