The unique geochemical coupling of organic molecules and mineral CaCO3provides a fluorescence signature detectable using conventional confocal scanning laser microscopy (CSLM). The surface microbial mats of open-water marine stromatolites (Bahamas) exist in a continuum of states ranging from a Type 1 (i.e., nonlithifying) to Type 2 (i.e., lithified micritic laminae present) to Type 3 (i.e., fused grain layer). An approach was developed here, that

Microspatial arrangements of sulfate-reducing microorganisms (SRM) in surface microbial mats (~1.5 mm) forming open marine stromatolites were investigated. Previous research revealed three different mat types associated with these stromatolites, each with a unique petrographic signature. Here we focused on comparing "non-lithifying" (Type-1) and "lithifying" (Type-2) mats. Our results revealed three major trends: (1) Molecular typing using the dsrA