Localization and assembly of proteins comprising the outer structures of the Bacillus anthracis spore
- 1 April 2009
- journal article
- Published by Microbiology Society in Microbiology
- Vol. 155 (4), 1133-1145
- https://doi.org/10.1099/mic.0.023333-0
Abstract
Bacterial spores possess a series of concentrically arranged protective structures that contribute to dormancy, survival and, ultimately, germination. One of these structures, the coat, is present in all spores. InBacillus anthracis, however, the spore is surrounded by an additional, poorly understood, morphologically complex structure called the exosporium. Here, we characterize three previously discovered exosporium proteins called ExsFA (also known as BxpB), ExsFB (a highly related paralogue ofexsFA/bxpB) and IunH (similar to an inosine–uridine-preferring nucleoside hydrolase). We show that in the absence of ExsFA/BxpB, the exosporium protein BclA accumulates asymmetrically to the forespore pole closest to the midpoint of the sporangium (i.e. the mother-cell-proximal pole of the forespore), instead of uniformly encircling the exosporium. ExsFA/BxpB may also have a role in coat assembly, as mutant spore surfaces lack ridges seen in wild-type spores and have a bumpy appearance. ExsFA/BxpB also has a modest but readily detected effect on germination. Nonetheless, anexsFA/bxpBmutant strain is fully virulent in both intramuscular and aerosol challenge models in Guinea pigs. We show that the pattern of localization of ExsFA/BxpB–GFP is a ring, consistent with a location for this protein in the basal layer of the exosporium. In contrast, ExsFB–GFP fluorescence is a solid oval, suggesting a distinct subcellular location for ExsFB–GFP. We also used these fusion proteins to monitor changes in the subcellular locations of these proteins during sporulation. Early in sporulation, both fusions were present throughout the mother cell cytoplasm. As sporulation progressed, GFP fluorescence moved from the mother cell cytoplasm to the forespore surface and formed either a ring of fluorescence, in the case of ExsFA/BxpB, or a solid oval of fluorescence, in the case of ExsFB. IunH–GFP also resulted in a solid oval of fluorescence. We suggest the interpretation that at least some ExsFB–GFP and IunH–GFP resides in the region between the coat and the exosporium, called the interspace.Keywords
This publication has 69 references indexed in Scilit:
- Recombinant Bacillus anthracis spore proteins enhance protection of mice primed with suboptimal amounts of protective antigenVaccine, 2008
- Cortex Peptidoglycan Lytic Activity in Germinating Bacillus anthracis SporesJournal of Bacteriology, 2008
- The integrin Mac-1 (CR3) mediates internalization and directsBacillus anthracisspores into professional phagocytesProceedings of the National Academy of Sciences of the United States of America, 2008
- Bacillus anthracis Exosporium Protein BclA Affects Spore Germination, Interaction with Extracellular Matrix Proteins, and HydrophobicityInfection and Immunity, 2007
- The BclB Glycoprotein of Bacillus anthracis Is Involved in Exosporium IntegrityJournal of Bacteriology, 2007
- Bacillus anthracis Spores of the bclA Mutant Exhibit Increased Adherence to Epithelial Cells, Fibroblasts, and Endothelial Cells but Not to MacrophagesInfection and Immunity, 2007
- Protective Role of Bacillus anthracis Exosporium in Macrophage-Mediated Killing by Nitric OxideInfection and Immunity, 2007
- Role ofBacillus anthracis Spore Structures in Macrophage Cytokine ResponsesInfection and Immunity, 2007
- Fully Virulent Bacillus anthracis Does Not Require the Immunodominant Protein BclA for PathogenesisInfection and Immunity, 2007
- The ExsY Protein Is Required for Complete Formation of the Exosporium of Bacillus anthracisJournal of Bacteriology, 2006