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Departments: Glycoconjugates in Host-Microbial Interactions

Artur Muszynski

Short Biography:
Dr. Muszyński is an Senior Research Scientist at the CCRC. He received his M.Sc. degree and his Ph.D. degree in Biology from the University of Silesia, Katowice, Poland, in 1999 and 2004 respectively. In 1998 he was awarded two semesters of Socrates Erasmus scholarship to study advanced biochemistry and microbiology at the Faculty of Science and Department of Microbiology, Aarhus University, Aarhus, Denmark. In 1999 and 2003 he was a visiting scientist at the Research Center Borstel, Leibniz-Center for Medicine and Biosciences Borstel, Germany in the laboratory of Prof. Otto Holst. As a Ph.D. candidate, Dr. Muszyński conducted research on characterization of lipopolysaccharides from pathogenic Yersinia enterocolitica O:3 under supervision of Prof. Dr. Joanna Radziejewska-Lebrecht and Prof. Dr. Otto Holst. In 2005 he joined the group of Dr. Russell Carlson at the Complex Carbohydrate Research Center, University of Georgia for his postdoctoral studies. Currently Dr. Artur Muszyński is an Associate Research Scientist faculty member at the CCRC successfully working on determining the chemical and structural properties of bacterial cell surface glycans and glycolipids including lipopolysaccharide (LPS), lipid A, capsular polysaccharide (CPS), and extracellular polysaccharides (EPS), and other bacterial glycans and elucidating their biological roles in host-microbe interactions. He is also involved in multiple collaborative projects with academia and industry. In addition to his research Dr. Muszyński’s supervises undergraduate students introducing to world of microbial glycobiology.

Research Interests:
The outer leaflet of the outer membrane of the gram-negative bacterial cell envelope is built of lipopolysaccharide (LPS). The LPS consists of three distinct structural regions; a rather conserved lipid A, a more variable core oligosaccharide (OS), and an even more variable O-antigen polysaccharide (OPS). These regions are known to play important roles in interacting with the defense mechanisms of the host cells. In addition LPS, as well as capsular polysaccharides (CPS) and bacterial extracellular polysaccharides (EPS) are essential for protecting bacteria from environmental stress and in symbiotic interactions.
Determination of chemical and structural properties of these glycan and glycolipid macromolecules is critical in understanding the mechanisms of the host-microbe interactions and, in the case of pathogenic bacteria, in searching for good vaccine candidates. Through past years of my work I was involved in studies on LPS or lipid A from pathogenic, Pseudomonas aeruginosa, Neisseria meningitidis, Neisseria gonorrhoeae, Francisella novicida, Fancisella tularensis, Moraxella catharrhalis, Yersinia pestis, Yersinia enterocolitica, Bulkholderia multivorans, Helicobacter pylori, Campylobacter jejuni, Xyllela fastidiosa, Rimerella antipestifer, Granulibacter bethesdensis and nitrogen fixing Rhizobium leguminosarum, Rhizobium galegae, Sinorhizobium meliloti, Rhizobium etli, Mesorhizobium loti, Herbaspirillum seropedicae, and on peptidoglycan in Micrococcus lutes and Neisseria sp.

My current research projects involve studies on structural and biological properties of Mesorhizobium loti EPS, roles of polysaccharides in biofilm formation, in pathogenic Campylobacter jejuni and Helicobacter pylori, and biochemical studies on lipopolysaccharide of Bradyrhizobium japonicum and its role in legume symbiosis.

These studies utilize various techniques used in biochemistry and microbiology laboratories and analytical techniques, particularly chromatography and mass spectrometry (GPC, GLC-MS, CI-MS, HPLC, TLC, ESI-MS, MALDI-TOF and TOF-TOF MS) and NMR spectroscopy.

Christine Szymanski

Short Biography:

Dr. Szymanski has been exploring bacterial glycomics for three decades, working on food pathogens since the early 1990s, with a particular emphasis on Campylobacter jejuni. She combines her expertise in food safety and animal health with novel therapeutic diagnostic platforms developed during her postdoctoral fellowship at the Naval Medical Research Center vaccine program (1996-2000), the key findings while employed at the National Research Council of Canada (2000-2008), and the translational advances during her tenure as an Alberta Innovates Technology Futures Scholar at the University of Alberta (2008-2016). She was the first to demonstrate that bacteria are capable of N-glycosylating proteins and is now exploiting these systems to create glycoconjugate vaccines and oral therapeutics through recombinant expression in Escherichia coli. Dr. Szymanski was also the first to demonstrate that viruses specific for bacteria express proteins that can be used as novel therapeutics in addition to their recognized diagnostic value. These viruses (bacteriophages) are the most abundant biological entity on earth (10+31) and are therefore a limitless resource for exploitation, especially in the area of glycomics.

Research Interests:

The Szymanski laboratory is a microbial glycobiology laboratory using multidisciplinary techniques and relevant model systems to: 1) characterize bacterial glycoconjugate pathways, 2) exploit bacteriophage recognition proteins that bind these structures, and 3) understand the protective benefits of host milk oligosaccharides to develop novel therapeutics and vaccines for the prevention of diarrheal diseases and post-infectious neuropathies such as Guillain-Barré Syndrome. These studies have also expanded our knowledge of carbohydrate metabolism by the gut microbiota and the transfer of antibiotic resistance between bacteria.

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Michael G Hahn

Short Biography:
Dr. Hahn received a B.S. in chemistry and a B.A. in Independent Studies in 1974 from the University of Oregon and his Ph.D. in biochemistry in 1981 from the University of Colorado. A postdoctoral research associate appointment at the University of Wisconsin-Madison in plant pathology followed, after which Dr. Hahn went to the Albert-Ludwigs-Universiät (Freiburg, Germany) with the support of an Alexander-von-Humboldt stipend. Following another postdoctoral research associate appointment at the Salk Institute (San Diego, CA), Dr. Hahn joined the CCRC in July 1986. Full publications: 77.

Research Interests:
Our laboratory studies the cell biology and biosynthesis of plant cell walls. Plant cell walls play major roles in the biology of plants. Examples of these roles include controlling the growth and shape of plant cells, tissues, organs, and ultimately the entire plant, regulating the movement of nutrients and signals within the apoplast and toward the plasma membrane, serving as the first line of defense against pathogens and environmental stresses, and acting as a source of signaling molecules important in plant development and defense. Plant cell walls are also the principal component of plant biomass, which has become a focal point in the search for alternative and renewable sources of energy (biofuels).
We are pursuing two broad research goals:

(A) We are investigating plant cell wall biosynthesis by looking at two families of genes, primarily in Arabidopsis, thought to encode glycosyltransferases involved in plant cell wall glycan biosynthesis: 1) GAlacturonosylTransferase-Like (GATL) proteins thought to be involved in pectin biosynthesis; 2) FUcosylTransferase (FUT) proteins thought to add fucosyl residues to diverse plant cell wall glycans.

(B) We have developed a large and diverse library of monoclonal antibodies against plant cell wall glycans. These antibodies are being used to determine the locations of diverse cell wall carbohydrate structures (epitopes) in Arabidopsis, switchgrass and poplar. These antibodies are also proving useful for plant cell wall mutant characterization studies, and for quantitating glycans in cell wall extracts.

Our laboratory utilizes a broad range of experimental approaches in these studies, including molecular genetic, biochemical, immunological and microscopic techniques.

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Russell W Carlson

Short Biography:
Dr. Carlson received his B.A. in chemistry from North Park College, Chicago, Illinois in 1968, and his M.S. and Ph.D degrees in biochemistry from the University of Colorado in 1974 and 1976, respectively. Dr. Carlson is Emeritus Professor of Biochemistry and Molecular Biology (BCMB), and of the Complex Carbohydrate Research Center (CCRC) at the University of Georgia (UGA), Athens, Georgia. Prior to retiring in 2014, Carlson was Professor of BCMB, Executive Technical Director of Analytical Services at the CCRC, and Adjunct Professor of Microbiology at UGA. His area of research is microbe-host interactions; specifically, the role that microbial cell surface carbohydrates have in determining the virulence of both animal and plant pathogens (and symbionts). He has nearly 200 peer-reviewed publications and his research was funded over the years by grants from the National Institutes of Health, the National Science Foundation, the United States Department of Agriculture, as well as contracts with the Centers for Disease Control.

Research Interests:
Research in Dr. Carlson’s group is focused on characterizing the molecular basis for the interaction between a bacterium and a plant or animal host cell. One system being studied is the symbiotic, nitrogen-fixing infection of host legumes by rhizobia bacteria. Carlson’s group also has projects directed toward characterizing the roles bacterial lipopolysaccharides (LPSs), lipooligosaccharides (LOSs) and capsular polysaccharides (CPSs) play in determining pathogenicity (in animal hosts) of such organisms as Salmonella enteritidis, Neisseria meningitidis, Hemophilus influenzae, Moraxella catahalis, and, recently, Bacillus anthracis. Both the plant symbiont and animal pathogen work are being undertaken in collaboration with several research groups in other universities. The following paragraphs briefly describe several of these projects.
The nitrogen-fixing symbiosis is a complex infection process in which the soil bacteria contain genes that are activated by flavonoid molecules produced by the host plant. These genes encode enzymes that synthesize a glycolipid, which is an acylated chitin oligosaccharide. In most cases, the glycolipids produced by each Rhizobium species are structurally modified, which results in their ability to interact only with a specific legume plant (e.g., Rhizobium leguminosarum biovar viciae infects peas but not alfalfa, while R. meliloti infects alfalfa but not peas). This molecular “recognition” process results in the stimulation of cell division in the legume root causing a nodule to form. The cells in this nodule are invaded by the rhizobia and are where nitrogenase is produced that reduces dinitrogen to ammonia. Other molecules on the surface of rhizobia are required for invasion of the root nodule cells by these bacteria. These are the outer membrane LPSs and CPSs. Specific structural changes occur in these molecules in response to the host plant which are crucial for infection. These structural changes and the genes responsible for them are presently under investigation by Carlson’s research group. Knowledge gained in understanding the molecular basis for Rhizobium-legume symbiosis may lead to improving the yield of important legume crops and increasing the fertility of soil for non-legume crops. Besides the potential benefit to crop yield and soil fertility that may be gained from new knowledge about Rhizobium-legume symbiosis, these studies also have a bearing on how the plant’s defense mechanism is regulated so that the growth of the bacteria is controlled by the host to establish a symbiotic rather than a pathogenic relationship. Details of this work are described in several relevant publications that are referenced below.

Carlson’s group, in collaboration with Dr. David Stephens at Emory University, has also worked on determining the structural basis for the virulence functions of the cell surface lipooligosaccharide (LOS) and capsular polysaccharide (CPS) from Neisseria meningitidis. These molecules contain novel structural features that inhibit the host’s defense response. In the case of the LOS these structural features include the synthesis of host-like structures to camouflage the bacterium, as well as modifications that inhibit serum killing, etc. The CPS structures also protect the bacterium from the host defense reponse as they are poorly immunogenic. However, it is known that isolated CPS can be conjugated to proteins and have proven to be effective vaccine antigens that prevent infection by several types of N. meningitidis. Thus, the objective of this work is to identify the virulence functions of LPS and CPS structures as well as identify optimal structures for the development of vaccine antigens. Several publications describing this work are in referenced below.

Carlson’s group, in collaboration with Dr. Conrad Quinn at the Centers for Disease Control and Dr. Geert-Jan Boons of the Complex Carbohydrate Research Center at UGA, is working on determining if there are potential carbohydrate structures in the cell wall of Bacillus anthracis that can be used for the development of therapeutics, vaccines, and diagnostics. Ever since the anthrax attacks surrounding the events of 9/11, there has been, as part of the biodefense initiative, a great deal of focus on the development of novel therapeutics, vaccine antigens, and diagnostic agents for the treatment, prevention, and identification of B. anthracis infections. The cell surface polysaccharides that surround the bacterial cell or are part of its cell wall are well documented virulence factors, they have been used for the preparation of commercially available vaccines for the prevention of a number of bacterial diseases, and they are also known to be the basis for the serotyping of numerous bacterial pathogens; both Gram-positive and Gram-negative. Therefore, B. anthracis cell wall carbohydrates were investigated to determine if they also have potential in these areas. Bacillus anthracis is a member of the B. cereus group of bacteria; all of which are quite closely related as determined by comparing genome sequences. Laboratory-grown cultures of B. anthracis produce very few cell wall carbohydrates. In fact, only two major carbohydrates have been characterized. One is from a coating that surrounds the spore, called the exosporium. It is an oligosaccharide that covers a collagen-like protein called BclA. The structure of this oligosaccharide was determined by the group of Charles Turnbough at the University of Alabama, Birmingham. This structure, various structural analogs, and their protein conjugates have been synthesized by the group of Geert-Jan Boons at the CCRC and immunochemically characterized in collaboration with Conrad Quinn at the Centers for Disease Control. A second is a cell wall polysaccharide from the vegetative cell wall of B. anthracis. The structure of this polysaccharide as well as that from closely related B. cereus strains that are pathogenic have been characterized at the Complex Carbohydrate Research Center. Both the structural and immunochemical analyses of these cell wall carbohydrates support their potential for the development of vaccines and diagnostics. In addition, the data also indicate that these carbohydrates may be important for the virulence of this pathogen.

Dr. Carlson’s research has been supported by the U. S. Department of Agriculture, the National Science Foundation, and the National Institutes of Health.

Maor Bar-Peled

Short Biography:
Dr. Bar-Peled received his B.S. in 1985 and his M.S. in 1988 from the Hebrew University of Jerusalem. He completed his Ph.D. studies in 1993 in the Department of Plant Genetics, Weizmann Institute of Science in Israel. In 1992, Dr. Bar-Peled was a recipient of the Science Prize given by the Feinberg Graduate School of the Weizmann Institute of Science and, in 1993, he received an Israeli Ministry of Education Award. Prior to coming to the University of Georgia, Dr. Bar-Peled spent five years in the Department of Energy Plant Research Laboratory, Michigan State University, as a postdoctoral fellow. Dr. Bar-Peled was also a visiting scientist in the Department of Molecular Biology at the Washington University School of Medicine in St. Louis.Full publications: 32

Research Interests:
Research in Dr. Bar-Peled’s group aims to understand, at the molecular level, the roles of complex glycans in living organisms. We are interested in the roles of cell surface glycans in cell-cell recognition, pathogenicity, and communication between micro-organisms and their plant or animal hosts. In addition, we are investigating how the cellular processes involved in the synthesis, regulation and assembly of plant cell walls can be modified to enable new cost-effective technologies for producing biofuels from plant biomass. Our research uses biochemical, molecular and cellular and bioinformatics techniques together with plant and microbial mutants and state of the art mass spectrometry and NMR spectroscopy.

Current research programs in the Bar-Peled lab are:

The role of cell surface glycans during the life-cycle of Rhizobium. We study the molecular events that trigger this free-living soil bacterium to alter its cell surface glycan and glycolipid composition in response to changes in its environmental.

The molecular mechanisms that allow Bacillus cereus to form spores that adhere to diverse surfaces. This common soil bacterium is a difficult to control food poisoning agent.

The relationship between cell surface glycan synthesis and the interactions between fungi and their plant and animal hosts. We study how fungi adhere to and penetrate host cells and how this is related to diseases caused by fungi.

The genes and enzymes involved in the synthesis of plant cell wall glycans. We study how glycan synthesis is regulated and how these glycans are formed in the Golgi and then transported to plasma membrane where they are assembled into a functional wall. Understanding such processes at a molecular level will enable the development of bioenergy crops that can be cost-effectively converted to liquid fuels.