David Gene Morgan, Ph. D
Assistant Scientist
Simon Hall 047D
812.856.1457
dagmorga@indiana.edu
I started doing electron microscopy in 1985 when I joined the group of Wah Chiu (then at the University of Arizona). Wah currently directs the National Center for Macromolecular Imaging (NCMI) at the Baylor College of Medicine, and is one of the founders of the general field of high resolution electron microscopy applied to structural biology. This field was quite small when I joined Wah's lab (for example, there were not enough participants to fill the 130 person limit at the first few Three Dimensional Electron Microscopy Gordon Research Conferences), and I can honestly say that during the first ten years I worked in the area, I knew essentially everyone doing that sort of work. The field has grown exponentially over the years, but I still stay in contact with most of the major groups through meetings and workshops.
I have worked on most of the possible types of structural biology samples that can be examined using EM. Wah's lab was initially focused on thin three-dimensional (3d) crystals of things like crotoxin (from the South American rattlesnake, Crotalus durissus terrificus) and gp32*I (a proteolytic fragment of the bacterio- phage T4 DNA helix destablizing protein, gp32), but the group also worked with 3d crystals of acetylcholinesterase (from the electric eel, Electrophorus electricus), two-dimensional crystals of tetanus toxin (a collaboration with J.P. Robinson at Vanderbilt University, which is also where I got my Ph.D. in Biochemistry prior to joining Wah's lab as a post-doc), several different single particle projects and helical assemblies of both E. coli recA and tobacco mosaic virus (TMV). B.V.V. Prasad in our group worked on several icosahedral viruses, including the earliest frozen hydrated imaging of rotavirus.
I took a short sabbatical from EM while I worked with Jerry Hazelbauer (then at Washington State University) on bacterial chemotaxis and motility, but then returned to the EM field where I studied the bacterial motility machinery with David DeRosier at Brandeis University. I was indoctrinated into helical symmetry in David's lab, and over several years, we published multiple papers about image analysis of helical objects and the helical structures of flagella and hooks from Salmonella typhimurium. We also studied S. typhimurium flagellar basal bodies and published papers dealing with both the wild-type structures and several mutant forms. In this work, the basal bodies were treated as non-symmetric single particles during the analysis, and only at the end was rotational symmetry enforced.
When I moved to a shared position with Chris Akey at the Boston University School of Medicine and Tom Rappaport at the Harvard Medical School, I switched from analyzing symmetrical objects from bacteria to true single particles (ribosomes) from eukaryotic organisms. We compared yeast and rabbit ribosomes and wrote several papers on the structure of ribosomes attached to Sec61p channels during co-translational translocation of nascent peptides across the ER (endoplasmic reticulum) membrane. I also helped with some of the initial work in Chris's group on the human Apaf-1/cytochrome c apoptosome. I even managed to remain connected to the bacterial motility field when I collaborated on the first of several publications about spirochete flagella with Nyles Charon at the West Virginia UniversityRobert C. Byrd Health Sciences Center.
After my long stay in the greater Boston area, I moved to the University of Colorado at Boulder, working with Dick McIntosh and David Mastronarde at the Boulder Laboratory for 3-D Electron Microscopy of Cells. We hoped to do cryo-electron tomography on chloroplasts, but the size of the organelles (similar to typical bacteria, which are too thick for most types of cryo-electron tomography) prevented us from making much progress. However, I did learn a tremendous amount about tomography in general and about both serialEM (Mastronarde's tomographic tilt series data collection program for FEI TEM's) and IMOD (the Boulder group's software for generating 3d volumes from tilt series images). I was also exposed to specimen preparation techniques like high pressure freezing and freeze substitution.
After my time in Boulder, I joined Holland Cheng, first at the Karolinska Institute in Stockholm and then at the University of California at Davis. Holland got his Ph.D. with Tim Baker (then at Purdue University) and Holland's group works on icosahedral viruses using the Polar Fourier Transform (PFT) software that he helped develop while in Tim's lab. I worked on a variety of icosahedral viruses and several tomography projects while in Holland's lab, and helped a graduate student finish a technical paper about a method of virus reconstruction. During my stay at UC Davis, I also helped David Mastronarde and Jacob Brink (of JEOL USA) port serialEM to several JEOL TEM's. I also started what has turned into an on-going collaboration with Paul Gottlieb at The City College of New York. Paul works on bacteriophages φ6 and φ12 from the genus Cystovirus. Though these membrane enclosed, dsRNA viruses infect various bacterial species (mostly Gram-negative species from the genus Pseudomonas), they are closely related to the Reoviridae family, a group of eukaryotic viruses that include the rotavirus that Prasad studied in Wah Chiu's lab when I began my career in electron microscopy.
While still at UCDavis, I also worked with Nigel Browning, now at the Pacific Northwest National Laboratory (PNNL). Nigel uses electron microscopy to study a variety of materials science problems, with an emphasis on developing new techniques. While with Nigel, I did a number of tomographic analyses, some computational work (both image simulation and novel analytical approaches to STEM images) and generally helped his group incorporate structural biology image processing techniques into the analysis of materials science specimens.
Since arriving on the Bloomington campus in the spring of 2008, I have overseen the installation of the JEOL JEM 3200FS, trained its new users and collaborated on many projects (as reflected in the Electron Microscopy Center's various publications I have co-authored since the 3200FS became operational). In a continuing collaboration with David Mastronarde and Jacob Brink, we have used the 3200FS as a test microscope for development of STEM tomography using serialEM. This is ongoing work, and we currently are thinking about ways to handle the large defocus gradient that occurs in STEM images with large fields of view. In addition to my work at Indiana University, I have been involved in the Indiana Microscopy Society, serving as president for the past 3 or 4 years.
I have also put together this web site, which is intended to be both a practical introduction for new users of the Electron Microscopy Center and also a tool for learning about the types of electron microscopy.