Alexandra Z. Worden is a microbial ecologist and genome scientist known for her expertise in the ecology and evolution of ocean microbes and their influence on global biogeochemical cycles. Worden’s research focuses on the physiology and ecology of eukaryotic phytoplankton, unicellular organisms that are responsible for a large portion of ocean primary production. Worden’s early work focused on methods development for directly investigating populations in the natural environment and their roles in the carbon cycle. This theme has persisted throughout her research career. Worden is recognized for establishing the importance of small eukaryotic phytoplankton known as picoeukaryotes. She initiated this research through an NSF Postdoctoral Fellowship in Microbial Biology and expanded it thereafter by adapting multiple molecular and omic methods to characterize the evolution and ecological contributions of these photosynthetic plankton, which are now known to be major ocean primary producers. At Scripps Institution of Oceanography, a different research pursuit on microbial interactions, while in the laboratory of Farooq Azam, led to her work that overturned the idea that Vibrio cholerae existed primarily attached to copepods in aquatic systems. This was considered important for understanding the ecology of this human pathogen and vectors for transmission of infective cells. During this period she and Azam introduced the concept of Ecosystems Biology, coining the term in a 2004 perspective. The concept was embraced by the scientific community in several later perspectives, and is being pursued by human microbiome-biologist Jeroen Raes and microbial oceanographer Edward DeLong. A Jacques Monod conference on Marine Eco-Systems Biology was initiated in 2015. Worden is also known for pioneering "targeted metagenomics" wherein cells of particular interest are separated from the masses using flow cytometry and genomes are then sequenced from only the cells of greatest interest. Using this approach Worden and collaborators at the DOE Joint Genome Institute sequenced partial genomes from a key group of uncultured eukaryotic algae whilst showing the distribution of these photosynthetic protists in the ocean. Most recently, her lab adapted these approaches to study uncultured unicellular predators in the ocean, and discovered giant viruses that infect Choanoflagellates, a widespread predator group related to animals. Remarkably, the viruses bring to the non-photosynthetic, predatory host complete bacteriorhodopsin-like photosystems that pump protons. Her laboratory also investigates ancestral components of land plants, evolutionary biology and distributions of uncultured taxa and interactions between viruses and phytoplankton host cells. In 2015, she and co-authors called for a "rethinking of the marine carbon cycle". Worden publishes in the fields of environmental microbiology, evolutionary biology, genome science and oceanography. She is a proponent of STEM education and innovation and has highlighted the need for relevant "...role models to inspire greater diversity and creativity" in science.
Worden attended Wellesley College, where she received a B.A. in history, and performed a concentration in Earth, Atmospheric and Planetary Sciences coursework at the Massachusetts Institute of Technology, and received a Ph.D. from the Odum School of Ecology in 2000. While at the Massachusetts Institute of Technology she worked in the laboratories of the marine geochemist and paleoceanographer John M. Edmond, the climate scientist Reginald Newell, and the biological oceanographer Sallie W. Chisholm. She had early exposure to engineering through computer programming and work after high school at BBN Technologies and with the Massachusetts Institute of Technology solar electric car project. At the time, the award winning MIT Solar Electric Vehicle Team included several individuals who then became leading innovators in the tech world, including Gill Pratt and Megan Smith, and the team was founded by Worden's brother, James Worden. Engineering and technology innovation have remained as a persistent component of her oceanographic research.
