AUTHOR=Mikelsaar Marika , Mändar Reet TITLE=Commentary: Gut Microbiome and Space Travelers' Health: State of the Art and Possible Pro/Prebiotic Strategies for Long-Term Space Missions JOURNAL=Frontiers in Physiology VOLUME=12 YEAR=2021 URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.651977 DOI=10.3389/fphys.2021.651977 ISSN=1664-042X