My research focuses on using imaging techniques to investigate biological systems at multiple scales, from macromolecular interactions and cellular signaling to community structure. A main topic of my recent work is investigating plant-microbe interactions using molecular genetics, live cell imaging methods, and super resolution microscopy.
As part of the Plant- Microbe Interfaces project (http://pmi.ornl.gov:8080/pmi/index.jsp), we are focused on understanding the genetic bases of molecular communication between Populus and its microbial consortia. In particular, my research focuses on the mechanisms a nd signaling events that promote bacterial attachment and colonization of Poplar roots. The mutualistic association between microbes and plant roots form an environment that is ideal for biofilm formation, including sufficient moisture and nutrients which are supplied by the plant host. The process of biofilm formation has been described and generally involves bacteria approaching a surface and becoming transiently attached. Some of these bacteria remain attached for extended periods of time and are thought to have transitioned from transient to permanent attachment. The transition from a motile to sessile (biofilm) lifestyle in bacteria is known to be mediated by levels of the second messenger bis-(3’-5’)-cyclic dimeric GMP (c-di-GMP). C-di-GMP is produced from GTP by the activity of diguanylate cyclases, identified by a GGDEF domain, and is degraded by phosphodiesterases, characterized by either a EAL or HD-GYP domain. Bacteria contain multiple members of these protein families, leading to complex regulatory pathways to precisely control c-di-GMP levels in response to environmental signals. Current projects include identifying the molecular pathways controlling c-di-GMP levels in selected microbes, including Pantoea isolates , that respond to specific conditions found in the Poplar rhizosphere using a combination of molecular genetics, biochemistry, and imaging methods.
Additional projects include the use of live cell imaging methods to investigate the spatial and temporal dynamics of bacterial colonization in real time, and the use of high resolution microscopy to elucidate lipid droplet formation in fission yeast. Much of our work utilizes advanced microscopy, including a Zeiss LSM 710 confocal microscope equipped with an environmental chamber for controlling temperature, humidity and CO2 levels, and a Zeiss Elyra microscope with super-resolution capabilities (structured illumination microscopy and photoactivated locallization microscopy).
Weston, D. J., Pelletier, D.A., Morrell-Falvey, J.L., Tschaplinski, T.J., Jawdy, S.S., Lu,T.S., Allen, S.M., Melton, S.J., Martin, M.Z., Schadt, C.W., Karve, A.A., Chen, J-G., Yang, X., Doktycz, M.J., and Tuskan, G.A. (2012). Pseudomonas fluorescens Induces Strain-Dependent and Strain-Independent Host Plant Responses in Defense Networks, Primary Metabolism, Photosynthesis, and Fitness. MPMI 25(6), 765-778. http://www.ncbi.nlm.nih.gov/pubmed/22375709
Guo, J., Morrell-Falvey, J.L., Labbe, J.L., Muchero, W., Kalluri, U.C., Tuskan, G.A., Chen, J. (2012) Highly Efficient Isolation of Populus Mesophyll Protoplasts and Its Application in Transient Expression Assays. PLoS One 7(9), e44908 (http://dx.doi.org/10.1371%2Fjournal.pone.0044908)
Feoktistova, A., Morrell-Falvey, J.L., Chen, J., Singh, N.S., Balasubramanian, M.B., Gould, K.L. (2012). The fission yeast SIN kinase, Sid2, is required for SIN asymmetry and regulates the SIN scaffold, Cdc11 Mol. Biol. Cell 23(9): 1636-1645. (http://www.ncbi.nlm.nih.gov/pubmed/22419817)
Suresh, A.K, Pelletier, D.A., Wang, W., Morrell-Falvey, J.L., Gu, B., Doktycz, M.J. (2012). Cytotoxicity induced by engineered silver nanocrystallites is dependent on surface coatings and cell types. Langmuir 28 (5), 2727-2735.
Wang, Z., Elkins, J.G., and Morrell-Falvey, J.L. (2011) Spatial and Temporal dynamics of biofilm formation and cellulose degradation by Caldicellulosiruptor obsidiansis and Clostridium thermocellum. AMB Express 1:30 (http://www.ncbi.nlm.nih.gov/pubmed/21982458)
Wang, Z., Hamilton-Brehm, S.D., Lochner, A., Elkins, J.G., and Morrell-Falvey, J.L. (2011) Mathematical modeling of hydrolysate diffusion and utilization in cellulolytic biofilms of the extreme thermophile Caldicellulosiruptor obsidiansis. Bioresour Technol 102(3), 3155-3162 (http://www.ncbi.nlm.nih.gov/pubmed/21075617)
Edwards, A.E., Siuti, P., Bible, A.N., Alexandre, G., Retterer, S.T., Doktycz, M.J., Morrell-Falvey, J.L. (2011) Characterization of Cell Surface and EPS Remodeling of Azospirillum brasilense Chemotaxis-like 1 Signal Transduction Pathway mutants by Atomic Force Microscopy. FEMS Micro Lett 314 (2), 131-139. (http://www.ncbi.nlm.nih.gov/pubmed/21105907)
Edwards, A.N., Fowlkes, J.D., Standaert, R.F., Pelletier, D.A., Doktycz, M.J., Morrell-Falvey, J.L. (2009) An in vivo imaging-based assay for detecting protein interactions over a wide range of binding affinities. Analyt. Biochem 395(2), 166-177. (http://www.ncbi.nlm.nih.gov/pubmed/19698693)
Hervey, W.J. 4th, Khalsa-Moyers,G., Lankford, P.K., Owens, E.T., McKeown, C.K., Lu, T.Y, Foote, L.J., Asano,K.G., Morrell-Falvey, J.L., McDonald, W.H., Pelletier, D.A., Hurst, G.B. (2009) “Evaluation of Affinity-Tagged Protein Expression Strategies using Local and Global Isotope Ratio Measurements” Analyt. Chem, 8(7), 3675-3688.
Pelletier, D.A., Hurst, G.B., Foote, L.J., Lankford, P.K., McKeown, C.K., Lu, T.Y., Schmoyer, D.D., Shah, M.B., Hervey, W.J. 4th, McDonald, W.H., Hooker, B.S., Cannon, W.R., Daly, D.S., Gilmore, J.M., Wiley, H.S., Auberry, D.L., Wang, Y., Larimer, F.W., Kennel, S.J., Doktycz, M.J., Morrell-Falvey, J.L., Owens, E.T., Buchanan, M.V. (2008) A general system for studying protein-protein interactions in Gram-negative bacteria. J. Proteome Res. 7(8), 3319-28. (http://www.ncbi.nlm.nih.gov/pubmed/18590317)