STAPHYLOCOCCUS EPIDERMIDIS IS AN OPPORTUNISTIC HUMAN PATHOGEN CONSISTENTLY ISOLATED AND DETECTED BY MOLECULAR ANALYSIS ON BOARD THE INTERNATIONAL SPACE STATION. THE FORMATION OF BIOFILMS IS A SIGNIFICANT PROCESS FOR S. EPIDERMIDIS TO ESTABLISH PATHOGENICITY AND FIVE DISTINCT BIOFILM MORPHOTYPES HAVE BEEN RECENTLY IDENTIFIED. THE GOAL OF THIS STUDY IS TO CHARACTERIZE THE BIOFILM FORMING CAPACITY OF ISS ISOLATED S. EPIDERMIDIS STRAINS AND TO INVESTIGATE THEIR PATHOGENICITY IN THE MODEL ORGANISM CAENORHABDITIS ELEGANS. FIRST WE SHALL PROVIDE THE FIRST COMPARATIVE GENOMIC INFORMATION OF S. EPIDERMIDIS STRAINS TO CHARACTERIZE STRAIN-SPECIFIC SEQUENCE VARIANTS AND THE IDENTIFICATION OF MUTATIONS IN BIOFILM-ASSOCIATED GENES THAT MAY HAVE BEEN INCURRED DURING SPACEFLIGHT. WE WILL ALSO EXAMINE THE PRESENCE OF THE CLUSTERED REGULARLY INTERSPACED SHORT PALINDROMIC REPEATS-CRISPR-ASSOCIATED PROTEINS (CRISPR-CAS) THAT CONFER BACTERIAL RESISTANCE TO FOREIGN DNA AND MAY PROVIDE AN ADDITIONAL METHOD OF PERSISTENCE TO SPACE FLIGHT CONDITIONS. USING QUANTITATIVE MICROSCOPIC ANALYSES CONFOCAL SCANNING LASER MICROSCOPY WILL BE USED TO CHARACTERIZE BIOFILM MORPHOTYPES AND EACH MORPHOTYPE WILL BE EVALUATED FOR ANTIBIOTIC RESISTANCE. TRANSCRIPTIONAL ANALYSIS AND PROTEOMIC DATA WILL DETERMINE HOW BIOFILM-ASSOCIATED GENE EXPRESSION AND PROTEIN PRODUCTION VARY AND HOW THESE VARIATIONS RELATE TO THE BIOFILM MORPHOTYPE PRODUCED. IN VIVO PATHOGENICITY TESTS WILL CULMINATE OUR INVESTIGATION INTO THE EFFECT OF S. EPIDERMIDIS BIOFILM MORPHOTYPES ON THE ABILITY TO ESTABLISH INFECTION IN THE MODEL ORGANISM CAENORHABDITIS ELEGANS. THIS WORK WILL HELP TO DETERMINE GENOMIC PHENOTYPIC AND PHYSIOLOGICAL BASIS FOR VARIOUS BIOFILM MORPHOTYPES FORMED BY ISS ISOLATED S. EPIDERMIDIS AND PROVIDE INSIGHT TO PATHOGENI ITY OF SPACE FLIGHT ISOLATED MICROORGANISMS WHERE ASTRONAUT IMMUNITY IS DECREASED AND THE AVAILABILITY OF ANTIBIOTICS IS LIMITED.