Biochemistry and Molecular Biology
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Donald Bryant

Donald Bryant

Main Content

  • Ernest C. Pollard Professor in Biotechnology and
  • Professor of Biochemistry and Molecular Biology
403C Althouse Laboratory
University Park, PA 16802
Phone: (814) 865-1992

Research Interests

Physiology, biochemistry, genetics, and genomics of photosynthetic bacteria

Graduate Programs


Research Summary

Genomics, structural and functional relationships, metabolism, physiology and ecology of chlorophototrophic bacteria

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 kingdoms: Cyanobacteria, Proteobacteria, Chlorobi, Chloroflexi, and Firmicutes. We recently discovered a previously unknown chlorophototroph, Candidatus Chloracidobacterium thermophilum, which is a member of the poorly characterized kingdom Acidobacteria ( 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 Chlorobaculum tepidum (Chlorobi), which can easily be manipulated genetically. Because Cyanobacteria perform oxygen-evolving photosynthesis but characterized Chlorobi are obligately photoautotrophic anaerobes, these two organisms provide an interesting contrast in physiology and metabolism. We additionally study natural phototrophic communities in Yellowstone National Park.

Octopus Spring

Figure 1. Left, Octopus Spring, an alkaline siliceous hot spring in the Lower Geyser Basin of Yellowstone National Park, WY. Right, microbial mat showing the upper, 1-2 mm green chlorophototrophic community from which Candidatus Chloracidobacterium thermophilum was isolated. The lower red layers are carotenoid-containing members of the anoxic community.

Long-term objectives of my laboratory are to understand the structure, function, assembly, and regulation of expression of bacterial photosynthetic apparatuses, principally those of members of the phyla Cyanobacteria and Chlorobi. To achieve these goals, we have obtained complete genomic sequences for all of the organisms we study. These data enable bioinformatics approaches that facilitate gene discovery and characterization. Genome sequences have been determined for 3 Cyanobacteria (6 in progress), 16 Chlorobi, 7 Chloroflexi, 11 Proteobacteria, and 1 member of the Acidobacteria (see We additionally use nextGen sequencing methods for transcription profiling of Synechococcus sp. PCC 7002 and C. tepidum, as well as for profiling gene expression patterns of the entire mat community from which Cab. thermophilum was isolated (see Figure 1). In a recent Multi-omics Analysis Experiment (MOAE, the “Mother Of All Experiments”), >15,000 genes were tracked in samples collected at hourly intervals over one diurnal cycle. 

The photosynthetic apparatus of cyanobacteria closely resembles that found in the chloroplasts of higher plants. We have developed sophisticated genetic tools to analyze gene function in Synechococcus sp. PCC 7002, and these have been used for metabolic engineering to improve biosolar hydrogen, biomass, and biofuels production in this robust cyanobacterium. The Chlorobi are specifically 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 natural transformation method for C. tepidum and have used this capability to define the pathways for bacteriochlorophyll and carotenoid biosynthesis in this organism as well as to characterize the structure of chlorophylls in the light-harvesting organelle, the chlorosome (Figure 2).


Bryant figure 2

Figure 2. Single and double-layer model of bacteriochlorophyll d structure in chlorosomes of a bchQRU mutant of Chlorobaculum tepidum; see Ganapathy et al. (2009) Proc. Natl. Acad. Sci. USA 106: 8515-8530 for details). 

Students and postdoctoral associates apply a broad combination of methods including microbial ecology, microbial physiology, genomics and bioinformatics, molecular genetics, protein biochemistry, and spectroscopic methods. We collaborate extensively with Dr. John H. Golbeck, Dr. David M. Ward of Montana State University (see, and Dr. G. Charles Dismukes, John W. Peters, Matthew C. Posewitz and other members of MURI project on biosolar hydrogen production (see NSF, DOE, NASA, Air Force Office of Sponsored Research, Pacific Northwest National Laboratory (DOE), and Penn State University currently provide financial support for our research. More detailed information about the research projects in my laboratory can be found on our laboratory website and through our recent publications.


pdf file CV of Dr. Donald Bryant (PDF)

Selected Publications

Publications from 2014:

  • Niedzwiedzki, D. M., Orf, G. S., Tank, M., Vogl, K., Bryant, D. A., and Blankenship, R. E. 2014. Photophysical properties of the excited states of bacteriochlorophyll f in solvents and in chlorosomes. J. Phys. Chem. B 118: 2295-2305.
  • Stolyar, S., Liu, Z., Thiel, V., Tomsho, L. P., Pinel, N., Nelson, W., Lindemann, S., Romine, M., Haruta, S., Schuster, S. C., Bryant, D. A. and Frederickson, J. K. 2014. Genome sequence of the thermophilic cyanobacterium Thermosynechococcus sp. strain NK55a. genomeA 2: e01060-13.
  • Bryant, D. A. 2014. A brief history of cyanobacterial research: past, present and future prospects… In: The Cell Biology of Cyanobacteria (Herrero, A. and Flores, E., eds.), pp. 1-5. Caister Academic Press, Norfolk, UK.
  • Miloslavina, Y., Sankar Gupta, K. B. S., Tank, M., Bryant, D. A., and de Groot, H. J. M. 2014. wPMLG-5 spectroscopy of self-aggregated BChl e in natural chlorosomes of Chlorobaculum limnaeum. Israel J. Chem. 54, 147-153.
  • Beliaev, A. S., Serres, M., Linggi, B. E., L. M. Markille, Isern, N. G., Chrisler, W. B., Kucek, L. A., Hill, E. A., Pinchuk, G. E., Bryant, D. A., Wiley, H. S., Romine, M. F., Frederickson, J. K., and Konopka, A. 2014. Interactions between cyanobacteria and heterotrophs under different trophic conditions. ISME J., in press.
  • Kjelleberg, S., Xie, C., Zhao, F., Huson, D. H., Drautz, D. I., Williams, R. B. H., Wittekindt, N. E., Tomsho, L. P., Gawjeski, J., Purbojati, R. W., Ng, W. J., Seah, H., Wuertz, S., Gisikov, M., Bryant, D. A., Little, P., Cohen, Y., and Schuster, S. C. 2014. Metagenomic and metatranscriptomic analyses of a microbial community driving wastewater purification. Genome Res., revision submitted.
  • Hartzler, D., Niedzwiedzki, D. M., Bryant, D. A., Blankenship, R. E., Pushkar, Y., and Savikhin, S. 2014. Triplet excited state energies and phosphorescence spectra of (bacterio)chlorophylls. J. Phys. Chem. Part B. 118: 7221-7232.
  • Kim, Y.-M., Nowack, S., Olsen, M., Becraft, E., Thiel, V. Bryant, D. A., Fredrickson, J. K., Ward, D. M. and Metz, T. O. 2014. Metabolomics analysis of a Yellowstone National Park hot spring chlorophototrophic microbial mat over a diel cycle supports hypothesized metabolisms of predominant inhabitants. Environ. Microbiol., in revision.
  • Hamilton, T. L., Bovee, R. J., Thiel, V., Sattin, S. R., Mohr, W., Schaperdoth, I., Gillhooly, W. P. 3rd, Lyons, T. W., Tomsho, L. P., Schuster, S. C., Overmann, J., Bryant, D. A., Pearson, A., and Macalady, J. L. 2014. Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake. Geobiology 12: 451-468.
  • Zhang, S., Li, Z., Shen, G., Golbeck, J. H. and Bryant, D. A. 2014. Vipp1 in Synechococcus sp. PCC 7002 is not essential but is required for photosystem I assembly. J. Biol. Chem. 289: 15904-15910.
  • Ludwig, M., Pandelia, M.-E., Chew, C. Y., Golbeck, J. H., Krebs, C., and Bryant, D. A. 2014. ChlR protein of Synechococcus sp. PCC 7002 is a transcription activator that uses an oxygen-sensitive [4Fe-4S] cluster to control genes involved in pigment biosynthesis. J. Biol. Chem. 289: 16624-16639.
  • Sinninghe Damsté, J.,  Rijpstra, W. I. C., Hopmans, E. C., Foesel, B. U., Wüst, P. K., Overmann, J., Tank, M. Bryant, D. A., Dunfield, P. F., and Stott, M. B. (2014). Ether- and ester-bound iso-diabolic acid and other lipids in Acidobacterium of subdivision 4. Appl. Environ. Microbiol. 80: 5207-5218.
  • Konopka, A., Bernstein, H. C., Melnicki, M. R., Hill, E. A., Kucek, L. A., Shen, G., Bryant, D. A., Zhang, S., Shen, G., and Beliaev, A. S. 2014. Effect of mono- and dichromatic light quality on growth rates and photosynthetic performance of Synechococcus sp. PCC 7002. Front. Microbio., in revision.
  • Gan, F., Zhang, S., Rockwell, N. C., Martin, S. S., Lagarias, J. C. and Bryant, D. A. 2014. Extensive remodeling of a cyanobacterial photosynthetic apparatus in far-red light. Science, in press.
  • Tank, M. and Bryant, D. A. 2014. Chloracidobacterium thermophilum gen. nov., sp. nov.: a microaerophilic, anoxygenic, and photoheterotrophic acidobacterium with chlorosomes and type-1 homodimeric reaction centers. Int. J. Syst. Evol. Microbiol., in revision.
  • Shively, J. M., Cannon G. C., Heinhorst, S., Fuerst, J. A., Bryant, D. A., Maupin-Furlow, J. A., Schüler, D., Pfeifer, F., Docampo, R., Dahl, C., Preiss, J, Steinbüchel, A., and Federici, B. A. (2014). Intracellular structures of prokaryotes: inclusions, compartments, and assemblages. Encyclopedia of Microbiology (Schaechter, M., ed.), in press. Elsevier, Amsterdam.
  • Therien, J. B., Zadvornyy, O., Posewitz, M. C., Bryant, D. A. and Peters, J. W. (2014) Growth of Chlamydomonas reinhardtii in acetate-free medium when co-cultured with alginate-encapsulated strains of Synechococcus sp. PCC 7002. Biotech. Biofuels, submitted for publication.
  • Junqueira, A. C. M., Purbojati, R. W., Chao, X., Ratan, A., Drautz, D. I., Tomsho, L. P., McGraw, J. J., Hake, C., Centoducatte, G. L., Paulo, D. F., Bryant, D. A., Azeredo-Espin, A. M. L., Kjelleberg, S., Linz, B. and Schuster, S. C. 2014. Environmental dispersal of human pathogens by airborne mechanical vectors. Biofilms Microbiomes, in revision.
  • Zhang, S. and Bryant, D. A. 2014. Learning new tricks from an old cycle: the TCA cycles of cyanobacteria, algae and plants. Perspect. Phycol., invited review, accepted subject to minor revisions.
  • Thiel, V., Tomsho, L. P., Burhans, R., Gay, S. E., Ramaley, R. F., Schuster, S. C., Steinke, L., and Bryant, D. A. 2014. Draft genome sequence of the moderately thermophilic bacterium Schleiferia thermophila strain Yellowstone) (Bacteroidetes). genomeA, in press.
  • Thiel, V., Tomsho, L. P., Burhans, R., Schuster, S. C., and Bryant, D. A. 2014. Draft genome of a sulfide-oxidizing, autotrophic Chloroflexus sp. strain MS-G (Yellowstone National Park, WY). genomeA, in press.
  • Zhao, C., Li, Z., Li, T., Zhang, Y., Bryant, D. A. and Zhao, J. 2014. High-yield production of extracellular type-I cellulose by a marine cyanobacterium. Proc. Natl. Acad. Sci. USA, submitted for publication.