Planetary protection and ESA's bacterial strain collection

Abstract

Introduction Microbial examination of flight hardware and cleanrooms is a major focus of planetary protection activities to control bioburden and to analyze the complexity of the cleanroom microbiome. Enriched isolates from samples collected during various missions, including ExoMars and JUICE, have been identified and deposited at the DSMZ to establish a special strain collection of bacterial species that can survive and adapt under extreme conditions. Cultures originally obtained from the International Space Station (ISS) or isolated within the Mars Analogues for Space Exploration project (MASE) complement the collection with additional strains. The collection was founded by the European Space Agency (ESA) and is publicly accessible via the online strain catalog at the DSMZ and is also integrated into the BacDive database. Objective ESA has implemented the public culture collection to facilitatethe distribution of bacterial isolates to the scientific community. This allows researchers to study specific properties of these microbes to gain insights into the survival and adaptation mechanisms in extreme environments. Current status Spacecraft are built in particlecontrolled clean rooms. Particles can affect the function of spacecraft instruments, and for missions under planetary protection restrictions, biological contamination must be limited as much as possible. A clean room is an extreme environment with constant control of humidity and temperature, air filtering, and surface disinfection. Bioburden and diversity studies have been performed for several missions (Smart-1, Rosetta, Herschel, ExoMars and Juice) in various European clean rooms to validate biological contamination control and reduction procedures. Swab and wipe samples were collected from clean room facilities and directly from spacecraft surfaces by our collaborators from DLR in Cologne and the University of Graz. Most isolates enriched from these samples have been identified and freeze dried at DSMZ for long-term storage. The collection currently contains about 900 isolates, with the predominant species belonging to the endospore forming genera Bacillus, Paenibacillus, Peribacillus and Priestia. Other representative species are from the genera Acinetobacter, Stenotrophomonas, Micrococcus, Kocuria and Staphylococccus. Selected isolates are now being genome sequenced to gain further insights and to refine its phylogenetic assignment.