Patrick Keeling’s research concentrates on the genomics, evolution, and cell biology of microbial eukaryotes, protists and fungi. The work touches on many areas, but two common themes are the process and history of endosymbiotic events, and the evolution of intracellular parasites. Mitochondria and plastids are organelles that arose by endosymbiosis, and have complex evolutionary histories. Keeling and his lab study how these organelles arose, integrated at the genomic level with the host cell, and changed over time, as well as more complex situations where one eukaryote takes up another leading to cells with several genomes. The work on parasitism focuses on how sophisticated intracellular parasites arise from free-living ancestors, and how this process affects their cells, genomes, and metabolism. In particular, the lab works on the evolution of two very different parasitic groups: the microsporidia and their massively reduced genomes, and the apicomplexans and their cryptic plastid organelles.