What Are Endospores?
Microorganisms are adaptive to their surroundings, they can sense and adapt accordingly to their environment. When they are in an environment which has exhausted their natural source of nutrition, they employ various survival strategies. One such strategy of bacteria is the production of endospores, usually initiated in nutrition deprivation scenarios. Endospores, as the name suggests, are seed-like formations produced within the bacteria. They are highly resistant, designed to ensure survival and preserve the genetic information under environmental stress. Endospores make survival possible for bacteria which would otherwise kill them in extreme conditions such as high temperature, pressure, chemical damage, irradiation, etc. Endospores of low gram-positive bacteria, in particular, survive through these conditions.
Also Read: Sporulation
Structure Of Endospores
Endospores have a unique cellular structure. It is surrounded by an outer covering which is proteinaceous. This coating provides enzymatic and chemical resistance to the spore. It is lined by a thick inner layer consisting of specialized peptidoglycan which forms the cortex. It is essential for the proper formation of the cortex as it brings about the dehydration of the spore, crucial to resist high temperatures. Beneath the cortex lies the cell-wall of the germ. This layer is made up of peptidoglycan which later develops to become cell wall of the bacteria post germination of endospores. Under this cell-wall, there is an inner membrane which acts as a permeability barrier protecting the bacteria against damage-causing chemicals. The core of the spore lies in the centre and is in a state of dehydration. It contains the genetic information of the bacteria such as DNA, dipicolinic acid(constitutes 10% of the dry weight of the spore), ribosomes and is crucial in the dormancy property exhibited by endospores. They also contain SASPs (Small, Acid Soluble Proteins) responsible for binding and condensing DNA. It is also responsible for the UV-light resistance property of endospores and protects them from DNA-damaging chemicals. In addition, it consists of exosporium which is an outer layer consisting of a glycoprotein.
Endospores Stain
Bacterial endospores can be visualized using a differential stain called the endospores stain. Endospores can form in the terminal, subterminal and central regions of vegetative cells. These spores are metabolically inactive and highly resistant. It produced as a defensive mechanism to survive in unfavourable conditions. A malachite green stain, which is a primary stain is applied to the endospores and the vegetative cells, which is facilitated by heat to help it penetrate through the endospores. Post this, cells are decolourized, resulting in the removal of stains from the vegetative cell only. To counterstain any cells which have been decolourized, Safranin is applied. Finally, the result is obtained with pink vegetative cells and dark green endospores. To explore more on Endospores and other related topics, register at BYJU’S.
Endospore Formation Steps
The phenomenon where an endospore is formed is known as sporogenesis or sporulation. This process is usually observed in the cells of bacteria under nutrient-deficient conditions when the endospore core tends to become increasingly dehydrated. Sporulation is a complicated process and takes seven stages to complete. Listed below are the stages:
1. Axial filament Formation – The S-I stage
The adjustment of the genetic material of the bacterial cell in the accurate centre plane
2. Septa Formation – The S-II stage
A septum known as forespore septum is formed as a result of the infolding of the plasma membrane into the cell lumen. Its creation causes a small segment of DNA to detach from the remaining genetic material.
3. Forespore Engulfment – The S-III stage
The newly formed immature spore is entirely engulfed by the membrane of the mother cell as it proceeds to grow. The engulfment causes the forespore to be enveloped by an intermembrane space and two plasma membrane.
4. Cortex Formation – The S-IV stage
The inner membrane space between the two membranes gives rise to the formation of the cortex. At this stage, the accumulation of dipicolinic acid and calcium in larger quantities is observed.
5. Protein coat Formation- The S-V stage
The cortex of the hence formed spore is covered with a protein coating
6. Spore Maturation – The S-VI stage
At this stage, the cell turns inactive metabolically and the core turns increasingly dehydrated.
7. Enzymatic destruction – The S-VII stage
Endospores are released as a result of the destruction of the enzymes of the spore mother cell. Discover furthermore about endospores and other interesting topics in biology by registering at BYJU’S.
Further Reading: Difference Between Gram-positive and Gram-negative Bacteria
Frequently Asked Questions
Q1
1. List an example of an aerobic endospore-forming bacteria.?
Q2
2. How can moist heat kill endospores?
It can kill endospores as the water becomes the heat that permeates in the endospore. It is possible only with moist heat and is better compared to dry heat to kill them.
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FAQs
Staining procedure:
- Cover the smears with a piece of paper towel within the border of the slide.
- Place the slide over a beaker of steaming water. ...
- Flood the paper towel with malachite green and let the slide steam for 3-5 minutes.
- Complete the rest of the procedure at the back sinks.
An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria from the Firmicute phylum. Endospore formation is usually triggered by lack of nutrients, and usually occurs in Gram-positive bacteria. In endospore formation, the bacterium divides within its cell wall.
What are the 7 stages of sporulation? ›
Stage I, decision to sporulate (no morphological phenotype); Stage II, completion of asymmetric division; Stage III, completion of engulfment; Stage IV cortex formation (pink) between the inner and outer forespore membrane; Stage V, coat assembly around the outer forespore membrane (blue); Stage VI, spore core ...
What are the steps of production of a bacterial endospore? ›
Endospore Formation Steps
- Axial filament Formation – The S-I stage. ...
- Septa Formation – The S-II stage. ...
- Forespore Engulfment – The S-III stage. ...
- Cortex Formation – The S-IV stage. ...
- Protein coat Formation- The S-V stage. ...
- Spore Maturation – The S-VI stage. ...
- Enzymatic destruction – The S-VII stage.
The nucleoid divides and the cell splits unequally to produce a small forespore containing a copy of the cell's DNA and a mother cell. The forespore is then engulfed by the mother cell, which further refines the forespore. Finally, the cortex and spore coat are thickened, prior to lysis and release of the endospore.
Which of the following is the correct order of steps in the endospore stain procedure? ›
Wirtz's Endospore Stain Procedure
- Make a smear of Bacillus and methanol fix.
- Flood the smear with malachite green stain.
- Allow the stain to sit for at least 30 minutes. ...
- Rinse the slide with distilled water.
- Flood the slide with safranin (0.25%) for 1-5 minutes.
- Rinse the slide with distilled water and let air dry.
endospore formation is called Sporogenesis . It is initiated by Certain Adverse Environmental Conditions . Formation of a new cell from an endospore is called Germination . This process is triggered by Favorable Growth Conditions.
What is the process of spore formation in bacteria? ›
2.1. Sporulation. Sporulation is the process by which a vegetative cell undergoes a developmental change to form a metabolically inactive and highly resistant endospore.
What are the spore forming structures? ›
In fungi, the spores are formed on a reproductive knob-like structure known as the sporangium. They produce minute haploid spores that grow into new organisms in favourable conditions. E.g., Aspergillus, Penicillium.
What are the processes in spore formation? ›
Formation of reproductive spores
Sporogenesis occurs in reproductive structures termed sporangia. The process involves sporogenous cells (sporocytes, also called spore mother cells) undergoing cell division to give rise to spores.
This revival process is classically divided into two major consecutive phases: (1) germination, during which the spore undergoes rehydration, release of dipicolinic acid (DPA), cortex hydrolysis, and coat disassembly (this phase is accompanied by transition from a phase-bright spore to a phase-dark cell, as manifested ...
What is spore Formation 7? ›
Spore Formation is an Asexual Reproduction technique. Many Spores are housed in sacs known as Sporangia. The plants produce hundreds of spores and the spore sac bursts. These spores are dispersed into the air, where they germinate and create a new plant under favorable conditions.
What is the structure and formation of endospore? ›
Endospore Structure
Below the protein coat, there is a thick layer called the cortex. The cortex provides resistance to high temperatures. The germ cell wall exists below the cortex. After the germination of endospore, the peptidoglycan layer will become the bacterial cell wall.
What is an endospore staining? ›
Endospores staining is the type of staining to recognize the presence spore in bacterial vegetative cells. The bacterial endospores need a staining which can penetrate wall thickness of spore bacteria.
What are the steps of the spore stain? ›
Staining procedure
Cover the slide with a piece of paper towel and place on staining rack over the water bath. Flood the paper towel on the slide with Malachite Green ( primary stain). Steam the slide for 5 to 7 minutes (mordant). After the time is up, carefully remove the slide from the water bath using forceps.
What type of staining procedure is the endospore stain? ›
The endospore stain is a differential stain that enables visualization of endospores and differentiation of spores from vegetative cells. The primary stain, malachite green, is a relatively weakly binding stain that attaches to the cell wall of vegetative cells and the spore wall of endospores and mature spores.
What are the steps of spore formation? ›
Spore formation:
- Spore Formation is an Asexual Reproduction technique.
- Many Spores are housed in sacs known as Sporangia.
- The plants produce hundreds of spores and the spore sac bursts.
- These spores are dispersed into the air, where they germinate and create a new plant under favorable conditions.
This method, called the endospore stain, uses either heat or long exposure time to entice the endospores to take up the primary stain, usually a water soluble dye such as malachite green since endospores are permeable to water.
Which of the following steps is followed for bacterial staining? ›
Bacteria are first stained with weakly alkaline solution of crystal violet and then treated with 0.5% iodine solution. This is followed by washing with water and then with alcohol or acetone. Bacteria which retain blue or purple colour are known as Gram (+) bacteria (e.g Bacillus subtilis).
