Susan Golden Lab
Circadian Rhythms of Gene Expression in Cyanobacteria
Cells of diverse organisms, from cyanobacteria to humans, use a circadian (24 h) clock to control physiological events and gene expression. The circadian clock of the cyanobacterium Synechococcus elongatus is a discrete nanomachine comprising three proteins — KaiA, KaiB, and KaiC — which interact progressively to set up the timekeeping mechanism, and two kinases whose activities are altered by engaging the Kai oscillator. Our research focuses on understanding the key events that enable the clock to tell time, become set to local time, and regulate global patterns of gene expression and metabolism. To address these research questions we use approaches of molecular genetics, genomics, and biochemistry, and work closely with structural biologists.
Functional Genomics in S. elongatus
The easy genetic manipulation of S. elongatus provides many strategies to understand the function and regulation of its genome. In addition to a suite of genetic tools that enable gene inactivation and overexpression and use of reporter genes, we employ a dense bar-coded transposon library that enables the fitness of thousands of mutants to
be assessed in a population under specific test conditions. This strategy helps to identify unknown genes that contribute to phenotypes of interest by an unbiased, quick, and inexpensive method.
Metabolic Engineering of Cyanobacteria for the production of Biofuels and other Molecules of Interest
Because cyanobacteria grow photosynthetically using water and CO2 and are easy to manipulate genetically, they are attractive organisms for the production of molecules that have industrial applications. One such application is the production of biofuels as a supplementation of or eventual replacement of petroleum fuels. We are using the powerful genetic tools that have been developed for S. elongatus to explore the production of biofuels in cyanobacteria.
James Golden Lab
Genetics, Molecular Biology, and Biotechnology of Cyanobacteria
Current areas of research include the development of improved genetic tools for cyanobacterial genetic engineering and the use of these tools to answer basic-science questions and for biotechnology applications. Our biotechnology-related research involves genetic engineering of cyanobacteria to synthesize bioactive natural products and biofuels. Other projects include identifying cyanobacterial genes related to resistance to grazing by amoebal and ciliate predators, the study of genes required for biosynthesis of cyanobacterial toxins, and the identification of cyanobacterial genes that affect fitness for growth during spaceflight or on Mars. These research projects include work with different strains of cyanobacteria, but focus on the laboratory model strain Synechococcus elongatus, strain PCC 7942, which has excellent genetics and is widely used for synthetic biology studies.
Past research has focused on the developmental biology of cyanobacterial heterocyst formation, with an emphasis on the genetic regulation of cellular differentiation and the cell-to-cell signaling mechanisms that control multicellular pattern formation. This research uses methods of genetics and molecular biology to understand basic principles of regulation and signaling pathways that control development in a simple prokaryotic multicellular organism, the filamentous cyanobacterium Anabaena (Nostoc), strain PCC 7120. Like all cyanobacteria, Anabaena uses light energy for photosynthesis. Anabaena is also capable of nitrogen fixation, a process that is incompatible with photosynthesis because the nitrogenase enzyme is destroyed by oxygen, a byproduct of photosynthesis. Anabaena solves this problem by spatially separating the two processes into different cell types: photosynthetic vegetative cells and nitrogen-fixing heterocysts. Anabaena grows as a very simple multicellular organism composed of filaments of vegetative cells containing about 10 percent heterocysts. Heterocysts differentiate from vegetative cells at semiregular intervals along the filament and supply fixed nitrogen to neighboring vegetative cells to support their growth. We identified a gene, patS, which encodes a small peptide that functions as a diffusible cell-to-cell signal that acts to control heterocyst pattern formation.