ENDOSPORES

ENDOSPORES

1. Some species of bacteria produce structures called endospores during a proces called sporulation.

   • Can thus be thought of as the dormant stage of a bacterial life cycle.
     • Vegetatice cell
     • Endospore-forming bacteria are commonly found in soil, and species of Bacillus.
       • The sporulation Process
         • Sporulation can be divided into several stages.
           • Bacillus subilis
             • The sporulation process take about 8 h and begins with asymetric cel division.

2. Endospore formation and germination.

   • During this process a vegetative cell is converted into a nongrowing, heat-resistent structure.
     • Cells of Bacillus, a typical endospore-forming bacterium.
       • This process involves three steps.
         • Activation
           • Retracility is being lost.
             • Occurs when endospores are heated for several mintes at an elevated but bublethal temperature.
         • Germination
           • Involves loss of microscopie refractility of the endospores.
             • Increased ability to be stained by dyes, and loss of resistance to heat and chemicals.
         • Outgrowth
           • The new vegetative cell is emerging.
             • Involves visible swelling due to water uptake and synthesis of RNA , proteins and DNA.

3. Ensospore Structure.

   • The structure of the endospore as seen with the electron microscope differs distinctly from that of vegetative cell.
     • Exoporium
       • Outermost layer
     • Spore coats
       • Layers of spore-specific proeins.
       • Cortex
         • Consists of loosely cross-linked peptidoglycan
         • Core
           • Contains the core wall, cytoplasmic membrane, cytoplasm, nucleoid, ribosomes, and other cellular assentials.
             • The endospore core and SASPs
               • Both contain a copy of the chromosome and other essential cellular components.
                 • SASPs
                   • These proteins are made during the sporulation process and have at least two funtions
                     • Bind tightly to DNA in the core and protect it from potential demage from ultravioleet radiation, desiccation and dry heat.
                     • As a carbon and energy source for the outgrowth of the new vegetative cell from the endospore during germination.