Cocci or Cocus Bacteria – Structure, Types and Examples

We all have heard about bacteria and what they can cause. But, we know very little about different types of bacteria. In this topic, we will discuss one of those bacteria that are Cocci. Furthermore, we will also discuss its type in the topic.



Cocci or Cocus Bacteria

Generally, the bacterium has a spherical, round, or ovoid shape. Besides, bacteria are characterized on the basis of their shapes into three classes- Spirochetes (Spiral-shaped), Cocci (spherical-shaped), and bacillus (Rod-shaped) cells.

Moreover, Cocci or Cocus is a bacterium that contains multiple genera like streptococci or staphylococci. In addition, they can grow in pairs, cluster or chains depending on the attachment and orientation during cell division. Also, they don’t have flagella and are non-motile.

Structure of Cocci

The structure of the cocci can vary amidst gram-negative and gram-positive bacterial wall types. Moreover, the cell formation for cocci can vary between gram-negative (thin peptidoglycan layer) and gram-positive (thick peptidoglycan layers). Whereas cocci can be pathogenic, symbiotic, or commensal that lives on the body of their host organism.

Explore more about Microorganisms –

Types of Cocci

Rod Bacteria vs Coccus Bacteria

Rod bacteria (bacillus) are generally cylindrical or rod-shaped. On the contrary, coccus is round or spherical shaped. Rod bacteria examples are Bacillus subtilis (B. subtilis) and Escherichia coli (E. coli).

  1. Coli is a large variety of bacteria that we find in the environment, food and intestine of animals and humans. Although most of the E. coli strains are harmless, on the contrary others can cause urinary tract infections, diarrhea, pneumonia, and respiratory disease.
  2. On the other hand, B. subtilis are pervasive bacteria that we commonly find in areas of soil, water, and air that are not pathogenic or not toxic to the environment and they do not pose any danger to humans, plants, and animals. Moreover, some strains of B. Subtilis are registered microbial pesticides.

Gram-Negative vs Gram-Positive

  1. If you have seen bacteria described as gram-negative or gram-positive they simply come down to the bacterial organism’s protective outer covering, refer to as membrane.
  2. Furthermore, gram-positive bacteria have large and thick membranes while gram-negative bacteria have thin but difficult to penetrate the membrane. In addition, this property of gram-negative bacteria make is predominantly resistant to antibiotics.

Diplococcus Bacteria

They are arranged in pairs which means that two coccus cells are connected. Furthermore, they can be gram-negative and gram-positive. Also, they can cause Pneumonia (Diplococcus pneumonia), Meningitis (Neisseria meningitides), and Gonorrhea (Neisseria gonorrhoeae).

Streptococcus Bacteria

Streptococcus Bacteria or streptococci are arranged in rows or in chains. Also, the chain or row varies in length.  Moreover, many of them are hemolytic which means they attack the red blood cell in the body. In addition, they are gram-positive bacteria that can cause many diseases that include scarlet fever, skin disorder erysipelas, pneumonia, rheumatic fever, tooth decay, and strep throat.

Staphylococcus Bacteria

Staphylococci bacteria arranges in grape-like clusters of cells. Also, they are non-motile, have high salt tolerance, and are gram-positive. Moreover, their growth is normal in mucous membranes and skin. But, they can cause illness when initiated into normally sterile sites in the body. Furthermore, they can cause wound infections, toxic shock syndrome, abscesses, and most common food poisoning.

Enterococcus Bacteria

They are arranged in short chains or pairs and are also referred to as enterococci. Furthermore, they are non-motile, gram-positive and can be located in the enteric nervous system. Besides, they have limited potential to cause illness. But, they can cause bacteremia (bacteria in the blood), urinary tract infections, and wound infections.

Solved Question on Cocci

Question. What is the shape of Cocci bacteria?

  1. Spherical
  2. Rectangular
  3. Rod-shaped
  4. Spiral

Answer. The correct answer is option A.

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