Bacteria Cell Wall Formation: 5 Facts You Should Know

In this article let’s see about the bacterial cell wall and 5 facts about it.

Bacteria are free-living unicellular organisms that lack a prominent nucleus. They are found in all environments, including organic matter, water, and soil. There are three shapes of bacteria: spheres, rods, and spirals.

Do bacteria produce cell walls?

The bacteria are made up of a complex cell wall that is rigid and made up of peptidoglycan which is like a mesh. It is of uniform thickness and surrounds the cytoplasmic structure which contains polysaccharides, proteins, and teichoic acid. the formation of bacterial cells helps in maintaining cell shape and prevents mechanical damage.

The main function of the cell wall is to maintain shape and play an important role during cell division. It acts as an interface between the cell and the environment; it also mediates interaction with bacteriophages and eukaryotic cells.

How are bacteria cells formed?

Bacterial cells undergo a simple division called binary division to form two new daughter cells that are identical to the parent cell.

Binary fission:

The bacterium has a singular circular chromosome that is present freely in the cytoplasm, they lack a membrane-bound nucleus. The chromosome is present in a specialized region called the nucleoid. The replication enzymes help the DNA to be copied at a region called the origin of replication.

DNA replication continues, and the two origins move in the opposite direction. The cell gets longer and the newly formed chromosome starts to separate.

The replication continues till the entire chromosome is copied and moves to the opposite end of the cell. The division of the cytoplasm takes place, in this process the cell membrane pinches inward and the septum (new dividing wall) is formed in the middle of the cell.

The septum splits in the middle and two new cells are released and it continues to live as a new individual.

bacteria cell wall formation
Binary fission of bacteria from Shutterstock

When cell walls are formed in bacteria cells?

The cell wall is formed in bacteria to maintain shape, provide protection, and also to withstand intracellular pressure. The cell wall is also required for cell division and growth. The cell wall is made up of peptidoglycans which protect the bacteria from osmotic lysis and mechanical forces.

The cytoplasm of the bacterium is usually hypertonic to the environment surrounding it, so the water from outside enters the cell. If the cell wall is absent the bacterium will burst due to the osmotic pressure created by the flow of water and it is called osmolysis.

What is needed for cell wall formation in a bacteria cell?

The cell wall of the bacterium is made up of peptidoglycan or murein. Peptidoglycan is a polymer that is made of an interlocking chain of identical peptidoglycan monomers. The monomer contains two amino sugars, N-acetyl glucosamine (NAG) and N-acetylmuramic acid (NAM).

The monomer chains are cross-linked to each other by a tetrapeptide that extends from the N-acetylmuramic sugar unit and creates a lattice-like structure. The four amino acids which are present in tetrapeptide are:

  • L-alanine
  • D-glutamine
  • L-lysine
  • D-alanine

Gram-Positive bacteria cell wall:

The cell wall of gram-positive bacteria is made up of 90% peptidoglycan with another glycopolymer teichoic acid that is embedded within the peptidoglycan layers. The teichoic acids help in the generation of the net negative charge that is essential for the development of proton motive force.

It also increases the rigidity of the cell wall and participates in cell division. During adverse conditions like high temperature and high salt concentrations, teichoic acid provides resistance.

Gram-negative bacteria cell wall:

The gram-negative bacteria cell wall is more complex than the gram-positive bacteria. The plasma membrane of the gram-negative bacteria is present on the outside of the peptidoglycan layer and is known as the outer membrane. It is made up of polar heads, fatty acid tails, and integral proteins.

The membrane contains a large molecule called the lipopolysaccharide (LPS) that is anchored to the outer membrane. It is made up of thee different components

  • O-polysaccaride
  • Core Polysaccaride
  • Lipid-A

The LPS contributes to the net negative charge and it stabilizes the outer membrane and protects the cell from the effect of chemical substances. The immune response in an infected host is triggered by the O-antigen and it also generates antibodies.  Lipid A acts as an endotoxin which affects the host and causes fever and diarrhea.

structure cell wall grampositive bacteria 600w 321840332
Structure of Bacterial Cell wall from Shutterstock

Where are bacteria cell walls Synthesized?

The synthesis of cell wall peptidoglycan is a complex process that involves various enzyme reactions in the inner side and the outer side of the cytoplasmic membrane.

During binary division, the peptidoglycan links are broken and new peptidoglycan monomers are added and the peptide cross-links are released.

Steps involved in synthesis:

 Step 1:

The autolysin enzyme breaks the glycosidic linkage between the peptidoglycan monomers and the peptide cross-bridges that link the sugars.

Step 2:

The cytosol produces peptidoglycan monomers and it binds to bactoprenol. The bactoprenols help in the transportation of peptidoglycan monomers across the cytoplasmic membrane and interact with transglycosidases to insert the monomers into the existing peptidoglycans.

Step 3:

The transglycosylase enzyme inserts and links the new peptidoglycan monomers in the break region.

Step 4:

Finally, the transpeptidase enzymes reform the cross-links between the layers of peptidoglycan and make the cell wall strong.

Conclusion:

The bacterial cell wall is made up of peptidoglycan that helps in maintaining shape and prevents cell wall lysis due to internal pressure.

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