Students, so in this lecture we are going to learn the endospores. So, these are also the structure which are present inside the cell wall. The endospores are the spores. These are the specialized resting cell formed by certain gram positive bacteria. For example, bacillus or clostridium, they are highly durable dehydrated cell with thick cell wall and additional layer. It can survive the extreme temperature, disinfectant, acid, bases, lack of water, toxic chemical and radiation. And the endospores of some of the thermophilic bacteria can survive 19 hours of boiling. So, in short the endospores these are the resting stage of bacteria, where these are metabolically inactive state. The bacterial cells or this spores cells, they are not metabolically active. In case of vegetative cell or the mother cell, they are metabolically active. So, this is the general cell division pattern which is followed by most of the bacteria. Let us take example of gram positive bacteria, say bacillus septilis which is having a rod shape. Normally the bacterial cell divides by binary efficient. Here as we know that in case of binary efficient, the cell, this is the cell and inside the cell there is a nuclear area which contain DNA. During the binary efficient, the DNA will start to replicate. Then after replication of DNA, the septum will start to develop right from the center of the cell. It will divide the center, the septum will divide the cell equally into two parts. After that the plasma membrane and cell wall to start to develop and after that the two cells it is separated in equal length or equal size from the mother cell. So, this is normally the binary efficient or this is the normal cell division of bacteria. But in case if the bacteria gets signal that the environment or the surrounding is adverse for the survival or the bacterial survival of the bacteria or if the environment is not suitable for the growth of bacteria, then instead of choosing binary efficient, they will add out for sporeolation. The sporeolation that is a dormant stage of bacteria where the cells or the spore cells will start to develop inside the cell. Here we can see this is the endospore and this is the parents. So, how the endospore is formed or how the bacteria convert themselves to endospore that we are going to study. So, this is the endospore as we have seen this is the parents cell and the spore which is formed inside the parents cell is called as endospore. The endospore is having four different layers. We can see here the outermost layer is called as exysporeum. After that there is a spore coat which is made up of dehydrated cells, then there is a core wall or there is a cortex which is formed by the peptidoglycanine cell wall components. Inside the cortex there is a core material or core which is made up of cytoplasm and nuclear material. So, this is the center core then there is a cortex then there is a core and then the outermost layer is exysporeum and above the exysporeum there is a mother's. So, how the process of spore formation takes place or what is the spore relation process? The process of converging the mother cell into spore form is called as spore relation. Now, we are going to see one by one. In first stage the DNA will start to replicate themselves in the mother cell. During this step DNA will elongate themselves and they will replicate in the mother cell. It will form a replica of original DNA. After that the instead of forming a septum through the center and the cell will add up to form a septum either in one of the pole of the cell. So, either in the left pole or right pole it will form a septum. So, in second stage it will start to form a septum which will during which the plasma membrane will start to surround the newly replicated DNA along with some cytoplasmic material. This process is called as spore spore formation. In third step the complete spore will get formed and the plasma membrane will completely surround them. After that the peptidoglycan layer will start to form above the or outside the spore. The spore quote is formed which is a thick layer of proteins around the outer membrane which makes the endospore resistance to the harsh chemical and after that maturation. So, we will see the schematic diagram of spore relation process. So, this is the stage 0 where this is the vegetative cell. Let us take example the cell aseptilist which is having the DNA material inside the cell. In the first step DNA will start to replicate, DNA will get elongated and it will start to replicate. It will form a replica of DNA. After replication of DNA the cell have choice to form a septum either from this side or this side. As we have seen in binary efficient in the binary efficient cell divides right through the center of the cell. When in case of spore formation the 70 percent portion is covered by mother cell and 30 percent portion it is covered by force pore. So, in the second step this newly replicated DNA will get separated and the plasma membrane will start to surround the newly replicated DNA along with some cytoplasmic material. In next step the plasma membrane will be covered with some peptidoglycan materials and cell wall will start to develop and the remaining cell or the mother cell will start to engulf the newly formed force pore. In next step after formation of spore pore the peptidoglycan layer or complete cell wall will form around the force pore which is known as cortex. After formation of cortex the nuclear materials which is present in the mother cell will disintegrate and it will be destroyed. After that the calcium ion will penetrate inside the cell and it will remove the water contained from the cell and it will form spore coat. So, spore coat will be formed after the formation of cortex. After formation of spore coat it will form a x-sporium and this x-sporium which maturate the spore which are highly durable which can withstand the extreme condition of temperature pH and all. Once the spore get matured then the spores are released into out of the cells or mother cells. Once the spores once the adverse condition passed out and the condition is or the environment is favorable for the growth of microorganisms. Again the spore convert them to vegetative cells this process is called as germination. So, vegetative cells before spore relation and after germination both vegetative cells are metabolically active whereas the endospor they are metabolically inactive. These are the dormant stage or resting stage of the bacteria which can withstand the extreme conditions. Again this is one of the schematic representation of the spore relation process. So, spore relation it is part of normal life cycle or can be triggered by adverse environmental conditions as I already explained. If the condition is not favorable for the growth of microorganism then the microorganisms or bacteria can adopt spore relation process instead of binded with the efficient or instead of normal cell division. The endospor do not carry out metabolic reactions like normal vegetative cells because it is a resting stage or it is a normal stage of bacteria. Endospor can remain dormant for thousands of years and the process of conversion of endospor to its vegetative cells is called as germination. Usually occurs when the environmental conditions become more favorable for the growth of microorganism. It can be triggered by physical or chemical damage to the spore code and then these vegetative cells which are metabolically active stage of bacteria.