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Project Progress

We constructed a model to simulate C, O, and S cycles, and growth of cyanobacteria and sulfur bacteria in a stratified hypersaline mat. The aim was to simulate microbial effects on the atmospheric chemistry of early Earth. Inputs to the mat system include photosynthetically active radiation (PAR), near infrared radiation (NIR), and temperature. Attenuation of PAR with each layer is modeled, and NIR attenuation depends on the abundance of bacteriochlorophyll a. The bacterial groups whose metabolism and growth are simulated include cyanobacteria (CYA), purple sulfur bacteria (PSB), colorless sulfur bacteria (CSB), and sulfur reducing bacteria (SRB). Growth of CYA occurs by either oxygenic or anoxygenic photosynthesis (AP), depending on the available substrate (O₂ or H₂S). PSB growth occurs by AP using NIR and H₂S or by chemosynthesis (CH), using O₂ and H₂S. Growth of CSB occurs via CH, also using O₂ and H₂S. SRB growth occurs via anaerobic CH utilizing SO₄ ^2- and creating H₂S in the process. The model consists of 10 layers (1 mm each), and gains density as biomass increases. Gas diffusion occurs between successive layers. The model was constructed in a Stellatm environment, and will be updated to include methanogens and decomposition before being programmed into an environment that is compatible with atmospheric simulations of early Earth.