Dr Barney Geddes

Post-doctoral Researcher
Barney Geddes

Group Leader

Professor Philip Poole.

Research Areas

Synthetic Biology. Metabolism. Plant-Microbe Interactions. 

Research Description

Engineering synthetic symbioses

Nitrogen (N) is one of the primary limiting nutrients for plant growth.  The high demand for N fertilization in agriculture has led to environmental catastrophe in some parts of the world due to intensive application of inorganic N fertilizers, while in others, yields of cereal crops are limited by the economic inaccessibility of such fertilizers. Both of these issues could be circumvented by transferring the ability to acquire biologically fixed N to cereal crops, a trait that is currently mostly limited to the symbiosis between legumes and N-fixing rhizobia.

Recent advances in synthetic biology have potentiated the cross-species transfer of the genes for N fixation while enforcing synthetic control of their regulation by refactoring nif genes. The Synthetic Symbiosis project (SynSym) aims to transfer N fixation to bacteria with the pre-existing ability to associate with cereal crops. A synthetic N-fixing symbiosis will by supported by using lock-and-key interactions to engineer tailored associations between N-fixing bacteria and cereal crops using established exophytic and endophytic interactions. Key components of these interactions include signal exchange between bacteria and the plant, optimizing carbon supply to bacteria to fuel N fixation, supporting aerobic N fixation through oxygen protection mechanisms and interrupting bacterial N-assimilation to increase N release to the plant.


Geddes, B. A., Ryu, M., Mus, F., Garcia Costas, A., Peters, J. W., Voigt, C. A., and Poole, P. S. (2015). Use of Plant Colonizing Bacteria as Chassis for Transfer of N2-Fixation to Cereals. Current Opinion in Plant Biotechnology. 32: 216-222.
Geddes, B. A., González, J. E., and Oresnik, I. J. (2014). Exopolysaccharide Production in Response to Medium Acidification is Correlated With an Increase in Competition for Nodule Occupancy. Molecular Plant-Microbe Interactions. 27 (12): 1307-1317.
Geddes, B A., and Oresnik, I. J. (2014). Physiology, Genetics and Biochemistry of Carbon Metabolism in the α-Proteobacterium Sinorhizobium meliloti. Canadian Journal of Microbiology. 60 (8): 491-507.
Geddes, B. A., Hausner, G., and Oresnik, I. J. (2013). Phylogenetic Analysis of Erythritol Catabolic Loci Within the Rhizobiales and Proteobacteria. BMC Microbiology. 13 (46).
Geddes, B. A., and Oresnik, I. J. (2012). Inability to Catabolize Galactose Leads to Increased Ability to Compete for Nodule Occupancy in Sinorhizobium meliloti. Journal of Bacteriology. 194 (18): 5044-5053.
Geddes, B. A., and Oresnik, I. J. (2012). Genetic Characterization of a Complex Locus Necessary for the Transport and Catabolism of Erythritol, Adonitol and L-Arabitol in Sinorhizobium meliloti. Microbiology. 158 (8): 2180-2191.
Ding, H., Yip, C. B., Geddes, B. A., Oresnik, I. J., and Hynes, M. F. (2012). Glycerol Utilization by Rhizobium leguminosarum Requires an ABC Transporter and Affects Competition for Nodulation. Microbiology. 158 (5): 1369-1378.
Geddes, B. A., Pickering, B. S., Poysti, N. J., Collins, H., Yudistira, H., and Oresnik, I. J. (2010). A Locus Necessary for the Transport and Catabolism of Erythritol in Sinorhizobium meliloti. Microbiology. 156 (10): 2970-2981.