BIOFILM FORMATION AND ITS CONCOMITANT RISK OF CAUSING EQUIPMENT MALFUNCTION AND HUMAN ILLNESSES IS A PROBLEM THAT NEEDS TO BE ADDRESSED TO ENABLE SAFE LONG-TERM HUMAN SPACE EXPLORATION. WITH THAT OBJECTIVE, THIS PROPOSAL AIMS TO CHARACTERIZE BIOFILM GROWTH DURING ONE ISS INCREMENT IN TERMS OF MASS, THICKNESS, MORPHOLOGY, AND ASSOCIATED GENE EXPRESSION USING DIFFERENT SPACEFLIGHT-RELEVANT MICROBIAL SPECIES AND MATERIAL SUBSTRATA. THIS PROJECT ALSO AIMS TO ELUCIDATE THE BIOMECHANICAL AND TRANSCRIPTOMIC MECHANISMS INVOLVED IN THE FORMATION OF THE COLUMN-AND-CANOPY BIOFILM ARCHITECTURE OBSERVED IN SPACE. THE EXPERIMENT IS DESIGNED TO ASSESS THE EXPRESSION OF GENES ASSOCIATED WITH CONFERRING MICROORGANISMS WITH RESISTANCE TO OXIDATIVE STRESS, ACIDITY, AND ANTIMICROBIALS IN BIOFILMS FORMED IN SPACE, AND TO DETERMINE PHYSICAL MECHANISMS OF MATERIAL/MICROORGANISMS INTERACTION IN BIOFILMS. THE EXPERIMENT WILL BE CONDUCTED USING BIOSERVE'S BIOCELLS HOUSING SUBSTRATA COUPONS EXPOSED TO DIFFERENT MICROORGANISMS AND MEDIA. POST-FLIGHT ANALYSES OF FIXED SAMPLES INCLUDE CONFOCAL LASER SCANNING MICROSCOPY AND RNA-SEQUENCING. THE SIGNIFICANCE OF THIS PROJECT STEMS FROM GAINING VALUABLE NEW KNOWLEDGE THAT MAY LEAD TO IMPROVED METHODS AND/OR MATERIAL PROPERTIES FOR CONTROLLING BIOFILM FORMATION DURING LONG DURATION SPACE MISSIONS. THE SELECTION OF BACTERIAL SPECIES, GROWTH MEDIA, AND SUBSTRATA MATERIAL MAKE THE RESULTS APPLICABLE TO A) THE SAFETY AND MAINTENANCE OF CREWED SPACECRAFT, B) PLANETARY PROTECTION, C) MITIGATION OF BIOFILM-ASSOCIATED ILLNESSES ON THE CREW, AND D) BIOFILM-ASSOCIATED ILLNESSES ON EARTH, THUS MAKING IT RELEVANT NOT ONLY TO THIS RESEARCH ANNOUNCEMENT, BUT ALSO TO NASA S HUMAN EXPLORATION AND OPERATIONS DIRECTORATE, SPACE BIOLOGY PROGRAM, AND HUMAN RESEARCH ROADMAP.