- Ph.D. 1991 Plant Pathology, Washington State University
- M.S. 1986 Plant Pathology, Oregon State University
Projects in the Virology Lab:
Viruses parasitic to bacteria (bacteriophages - phages') are the most abundant and most diverse form of life' on the planet. Some phages kill dangerous bacteria, and therefore are potentially useful to humans. Our lab takes both basic and applied approaches to studying phages of the anthrax bacterium, Bacillus anthracis. At the basic level, we ask: How can we quickly distinguish these phages from one another and how many different types of B. anthracis phages are there in the soil community: what is the species richness'? Our applied research includes characterization of phages that kill B. anthracis. This bacterium has a long and ugly history in terms of human and livestock disease, and now bio-terrorism, so there is plenty of interest in controlling damage.
The student projects currently underway range from standard virology to phage-based therapy and decontamination, to phage-bioinformatics. Students may work on growing, isolating and characterizing phages (using a safe-strain Bacillus host) which feeds data into several projects:
Initially, phages are identified, named and characterized by structural protein content. Phage protein profiles help with an ongoing project describing the number of different phages specific to B. anthracis in soils (species richness'). Our first publication on the species richness of 1 soil sample is in preparation as Gabe Connell completes his MS degree.
Phage DNA data feeds into our growing UNI-phage data base, which we use to compare our phage DNA to others, using web-based bioinformatics tools. This helps us to characterize phage genes that might code for bacteria-binding-and-bursting enzymes. Our collaborations with Michael Thomas, Associate Prof. - Bioinformatician, Idaho State University, has resulted in a nearly complete DNA sequence for phage SBP8a that was characterized as adhering to B. anthracis spores.
Last, and most exciting, we have current collaborations with certified bio-containment labs (elsewhere). Students help test our candidate phages here at UNI (against safe strains) for spore-adherence and bacteria-killing ability, then send the best ones out for testing. Since the number of phages is nearly uncountable, the opportunities are great. Phage SBP8a did not prove effective against really high spore doses in mice models, but we are currently seeking funding to have similar tests carried out at lower, more meaningful spore doses.
Our 'Battlelle-Iowa State Board of Regents'-funded project saw the design and development of a spore detection prototype, which was tested successfully (under sub-contract, at BSL3, with Ames Strain spores). This device made use of quartz-crystal microbalance technology, coupled with our selected bacteriophages (as spore-binding affinity reagents). We are currently seeking funding to move the project into the next development stage, where we will improve phage selection and simplify/miniaturize the detector hardware.
We collaborate with the Molecular Biology, Environmental Microbiology, Plant Molecular Biology, Plant Anatomy and Immunology Labs in the Department of Biology and with the Computer Science Department. Collaborative projects might also include: grapevine bacterial or virus disease research, and plant disease research projects.
- Xiaofeng Fu, Michael H. Walter, Angel Paredes, Marc C. Morais, Jun Liu. 2010. The mechanism of DNA ejection in the Bacillus anthracis spore-binding phage 8a revealed by cryo-electron tomography. Nature Structural and Molecular Biology. MS in Review
- Walter, M. H., King, K. V. and R. Aldenderfer. Lack of in vivo bacteriophage efficacy against high doses of Bacillus anthracis spores. Applied & Environmental Microbiology (ms in review).
- Walter, M. H. 2003. Efficacy and durability of Bacillus anthracis bacteriophages used against spores. Journal of Environmental Health 66(1):9-15.
- Walter, M. H. and Dylan D. Baker. 2003. Three Bacillus anthracis bacteriophages from topsoil. Current Microbiology 47:55-58.
- Patent: # 7,374,874, Issued May 20, 2008. Bacteriophages that Infect Bacillus Bacteria (ANTHRAX). The invention provides bacteriophages that infect Bacillus bacteria, including Bacillus anthracis, and compositions containing the bacteriophages. The invention also provides methods for using the bacteriophages of the invention to prevent and treat infection of an organism by Bacillus bacteria. Methods and materials to decontaminate a surface or an organism that is contaminated with Bacillus bacteria or Bacillus spores is also provided. Filed April 22, 2003.