All You Need To Know About Endospores

 

Some bacteria are found to produce dormant, tough, and non-reproductive structures called endospores. Endospores enable bacteria to remain dormant for several years. There have been discoveries of endospores that had remained viable for 10,000 years. Revival of spores that were millions of years old has been claimed. When the environment around the endospore becomes favorable, it tends to reactivate itself from the vegetative state. Most of the bacteria do not show the ability to form endospores, but the ones who possess the ability belong to genera Bacillus and Clostridium. Some other species of bacteria that produce endospores belong to the genera Thermoactinomyces, Sporolactobacillus, Desulfotomaculum, Oscillospira, and Sporosarcina. The genetic material of the bacterium, including DNA, ribosomes, and huge amounts of dipicolinic acid, is found in endospores. Dipicolinic acid is a chemical substance found only in spores and accounts for up to 10% of the dry weight of mature endospores. It helps the endospore to maintain dormancy in drastic conditions of ultraviolet radiation, desiccation, high temperature, extreme freezing as well as chemical disinfectants.

Formation Of Endospore:

A single endospore forms within some bacteria when they are starved, especially when there aren't enough carbon and nitrogen sources. The procedure is known as sporulation.

The DNA replicates first, followed by the formation of a cytoplasmic membrane septum at one end of the cell. A forespore is formed when the second layer of cytoplasmic membrane grows around one of the DNA molecules, the one that will become part of the endospore. Both membrane layers then produce peptidoglycan in the space between them to form the first protective coat, the cortex, which lies close to the germ cell wall and will eventually form the bacterium's cell wall upon germination.

In addition, calcium dipocolinate is integrated into the developing endospore. Around the cortex, a spore coat made of a keratin-like protein forms. An exosporium, a lipid, and a protein-based outer membrane are occasionally observed.

Finally, the bacterium's remaining components are destroyed, and the endospore is expelled. Sporulation takes about 15 hours on average.

How Endospore Works:

The endospore's chemical resistance is assumed to be due to the impermeability of the spore coat. Endospores' heat resistance is related to a number of factors:

1. The endospore's DNA may be stabilized and protected by calcium-dipicolinate, which is plentiful within the endospore.

2. The endospore's DNA is saturated with small acid-soluble proteins (SASPs), which protect it from heat, dryness, chemicals, and radiation.

3. During germination, they also serve as a carbon and energy source for the development of a vegetative bacterium.

4. The cortex may osmotically drain water from the endospore's interior, and the resulting dehydration is thought to play a key role in the endospore's heat and radiation resistance.

Diseases Caused By Endospore-forming Bacteria:

Though they are harmless before they germinate, they are found to be involved in the transmission of a few diseases to humans. Infections transmitted by endospores include:

1. Bacillus anthracis causes anthrax; endospores can be inhaled, ingested, or introduced into wounds, where they germinate and the vegetative bacteria reproduce.

2. Endospores penetrate anaerobic wounds, germinate, and the vegetative bacteria reproduce. Tetanus is caused by Clostridium tetani.

3. Endospores of Clostridium botulinum penetrate the anaerobic environment of inadequately canned food, germinate, and then proliferate, causing botulism.

4. Clostridium perfringens cause gas gangrene; endospores penetrate anaerobic wounds, germinate, and the vegetative bacteria then proliferate.

5. Antibiotics damage the normal microbiota of the intestines, allowing C. difficile endospores to survive and germinate and replicate until the microbiota is restored, resulting in pseudomembranous colitis (Clostridium difficile).