AGXX-GOX: Novel antimicrobial surfaces for safe long-term space missions Raw sequence reads

In this study, we are investigating the long-term antibacterial effect of two innovative, bioactive surface coatings - AGXX and GOX - during SIRIUS19, a 4-months simulated space mission taking place inside the NEK facility at the IBMP in Moscow, Russia. The overall objective is the prevention and elimination of bacterial contamination within crewed spacecrafts during future long-duration space missions. AGXX is an antimicrobial surface coating that combines the two noble metals silver (Ag) and ruthenium (Ru) into micro-galvanic cells conditioned with ascorbic acid. The antimicrobial properties of AGXX result from the release of reactive oxygen species (ROS) which are formed through a series of redox reactions. The second antimicrobial coating, GOX, consists of chemically modified graphene oxide. Through a positive surface charge and its flexible scaffold, GOX can multivalently bind and immobilise bacteria via electrostatic attraction. Sterile samples of AGXX- and GOX-coated cellulose fleece, as well as uncoated control samples, were exposed to the atmosphere within the SIRIUS habitat for 1 month, 2 months and 4 months. In parallel, a reference experiment with the same materials and time points was set up inside a non-isolated control environment with high human traffic (microbiology laboratory). Following exposure, molecular and cultivation-based methods were used to analyse the bacterial communities surviving on the materials. Our work reveals the development of microbial communities in a closed habitat simulating space travel conditions in comparison with an open control habitat. Bacterial isolates in the closed habitat seem to be dominated by human commensal microorganisms, many of them multi-resistant, while those from the open habitat are dominated by a variety of environmental, nonpathogenic bacteria, pointing towards competition between commensal and environmental organisms in the open habitat. Our study further demonstrates the promising antimicrobial activity of the two antimicrobial surface coatings with properties suited to be used in future long-term space missions. Both significantly reduced bacterial growth on contamination-prone surfaces in the SIRIUS19 habitat simulating spaceflight conditions (minus microgravity).