Current and past research projects include: (i) harmful algal blooms, especially toxic cyanobacterial blooms in Lake Erie; (ii) the regulation of oxygenic and anoxygenic photosynthesis in cyanobacterial mats, and how this relates to the oxygenation of Earth's atmosphere; (iii) in collaboration with David Sherman, the genomic underpinning of natural products including toxins, antibiotics, and anti-cancer compounds; (iv) Genetics, biochemistry, physiology, and genomics of Mn(II)-oxidizing bacteria that catalyze the formation of biogenic Mn oxides; (v) Diversity and function of microbial communities in deep-sea hydrothermal plumes; and (vi) microbial community genomics of acid mine drainage (AMD).