Molecular Biology of Spore Germination

Prof A Moir

My laboratory uses molecular biological and genetic approaches in Bacilli to study spore structure and function, and to elucidate the mechanism of spore germination.

Bacterial endospores are the most resistant form of any microbe, and sporeformers include harmless and beneficial soil microbes, producers of bacterial insecticides, and also toxin producers and pathogens. The germination apparatus in the spore is responsive to specific chemical signals in the environment, inducing major changes in spore morphology as the spore properties that ensure dormancy are lost. It is a paradox that a biological mechanism can be resistant to chemical and physical insult in the dormant spore, and yet can interact with specific germinant signals, such as particular amino acids, sugars and ribosides.

Our work has identified three proteins, that together form a receptor which detects a particular germinant and then transduces the stimulus, in an as yet poorly-understood manner. The Bacillus subtilis genome encodes five sets of homologues, and it appears that the ability to respond to different chemical signals has evolved by operon duplication and divergence. We are studying these and other protein components of the germination apparatus in B. subtilis, the most amenable model system, and in B. cereus, a food pathogen. We also study the structure and function of the exosporium, which forms an outer envelope round B. cereus spores. We have identified a number of exosporium proteins, and are using a mutant analysis to define which proteins are important for assembly of the exosporium. Research in our lab is funded by the BBSRC.

Figure Legend - An EM photograph of a cross section of a Bacillus cereus spore; an electron-transparent peptidoglycan cortex, coat layers and a loose exosporium surround the spore core.

Selected Publications

Localization of the GerD spore germination protein in the Bacillus subtilis spore. Mongkolthanaruk W, Robinson C, Moir A. Microbiology. 2009 Apr;155(Pt 4):1146-51.

Senior, A and Moir, A (2008) The Bacillus cereus GerN and GerT protein homologs have distinct roles in spore germination and outgrowth, respectively. J. Bacteriol. 190, 6148-6152.

Ball, D.A., Taylor, R., Todd, S.J., Redmond, C., Couture-Tosi, E. Sylvestre, P., Moir, A. and Bullough, P.A. (2008) Structure of the exosporium and sublayers of spores of the Bacillus cereus family revealed by electron crystallography. Mol Microbiol. 68, 947-958.

Jervis, A.J., Thackray, P.D., Houston, C.W., Horsburgh, M.J. & Moir, A. (2007) SigM-responsive genes of Bacillus subtilis and their promoters. J. Bacteriol. 189, 4534-4538.

Johnson, M.J., Todd, S.J., Ball, D., Shepherd, A.M. Sylvestre, P. & Moir, A (2006). ExsY and CotY are required for the correct assembly of the exosporium and spore coat of Bacillus cereus. J. Bacteriol. 188, 7905-7913.

Bailey-Smith, K, Todd, S.J., Southworth, T.W , Proctor, J & Moir, A. (2005) The ExsA protein of Bacillus cereus is required for assembly of coat and exosporium onto the spore surface. J. Bacteriol. 187, 3800-3806.