Biochemistry and Molecular Biology
Penn State Science
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Ming Tien

Ming Tien

Main Content

  • Professor of Biochemistry
305 South Frear Laboratory
University Park, PA 16802
Email: mxt3@psu.edu
Phone: (814) 863-1165

Research Interests

Characterization and biochemical analysis of cellulose synthesis in a variety of organisms.

Mechanism and regulation of fungal degradation of lignin.

Dissimilatory Iron reduction

Graduate Programs

BGC, BMMB, PLBIO

Research Summary

The Tien Lab has two main research areas. Initial impression is that they are not related; however, they share the common theme of increasing the efficiency of biofuel production - one through understanding the synthesis of biomass and the other in understanding how it is degraded.

The Tien Lab also does research into dissimilatory iron reduction, with applications in alternative energy and bioremediation.

The study of cellulose synthesis

Cellulose is the most abundant biopolymer on earth. Every day, a vast quantity of solar energy is stored in the form of chemical bonds through the process of photosynthesis. One major sink for this carbon biopolymer is the cell wall, which is comprised of 20 to 90% cellulose, making cellulose an abundant, renewable energy source just waiting to be utilized. However, the natural crystallinity of cellulose, along with other cell wall components like lignin, make plant biomass recalcitrant to degradation, and the amount of energy input required to bread down cellulose significantly reduces the yield. But what if one could modify the synthesis of cellulose to better suit our energy, and other needs?

Our research attempts to uncover the fundamental nature of cellulose synthesis and its obligate proteins. We are trying to better understand how these proteins function so that informed decisions can be made on how to modify cellulose synthesis. Cellulose synthesis research is currently the main focus of Tien Lab.

Our lab studies cellulose synthesis in three main model organisms: the cellulose synthesizing bacteria Gluconacetobacter hansenii, the moss Physcomitrella patens, and the model plant, Arabidopsis thaliana. In Gluconacetobacter, the cellulose synthase operon encodes 3 proteins - AcsAB, AcsC, and AcsD, which work in conjunction to synthesize and extrude cellulose outside of the cell. In higher plants, including Arabidopsis, there are multiple cellulose synthase proteins (CesAs) that assemble at the plasma membrane to form a cellulose generating mega complex (theorized to be up to 4 Megadaltons in size). Evidence suggests that different isoforms of the CesA proteins are required in a specific arrangement and stoichiometry in order to successfully synthesize cellulose. To approach our research we use many classical biochemical techniques such as western blotting, Blue Native PAGE, formaldehyde crosslinking, immunoprecipatation, in vitro cellulose synthesis assays, column purification of cellulose synthase proteins, heterologous expression, X-ray crystallography, isothermal titration calorimetry, plant transgenics, analytical ultracentrifugation, 2-D PAGE, proteomics, and other various ways to assess, purify, and characterize proteins biochemically.

Fungal lignin biodegradation

The degradation of lignin plays a key role in carbon recycling on earth. Lignin, an aromatic polymer, is second only to cellulose in abundances as a renewable carbon source and accounts for approximately 20% of all the carbons fixed by photosynthesis. Lignin is nature’s plastic imparting rigidity to woody biomass and conferring resistance to wood from most forms of microbial attack. The degradation of lignin is brought about predominantly by filamentous fungi. Due to the heterogeneity of woody biomass, an ensemble of enzymes is required to degrade this substrate to carbon dioxide. Both hydrolytic and oxidative enzymes are involved. The hydrolytic enzymes are used for depolymerization of cellulose whereas the oxidative enzymes are used for depolymerization of lignin. Our past research efforts have focused on the enzymology and regulation of the oxidative enzymes. These oxidative enzymes generate free radicals in lignin resulting in its depolymerization.

Despite years of research by many labs, the identity of the enzymes involved in wood degradation is still not known. Our past efforts have focused on mechanistic studies of peroxidases, Mn peroxidase and lignin peroxidase. However, to degrade wood, an ensemble of enzymes is required. The recent completion of the sequencing of a fungal genome, Phanerochaete chrysosporium and advances in methodology/instrumentation now allows us to identify all of the proteins produced to degrade wood. We are using a proteomics approach toward identifying all of the extracellular proteins produced by P. chrysosporium when grown on wood. Protein spots are excised from 2-dimensional gels, digested with trypsin and the peptides are sequenced by LC/MS/MS. Using this method, we are in the process of identifying the greater than 40 proteins produced when P. chrysosporium degrades oak. Ongoing research involves determining the role of the wood substrate on enzyme production and the succession of enzymes involved in degradation of wood.

Dissimilatory Iron reduction
Micro-organisms are known to use over 20 elemental systems other than O2 to accept electrons during respiration. Of these, only 6 are known to be respired in solid form: S, As, Se, U, Fe, Mn. Of these six, the ability to reduce iron is the most common among deeply branching members of Archaea and Bacteria. Microbial Fe respiration is important because it dominates reduction of iron in a large number of natural systems today. Interest in this process, largely focused on Shewanella and Geobacter, has intensified recently because bioreduction of iron oxides releases co-precipitated or sorbed contaminants in the subsurface. Using the Shewanella oneidensis, we aim to elucidate the biochemical mechanism of iron reduction. Collaborating with Dr. Susan Brantley at Penn State’s Department of Geoscience, we have utilized a protemics approach toward understanding the enzymology of this process. Using 2-D gel electrophoresis, we have identified a number of proteins that are uniquely expressed under iron-reducing growth conditions. Because S. oneidensis has been recently sequenced, we have used trypsin fingerprinting using MALDI/TOF mass spectroscopy. In addition, we are the first team to develop an in vitro (cell-free) model system derived from Shewanella wherein membrane fractions directly reduce solid-phase Fe minerals. Ongoing research aims to purify the enzymes involved in this process.

Selected Publications

  • SO2907, A putative TonB-dependent receptor, is involved in dissimilatory iron reduction by Shewanella oneidensis MR-1. Qian Y, Shi L, Tien M. J Biol Chem. 2011 Aug 3.
  • Mapping the Iron Binding Site(s) on the Small Tetraheme Cytochrome of Shewanella oneidensis MR-1. Qian Y, Paquete CM, Louro RO, Ross DE, Labelle E, Bond DR, Tien M. Biochemistry. 2011 Jul 19;50(28):6217-24.
  • Identification of an extracellular polysaccharide network essential for cytochrome anchoring and biofilm formation in Geobacter sulfurreducens. Rollefson JB, Stephen CS, Tien M, Bond DR. J Bacteriol. 2011 Mar;193(5):1023-33.
  • Genome sequence of a cellulose-producing bacterium, Gluconacetobacter hansenii ATCC 23769. Iyer PR, Geib SM, Catchmark J, Kao TH, Tien M. J Bacteriol. 2010 Aug;192(16):4256-7. Epub 2010 Jun 11.
  • Haiying Liang, Christopher J. Frost, Xiaoping Wei, Nicole R. Brown, John E. Carlson, Ming Tien (2008) "Improved sugar release from lignocellulosic material by introducing a tyrosine-rich cell wall peptide gene in poplar" CLEAN - Soil, Air, Water
  • Scott M. Geib, Timothy R. Filley, Patrick G. Hatcher, Kelli Hoover, John E. Carlson, Maria del Mar Jimenez-Gasco, Akiko Nakagawa-Izumi, Rachel L. Sleighter, and Ming Tien (2008) “Lignin degradation in wood-feeding insects” Proc. Natl. Acad. Sci. 105, 12932-12937
  • Sato, S., F. Liu, H. Koc, and M. Tien, Expression analysis of extracellular proteins from Phanerochaete chrysosporium grown on different liquid and solid substrates. Microbiology, 2007. 153, 3023-3033.
  • Abbas, A., H. Koc, F. Liu, and M. Tien, Fungal degradation of wood: initial proteomic analysis of extracellular proteins of Phanerochaete chrysosporium grown on oak substrate. Curr. Genet., 2005. 47, 49-56.
  • Characterization of an electron conduit between bacteria and the extracellular environment. Hartshorne RS, Reardon CL, Ross D, Nuester J, Clarke TA, Gates AJ, Mills PC, Fredrickson JK, Zachara JM, Shi L, Beliaev AS, Marshall MJ, Tien M, Brantley S, Butt JN, Richardson DJ. Proc Natl Acad Sci U S A. 2009 Dec 29;106(52):22169-74
  • Kinetic characterization of OmcA and MtrC, terminal reductases involved in respiratory electron transfer for dissimilatory iron reduction in Shewanella oneidensis MR-1. Ross DE, Brantley SL, Tien M. Appl Environ Microbiol. 2009 Aug;75(16):5218-26
  • Microbial community profiling to investigate transmission of bacteria between life stages of the wood-boring beetle, Anoplophora glabripennis. Geib SM, Jimenez-Gasco Mdel M, Carlson JE, Tien M, Jabbour R, Hoover K. Microb Ecol. 2009 Jul;58(1):199-211
  • The first genome-level transcriptome of the wood-degrading fungus Phanerochaete chrysosporium grown on red oak. Sato S, Feltus FA, Iyer P, Tien M. Curr Genet. 2009 Jun;55(3):273-86.
  • Effect of host tree species on cellulase activity and bacterial community composition in the gut of larval Asian longhorned beetle. Geib SM, Jimenez-Gasco Mdel M, Carlson JE, Tien M, Hoover K. Environ Entomol. 2009 Jun;38(3):686-99
  • Lignin degradation in wood-feeding insects. Geib SM, Filley TR, Hatcher PG, Hoover K, Carlson JE, Jimenez-Gasco Mdel M, Nakagawa-Izumi A, Sleighter RL, Tien M. Proc Natl Acad Sci U S A. 2008 Sep 2;105(35):12932-7
  • Characterization of protein-protein interactions involved in iron reduction by Shewanella oneidensis MR-1. Ross DE, Ruebush SS, Brantley SL, Hartshorne RS, Clarke TA, Richardson DJ, Tien M. Appl Environ Microbiol. 2007 Sep;73(18):5797-808
  • Expression analysis of extracellular proteins from Phanerochaete chrysosporium grown on different liquid and solid substrates. Sato S, Liu F, Koc H, Tien M. Microbiology. 2007 Sep;153(Pt 9):3023-33.
  • Reduction of soluble and insoluble iron forms by membrane fractions of Shewanella oneidensis grown under aerobic and anaerobic conditions. Ruebush SS, Brantley SL, Tien M. Appl Environ Microbiol. 2006 Apr;72(4):2925-35.
  • Nano-assembly of manganese peroxidase and lignin peroxidase from P. chrysosporium for biocatalysis in aqueous and non-aqueous media. Patel DS, Aithal RK, Krishna G, Lvov YM, Tien M, Kuila D. Colloids Surf B Biointerfaces. 2005 Jun 10;43(1):13-9.
  • Fungal degradation of wood: initial proteomic analysis of extracellular proteins of Phanerochaete chrysosporium grown on oak substrate. Abbas A, Koc H, Liu F, Tien M. Curr Genet. 2005 Jan;47(1):49-56. Epub 2004 Nov 18.
  • Romero, H. M., Jensen, P., Berlett, B, Pell, E. and Tien, M. (2004) “The Plastidial Peptide Methionine Sulfoxide Reductase is an Important Component of the Response of Arabidopsis to Oxidative Stress in the Chloroplast” Plant Phys. .
  • Ruebush, S. S.; Icopini, G. A.; Brantley, S. L.; Tien, M. “In Vitro Enzymatic Mineral Oxide Reduction by Membrane Fractions from Shewanella oneidensis MR1” Enzyme Microb. Technol. 2004.
  • Icopini, G.A., A.D. Anbar, S.S. Ruebush, M. Tien, and S.L. Brantley, Iron isotope fractionation during microbial reduction of iron: The importance of adsorption. Geology, 2004. 32: p. 205–208.
  • Varela, E., T. Mester, and M. Tien, Culture conditions affecting biodegradation components of the brown-rot fungus Gloeophyllum trabeum. Arch. Microbiol., 2003. 180(4): p. 251-256.
  • Varela, E. and M. Tien, Effect of pH and Oxalate on Hydroquinone-Derived Hydroxyl Radical Formation during Brown Rot Wood Degradation. Appl. Environ. Microbiol, 2003. 69(10): p. 6025-6031.
  • Banci, L., Bartalesi, I., Ciofi-Baffoni, S. and Tien, M. (2003) “Unfolding and pH studies on manganese peroxidase: Role of heme and calcium on secondary structure stability” Biopolymers 72: 38-47.
  • Mester, T. and M. Tien (2001). "Oxidation mechanism of Ligninolytic Enzymes Involved in the Degradation of Environmental Pollutants." Intern. Biodet. Biodeg. 46: 51-59.
  • Mester, T. and M. Tien (2001). "Engineering of a manganese-binding site in lignin peroxidase isozyme H8 from Phanerochaete chrysosporium." Biochem. Biophys. Res. Commun. 284(3): 723-728.
  • Mester, T., K. Ambert-Balay, et al. (2001). "Oxidation of a tetrameric nonphenolic lignin model compound by lignin peroxidase." J. Biol. Chem. 276(25): 22985-22990.