Characterization of Spacesuit Associated Microbial Communities and Their Implications for NASA Missions.

David Danko,Mary S Bell,Maria A Sierra,Rachid Ounit,Nitin K Singh,Aaron B Regberg,Michelle Rucker,Ganesh Babu Malli Mohan,Christopher E Mason,Niamh B O’Hara,Kasthuri Venkateswaran

doi:10.3389/fmicb.2021.608478

Abstract

BackgroundCrewed National Aeronautics and Space Administration (NASA) missions to other solar system bodies are currently being planned. One high-profile scientific focus during such expeditions would be life detection, specifically the discovery of past or present microbial life, if they exist. However, both humans and associated objects typically carry a high microbial burden. Thus, it is essential to distinguish between microbes brought with the expedition and those present on the exploring planets. Modern spacesuits are unique, customized spacecraft which provide protection, mobility and life support to crew during spacewalks, yet they vent, and the mobility of microbes through spacesuits has not been studied.ResultsTo evaluate the microbial colonization of spacesuits, NASA used an Extravehicular Activity swab kit to examine viable microbial populations of 48 samples from spacesuits using both traditional microbiological methods and molecular sequencing methods. The cultivable microbial population ranged from below the detection limit to 9 × 102 colony forming units per 25 cm2 of sample and also significantly varied by the location. The cultivable microbial diversity was dominated by members of Bacillus, Arthrobacter, and Ascomycota. However, 16S rRNA-based viable bacterial burden ranged from 105 to 106 copies per 25 cm2 of sample. Shotgun metagenome sequencing revealed the presence of a diverse microbial population on the spacesuit surfaces, including Curtobacterium and Methylobacterium from across all sets of spacesuits in high abundance. Among bacterial species identified, higher abundance of Cutibacterium acnes, Methylobacterium oryzae, and M. phyllosphaerae reads were documented.ConclusionThe results of this study provide evidence that identical microbial strains may live on the wrist joint, inner gauntlet, and outer gauntlet of spacesuits. This raises the possibility, but does not confirm that microbial contaminants on the outside of the suits could contaminate planetary science operations unless additional measures are taken. Overall, these data provide the first estimate of microbial distribution associated with spacesuit surfaces, which will help future mission planners develop effective planetary protection strategies.

Highlights

Several spacefaring nations and private corporations are planning to send humans and spacecraft to other planets such as Mars, to search for evidence of habitats that could support life (NRC, 2014)
All controls were analyzed for all microbiological and molecular biological examinations (5 samples, Table 1). All these 48 samples were categorized into sets (n = 7 sets) based on the suit types or sample collection dates (Table 1). Metadata such as locations, type of suits, materials of spacesuits, and date of collection are given in Supplementary Table 1
We established that viable microbes are present on the wrist assemblages of spacesuits, that certain microbial strains can survive on all three components of the wrist assembly without being found in corresponding controls, and that these microbes broadly resemble those of human commensal skin microbiomes

Summary

Introduction

Several spacefaring nations and private corporations are planning to send humans and spacecraft to other planets such as Mars, to search for evidence of habitats that could support life (NRC, 2014). A team at the Johnson Space Center (JSC) at NASA has developed a prototype Extravehicular Activity (EVA) swab kit that is suitable for handling by the astronauts in spacesuits to collect microbial samples aseptically, aiming to profile microorganisms associated with spacesuits (Rucker et al, 2018). In this communication, a microbial characterization associated with wrist joints of flight Extravehicular Mobility Unit (EMU), Modified Advanced Crew Escape System and Orion Crew Survival System (MACES/OCSS) spacesuits was carried out to evaluate the form, fit and function of the EVA swab tool; that functional testing provided an opportunity to characterize the typical microbial contamination on spacesuits. Modern spacesuits are unique, customized spacecraft which provide protection, mobility and life support to crew during spacewalks, yet they vent, and the mobility of microbes through spacesuits has not been studied

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