Difference Between Spore and Cyst in Bacteria

Main Difference – Spore vs Cyst in Bacteria

Spore and cyst are two resting or dormant forms of bacteria. Microorganisms like Bacteria produce resting units under unfavorable environmental conditions such as extreme temperature, less moisture, and insufficiency of food. The spores and cysts differ in the way they form and the degree of resistant to the unfavorable conditions. The main difference between spore and cyst in bacteria is that spore is a reproductive cell, containing a thick cell wall to face harsh environmental conditions whereas cyst is a group of cells, which come together to protect the organism from harsh environmental conditions. Cysts are not reproductive cells. Spores are more resistant to harsh environmental conditions than cysts.

Key Areas Covered

1. What is a Spore in Bacteria
      – Definition, Features, Function
2. What is a Cyst in Bacteria
      – Definition, Features, Function
3. What are the Similarities Between Spore and Cyst in Bacteria
      – Outline of Common Features
4. What is the Difference Between Spore and Cyst in Bacteria
      – Comparison of Key Differences

Key Terms: Bacteria, Cyst, Encystment, Endocyst, Endospore, Excystation, Harsh Environmental Conditions, Reproductive Cells, Spore

What is a Spore in Bacteria

A spore is a highly resistant and dormant structure formed by bacteria in response to harsh environmental conditions. Therefore, spores help bacteria to survive during adverse environmental conditions. Some of these adverse environmental conditions include extreme temperatures, desiccation, high UV irradiation, and enzymatic destruction. Sterilization, pasteurization, and antimicrobial treatments cannot destroy bacterial spores.

Figure 1: Bacillus endospores

Different types of bacteria produce different types of spores. They are endospores, exospores, myxospores, and cysts. Endospores consist of the most complex structure and they are the most resistant type of bacterial spores. Endospores are produced by low G+C gram positive bacteria. The outermost layer of an endospore is a proteinaceous coat, which provides protection against enzymes and chemicals. Beneath the proteinaceous coat, the cortex, which is a specialized layer of peptidoglycans, is found. The cortex protects bacterial spore from dehydration. The cortex also provides the resistant against extreme temperatures. After the germination of the spore, the cortex becomes the new cell wall of the bacteria. Beneath the cortex, an inner membrane can be identified, which serves as the major permeability barrier for chemicals. Bacterial DNA, along with ribosomes and a large amount of dipicolinic acid can be found at the center of the spore. Small acid-soluble proteins (SAPs) are tightly bound to the condensed bacterial DNA. These proteins protect DNA from UV and other chemicals. The endospores of Bacillus are shown in figure 1.

What is Cyst in Bacteria

A cyst is a type of spore that is produced by the bacteria in response to unfavorable environmental conditions. The formation of cysts is referred to as encystment. The encystment allows the dispersal of bacteria from one location to another. Cysts are less resistant structures than spores. They form a group of cells called endocyst. In cysts, the cell feeding metabolism, and locomotion are ceased.

Figure 2: Cyst

When the environmental conditions become favorable, cysts germinate, producing a new individual. Cysts also consist of a peptidoglycan-rich cell wall. The breakdown on this cell wall in favorable environmental conditions is called excystation. Protists and nematodes also produce cysts. A cyst of a protist is shown in figure 2.

Similarities Between Spore and Cyst in Bacteria

Spores and cysts are resting units of bacteria, which are produced to undergo harsh environmental conditions.
Both spores and cysts consist of thickened cell walls.
Feeding, metabolic processes, and the locomotion are arrested in both spores and cysts.
Both spores and cysts allow the dispersal of bacteria.
When the conditions of the environment are favorable, both spores and cysts germinate into new individuals.

Definition

Spore: A spore is a quiescent form of some bacteria that is difficult to destroy and is resistant to environmental stress.

Cyst: A cyst is a dormant form of bacteria that is produced in response to unfavorable environmental conditions.

Reproductive Cell

Spore: Spores are reproductive cells.

Cyst: Cysts are not reproductive cells.

Significance

Spore: Spores disperse through air currents.

Cyst: Cysts form cell groups called endocyst to be protected from unfavorable environmental conditions.

Unfavorable Environmental Conditions

Spore: Spores are more resistant to unfavorable environmental conditions.

Cyst: Cysts are less resistant compared to spores.

Cell Wall

Spore: Spores consist of peptidoglycan layers in addition to the normal cell wall of bacteria.

Cyst: Cysts consist of a tough and waterproof cell wall.

Conclusion

Spore and cyst are two resting stages of bacteria. Spore consists of more thickened cell wall when compared to a cyst. Therefore, spores are more resistant to harsh environmental conditions. Both spores and cysts serve as dispersal units of bacteria. The main difference between spore and cyst in bacteria is their structure and resistance to harsh environmental conditions.

Reference:

1. “Bacterial Endospores.” Department of Microbiology. N.p., n.d. Web. Available here. 12 Aug. 2017.
2. Revolvy, LLC. “Microbial cyst.” Revolvy. N.p., n.d. Web. Available here. 12 Aug. 2017.

Image Courtesy:

1. “Image 1” (Public Domain) via PIXINO
2. “Entamoeba histolytica 01” By Photo Credit:Content Providers(s): CDC/ Dr. George Healy – from the Centers for Disease Control and Prevention’s Public Health Image Library (PHIL), with identification number #1474.Note: ( Public Domain) via Commons Wikimedia