23. The stage of endospore formation. Germination of endospore.

Endospores is a special type of resting cells of gram-positive bacteria that form within the cytoplasm of the mother cell. In each bacterial cell is formed by one of endospores. Endospores have a multi-layer protein covers, outer and inner membranes cortex. Moreover, they are resistant to high temperatures and radiation, normally lethal to vegetative cells.

Formation of endospores, a process that occurs only in the world of prokaryotes. Stages of formation of endospores in bacteria of the genus Bacillus and Clostridium.the formation of endospore 0 the first in this stage the cell which is going to form the endospore, enlarges in this size and its chromatin material condences attain the shape of an axial filament reaching from one end to the another end of cell

1 Replication and formation of axial filament. there’s a change in the metabolic activity of the cell

2 Septation. the plasma membrane start invaginating towards the one end of the cell. This invagination grows centripetally and both the end unite to form a spore septum. septum formation ends by the formation of a small spore known as fore spore. the genetic material also get transported to this structure. Resulting in the structure encircled by two membranes.

3 Mother cell membranes engulfs fore spore. Spore septum of both i.e. mother cell and fore spore grows around the protoplasm of fore spore by a process called engulfment. thus fore spore lies freely in the cytoplasm of mother cell.

mother cell chromosome is destroyed and a cortex, made up of peptidoglycan layer is placed between the two membranes surrounding the fore spore protoplast. This cortex will be important in providing heat resistance and maintaining dormancy to the spore

4 Mother cell chromosome destruction. cell wall of peptidoglycan is synthesized outside the plasma membrane of fore spore. this structure is called as spore wall. In this stage layers of coat proteins are deposited on the outer membrane

5 deposition of coat proteins. There’s deposition of peptidoglycan cortex between the spore wall and cell membrane. The protoplasm condenses and synthesize dipliconic acid which deposition occurs on cell membrane. There’s an increase in the concentration of Calcium, arginine and glutamic acid in the spore cytoplasm. Spore wall become multilayered.

6 Maturation. Completing development. The mother cell – now called sporangium – releases the mature spore

7 the mother cell releases spore. Spore are resistant to many environmental stresses, that would be kill vegetative cells. The nature of this resistance is due, in part to a spore’s having only 10-30% of a vegetative cell’s water content. Spores also contain small acid-soluble proteins that bind to and protect DNA from damage by UV light and various toxic chemicals.

Germination of endospore

Favorable growth conditions signal the process of endospore germination. Germination of a spore results in a break in the spore wall and the outgrowing of a new vegetative cell. The newly formed vegetative cell is capable of growth and reproduction. A single spore upon germination forms a single vegetative cell. Germination occurs in following steps: Activation: Even in the presence of favorable conditions, the spore will not germinate until its protective spore coat is not damaged. Conditions such as heat, acidity, abrasion or compounds containing free sulphydryl groups activate the spore to germinate.  Initiation: once activated, the spore will germinate provided the environment is suitable. Different signaling effectors exist for different species. Binding of effector stimulates autolytic enzymes that degrade the peptidoglycan of cortex. Water is absorbed and calcium dipicolinate is released.  Outgrowth: once the cortex and outer layers is degraded, a new vegetative cell consisting of spore protoplast and its wall emerges. This is followed by active biosynthetic activity and process terminates with cell division.