His primary research focus is microbial physiology and the environmental and evolutionary influence on physiological variation. For example, how do modern day gradients in environmental parameters (e.g. light, nitrogen, Fe availability) influence the genomic contents and cellular regulation in marine microbes? How have dramatic shifts in the global redox state over the past 4 billion years constrained the evolution of biochemical pathways and biogeochemical cycles? An integrated approach of wet-lab organismal work, field studies, and bioinformatics analyses is used to address these questions.