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Donald A. Bryant

Ernest C. Pollard Professor of Biotechnology and Professor of Biochemistry and Molecular Biology

235 South Frear Laboratory, University Park, PA 16802
Phone: (814) 865-1992
Fax: (814) 863-7024
E-mail: dab14@psu.edu

B.S. in Chemistry, Massachusetts Institute of Technology
Ph.D. in Molecular Biology, University of California, Los Angeles

Don Bryant's CV

Bryant Lab Web Site

Genomics, structural and functional relationships, metabolism, and physiology of photosynthetic bacteria (chlorophototrophs)

Photosynthesis, the chlorophyll-dependent conversion of light energy into chemical energy with the ensuing reduction of carbon dioxide to biomass, is arguably the most important biological process on Earth. Among prokaryotes, the ability to use chlorophylls to capture and convert light into biochemical energy was until very recently believed to occur in members of only five eubacterial phyla: Cyanobacteria, Proteobacteria, Chlorobi, Chloroflexi, and Firmicutes. We recently discovered a previously unknown chlorophototroph, Candidatus Chloracidobacterium thermophilum, which is a member of the poorly characterized phylum Acidobacteria (http://www.sciencemag.org/cgi/content/abstract/317/5837/523). Current research in my laboratory focuses on a wide variety of topics in photosynthesis in bacteria, including structure-function relationships of proteins, biogenesis of the photosynthetic apparatus, gene regulation, and photosynthetic physiology. We principally study two model organisms: the unicellular, marine cyanobacterium Synechococcus sp. PCC 7002 and the moderately thermophilic green sulfur Chlorobium tepidum. Both organisms can easily be manipulated genetically. Since cyanobacteria perform oxygen-evolving photosynthesis while the green sulfur bacteria are obligately anaerobic photoautotrophs, these two organisms provide an interesting contrast in physiology and metabolism. More recently, through genomic and metagenomic DNA sequencing, we have also begun to investigate members of the phylum Chloroflexi.

The major long-term objectives of my laboratory are to understand the structure, function, assembly, and regulation of expression of the cyanobacterial and green sulfur bacterial photosynthetic apparatuses. To achieve these goals, we have actively sought to obtain complete genomic sequence information for the classes of organisms we study to enable bioinformatics approaches that can facilitate gene discovery and characterization. By the end of 2007, we will have determined the genome sequences of 3 cyanobacteria, 12 green sulfur bacteria (Chlorobi), 7 filamentous anoxygenic phototrophs (Chloroflexi), and 1 acidobacterium (see http://www.bmb.psu.edu/faculty/bryant/lab/index.htm). The photosynthetic apparatus of cyanobacteria closely resembles that found in the chloroplasts of higher plants. Because cyanobacteria can be experimentally manipulated like other procaryotes, and because relatively sophisticated genetic methods can be employed with these organisms, cyanobacteria provide unique opportunities as model systems for understanding oxygenic photosynthesis. The experimental approach used in my laboratory is to apply the techniques of molecular genetics and recombinant DNA methodologies to perform structural and functional analyses of the photosynthetic apparatus and to study processes that control gene expression in these organisms. The green sulfur bacteria are exquisitely and uniquely adapted for survival in low-light environments and are important in reducing carbon and nitrogen while oxidizing sulfide in anoxic environments. We have developed a reliable method for natural transformation of Chlorobium tepidum and have used this capability to define the pathways for bacteriochlorophyll and carotenoid biosynthesis in this organism as well as to characterize the light-harvesting organelle, the chlorosome. Finally, in recent years we have begun to develop methods to modify cyanobacteria for improved biosolar hydrogen, biomass, and biofuels production.

Students and postdoctoral associates apply a broad combination of methods involving molecular genetics, protein biochemistry, microbial physiology and spectroscopic methods. We collaborate extensively with Dr. John H. Golbeck (http://www.bmb.psu.edu/faculty/golbeck/golbeck.html), Dr. David M. Ward of Montana State University (see http://landresources.montana.edu/dward/), and Dr. G. Charles Dismukes and other members of MURI project on biosolar hydrogen production (see http://www.princeton.edu/~catalase/). NSF, DOE, USDA, Air Force Office of Sponsored Research, and the University currently provide financial support for the research projects in the laboratory. More detailed information about the research projects in my laboratory can be found on our laboratory website http://www.bmb.psu.edu/faculty/bryant/lab/index.htm) and through our recent publications (see below).

Representative Publications:

  • Kim, H., Bryant, D. A. and Savikhin, S. 2007. High photostability of aggregates of bacteriochlorophyll c: evidence for triplet exciton formation. Biophys. J., submitted for publication.

  • Oostergetel, G. T., Reus, M., Gomez Maqueo Chew, A., Bryant, D. A., Boekema, E. J., and Holzwarth, A. R. 2007. Long-range organization of bacteriochlorophyll in chlorosomes of Chlorobium tepidum investigated by cryo-electron microscopy. FEBS Lett., submitted for publication.

  • Shen, G., Schluchter, W. M. and Bryant, D. A. 2007. Biogenesis of phycobiliproteins. I. cpcS-I and cpcU mutants of the cyanobacterium Synechococcus sp. PCC 7002 identify a heterodimeric phycocyanobilin lyase specific for  b–phycocyanin and allophycocyanin subunits. J. Biol. Chem., submitted for publication.

  • Saunée, N. A., Williams, S. R., Bryant, D. A. and Schluchter, W. M. 2007. Biogenesis of phycobiliproteins. II. CpcS-I and CpcU comprise the heterodimeric bilin lyase that attaches phycocyanobilin to Cys-82 of b–phycocyanin and Cys-81 of allophycocyanin subunits in Synechococcus sp. PCC 7002. J. Biol. Chem., submitted for publication.

  • Gomez Maqueo Chew, A., Frigaard, N.-U., and Bryant, D. A. 2007. Identification of the gene encoding geranylgeranyl reductase, BchP, in Chlorobaculum tepidum. J. Bacteriol., submitted for publication.

  • Bryant, D. A., Garcia Costas, A. M., Maresca, J. A., Gomez Maqueo Chew, A., Klatt, C. G., Bateson, M. M., Tallon, L. J. Hostetler, J., Nelson, W. C., Heidelberg, J. F., Ward, D. M. 2007. “Candidatus Chloracidobacterium thermophilum”: an aerobic phototrophic acidobacterium. Science 317: 523-526.
  • Gomez Maqueo Chew, A., and Bryant, D. A. 2007. Chlorophyll biosynthesis in bacteria: the origins of structural and functional diversity. Annu. Rev. Microbiol. 61: 113-129.
  • Garcia Costas, A. M., Graham, J. E., and Bryant, D. A. 2007. Ketocarotenoids in chlorosomes of Candidatus Chloracidobacterium thermophilum. In: Proceedings Photosynthesis Research 2007 (J. F. Allen, B. Osmond, J. H. Golbeck, and E. Gantt, eds.), in press. Springer, Berlin.

  • Shen, G., Balasubramanian, R., Wu, Y., Wang, T., Hoffart, L. M., Krebs, C., Bryant, D. A. and Golbeck, J. H. 2007. The SufR transcriptional repressor binds to the promoter region of the sufBCDS operon as a homodimer and coordinates [4Fe-4S]1+, 2+ cluster. J. Biol. Chem., in press.

  • Gomez Maqueo Chew, A., Frigaard, N.-U., and Bryant, D. A. 2007. Bacteriochlorophyllide c C-82 and C-121 methyltransferases are essential for adaptation to low light in Chlorobaculum tepidum. J. Bacteriol. 189: 6176-6184.

  • Maresca, J. A., Graham, J. E., Wu, M., Eisen, J. A. and Bryant, D. A. 2007. Identification of a fourth family of lycopene cyclases in photosynthetic bacteria. Proc. Natl. Acad. Sci. USA 104: 11784-11789.

  • Inoue-Sakamoto, K., Gruber, T. M., Christensen, S. K., Sakomoto, T. and Bryant, D. A. 2007. Group 3 sigma factors in the marine cyanobacterium Synechococcus sp. PCC 7002 are required for growth at low temperature. J. Gen. Appl. Microbiol. 53: 89-104.
  • Ikonen, T. P., Li, H., Psencik, J., Laurinmaki, P., Butcher, S. J., Frigaard, N.-U., Serimaa, R. E., Bryant, D. A. and Tuma, R. 2007. X-ray scattering and electron cryomicroscopy study on the effect of carotenoid biosynthesis to the structure of Chlorobium tepidum chlorosomes. Biophys. J. 93: 620-628.
  • Kim, H., Li, H., Maresca, J. A., Bryant, D. A. and Savikhin, S. 2007. Triplet exciton formation as a novel photoprotection mechanism in chlorosomes of Chlorobium tepidum. Biophys. J. 93: 192-201.

  • Klatt, C. G., Bryant, D. A. and Ward, D. M. 2007. Comparative genomics provides evidence for the 3-hydroxypropionate autotrophic pathway in filamentous anoxygenic phototrophic bacteria and in hot spring microbial mats. Environ. Microbiol. 9: 2067-2078.

  • Antonkine, M. L., Maes, E. M., Czernuszewicz, R. S., Brietenstein, C., Bill, E., Falzone, C. F., Balasubramanian, R., Yang, F., Bryant, D. A. and Golbeck, J. H. 2007. Chemical rescue of a site-modified ligand to a [4Fe-4S] cluster in a bacterial di-cluster ferredoxin. Biochim. Biophys. Acta 1767: 712-724.
  • Frigaard, N.-U. and Bryant, D. A. 2007. Genomic and evolutionary perspectives on sulfur metabolism in green sulfur bacteria. In: Microbial Sulfur Metabolism (Proceedings of the International Symposium on Microbial Sulfur Metabolism), C. G. Friedrich and C. Dahl, eds., Münster, Germany, June 29-July 02, 2006, pp. 60-76. Springer, Dordrecht, The Netherlands.
  • Frigaard, N.-U. and Bryant, D. A. 2007. Genomic insights into the sulfur metabolism of phototrophic sulfur bacteria. In: Advances in Photosynthesis and Respiration, Vol. X, Sulfur Metabolism in Phototrophic Organisms, C. Dahl, R. Hell, D. B. Knaff, and T. Leustek, eds., in press. Springer, Dordrecht, The Netherlands.

  • Woodger, F. J., Bryant, D. A. and Price, G. D. 2007. Transcriptional regulation of the CO2-concentrating mechanism in the euryhaline, coastal-marine cyanobacterium, Synechococcus sp. PCC7002: role of NdhR/CcmR. J. Bacteriol. 189: 3335-3347.

  • Gomez Maqueo Chew, A. and Bryant, D. A. 2007. Characterization of a plant-like protochlorophyllide a divinyl reductase in green sulfur bacteria. J. Biol. Chem. 282: 2967-2975.
  • Maresca, J. A., and Bryant, D. A. 2006. Identification of two genes encoding new carotenoid-modifying enzymes in the green sulfur bacterium Chlorobium tepidum. J. Bacteriol. 188: 6217-6223.
  • Bryant, D. A. and Frigaard, N.-U. 2006. Prokaryotic photosynthesis and phototrophy illuminated. Trends Microbiol. 14: 488-496.
  • Li, H., Frigaard, N.-U., and Bryant, D. A. 2006. Molecular contacts for chlorosome envelope proteins revealed by cross-linking studies with chlorosomes from Chlorobium tepidum.  Biochemistry 45: 9095-9103.

  • Shen, G., Saunée, N. A., Williams, S. R., Gallo, E. F., Schluchter, W. M. and Bryant, D. A. 2006. Identification and characterization of a new class of bilin lyase: the cpcT gene encodes a bilin lyase responsible for attachment of phycocyanobilin to Cys-153 on the b-subunit of phycocyanin in Synechococcus sp. PCC 7002. J. Biol. Chem. 281: 17768-17778.

  • Nomura, C. T., Sakamoto, T. and Bryant, D. A. 2006. Roles for heme-copper oxidases in extreme high light and oxidative stress response in the cyanobacterium Synechococcus sp. PCC 7002. Arch. Microbiol. 185: 471-479.
  • Ley, R. E., Harris, J. K., Wilcon, J., Spear, J. R., Miller, S. R., Bebout, B. M., Maresca, J. A., Bryant, D. A. and Pace, N. R. 2006. Unexpected diversity and complexity from the Guerrero Negro hypersaline microbial mat. Appl. Env. Microbiol. 72, 3685-3695.
  • Sakuragi, Y., Maeda, H., DellaPenna, D. and Bryant, D. A. 2006. a-Tocopherol plays a role in photosynthesis and macronutrient homeostasis that is independent of its antioxidant function in the cyanobacterium Synechocystis sp. PCC 6803. Plant Physiol. 141: 508-521.
  • Balasubramanian, R., Shen, G., Bryant, D. A, and Golbeck, J. H. 2006. Assembly of iron sulfur clusters in cyanobacteria: regulatory roles of sufA and iscA genes in redox sensing and iron metabolism in the cyanobacterium Synechococcus sp. PCC 7002. J. Bacteriol. 188: 3182-3191.
  • Frigaard, N.-U. and Bryant, D. A. 2006. Chlorosomes: antenna organelles in green photosynthetic bacteria. In: Complex Intracellular Structures in Prokaryotes (Shively, J. M., ed.), Microbiology Monographs, Vol. 2, pp. 79-114, Springer, Berlin, Germany.
  • Shively, J. B., Cannon, G. C., Bryant, D. A., DasSarma, S., Bazylinski, D., Preiss, J., Steinbüchel, A., and Docampo, R. 2006. Bacterial Inclusions. In: Encyclopedia of Life Sciences, Nature Publishing Group, Macmillan Reference Ltd., London, United Kingdom. http://www.els.net/

  • Nomura, C. T., Persson, S., Shen, G. Inoue-Sakamoto, K. and Bryant, D. A. 2006. Characterization of two cytochrome oxidase operons in the marine cyanobacterium Synechococcus sp. PCC 7002. Inactivation of ctaDI affects the PS I:PS II ratio. Photosynth. Res. 87: 215-228.

  • Frigaard, N.-U., Gomez Maqueo Chew, A., Maresca, J. A. and Bryant, D. A. 2006. Bacteriochlorophyll biosynthesis in green bacteria. In: Advances in Photosynthesis and Respiration, Vol. 25, B. Grimm, R. Porra, W. Rüdiger, and H. Scheer (eds.), Chlorophylls and Bacteriochlorophylls: Biochemistry, Biophysics, Functions and Applications, pp. 201-221. Springer, Dordrecht, The Netherlands.
  • Sakuragi, Y. and Bryant, D. A. 2006. Genetic manipulation of quinone biosynthesis in cyanobacteria. In: Advances in Photosynthesis and Respiration, Vol. 24, J. H. Golbeck (ed.) Photosystem I: The light-driven plastocyanin:ferredoxin oxidoreductase in photosynthesis, pp. 205-222. Springer, Dordrecht, The Netherlands.

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