Cyanobacteria are a diverse group of oxygenic, photosynthetic bacteria that inhabit virtually every major aquatic and terrestrial biome. They have played important evolutionary and ecological roles on Earth. Cyanobacteria have an ancient history dating back at least 3.5 billion years. They diversified to become some of the most successful and ecologically significant organisms on Earth, with respect to longevity and impact on the Earth’s early environment. It is widely believed that caynobacteria were responsible for the conversion of the Earth’s early anaerobic atmosphere to an aerobic one through oxygenic photosynthesis – a pivotal event that led to the evolution of diverse life on Earth. Ancient cyanobacteria also were the progenitors of modern day chloroplasts of plants.
Many cyanobacteria are major suppliers of fixed nitrogen through the process of nitrogen fixation and play important roles in the oceans and in nutrient-depleted regions. While carbon fixation, through photosynthesis, arose early in the evolution of organisms, it is not known when nitrogen fixation first occurred. Two conflicting hypotheses have been proposed: 1) that nitrogen fixation genes are ancient and that the primary nitrogen fixation enzyme, nitrogenase, had a different function originally (detoxification) and 2) that nitrogen fixation is a more recent acquisition. Cyanobacteria exist primarily as free-living bacteria, although some form symbiotic associations with a variety of other organisms.
The overall goals in my laboratory are: 1) to study the evolution of nitrogen fixation genes in bacteria; 2) to study the variation, evolution, excision, and function of insertion elements in cyanobacteria that are excised from within specific genes during heterocyst differentiation and subsequent nitrogen fixation; and 3) to study the molecular interactions of cyanobacterial-plant symbioses.
My students use molecular biology, phylogenetics, and bioinformatics approaches in their research. They use a variety of methods such as PCR, DNA sequencing, microarray analysis, computational analyses using bioinformatics tools to compare sequences, identify functional regions of DNA, and generate phylogenetic trees. We work closely with the Center for Bioinformatics and Functional Genomics.
Henson, B.J., L.E. Pennington, L.E. Watson, and S.R. Barnum. 2007, in press. Excision of the nifD element in heterocystous cyanobacteria. Archives of Microbiology.
Barnum, S. R. 2005 copyright. Biotechnology: An Introduction, 2nd ed. Wadsworth Publishing Company, Belmont, California.
B. Henson, L. E. Watson, and S. R. Barnum. 2005. Characterization of a 4 kb variant of the nifD element in Anabaena sp. Strain ATCC 33047. Current Microbiology 50:129-132.
B. Henson, L. E. Watson, and S. R. Barnum. 2004. The evolutionary history of nitrogen fixation as assessed by nifD. Journal of Molecular Evolution 58:390-399.
B. Henson, S. M. Hesselbrock, L. E. Watson, and S. R. Barnum. 2004. Molecular phylogeny of the heterocystous cyanobacteria (Subsections IV and V) based on nifD. International Journal of Systematic and Evolutionary Microbiology. [DOI 10.1099/ijs.0.02821-0] http://ijs.sgmjournals.org/cgi/content/full/54/2/493
F. Fang and S. R. Barnum. 2004. Expression of the heat shock gene hsp16.6 and promoter analysis in the cyanobacterium Synechocystis sp. PCC 6803. Current Microbiology 49:192-198.
F. Fang and S. R. Barnum. 2003. The heat shock gene, htpG, and thermotolerance in the cyanobacterium, Synechocystis sp. PCC 6803. Current Microbiology 47:341-346.
B. Henson, L. E. Watson, and S. R. Barnum. 2002. Molecular differentiation of the heterocystous cyanobacateria, Nostoc and Anabaena, based on complete nifD sequences. Current Microbiology 45:161-164.
Lee, S., H. A. Owen, D. J. Prochaska, and S. R. Barnum. 2000. HSP16.6 is involved in the development of thermotolerance and thylakoid stability in the unicellular cyanobacterium, SynechocystisD sp. PCC 6803. Current Microbiology 40:283-287.
Lee, S., D.J. Prochaska, F. Fang, and S.R. Barnum. 1998. A 16.6 kDa protein in the cyanobacterium, Snynechocystis sp. PCC 6803 plays a role in the heat shock response. Current Microbiology 37:403-407.
Blondin, P. A., Kirby, R. J., and Barnum, S.R. 1993. The heat shock response and acquired thermotolerance in three strains of cyanobacteria. Current Microbiology 26:79-84.
Perkins, D. R. and Barnum, S. R. 1992. DNA sequence and analysis of a cryptic 4.2 kb plasmid from the filamentous cyano-bacterium, Plactonema sp. Strain PCC 6402. Plasmid 28:170-176.
Clough, R. C., Matthis, A. L., Barnum, S. R., and Jaworski, J. G. 1992. Purification and characterization of 3-ketoacylacyl carrier protein synthase III from spinach. Journal Biological Chemistry 267:20992-20998.
Froehlich, J., Poorman, R., Reardon, E., Barnum, S. and Jaworski, J. G. 1990. Purification and characterization of acyl carrier protein from two cyanobacteria species. European Journal Biochemistry 193:817-825.
Smoker, J. A., Owen, H. A., and Barnum, S. R. 1990. Localization of proteins in filamentous cyanobacteria using immunogold electron microscopy. Methods in Molecular and Cellular Biology 2:59-65.
Smoker, J. A., Owen, H. A., and Barnum, S. R. 1990. Immunolocalization of Rubisco in the nitrogen fixing cyanobacterium, Plectonema boryanum. Protoplasma 156:113-116.
Smoker, J. A. and Barnum, S. R. 1990. Nitrogenase activity in a filamentous, nonhterocystous cyanobacterium. Archives of Microbiology 153:417-421.
Smoker, J. A., Lehmen, L., Owen, H. A., and Barnum, S.R. 1989. Ultrastructure of the nitrogen fixing fila-mentous, nonheterocystous cyanobacterium, Plectonema boryanum. Protoplasma 152:130-135.