Alexandra Worden

Alexandra Zoe Worden
Alexandra Z. Worden in 2017
Born	Middlesex County, Massachusetts, United States
Residence	Santa Cruz, California, United States
Nationality	American
Known for	work on Biogeochemical cycling, Evolutionary biology
Scientific career
Fields	Microbiology, Oceanography
Institutions	Monterey Bay Aquarium Research Institute
Doctoral advisor	Brian Binder

Alexandra (Alex) Z. Worden (born 1970) is a marine microbial ecologist and genome scientist. She leads the microbial ecology research group at the Monterey Bay Aquarium Research Institute where she holds the position of Senior Scientist. Her laboratory also bridges with the Ocean Sciences Department at the University of California Santa Cruz where she is Professor Adjunct.

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 (photosynthetic uptake of atmospheric carbon dioxide). Worden’s early work focused on methods development for directly investigating populations in the nature environment and their roles in the carbon cycle. This theme has persisted throughout her research career.

As a postdoctoral fellow at Scripps Institution of Oceanography Worden was recognized for establishing the importance of small eukaryotic phytoplankton known as picoeukaryotes. A second study by Worden while in the laboratory of Farooq Azam overturned the idea that Vibrio cholerae existed primarily attached to copepods in aquatic systems. This was considered important for understanding ecology of this human pathogen and vectors for transmission of infective cells. She and Azam also introduced the concept of Ecosystems Biology (also spelled Eco-systems Biology or (Eco)-systems 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 pioneered eukaryotic "targeted metagenomics" wherein cells of particular interest are separated from the masses using flow cytometry (on a ship) 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 uncultured eukaryotic algae whilst showing the distribution of these photosynthetic protists in the ocean. 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.