Microbiology - The Structure and Function of Bacteria Components

Hello everyone, still on Microbiology and bacteriology, I will be discussing today the foundation of bacteriology which has to do with the structure and function of Bacteria components. Let's continue without wasting any time at all. Remember that I said that the study of Bacteria is Bacteriology and the study of microorganisms is microbiology.

I am sure you must have heard of the definition where Bacteria are described as microscopic, single-celled organisms that exist both inside and outside organisms. Bacteria are made up of appendages, attached to its cell which helps them achieve whatever their daily activities. These appendages include the Flagella, fimbriae, and Pilus. Bacteria are covered by the cell envelope which has multiple layers and encloses the endospore of the bacteria. In bacteria, there are components that include the Ribosome, the bacteria chromosome, and the plasmid. Bacteria do not have a nucleus, they possess nucleoids.

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The Flagella's primary function in the bacteria is motility. it helps the bacteria to beat around. The flagella are made up of the basal body, which has different protein rings and is attached to the cell envelope, which is followed by the hook of the flagella, then the filament of the flagella. Flagella can exist in different forms in bacteria. They can exist as a single flagellum in one pole of the bacteria known as Monotrichous flagella, common in Vibrio bacteria. They can exist in multiple forms coming from one end of the bacteria known as lophotrichous with an example of bacteria that possesses this type of flagella type being the pseudomonas specie. It can exist as a single flagellum at both polar ends of the bacteria, known as amphitrichous, and it can exist all around the bacteria, known as the peritrichous type of flagella with an example of bacteria with such type of flagella being E.coli.

Fimbriae are the next thing to be discussed. Some people say it is the same thing with the pilus, but actually, the fimbriae and the pilus can be differentiated. Its first difference is that the fimbriae are shorter and thinner than the pilus. The fimbriae are more supplied around the bacteria in comparison to the pilus. The fimbriae are formed from the bacterial chromosome, and they are responsible for attachment and adherence to different surfaces. Fimbriae are found in gram-positive and negative bacteria. Pili are lesser than the fimbriae in bacteria, and they are longer and thicker than fimbriae. The pili originate from the plasmid of the bacteria and are responsible for bacteria conjugation. Pili are found in gram-negative bacteria. When I say bacteria conjugation, I mean the ability of a bacteria to become resistant to certain types of drugs. Bacteria plasmids in an organism with the aim of being resistant will create a pilus, as well as create more plasmids that can be transferred alongside genetic material to other bacteria. The pilus is attached from one bacteria to another which is usually a bacteria that is a fertility factor positive to a fertility factor negative where the replicated plasmid is transferred to the other bacteria.

Going into the bacteria is the endospore which is found only in certain types of bacteria such as clostridium species, and Bacillus Antracis, which allows bacteria to be resistant to harsh environments such as high temperatures, fewer nutrients, chemicals, and UV radiation. In other to do this, the bacteria replicates its DNA, which starts to conjugate toward different end poles, where cell membrane septa start to form creating a forespore, where the mother DNA starts to degrade and form a peptidoglycan layer around the daughter DNA which was formed. In the cell, calcium starts to get into the cell, and water leaves the cytoplasm, after which keratin coatings are added to the spore, after which the spore is released out of the vegetative cell allowing the endospore to survive in the harsh environment.

The cell envelope is another component of the bacteria. It has two layers which are the Capsule and the Slime layer. The capsule is made up of a polysaccharides layer which is organized, while the slime layer is made up of polysaccharides that are loosed. The capsule is responsible for bacteria virulence factor, which is the ability to evade the immune system and infect. The bacteria capsule is responsible for the inability of white blood cells such as macrophages and neutrophils to phagocytose the bacteria. Example of bacteria that possesses capsules are; Streptococcus pneumonia, Haemophilus influenza, and Neisseria meningitides. The slime layer allows adherence to cell surfaces within the host cell, as well as adhering to foreign substances.

The Cell envelope is made up of inner layers and one is the outer membrane which is a phospholipid bilayer, and it is present in gram-negative bacteria. It is made up of an endotoxin known as Lipopolysaccharides which is made up of lipid A, core polysaccharide, and the O-antigen. Lipid A is responsible for stimulating white blood cells to release cytokines. When the immune system is exposed to the bacteria and starts to produce antibodies, the O-antigen serves as the attachment site for the bacteria.

The Cell wall is the next component of the cell envelope, which gives shape to the bacteria such as the cocci in round or spherical bacteria and so on, and it is present in both gram-positive and negative bacteria. It is made up of peptidoglycans which is a combination of protein and sugar. In the sugar molecule, it is made up of N-acetyl muramic acid, and N-acetyl glucosamine which is bonded together by peptide chains that are formed by the transpeptidase enzyme. In the peptidoglycan layer, gram-positive bacteria possess Lipoteichoic acid which extends from the inner membrane to the cell wall and stimulates white blood cells. Also, the Teichoic acid extends through the cell wall but doesn't come from the inner cell membrane. While both types of bacteria possess a peptidoglycan layer, gram-positive bacteria possess a thick peptidoglycan layer while gram-negative bacteria possess a thin peptidoglycan layer. The inner membrane is a phospholipid bilayer made up of proteins such as penicillin-binding proteins and enzymes, and it is found in both gram-positive and negative bacteria.

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Reference
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