“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."
Two UC Davis Department of Entomology and Nematology faculty members are now full professors, and a third faculty member has achieved tenure as associate professor.
Molecular geneticist and physiologist Joanna Chiu, vice chair of the department, and community ecologist Louie Yang were promoted from associate professors to professors, effective July 1. Community ecologist Rachel Vannette was promoted from assistant professor to associate professor.
Professor Chiu joined the Department of Entomology and Nematology in 2010 as an assistant professor and advanced to associate professor and vice chair in 2016. She received her bachelor's degree in biology and music from Mount Holyoke College, Mass., and her doctorate in molecular genetics in 2004 from New York University, New York. She served as a postdoctoral fellow from 2004 to 2010 in chronobiology (biological rhythms and internal clocks)--molecular genetics and biochemistry--at the Center for Advanced Biotechnology and Medicine, at Rutgers, the State University of New Jersey.
Chiu's research expertise includes molecular genetics of biological timing and posttranslational regulation of proteins. She uses animal models including Drosophila melanogaster and mice to study the mechanisms that regulate circadian and seasonal physiology and behavior. Major grants from the National Institutes of Health and the National Science Foundation fund her biological rhythms research. In addition to her research in biological rhythms, Chiu also aims to leverage her expertise in genomics to address key issues in global food security.
In 2019, she was named one of 10 UC Davis Chancellor's Fellows, an honor awarded to associate professors who excel in research and teaching.
Chiu and Yang co-founded and co-direct (with Professor Jay Rosenheim) the campuswide Research Scholars Program in Insect Biology, launched in 2011 to provide undergraduates with a closely mentored research experience in biology. The program crosses numerous biological fields, including population biology; behavior and ecology; biodiversity and evolutionary ecology; agroecology; genetics and molecular biology; biochemistry and physiology; entomology; and cell biology. The goal is to provide academically strong and highly motivated undergraduates with a multi-year research experience that cultivates skills that will prepare them for a career in biological research.
Professor Yang, who holds a bachelor's degree (ecology and evolution) from Cornell University, 1999, received his doctorate from UC Davis in 2006, and joined the UC Davis faculty in 2009. In 2013, he received a prestigious National Science Foundation Faculty Early Career Development Award of $600,000. He was named a UC Davis Hellman Fellow in 2012; the Hellman Family Foundation contributes funds to support and encourage the research of promising assistant professors who exhibit potential for great distinction in their research. He was promoted to associate professor in 2015.
Yang won the 2018 Outstanding Faculty Academic Advising Award from NACADA, also known as the Global Community for Academic Advising; and the 2017 Faculty Advisor Award of Excellence in NACADA's Pacific Region 9, comprised of California, Nevada and Hawaii.
Yang says of the research underway in his lab: “We study how species interactions change over time. We apply a diversity of approaches and perspectives to a diversity of systems and questions. We do experimental community ecology. We also use observational methods, meta-analysis, conceptual synthesis, ecosystem perspectives, and theoretical models. We like data, and we like learning new things.”
Associate Professor Vannette joined the UC Davis Department of Entomology and Nematology in 2015 after serving as a postdoctoral fellow at Stanford University's biology department, where she was a Gordon and Betty Moore Foundation Postdoctoral Fellow from 2011 to 2015 and examined the role of nectar chemistry in community assembly of yeasts and plant-pollinator interactions.
Vannette received her bachelor of science degree, summa cum laude, in 2006 from Calvin College, Grand Rapids,Mich., and her doctorate from the University of Michigan's Department of Ecology and Evolutionary Biology, Ann Arbor, in 2011. She received a Hellman Fellowship grant in 2018 and a National Science Foundation Faculty Early Career Development Award in 2019 to study microbial communities in flowers and a National Science Foundation grant to support work on solitary bee microbiomes.
Of her research, Vannette says: “ All plants are colonized by microorganisms that influence plant traits and interactions with other species, including insects that consume or pollinate plants. I am interested in the basic and applied aspects of microbial contributions to the interaction between plants and insects. I also use these systems to answer basic ecological questions, such as what mechanisms influence plant biodiversity and trait evolution.”
“The Vannette lab is a team of entomologists, microbiologists, chemical ecologists, and community ecologists trying to understand how microbial communities affect plants and insects (sometimes other organisms, too),” she says. “We often study microbial communities in flowers, on insects or in soil. We rely on natural history observations, and use techniques from chemical ecology, microbial ecology and community ecology. In some cases, we study applied problems with an immediate application including pathogen control or how to support pollinators. Other questions may not have an immediate application but are nonetheless grounded in theory and will contribute to basic knowledge and conservation (e.g. how can dispersal differences among organisms affect patterns of abundance or biodiversity?)”
Zemenick, who began work July 1, first traveled to Sagehen while in graduate school and conducted dissertation research there on how plant visitors shape floral microbial communities.
What sparked Ash's interest in entomology? "I first became interested in entomology as an undergraduate student at the University of Michigan. I learned how important insects are in agroecosystems, and how their intricate, overlapping interactions can have strong impacts on sustainable management and crop production."
As a youngster, "I was kind of afraid of bugs--at least when they were in the house--but once I started learning about them I was so fascinated. This was solidified when I took Bug Boot Camp (the Insect Taxonomy and Field Ecology" course taught at the Sagehen Field Station by ant specialist Phil Ward, professor of entomology, UC Davis Department of Entomology and Nematology) where I fell in love with parasitoid wasps."
Zemenick, a native of Grosse Pointe Woods, Mich., received a doctorate in ecology from UC Davis in September 2017, studying with Jay Rosenheim, distinguished professor of entomology, and with assistant professor Rachel Vannette, a Hellman fellow.
And now, in a near full-circle move, Zemenick is back home.
The Sagehen Field Station, headquartered in Truckee on a 9000-acre site on the western slope of the Sierra Nevada, has focused on research and teaching since 1951. It serves as the hub of a broader network of research areas known as the Central Sierra Field Research Stations, comprised of not only the Sagehen Creek Field Station, but Central Sierra Snow Laboratory, Onion Creek Experimental Watershed, Chickering American River Reserve, and North Fork Association Lands, according to the website.
The surrounding watershed is also available to researchers and classes through an agreement with the Forest Service and includes extensive stands of yellow pine, mixed conifer, and red fir forests, as well as sagebrush fields, scattered mountain meadows, and fens (marshland).
More than 80 graduate students--including Zemenick--have worked on their projects at Sagehen, completing their degrees on such topics as behavioral studies of dark-eyed juncos, stream runoff modeling, bees/butterflies in mountain montane meadows, and GIS as a tool for reserve master planning.
In addition to managing the Sagehen Creek Field Station, Zemenick will coordinate requests to work at Chickering American River Reserve as well as North Fork Association Lands. As Chickering and the North Fork lands are privately owned, user visits are negotiated with the private land partners.
Zemenick returns to California after serving as a National Science Foundation postdoctoral fellow in the Weber lab at Michigan State University. "I studied how plant-mite interactions directly and indirectly influence leaf microbial communities and subsequent invasibility by pathogens."
"I co-created, built and directed Project Biodiversify, an online repository of teaching tools to promote diversity, inclusion and belonging in STEM classrooms," said Zemenick. The federally funded Michigan State University project "includes how biological research applies to current societal problems and highlighted what it is like to be a biologist. The materials are comprised of examples provided by biologists that self-identify as being part of underrepresented group(s) in STEM (e.g. in terms of race, ethnicity, gender, sex, sexuality, income, nationality, immigrant status, cognitive and physical ability, etc.)." The project was recently awarded a University Level Excellence in Diversity Award for work promoting diversity, equity and inclusion (DEI) in biology education.
Zemenick will continue pursuing ecology and environmental science involving plants, insects, microbes, ecological networks, natural history, and discipline-based education research. Leisure time includes such interests as naturalizing, backpacking, climbing and biking. "I hiked the Nüümü Poyo (John Muir) Trail in 2009 and love the mountains," the ecologist related.
(Editor's Note: Science writer Kathleen Wong of the UC Natural Reserve System contributed to this story.)
Jacob “Jake” Francis, a member of the Vannette lab since 2020, received a National Science Foundation (NSF) Postdoctoral Research Fellowship in Biology (PRFB) to study secondary metabolites in nectar and their consequences for microbes and pollinators. His project is titled “Genetic Signal and Ecological Consequences of Toxic Nectar in Plant-Pollinator Microbe Interactions.”
Jacob “Jake” Cecala, who just received his doctorate from UC Riverside and will join the Vannette lab this fall, received a postdoctoral fellowship granted by the USDA's National Institute of Food and Agriculture to study the effects of water availability and pesticide use on bees and bee-microbe associations.
Jacob 'Jake' Francis
“Plants produce complex suites of chemicals in their vegetation and flowers that impact ecological interactions with herbivores, microbes, and pollinators,” Francis explained in his application. “These plant-produced chemicals are important to human society; they can be poisonous to livestock, mediate crop disease, and offer natural chemical libraries for drug discovery. While the consequences of these compounds in vegetative tissues has been extensively studied, much less is known about how specialized chemicals in pollen and nectar impact plants' interactions with pollinators and flower-inhabiting microbes.”
“Many flowers harbor communities of beneficial and/or pathogenic fungi and bacteria that can impact pollinator behavior and health,” Francis pointed out. “Through a combination of genomic studies, manipulative experiments, and simulation modeling, this postdoctoral project will test the link between plant genomes, specialized chemistry, floral microbiome, and pollinator behavior.”
Francis will focus on a highly bioactive class of nectar compounds, pyrrolizidine alkaloids, produced by the naturalized non-native plant purple viper's bugloss, Echium plantagineum. He will characterize the alkaloid content of the nectar and vegetation of 150 plants across three populations.
His NSF grant involves collecting and isolating nectar microbes from Echium and co-flowering species and testing whether Echium-collected microbes are better able to grow in the presence of toxic alkaloids than other nectar microbes. Francis also will test how microbial growth and nectar alkaloid content interactively impact nectar consumption by bumblebees. Throughout this process, he will receive extensive training in microbiological and genetic techniques from his sponsoring scientists, assistant professor Rachel Vannette and Daniel Kliebenstein, a professor in the UC Davis Department of Plant Sciences.
Francis received his doctorate in 2020 from the University of Nevada, Reno, working with advisor Anne Leonard of the Department of Biology's Program in Ecology, Evolution and Conservation Biology. He holds a bachelor's degree from the University of North Carolina Asheville (2011) in ecology and evolution, summa cum laude, with distinction as both a research scholar and an honors scholar.
Active in the Ecological Society of America (ESA), Francis delivered an invited presentation at ESA's 2021 meeting on “Pollinator Nutrition from a Plant's Eye View: Floral Reward Macronutrients Predict Patterns of Pollen Movement in a Co-Flowering Plant Community.” Francis is also interested in sharing the excitement of entomology with students: At ESA's 2011 meeting, he presented at an organized session on “Pair Power Collaboration with ESA's Next Generation of Ecologists (undergraduates) as Evidence of Earth Stewardship.” He has also delivered presentations at the Entomological Society of America meetings.
Francis most recently has co-authored research on “Microbes and Pollinator Behavior in the Floral Marketplace” in Current Opinions in Insect Science; and has published in journals such as Current Biology and Behavioral Ecology.
Cecala joined the doctoral program at UC Riverside in 2015, receiving his PhD in entomology in 2021. He was advised by associate professor Erin Wilson-Rankin (formerly of the Louie Yang lab, UC Davis). His dissertation: “Commercial Plant Nurseries as Habitat for Wild Bees.”
“Microbes inhabiting floral nectar have garnered attention due to their potential to alter interactions between bees and flowers, and thus influence pollination,” Cecala related. “These bacteria and yeasts, just like macroorganisms, can be subjected to non-target impacts of agricultural pesticides, potentially affecting bee behavior and crop pollination. Neonicotinoids are the most widely used class of insecticides worldwide and can alter certain microbial communities, yet we know nothing of how they impact nectar microbes. Furthermore, irrigation (i.e., plant water availability) influences neonicotinoid translocation through plant tissues and nectar properties, yet the impacts of this agricultural practice on nectar microbes also remain unstudied.”
Jake Cecala will investigate how neonicotinoids and plant water availability interact to affect nectar microbes and ultimately pollination. “Specifically, I will test (1) how neonicotinoids affect the taxonomic composition of nectar microbes in plants grown under differing watering regimes; (2) how these altered microbial communities affect nectar consumption by solitary bees; and (3) how this translates to pollination and seed set under semi-field conditions.”
“This project aims to understand how these commonplace agricultural practices may influence pollination via the floral microbiome, in hopes of further integrating sustainable pest and pollinator management in North American agriculture,” noted Cecala. The project aligns with the Agriculture and Food Research Initiative (AFRI) Farm Bill Priority Area "Plant Health, Production, and Plant Products.”
Cecala holds a master's degree in biological sciences (2015) from California State Polytechnic University, Pomona, where he completed his thesis, “Bee Visit Frequency and Time of Day Effects on Cumulative Pollen Deposition in Watermelon” with professor Joan Leong, who was a doctoral student of the late Robbin Thorp, UC Davis distinguished emeritus professor. Cecala was awarded his bachelor's degree in biology, summa cum laude, with a minor in French, also from Cal Poly Pomona.
Cecala is also a 2013 graduate of The Bee Course, sponsored by the American Museum of Natural History, held annually at the Southwestern Research Station, Portal, Ariz. Professor Thorp served as one of the longtime instructors.
At the Wilson-Rankin lab, Cecala researched wild bee biodiversity and resource use in agricultural areas; floral resource quality, pesticides and their impacts on bee health and fitness; and plant-pollinator interaction networks in coastal sage scrub habitats.
Among his most recent research publications, he co-authored articles on
- “Diet Quality and the Effects of Chronic Oral Imidacloprid Exposure on the Alfalfa Leafcutting Bee, Megachile rotundata” in the Journal of Economic Entomology.
- “Differential Feeding Responses of Several Bee Species to Sugar Sources Containing Iridomyrmecin, an Argentine Ant Trail Pheromone Component” in the Journal of Insect Behavior.”
- “Floral Bagging Differentially Affects Handling Behaviors and Single-Visit Pollen Deposition by Honey Bees and Native Bees,” in Ecological Entomology.
- “Mark-Recapture Experiments Reveal Foraging Behavior and Plant Fidelity of Native Bees in Plant Nurseries” in Ecology.
- “Wild Bee Conservation within Urban Gardens and Nurseries: Effects of Local and Landscape Management” in Sustainability.
Active in the Entomological Society of America and its Pacific Branch (PBESA), Cecala drew recognition at PBESA meetings for his award-winning poster and an oral presentation.
His presentation on “Pollinators and Plant Nurseries: How Ornamental Plant Management Impairs Solitary Bee Fitness” won “best lightning talk” at EcoSlam 2019, hosted by the UC Riverside's Center for Conservation Biology./bold>
His presentation, from 4:10 to 5 p.m., Wednesday, May 26, will be hosted by community ecologist Rachel Vannette, assistant professor, UC Davis Department of Entomology and Nematology. Access the Zoom link here.
"All ecosystems are shaped and, to a certain degree, regulated by microorganisms," Ceja-Navarro says in his abstract. "Microorganisms on multiple trophic levels interact with each other and with their surrounding environment. For example, in the rhizosphere, protozoa and nematodes regulate the dynamics and turnover of bacterial and fungal communities associated with plants. While doing so, protists and nematodes increase nutrient availability and even trigger certain trait expression in the microbes."
"In order to understand and predict the ecosystem's capacity to remain stable, resist, and recover from environmental stress, it is essential to identify key biological players across trophic levels and understand well their contributions to the maintenance of complex systems," he points out. "This applies to all ecosystems where trophic complexity exists, from insects' gut microbiome, to the rhizosphere of a plant, or complex terrestrial and aquatic ecosystems. In this presentation, I will share my experiences with the use of multi-‘omics and chemical analyses to characterize microbial community composition, the distribution of microbial function, and trophic associations in the gut of insects, the rhizosphere of plants, and a soil chronosequence. Overall, my research shows that environmental filtering is key driver for microbial community composition and function across kingdoms offering clues on the susceptibility of microbial food webs to environmental change."
Ceja-Navarro focuses his research program on the study of multitrophic interactions in ecosystems such as digestive tracts of insects and soil. Specific focus topics of research include: (1) the study of arthropods as microbial bioreactors; (2) co-evolution of insects' digestive tract physical structure and microbial function for the transformation of recalcitrant molecules such as lignocellulose; and (3) environmental engineering and regulation of ecosystem services driven by the multitrophic interactions among the members of the food web of complex ecosystems, their contributions to ecosystems function, and responses to environmental change.
"As a scientist, my goal is to develop and apply innovations in the fields of molecular biology, biotechnology, bioinformatics, and chemical engineering using multidisciplinary tools to understand the mechanisms that control multitrophic interactions in diverse biological systems," he writes on his website. "I combine my passion for the study of the arthropod microbiome with my continuing fascination with soil complexity, to work on a research line that considers the cross-kingdom interactions (the associations between bacteria, fungi, protists, and nematodes), host-microbe interactions in soil microarthropods (ticks, springtails, mites), and the effect of these associations on processes such as biogeochemical cycling, biomass conversion, the evolution of the microbiome in the environment."
Ceja-Navarro holds a bachelor's degree in chemical engineering (2005) from Instituto Tecnologico de Celaya. Guanajuato, Mexico, and a doctorate in biotechnology (2009) from Centro de Investigacion y de Estudios Avanzados del I.P.N. Mexico City, Mexico. He participated in the leadership development program at the Lawrence Berkeley National Laboratory/UC Berkeley Program, Berkeley Haas School of Business, in 2015-2016.
His credentials include postdoctoral researcher at the Lawrence Berkeley National Laboratory (LBNL) Climate and Ecosystem Sciences, Division, Berkeley, from 2010 to 2014; and project scientist from 2014-2016. He was promoted to research scientist in June 2016.
In a YouTube presentation titled "Beetles, Biofuel and Coffee," Ceja-Navarro discussed his research on the microbial populations found the guts of insects, specifically the coffee berry borer that may lead to better pest management; and the Passalid beetle, which could lead to improved biofuel production.
LBNL, commonly referred to as Berkeley Lab, conducts scientific research on behalf of the Department of Energy. The lab, located in the hills of Berkeley, overlooks the UC Berkeley campus.
Cooperative Extension specialist Ian Grettenberger coordinates the spring seminars, which take place every Wednesday at 4:10 p.m. He may be reached at email@example.com for any technical issues.