Endospores

Endospores

1. Certain species of Bacteria produce structures called endospores during a process called sporulation.

   • Endospores function as survival structures and enable the organism to endure unfavorable growth conditions.
     • Endospore formation and germination
       • During this process a vegetative cell is converted into a nongrowing heat-resistent structure.
         • Cells do not sporulate when they are actively growing.
           • Cells of Bacillus, a typical endospore-forming bacterium.
             • The process involves three steps:
               • Activation
                 • Occurs when endospores are heated for several minutes at elevated but sublethal temperature.
               • Germination
                 • A rapid process
                   • Involves loss of microscopic refractility of the endospore.
               • Outgrowth
                 • Involves visible swelling due to water uptake and synthesis of RNA, proteins, and DNA.
     • Endospore structure
       • The structure of the endospore as seen with the electron microscope differs distinctly from that of vegetative cell.
         • Exosporium
           • The outermost layer,
             • A thin protein covering.
         • Spore coats
           • Composed of layers of spore-specific proteins.
           • Cortex
             • Consist of loosely cross-linked peptidoglycan.
             • Core wall
               • Cytoplasmic membrane, cytoplasm, nucleoid, ribosomes, and other cellular essentials.
     • Enodospore Core and SASPs
       • Both contain a copy of the chromosome and other essential cellular components.
         • The endospore core contains high levels of small acid-soluble proteins (SASPs).
           • These proteins are made during the sporulation process, and have at least two functions:
             • Bind tightly to DNA in the core and protect it from potential damage from ultraviolet radiation, desiccation, and dry heat.
             • As a carbon and energy source for the outgrowth of a new vegetative cell from the endospore during germination.
     • The sporulation Process
       • A complex series of events in cellular differentiation.
         • Sporulation can be divided into several stage.
           • The sporulation process takes about 8 hours and begin with asymmetric cell division.