Bacterial Endospores

Abstract

The spores of bacteria formed mainly by members of the genera Bacillus and Clostridium are termed endospores because they develop singly within the mother or sporangial cells. Spore formation is a complex differentiation process involving two cells and a programme of gene expression requiring intracellular communication. Endospores exhibit complete metabolic dormancy and extreme resistance to multiple environmental insults, and can survive for centuries. The production of resistant spores by certain pathogenic bacterial species contributes to their transmission and difficulties in preventing their reoccurrence. Dormancy and resistance properties derive from alterations in the spore cell cytoplasmic contents, including dehydration, and from multiple integument layers. When presented with a nutrient‐rich environment, spores can rapidly germinate and re‐enter vegetative growth cycle.

Key Concepts:

  • Bacterial endospores can survive for decades and are highly resistant to numerous environmental insults.

  • The resistance properties of bacterial endospores contribute to their roles in food spoilage and in human and animal pathogenesis.

  • Bacterial endospores are cells with specialised modifications to their structure and contents.

  • Bacterial endospores are produced via a simple developmental process involving cooperative and regulated gene expression of two cells.

  • Heat resistance of bacterial endospores is determined by several factors, the most important being the relative dehydration of the spore core.

  • Bacterial endospores possess a unique mode of resistance to UV irradiation involving specialised DNA‐binding proteins.

Keywords: differentiation; disinfection; dormancy; endospore; heat resistance; spore; spore‐forming bacteria; sterilisation

Figure 1.

Phase‐contrast light microscopic images of unstained cells of Bacillus megaterium: (a) actively multiplying vegetative cells; (b) sporangial cells containing phase‐dark prespores; (c) sporangial cells containing phase‐bright immature spores and (d) free mature spores after sporangial autolysis.

Figure 2.

Electron microscopic image of a metal‐stained mature spore of B. megaterium QMB1551 in transverse section. The spore contains a central core consisting of a faintly visible plasma membrane (IM) surrounding a cytoplasm that includes light‐staining DNA regions (NP) and dark‐staining ribosome granules (CP). Surrounding the core is a thin, darkly stained primordial cell wall and a contiguous unstained cortex (CX‐PCW). Surrounding the cortex is a lightly stained inner coat, an intermittently visible outer membrane and a thin outer coat (C‐OM). Enveloping all is a loosely fitting exosporium (EX). Bar, 200 nm.

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Further Reading

Cairns MD, Stabler RA, Shetty N and Wren BW (2012) The continually evolving Clostridium difficile species. Future Microbiology 7(8): 945–957.

Campbell CG, Kirvel RD, Love AH et al. (2012) Decontamination after a release of B. anthracis spores. Biosecurity and Bioterrorism 10(1): 108–122.

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de Hoon MJ, Eichenberger P and Vitkup D (2010) Hierarchical evolution of the bacterial sporulation network. Current Biology 20(17): R735–R745.

McKenney PT, Driks A and Eichenberger P (2013) The Bacillus subtilis endospore: assembly and functions of the multilayered coat. Nature Reviews Microbiology 11(1): 33–44.

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How to Cite close
Mury, Sean P, and Popham, David L(Feb 2014) Bacterial Endospores. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0000300.pub2]