Fungi Cell Wall And Bacteria Cell Wall: 5 Important Facts


In this post you will find the information about fungi cell wall and bacteria cell wall, their five important facts and detailed information about chitin and peptidoglycan.

Fungi cell wall and bacteria cell wall are both heteropolymers made up of complex polysaccharides. Chitin is the main component of fungi cell wall while bacteria has peptidoglycan.

Similarities between fungi cell wall and bacteria cell wall

Bacteria and fungi share many similarities to their cell wall. Both have the cell wall made of polysaccharides, while both contains a sugar called N-acetyl glucosamine. In addition bacterial cell wall posses extra sugar derivative called N-acetyl muramic acid which makes them unique from other organism.

Few are the points given below :

  • Fungi Cell Wall And Bacteria Cell Wall : Both bacteria and fungi are prokaryotes, meaning they do not have nuclei. And while all prokaryotes contain DNA, in bacteria, it’s found in a single, thick strand of DNA.
  • The main difference between bacterial cell walls and fungal cell walls is their composition: In bacteria, we find a layer of peptidoglycan outside of its cell membrane that makes up its cell wall. This substance gives off a purple color when stained with Gram-positive dyes (hence Gram-positive), which is what makes staining techniques such as Gram staining work so well.
  • A major similarity between bacterial and fungal cell walls is that both are made from polysaccharides—chains of sugar molecules linked together. In fact, both types of cells use glucans to make up part of their structure.
  • Glucans are also known as glycans—the gly part means sugar. A second similarity between bacterial and fungal cell walls is chitin, a polysaccharide made from N-acetylglucosamine units connected by beta bonds.
  • Chitin forms structural components in both types of cells. It’s even used to make armor!

Are fungi cell wall and bacteria cell wall same?

No, bacteria and fungi cell wall are not same because of the cell wall composition. However, the few composition of cell wall is similar to each other. In contrast to bacteria, fungal cells are composed of chitin. This is a polysaccharide with a molecular structure similar to that of cellulose found in plants.

One of chitin’s primary functions is to provide strength to fungal cell walls; however, unlike plants or animals, fungi have no need for digestive organs as they absorb nutrients from their environment through pores called chitinous stomata. As such, fungi are saprobes—organisms that break down decaying matter and recycle its nutrients back into new life.

The key difference between chitin and cellulose is that while both polysaccharides are made up of glucose molecules linked together by glycosidic bonds, chitin contains nitrogen atoms while cellulose does not. Additionally, while both compounds can be broken down by enzymes produced by microbes living on our skin (such as proteases), only chitin can be broken down by enzymes produced by microbes living in our gut (such as amylase).

Do both bacteria and fungi have cell walls?

Yes, the fungi and bacteria both contains cell wall. But the difference is fungi cell wall is made up of chitin which is a homopolymer consisting of single repeating unit of N-acetyl glucosamine while bacterial cell wall is composed of peptidoglycan , made up of two derivatives of sugar (NAG and NAM) and peptides.

There are two sugar derivatives present in peptidoglycan, these two sugars are cross-linked by the peptides projections. Bacterial cell wall is unique because of peptidoglycan, no other organism have it. On the basis of peptidoglycan,

Bacteria are classified into two categories:

  • Gram-positive bacteria
  • Gram-negative bacteria

Gram-positive bacteria have thick peptidoglycan of about 20-80nm while Gram-negative bacteria have thin layer of about 7-8nm. Sugars present in peptidoglycan are modified sugars containing acetyl and amine group. The sugars are NAM (N-acetyl muramic acid) and NAG(N- acetyl glucosamine).

Both the sugars are joined by β 1-4 glycosidic bond. Several amino acids are attached to the side  of NAM. These amino acids may get vary according to the type of species. These side chain gets cross linked with other amino acid side chain. The cross linking is done by penta-glycine bridge. All these cross linking forms a 3- dimensional structure which is rigid in nature.

Chitin is made up of structural homopolysaccharides which means that it is made up of only single repeating unit of N-acetyl-β-D- glucosamine. And these repeating units are joined by β 1-4 glycosidic bond. Chitin is a main component of fungal cell wall and it is also found in the exoskeleton of Insects, lobster, crabs.

Difference between Fungi cell wall and Bacteria cell wall

Bacterial cell wallFungal cell wall
Mainly composed of PeptidoglycanMainly composed of Chitin
Peptidoglycan is only found in bacterial cellsChitin is main component of fungal cell wall and also present in the exoskeleton of insects.
Peptidoglycan is made up of sugars and amino acidsChitin is made up of structural homopolysaccharides.
The sugars are NAM (N-acetyl muramic acid) and NAG(N- acetyl glucosamine). Only single repeating unit of N-acetyl-β-D- glucosamine is present.
Both the sugars are joined by β 1-4 glycosidic bond.Repeating units are joined by β 1-4 glycosidic bond.

ChitinMain component of Fungi cell wall

As earlier stated chitin is a structural complex polysaccharide mainly found in cell wall of fungi but also some crustaceans, arthropods also have it in their exoskeleton. It is insoluble in water and many other solvents. Chitin is a polymer of N-acetyl glucosamine where amino group borne at carbon 2 is acetylated to form -NHCOCH3.  The linkage between adjacent monomers is β (1-4). Like cellulose, chitin is a linear unbranched polymer where the adjacent monomers lie at an angle of 1800 .

Structure of the chitin molecule, showing two of the N-acetylglucosamine units that repeat to form long chains in β-(1→4)-linkage from Wikipedia

Chitin is the second most abundant organic material. Its appearance is both soft and leathery therefore it provides both strength and elasticity. Chitin can also be incorporated with calcium carbonate and fibrous proteins to form hard structures. Like water molecule cannot pass through the chitin layer,  helps the body to prevent  evaporation. However, unlike plants, which use chlorophyll to capture sunlight and convert it into energy via photosynthesis, fungi produce energy using a process known as heterotrophy where they consume organic matter like dead leaves and decomposing plant matter.

PeptidoglycanMain component of Bacteria cell wall

It is a unique component of bacterial cell made up of peptides and sugars. Peptidoglycan make the cell wall o bacteria which is responsible for the rigidity and shape of the cell. Peptidoglycan is a heteropolymer made up of suagr backbone also called glycans. These backbone have multiple peptide links or amino acid chains projecting towards each other. These peptides projections are cross linked with each other by penta-glycine linkage.

fungi cell wall and bacteria cell wall
The structure of peptidoglycan from Wikipedia

One bacteria contain only one macromolecule of peptidoglycan. It is porous in nature and not a major permeability factor. The important of function of cell wall is that it prevents burst of bacterial cell  due to osmotic pressure. When bacteria divides to form two new daughter cells, in this stage it lacks the cell wall, and condition inside the cell wall is hyper-osmotic. After sometime they start generating the cell wall which prevents the bacteria to burst from osmotic pressure.

Conclusion

Fungi cell wall and bacteria cell wall are both heteropolymers made up of complex polysaccharides. Chitin is the main component of fungi cell wall while bacteria has peptidoglycan. Both structures provide rigidity and strength to the cell. Peptidoglycan is unique to bacteria only while chitin is present in fungi as well as some crustaceans and arthropods have it in their exoskeleton.

Saif Ali

Hi, I am Saif Ali. I obtained my Master's degree in Microbiology and have one year of research experience in water microbiology from  National Institute of Hydrology, Roorkee. Antibiotic resistant microorganisms and soil bacteria, particularly PGPR, are my areas of interest and expertise. Currently, I'm focused on developing antibiotic alternatives. I'm always trying to discover new things from my surroundings.  My goal is to provide readers with easy-to-understand microbiology articles. If you have a bug, treat it with caution and avoid using antibiotics to combat SUPERBUGS. Let's connect via LinkedIn.

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