It is generally assumed that modern microbial life relies on buried or transported organic carbon generated by plant primary productivity on the surface. However, in environments where organic carbon is depleted or is biologically unavailable, environmental microorganisms will utilize reduced inorganic elements including Fe, as energy sources (electron donors) for cellular respiration. Respiration in these environments can occur aerobically using molecular oxygen (O2) or anaerobically in the absence of O2 using an alternative electron acceptor such as nitrate. These metabolic reactions while generating chemical energy supporting microbial life will in turn alter environmental chemistry impacting water quality and/or nutrients available to other living organisms. These metabolically active microorganisms are also susceptible to viral infection. Not only can viral-mediated cell-lysis change available carbon pools, it will directly change microbial community structure thus also influencing biogeochemistry. Research conducted in the Weber Laboratory has focused on interactions between microorganisms and geochemical cycling in the present and in the past.