Abstract:
Outer membrane vesicles (OMVs), produced by nonpathogenic Gram-negative bacteria,
have potentially useful biotechnological applications in extraterrestrial extreme environments.
However, their biological effects under the impact of various stressors have to be elucidated
for safety reasons. In the spaceflight experiment, model biofilm kombucha microbial
community (KMC) samples, in which Komagataeibacter intermedius was a dominant
community-member, were exposed under simulated Martian factors (i.e., pressure,
atmosphere, and UV-illumination) outside the International Space Station (ISS) for 1.5 years.
In this study, we have determined that OMVs from post-flight K. intermedius displayed
changes in membrane composition, depending on the location of the samples and some
other factors. Membrane lipids such as sterols, fatty acids (FAs), and phospholipids (PLs)
were modulated under the Mars-like stressors, and saturated FAs, as well as both
short-chain saturated and trans FAs, appeared in the membranes of OMVs shed by both
post-UV-illuminated and “dark” bacteria. The relative content of zwitterionic and anionic
PLs changed, producing a change in surface properties of outer membranes, thereby
resulting in a loss of interaction capability with polynucleotides. The changed composition
of membranes promoted a bigger OMV size, which correlated with changes of OMV fitness.
Biochemical characterization of the membrane-associated enzymes revealed an increase
in their activity (DNAse, dehydrogenase) compared to wild type. Other functional membraneassociated capabilities of OMVs (e.g., proton accumulation, interaction with linear DNA,
or synaptosomes) were also altered after exposure to the spaceflight stressors. Despite
alterations in membranes, vesicles did not acquire endotoxicity, cytotoxicity, and neurotoxicity. Altogether, our results show that OMVs, originating from rationally selected nonpathogenic
Gram-negative bacteria, can be considered as candidates in the design of postbiotics or
edible mucosal vaccines for in situ production in extreme environment. Furthermore, these
OMVs could also be used as promising delivery vectors for applications in Astromedicine.
