Bacterial Cell Structure
A bacterial cell structure is delineated by a complex chemical cell wall. It outlines the plasma membrane. The space between the cell wall and the plasma membrane is called the Periplasmic space. The structure of a bacterial cell is an ancient type cell. It does not contain any membrane bound cell organelles like – chloroplast, endoplasmic reticulum, mitochondria etc. The deoxyribonucleic acid (DNA), the genetic material of the bacterial cell is present in a discrete region, called the nucleoid. No histone proteins are associated with the nucleic acid. The genetic material is not separate from the cytoplasm. The ribosomes present in the bacterial cell structures are of 70s type. The mode of locomotion is by using flagella. In some bacteria, the whole cell might be enclosed within a capsule.
The cellular organization of a bacterial cell structure is given below –
- Cell envelop –
- A complex layer is found outside the bacterial cell, which delineates the bacteria, is called the cell envelop. It has three basic layers –
- The glycocalyx
- The cell wall
- The plasma membrane
- Protoplasm –
- A dense gelatinous solution is found all over the cell, which is the prominent site for all metabolic activities within the cell. It is called the plasma membrane. The protoplasm contains all the cell organelles in it.
- Appendages –
- A bacterial cell may contain either or both of the cell appendages mentioned below –
- Mobility appendages – these help in the locomotion of the bacterial cell. E.g – axial filaments and flagella
- Attachment appendages – the fimbriae and the pili help in the attachment of the cell with other cell types, base for support or prey.
Cellular function of a bacterial cell
- Flagella – this cell organelle is important for the locomotion (movement) of the bacteria.
- Fimbriae and Pili – these cell appendages are meant for attachment to other surfaces. The bacterium needs these during mating.
- Capsule and slime layer – these are important to provide resistance to phagocytosis (cell attacks) and adherence to other cell surfaces.
- Plasma membrane – the plasma membrane is selectively permeable, not allowing all molecules to pass through it. These help in the transport of the nutrients and wastes inside and outside the cell respectively. Several metabolic processes take place inside them.
- Periplasmic space – these spaces are the store for the several hydrolytic enzymes and binding proteins. This is an essential site for uptake of nutrients and processing of the nutrients for energy.
- Mesosomes – mesosomes aim at the formation of the cross wall structures within the cell, which would distribute the chromosomes during cell division.
- Nucleoid – the site of the genetic material is named as the nucleoid.
- Ribosomes – the ribosomes are essential for the synthesis of the proteins inside the cell.
- Gas vacuole – the buoyancy for floating is possible because of the gas vacuoles present inside the cells.
- Endospores – endospores are required for survival during any unfavorable conditions.