Ad meliora: Space microbial research for the benefit of humanity

Abstract

When humans go to space, they take their microbes with them. Microbiomes benefit many aspects of human health, but little is known about how spaceflight affects the physiology of our microbial commensals. The functional composition of the human vaginal microbiomes (i.e. eubiosis vs. dysbiosis) is well established and Gardnerella vaginalis is known to drive dysbiosis, being implicated in the development of bacterial vaginosis (BV). In fact, 10% of the medical issues arising during spaceflight are genitourinary, a decent portion from female astronauts, despite being underrepresented in space missions. Because G. vaginalis is a key species driving microbial dysbiosis, this thesis aimed to uncover the biological pathways of G. vaginalis affected by space conditions, particularly the lack of gravity (i.e. microgravity), and the potential implications it holds for human health in space. Untargeted Metabolomics by Gas Chromatography Mass Spectrometry was conducted to assess the changes in bacterial metabolites when G. vaginalis was subjected to simulated microgravity. In the process, a mix of supervised and unsupervised multivariate analysis methods were explored. Our result suggests that microbial metabolic changes induced by microgravity may alter the redox status which, in turn, may favour the growth of different species of bacteria in a reduced anaerobic environment. Additionally, we found eight compounds whose relative concentrations were reduced in comparison to gravity control after cross-validation. These include hydroxybenzoic acid and the amino acids aspartate, glutamate and (hydroxy)lysine with known specific roles on cellular responses. The former, for instance, is known to have estrogenic activity and antimicrobial properties and to affect bioavailability of metronidazole, the first line of drug to treat BV. These findings demonstrate that simulated microgravity has the potential of altering microbial metabolic responses that may lead to disturbances of the microbiomes and alterations on host physiology. The space environment has been viewed as an environment for accelerated disease modelling. Understanding metabolic and physiological responses to space will help humanity on Earth and to establish safe and long-term space exploration programs.