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Donald A. Bryant

Academy Professor, Ernest C. Pollard Professor Emeritus of Biotechnology, and Professor Emeritus of Biochemistry and Molecular Biology
Donald Bryant

About Me

I grew up on a dairy farm in north central Kentucky and became interested in science at an early age. I fulfilled a long-time dream by attending Massachusetts Institute of Technology as an undergraduate, where I obtained a B. Sc. with honors in Chemistry and Biology in 1972. I became interested in bioenergetics as an undergraduate, so I moved to University of California-Los Angeles for graduate school, where I became a member of the first class of students in a new NIH-sponsored training program in molecular biology. I quickly decided that photosynthesis was the topic I wished to pursue in the fall of 1972, and I started working with Alexander N. Glazer and Frederick Eiserling, beginning a lifelong research affiliation with cyanobacteria. After completing my Ph. D. training, I was a postdoctoral fellow in the laboratory of Roger Y. Stanier and Germaine Cohen-Bazire at the Institut Pasteur in Paris from 1977 to 1979, and I then joined the laboratory of Roderick K. Clayton at Cornell University from 1979 to 1981. Finally, I joined the faculty at Penn State in September 1981 and have been here since then, rising to the level of professor in 1991. I spent sabbaticals in Switzerland (1989-1990), Australia (1996-1997), Rockville, MD (TIGR), and Bozeman, Montana (twice; 2010-2011 and 2017-2018). 

I am now a microbial (eco)physiologist, who has applied cutting-edge genomics, genetics, biochemistry, and molecular biology to study chlorophototrophic bacteria—Cyanobacteria, Chloroflexi, Chlorobi, and Acidobacteria—for 49 years. My recent studies demonstrating that cyanobacteria extensively remodel their photosynthetic apparatus by synthesizing new chlorophylls, phycobiliproteins, and reaction centers in far-red light explains how these organisms can grow at the bottom of dense microbial mats [Science 345:1312-17 (2014) and Science 353:aaf9178 (2016)]. Introduction of this capability into crop plants could significantly increase their productivity by expanding the usable light for photosynthesis into the far-red range (700–800 nm). In an elegant example of my broad expertise to solve a previously intractable problem, we elucidated (bacterio-)chlorophyll and carotenoid biosynthetic pathways in green sulfur bacteria, and this directly led to structures for the BChl supramolecular structures in chlorosomes, their light-harvesting complexes. My deep knowledge of photosynthesis and metabolism is represented by studies of microbial mats in Yellowstone hot springs, where 17 chlorophototrophic members from six phyla and ~325 total bacteria “species” occur. Using systems biology/-omics approaches, we and our collaborators have made impressive progress in advancing our understanding of the structure, interdependence, and integration of members of such communities. The discovery of Chloracidobacterium thermophilum [Science 317:523-526 (2007)], the first chlorophototrophic member of the phylum Acidobacteria, is already featured in microbiology textbooks. Finally, our recent demonstration that cyanobacteria have a complete tricarboxylic acid cycle decisively overturned the belief, accepted for ~50 years, that the cyanobacterial TCA cycle is branched [Science 334:1551-1553 (2011)] and provides new opportunities for metabolic engineering. These are just a few highlights of a research career spanning five decades. To date (January 2021) I have studied chlorophototrophic bacteria for 49 years, and I have published (or submitted) ~433 papers and books since 1972, including ~190 papers over the past decade. These research products have received ~28,294 total citations (>9,697 since 2015), per Google Scholar. The h-index for these publications is currently 87 (87 publications with ≥87 citations; 50 since 2015) and the i10-index is 342 (i.e., 342 papers with ≥10 citations) and 231 with 10 new citations since 2015. The book “The Molecular Biology of Cyanobacteria,” published in 1994, has received ~4,200 total citations


Professional Preparation

Massachusetts Institute of Technology Chemistry/Biology B. Sc. 1972
University of California, Los Angeles Molecular Biology Ph. D. 1977
Institut Pasteur (RY Stanier, G Cohen-Bazire) Microbiology Postdoc 1977-1979
Cornell University (RK Clayton) Biophysics Postdoc 1979-1981

Academic Appointments

1981—present Assistant, Associate, (1986) and Full Professor (1991), Department of Biochemistry and Molecular Biology, The Pennsylvania State University
2009—2015 Adjunct Research Professor, Chemistry & Biochemistry, Montana State University
2013—2018 Visiting Professor, Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University, Singapore
2015— 2020 Research Professor, Chemistry & Biochemistry, Montana State University 


Research Interest

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


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 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, 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 have principally studied 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. More recently, we have studied several terretrial cyanobacteria that can acclimate to use far-red/niear-infra red radiation to perform oxygenic photosynthesis. Because Cyanobacteria perform oxygen-evolving photosynthesis but characterized Chlorobi are obligately photoautotrophic anaerobes, these two organisms provide an interesting contrast in physiology and metabolism. Finally, we additionally study natural chlorophototrophic communities in mat communities in Yellowstone National Park, WY. 

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. In total, genome sequences for about 100 chlorophototroph organisms have been determined since 2000. We additionally use nextGen sequencing methods for transcription profiling of Synechococcus sp. PCC 7002 and Cba. 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.  

Bryant Research figures

Figure 1. Left, Octopus Spring, an alkaline siliceous hot sprin 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. 


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 Cba. 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 Research 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, among numerous other scientists world-wide. 


Scientists solve structure enabling cyanobacteria to thrive in low light


Honors and Awards


B. Sc. in Chemistry with honors, Massachusetts Institute of Technology

1972 - 1976

U. S. Public Health Service Pre-doctoral Traineeship, Univ. of California-Los Angeles (Advisors: Alexander N. Glazer and Frederick A. Eiserling)

1977 - 1979

N.S.F.-C.N.R.S. Postdoctoral fellowship (U.S.--France exchange program).

1992 - present

Ernest C. Pollard Professor of Biotechnology

1995 - present

Fellow, American Academy of Microbiology


Daniel R. Tershak Memorial Teaching Award, Dept. of Biochemistry and Molecular Biology, The Pennsylvania State University


Brown & Williamson Distinguished Lecturer, University of Louisville, Department of Biology

2011 - present

Fellow, American Association for the Advancement of Science


Daniel I. Arnon Lecturer, University of California, Berkeley

2012 - 2018

Member (elected), Board of Governors, American Academy of Microbiology


D. C. White Research and Mentoring Award, American Society for Microbiology

2020 Charles F. Kettering Award (for photosythesis research) American Society for Plant Biologists


Selected Publications

214. 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. 

278. Zhang, S. and Bryant, D. A. 2011. The cyanobacterial tricarboxylic acid cycle. Science 334, 1551–1553. 278. 

329. 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 345, 1312–1317. 

370. Ho, M.-Y., Shen, G., Canniffe, D. P., Zhao, C., and Bryant, D. A. 2016. Light-dependent chlorophyll f synthase is a highly divergent paralog of PsbA of Photosystem II. Science 353, aaf9178. doi: 10.1126/science.aaf9178. 

394. Bryant, D. A., and Canniffe, D. P. 2018. How Nature designs antenna proteins: design principles and functional realization of light-harvesting antenna systems in chlorophototrophic prokaryotes. J. Phys. B: At. Mol. Opt. Phys. 51, 033001. doi: 10.1088/1361-6455/aa9c3c

395. Chen, G. E., Canniffe, D. P, Barnett, S. F. H., Hollingshead, S., Brindley A. A., Vasilev, C., Bryant, D. A. Hunter, C. N. 2018. Complete enzyme set for chlorophyll biosynthesis in Escherichia coli. Sci. Adv. 4, eaaq1407. doi: 10.1126/sciadv.aaq1407.

396. Thiel, V., Tank, M. and Bryant, D. A. 2018. Diversity of chlorophototrophic bacteria revealed in the omics era. Annu. Rev. Plant Biol. 69, 21–49. doi: 10.1146/annurev-arplant-042817-040500

400. Zill, J. C., He, Z., Tank, M., Canniffe, D. P., Ferlez, B. H., Lahav, Y., Bellstedt, P., Alia, A., Schapiro, I., Golbeck, J. H., Bryant, D. A. and Matysik, J. 2018. 15N-Photo-CIDNP MAS NMR analysis of reaction centers of Chloracidobacterium thermophilum. Photosynth. Res. 137, 295–305. doi: 10.1007/s11120-018-0504-1

402. Günther, L. M., Löhner, A., Reiher, C., Kunsel, T., Jansen, T. L. C., Tank, M., Bryant, D. A., Knoester, J., and Köhler, J. 2018. Structural variations in chlorosomes from wild-type and a bchQR mutant of Chlorobaculum tepidum revealed by single-molecule spectroscopy. J. Phys. Chem. Part B, 122, 6712–6723.  doi: 10.1021/acs.jpcb.8b02875

404. Canniffe, D. P., Thweatt, J. L., Gomez Maqueo Chew, A., Hunter, C. N. and Bryant, D. A. 2018. A paralog of phytol reductase catalyzes the formation of 1,2-dihydro-carotenoids in green sulfur bacteria. J. Biol. Chem. 293, 15233–15242. doi:10.1074/jbc.RA118.004672

405. Tank, M., Garcia Costas, A. M., and Bryant, D. A. 2018. Genus: Chloracidobacterium. In: Bergey’s Manual of Systematics of Bacteria and Archaea (W. B. Whitman, supervising editor), John Wiley & Sons, New York. doi: 10.1002/9781118960608.

407. Thiel, V., Garcia Costas, A. M., Fortney, N. W. W., Martinez, J. N., Roden, E. E., Boyd, E. S., Ward, D. M. and Bryant, D. A. 2019. “Candidatus Thermonerobacter thiotrophicus,” a non-phototrophic, sulfate-reducing member of the phylum Chlorobi that inhabits hot-spring communities. Front. Microbiol. 9, 3159.  doi: 10.3389/fmicb.2018.03159

408. Shen, G., Canniffe, D. P., Kurashov, V., Ho, M.-Y., van der Est, A., Golbeck, J. H. and Bryant, D. A. 2019. Improved heterologous expression of chlorophyll f synthase in Synechococcus sp. PCC 7002: isolation and initial characterization. Photosynth. Res. 140, 77-92. doi: 10.1007/s11120-018-00610-9

411. Ho, M.-Y., Bryant, D. A. 2019. Global transcription profiling of the cyanobacterium Chlorogloeopsis fritschii PCC 9212 in far-red light: insights into the regulation of chlorophyll d biosynthesis. Front. Microbiol. 10, 465. doi: 10.3389/fmicb.2019.00465

414. He, Z., Kurashov, V., Ferlez, B., Tank, M., Golbeck, J. H., and Bryant, D. A. 2019. Homodimeric type-1 reaction centers of Chloracidobacterium thermophilum (Acidobacteria): I. Biochemical and biophysical characterization. Photosynth. Res. 142, 87-103. doi: 10.1007/s11120-019-00650-9

415. Ho, M.-Y., Niedzwiedzki, D. M., MacGregor-Chatwin C., Gerstenecker, G., Hunter, C. N., Blankenship, R. E., and Bryant, D. A. 2019. Extensive remodeling of the photosynthetic apparatus alters energy transfer among photosynthetic complexes when cyanobacteria acclimate to far-red light. Biochim. Biophys. ActaBioenergetics, invited article, in press. doi:  10.1016/j.bbabio.2019.148064

416. Gisriel, C., Shen, G., Kurashov, V., Ho, M.-Y., Zhang, S., Williams, D., Golbeck, J. H., Fromme, P., Bryant, D. A. 2020. The structure of Photosystem I acclimated to far-red light illuminates an ecologically important acclimation process in photosynthesis. Sci. Adv. 6, eaay6415. doi: 10.1126/sciadv.aay6415

417. Bryant, D. A., Shen, G., Turner, G. M., Soulier, N., Laremore, T. N., and Ho, M.-Y. 2020. Far-red-light allophycocyanin subunits play a role in chlorophyll d accumulation in far-red light. Photosynth. Res. 143, 81-95.  doi: 10.1007/s11120-019-00689-8

418. Steinke, L., Slysz, G. W., Lipton, M. S., Klatt, C., Moran, J. J., Romine, M. F., Wood, J. M., Anderson, G., Bryant, D. A. and Ward, D. M. 2020. Short-term stable isotope probing of proteins reveals taxa incorporating inorganic carbon in a hot spring microbial mat. Appl. Environ. Microbiol. 86, e01829-19.  doi: 10.1128/AEM.01829-19

419. Charles, P., Kalendra, V., He, Z, Khatima, M. H., Golbeck, J. H., van der Est, A., Lakshmi, K. V., and Bryant, D. A. 2020. Two-dimensional 67Zn HYSCORE spectroscopy reveals that a Zn- bacteriochlorophyll aP dimer is the primary donor (P840) in the type-1 reaction centers of Chloracidobacterium thermophilum. Phys. Chem. Chem. Phys. 22, 6457–6467. doi: 10.1039/c9cp06556c

420. Cherepanov, D. A., Shelaev, I. V., Gostev, F. E., Aybush, A. V., Mamedov, M. D., Shen, G., Nadtochenko, V. A., Bryant, D. A., Semenov, A. Yu., and Golbeck, J. H. 2020. Evidence that chlorophyll f functions solely as an antenna pigment in far-red-light photosystem I from Fischerella thermalis PCC 7521. Biochim. Biophys. ActaBioenerg. 1861, 148184. doi: 10.1016/j.bbabio.2020.148184

423. Bryant, D. A., Hunter, C. N., and Warren, M. J. 2020. Biosynthesis of the modified tetrapyrroles—the pigments of life. J. Biol. Chem. 295, 6888–6925. doi: 10.1074/jbc.REV120.006194

425. Gisriel, C. J., Wang, J., Brudvig, G. W., and Bryant, D. A. 2020. Opportunities and challenges for assigning cofactors in cryo-EM density maps of chlorophyll-containing proteins. Commun. Biol. 3, 408. doi/10.1038/s42003-020-01139-1

429. Soulier, N. T., Laremore, T. N., and Bryant, D. A. 2020. Characterization of cyanobacterial allophycocyanins absorbing far-red light. Photosynth. Res. 145, 189-207. doi: 10.1007/s11120-020-00775-2

432. Soulier, N. T., and Bryant, D. A. 2021. The structural basis of far-red light absorbance by allophycocyanins. Photosynth. Res. 147, 11-26. doi: 10.1007/s11120-020-00787-y