Synthetic Biologist Sean Leonard and Honey Bee Gut Bacteria

Synthetic biologist Sean Leonard, a research scientist at the Lawrence Livermore Laboratory, will deliver a UC Davis Department of Entomology and Nematology seminar on "Engineering Honey Bee Gut Bacteria to Activate Immunity and Limit Pathogens" on Wednesday, Oct. 29.

He will present the seminar at 12:10 in 122 Briggs Hall and also on Zoom. The Zoom link: https://ucdavis.zoom.us/j/95882849672.

"Honey bees are essential pollinators threatened by colony losses linked to the spread of parasites and pathogens," Leonard writes in his abstract. "In this talk I will discuss how we developed a microbial synthetic biology approach for manipulating bee gene expression and protecting bee health. We engineered a symbiotic bee gut bacterium, Snodgrassella alvi, to induce eukaryotic RNA interference (RNAi) immune responses."

Improve Honey Bee Survival

"We show that engineered S. alvi can stably recolonize bees and produce double-stranded RNA to activate RNAi and repress host gene expression, thereby altering bee physiology, behavior, and growth," he continued. "We used this approach to improve bee survival after a viral challenge, and we show that engineered S. alvi can kill parasitic Varroa mites by triggering the mite RNAi response. This symbiont-mediated RNAi approach may be a tool for studying bee functional genomics and potentially for safeguarding bee health. I will discuss recent developments extending this work and other work in bee microbiome engineering, and considerations for extended symbiont-mediated RNAi more broadly."

Leonard will be introduced by doctoral candidate Lexie Martin of the lab of community ecologist Rachel Vannette, associate professor and vice chair of the UC Davis Department of Entomology and Nematology. Martin previously worked with him in a lab at the University of Texas, Austin, where he was a graduate student and she, an undergraduate. "He did work on engineering honey bee bacterial symbionts using RNAi--and got a cool Science paper out of it," she told the Department of Entomology and Nematology in an email. "He now works at the Lawrence Livermore and studies biocontainment of genetically engineered microbes."

The paper: "Engineered Symbionts Activate Honey Bee Immunity and Limit Pathogens," published Jan 31, 2020 in Science. 

"Honey bees are prone to parasitism by the Varroa mite, which is a vector for several bee pathogens," Leonard and his colleagues wrote in the Science paper. "However, honey bees are also host to the symbiotic gut bacterium Snodgrassella alvi. Leonard et al. engineered S. alvi to produce double-stranded RNA (dsRNA)—a stimulus for insect RNA interference defense responses—from a plasmid containing two inverted promoters tagged with a fluorescent label (see the Perspective by Paxton). This dsRNA module can be targeted to interfere with specific bee genes as well as crucial viral and mite genes. The authors found that gene expression could be blocked for at least 15 days as the symbionts established in the bees' guts and continuously expressed the dsRNA constructs. S. alvi with specifically targeted plasmids not only suppressed infection with deformed wing virus but also effectively reduced Varroa mite survival."

Leonard, who joined the Lawrence Livermore Laboratory in September of 2021 as a postdoctoral researcher and advanced to research scientist in December of 2024, holds a bachelor of science degree (2006) in biology/chemistry from Loyola University, Maryland. He received his master's degree in biotechnology (2013) from the University of Texas (UT), San Antonio, and his doctorate in synthetic biology  (2020) from UT, Austin. 

"I work to understand the utility and risks of biological design methods, and manipulate symbiont and environmental communities for human benefit," he writes on LinkedIn.