WITH A FOSSIL RECORD THAT DATES BACK 3.7 BILLION YEARS STROMATOLITES REPRESENT ONE OF THE MOST ANCIENT KNOWN ECOSYSTEMS ON EARTH. THESE LONG-LIVED COMMUNITIES FORM LAMINATED SEDIMENTARY STRUCTURES AS A RESULT OF THE SYNERGY BETWEEN MICROBIAL METABOLISMS AND THE ENVIRONMENT. INVESTIGATIONS OF EXTANT STROMATOLITES REPRESENT A UNIQUE OPPORTUNITY TO UNDERSTAND THE FEEDBACK THAT OCCURS BETWEEN STROMATOLITE COMMUNITIES AND THEIR ENVIRONMENT. TO BEGIN TO EXAMINE THE INTERACTIONS BETWEEN STROMATOLITES AND THEIR ENVIRONMENT IT IS CRITICAL TO CHARACTERIZE THE STROMATOLITE MICROBIOME HERE DEFINED AS THE COLLECTION OF GENOMES OF THE STROMATOLITE MICROBIAL COMMUNITY. THE OVERALL OBJECTIVE OF MY DISSERTATION IS TO COMPARE THE MICROBIOMES OF STROMATOLITE-FORMING MICROBIAL COMMUNITIES FROM ENVIRONMENTALLY DIVERSE SITES. THE RESULTS WILL IDENTIFY POTENTIAL GENETIC PATHWAYS METABOLITES AND EXTRINSIC FACTORS THAT INFLUENCE STROMATOLITE FORMATION. MY CENTRAL HYPOTHESIS IS THAT STROMATOLITES HAVE A UNIQUE MICROBIAL CONSORTIUM THAT DRIVES THE FORMATION OF DISCREET MICROENVIRONMENTS WITHIN THE STROMATOLITE COMMUNITIES WHICH IN TURN INFLUENCES THE EXTENT OF CARBONATE PRECIPITATION. FOR THIS RESEARCH I WILL TARGET THE HYPERSALINE STROMATOLITES OF HAMELIN POOL IN SHARK BAY WESTERN AUSTRALIA. HAMELIN POOL IS THE LARGEST MODERN STROMATOLITE ECOSYSTEM IN THE WORLD WITH A SHORELINE OF 135 KM ALMOST ENTIRELY POPULATED WITH STROMATOLITES. ENVIRONMENTAL PARAMETERS SUCH AS TEMPERATURE SALINITY AND WATER DEPTH VARY EXTENSIVELY THROUGHOUT HAMELIN POOL. SPECIFICALLY I PROPOSE TO: OBJECTIVE 1: COMPARE THE METAGENOMES OF THE THREE-DOMINANT STROMATOLITE-FORMING MAT TYPES FROM HAMELIN POOL SHARK BAY. CURRENTLY I HAVE GENERATED NINE METAGENOMIC LIBRARIES TO THE THREE DOMINANT STROMATOLITE-FORMING MAT TYPES. I PROPOSE TO COMPARE THE METAGENOMES TO ELUCIDATE WHETHER THERE IS A FUNCTIONAL GENE SIGNATURE FOR EACH MAT TYPE. OBJECTIVE 2: ELUCIDATE THE METABOLIC PROFILES OF THE THREE-DOMINANT STROMATOLITE-FORMING MAT TYPES FROM HAMELIN POOL SHARK BAY USING UNTARGETED METABOLOMICS. I PROPOSE TO USE AN UNTARGETED METABOLOMICS APPROACH THAT WILL PROVIDE A COMPREHENSIVE AND UNBIASED ASSESSMENT OF THE STROMATOLITE FORMING MATS AND POTENTIALLY IDENTIFY NOVEL SMALL MOLECULES AND FUNCTIONS. I WILL THEN LINK THE RECOVERED METABOLITES TO THE METAGENOME USING METABOLIC PATHWAY ASSOCIATION ANALYSIS. OBJECTIVE 3: CORRELATE VARIOUS ENVIRONMENTAL FACTORS WITH STROMATOLITE COMMUNITY COMPOSITION AND METABOLIC FUNCTION THROUGHOUT HAMELIN POOL SHARK BAY. IN ADDITION TO THE NINE METAGENOMES DESCRIBED IN OBJECTIVE 1 I HAVE GENERATED AN ADDITIONAL 26 METAGENOMES FROM OTHER SITES WITHIN THE POOL. NOT ALL STROMATOLITE TYPES WERE FOUND IN EACH SITE BUT THE ADDITIONAL METAGENOMES PROVIDE A BROAD GEOGRAPHICAL REPRESENTATION OF THE POOL AS WELL AS CORRESPONDS TO THE LOCATIONS OF THE FIVE CURRENTLY DEPLOYED DATA LOGGERS. THE DATA LOGGERS HAVE BEEN DEPLOYED SINCE 2012 AND RECORD TEMPERATURE SALINITY AND WATER DEPTH. MULTIVARIATE ANALYSES WILL BE TO ASSESS WHETHER THERE IS A STRONG ASSOCIATION BETWEEN THE DIFFERENT ENVIRONMENTAL VARIABLES AND THE METAGENOMES. RELEVANCE: MY RESEARCH PLAN DIRECTLY ADDRESSES NASA S PLANETARY SCIENCE GOALS AS BIOLOGICALLY INDUCED PRECIPITATION OF CALCIUM CARBONATE LEAVES BEHIND DISTINCTIVE FABRICS AND SEDIMENTARY STRUCTURES IN THE FOSSIL RECORD AND THUS STROMATOLITES CAN SERVE AS IMPORTANT BIOMARKERS. ELUCIDATING THE PROCESSES BY WHICH THESE BIOMARKERS FORM ON EARTH WILL HAVE IMPORTANT IMPLICATIONS IN OUR UNDERSTANDING OF EARLY SOLAR SYSTEM HABITABILITY AND OUR SEARCH FOR LIFE ELSEWHERE.