Research Interests

Physiological, biochemical, genetic and genomic analysis of cellular differentiation in filamentous cyanobacteria - Symbiotic interactions. Our experimetnal system is the filamentous cyanobacterium Nostoc punctiforme. N. punctiforme is unique in that, depending on environmental signals, its vegetative cells can differentiate into three distinct and mutually exclusive cell types: nitrogen-fixing heterocysts (when limited for combined nitrogen), spore-like akinetes (when energy stressed), and motile by gliding hormogonium filaments (under conditions both positive and negative for growth). Moreover, N. punctiforme can fix nitrogen in free-living and plant-associated symbiotic growth states. The plant partners span the phylogenetic spectrum from Bryophyte hornworts and liverworts, to Gymnosperm cycads, and the Angiosperm family Gunneraceae. When in symbiotic association, the plant partners control the differentiation and physiological behavior of hormogonia (the infective units) and heterocysts (the functional units). The genome of N. punctiforme, at 9.059 Mbp, is large for a bacterium and is distributed between an 8.23 Mbp circular chromosome and five plasmids ranging from 26 to 354 kbp. We apply biochemical, genetic and genomic (proteomic and transcriptomic) approaches to identify and manipulate the regulatory pathways of free-living and symbiotic cellular differentiation of N. punctiforme.