- Author: Kathy Keatley Garvey
“This is the first paper documenting induction/stimulation of pollen germination by non-plants,” said Christensen, a doctoral candidate in the Microbiology Graduate Group who joined the Vannette lab in January 2019. “Nectar-dwelling Acinetobacter bacteria, commonly found in flowers, stimulate protein release by inducing pollen to germinate and burst, benefitting Acinetobacter.”
The article, “Nectar Bacteria Stimulate Pollen Germination and Bursting to Enhance Microbial Fitness,” is online July 28 and will be in print in the Oct. 11th edition of the journal Current Biology.
Christensen, who co-authored the paper with community ecologist and associate professor Vannette, and former Vannette lab member Ivan Munkres, collected California poppies, Eschscholzia californica, from the UC Davis Arboretum and Public Garden, and Acinetobacter primarily from the Stebbens Cold Canyon Reserve, a unit the UC Natural Reserve System that encompasses the Blue Ridge Berryessa Natural Area in Solano and Napa counties.
The question—“How do organisms actually eat pollen?”--has been a long-standing one, Vannette said, “because pollen is well-protected by a layers of very resistant biopolymers and it's unclear how pollen-eaters get through those protective layers.”
“The finding that bacteria--in this case a specific genus of bacteria-- can cause premature pollen germination and release of nutrients-- is cool for a number of reasons,” said Vannette, a UC Davis Hellman Fellow. “First, Shawn's results are very novel--no one has described this phenomenon before! Second, Acinetobacter is a genus of bacteria that are very common in flowers. They are usually among the most abundant bacteria in nectar and are often found on other floral tissues, including pollen, stigmas etc.”
Christensen, an evolutionary biologist turned microbiologist, studies Acinetobacter and other nectar microbes and their potential influences on pollen for nutrient procurement, as well as the metabolomics of solitary bee pollen provisions.
The UC Davis doctoral student is a recipient of two research awards: the Maurer-Timm Student Research Grant, a UC Davis award for research conducted in the Natural Reserves; and a Davis Botanical Society research award, specifically for this project.
Shawn holds a bachelor of science degree in evolutionary biology from University of Wisconsin-Madison. “I studied reducing ecological impacts of phosphorus runoff, ethnobotany and domestication traits in Brassica rapa, botanical field excursions of all kinds, the evolution of chemical sets in the early origins of life, and now plant-microbe-pollinator interactions."