Bacteria are the most abundant organisms in soil, and their activities can have major consequences for plant health. Pathogenic bacteria can devastate the productivity and quality of crops, whereas other species can directly promote plant development. These beneficial bacteria act through diverse mechanisms, including converting nutrients into forms that can be more easily broken down by plants, limiting the spread of pathogens, and helping plants survive our rapidly changing climate. Harnessing the functions of beneficial bacteria has the potential to transform agriculture. A major challenge of the next century will be to determine how they can be employed to help feed the planet.
The Belin lab studies the biology of rhizobia, soil bacteria with the capacity to convert nitrogen gas in the atmosphere into plant-fertilizing ammonia. These rhizobia form intimate symbioses with legumes including soybean, alfalfa, pea, and clover, serving as sustainable alternatives to synthetic nitrogen fertilizers. We use quantitative, cell biological approaches to understand the factors that impact symbiotic productivity in the Bradyrhizobium genus of rhizobia.
The establishment of legume-rhizobia symbiosis requires incredibly complex developmental processes. Free-living rhizobia in the soil are attracted to signals released by plant roots, and in turn release symbiosis-specific signals that facilitate their colonization and invasion of roots. Once the rhizobia have invaded the inner layers of the root tissue, they are engulfed by plant cells to become intracellular (endo-) symbionts. These endosymbiotic bacteria and the plant cells they infect then proliferate to form a new organ known as the root nodule, consisting of plant cells that each harbor many hundreds of endosymbionts. During proliferation, both partners also shift their metabolic output for mutual benefit: endosymbionts shut down most basal metabolic activity to become powerhouses at nitrogen fixation (the conversion of gaseous nitrogen into ammonia), while legumes allocate much of the sugars derived from photosynthesis to support endosymbiont growth.
The legume-rhizobia symbiosis is a keystone example of inter-species cooperation, yet we still do not know many of the molecular details of these interactions. We currently have multiple funded projects available for technicians, graduate students, and postdocs to address the following questions:
How do rhizobia organize their membranes, and what are the roles of membrane organization during symbiosis?
Patterns of membrane fluidity in single Bradyrhizobium cells acquired by super-resolution microscopy.
(Belin et al., in prep)
How do bacteria adapt to the chemical and mechanical stresses presented during the invasion of legume roots?
Bradyrhizobia (green) colonizing and invading Aeschynomene legume roots (adapted from Bonaldi et al. MPMI 2011)
How are rates of rhizobia and nodule growth controlled - through which partner and
by what mechanisms?
Aeschynomene nodule growth and localization of Bradyrhizobia (green) in host cells (L) and nodules (R) (adapted from Belin et al. MPMI 2019)
Dr. Brittany Belin, Principal Investigator
Brittany received her B.S. in biochemistry and philosophy from the University of Notre Dame and her Ph.D. in biophysics at the University of California, San Francisco under the mentorship of Dr. Dyche Mullins. In 2015 she began to study plant-bacteria symbiosis as a post-doc in the laboratory of Dr. Dianne Newman at Caltech. Her laboratory at the Carnegie Institution for Science Department of Embryology, located on the Johns Hopkins campus, opens in August 2020. She is interested in cell biology and symbiosis in all of its forms.
Email: belin at carnegiescience dot edu
Zeke, Lab Mascot
Zelda, Lab Mascot
We are hiring!
As a newly-established research group, we have lots of positions to fill and would love for curious scientists of all stripes to consider joining! Specific openings can be found at the Carnegie Institution for Science job board. Applications for positions can also be sent year-round to Dr. Belin as follows:
Prospective Graduate Students should apply through the Cell, Molecular, Developmental Biology, and Biophysics (CMDB) graduate program at Johns Hopkins. Already in the program? Please e-mail Dr. Belin to connect!
Prospective Technicians, Staff Researchers, and Postdocs can apply by e-mailing Dr. Belin the following information: cover letter, one page summary of research interests and career goals, CV, reprints of recent publications (if available), and contact information for 3-5 references.
Belin, B.J.,Tookmanian, E.M., de Anda, J., Wong, G.C.L., Newman, D.K. (2019) Extended
Hopanoid Loss Reduces Bacterial Motility and Surface Attachment and Leads to Heterogeneity
in Root Nodule Growth Kinetics in a Bradyrhizobium-Aeschynomene Symbiosis. Mol Plant Microbe Interact. 2019 32 (10), 1415-1428.
Belin, B.J., Busset, N., Giraud, E., Molinaro, A., Silipo, A., Newman, D.K. (2018) Hopanoid
lipids: from membranes to plant-bacteria interactions. Nat. Rev. Microbiol. 16(5):304-315.
For a full list of Dr. Belin's publications, see Google Scholar.
Carnegie Institution for Science
Department of Embryology
3520 San Martin Drive
Baltimore, Maryland 21218
belin at carnegiescience dot edu