Structure of a typical bacterial cell

STRUCTURE OF A TYPICAL BACTERIAL CELL:

A bacterial cell mainly contains 3 layers 1)Capsule-outer

                                                                2)Cell wall-middle

                                                                3)plasma membrane-Inner

1)CAPSULE:

It is the a polysaccharide layer that lies outside the cell envelope of bacteria.

It is rigid and protects cells from engulfment by eukaryotic cells, such as macrophages.

Slime layer made of peptidoglycan which helps bacterial cell from desiccation(dryness) and to stick to objects and also helpful for adsorption. 

2)Cell wall:

 It is mainly of mucopolypeptide which is common in all bacteria.

Teichoic acid is present in gram-positive bacteria and absent in gram-negative bacteria.

The pathogenicity of the bacteria lies with in the cell wall.

Cell wall gives particular shape and protect the organelles of bacteria. 

Plasmamembrane:

It is the innermost layer of bacterial cell

The inner inversions are called mesosomes.

Mesosomes are helpful for :

    1)DNA replication

    2)binary fission

    3)Respiration

                   

                       

Flagella:

Flagella is made up of a protein called flagellin.

They are out growths of cell wall.

Flagella are absent in coccoi,bacillus,so they are non-motile bacteria.

bacteria without flagella-Atrichous

                single flagella-  Monotrichous

   tuft of flagella an end -Lophotrichous  

one or many on both side-Amphitrichous

many flagella are present all over -Peritrichous  

                            

PILI/FIMBRIAE:

These structures are present on bacteria cell surface and smaller than flagella.

They are made up of fimbrellin.

It is used as attachment of 2 individuals,sex pili are helpful for reproduction.

Pili are absent in gram-positive bacteria

          present in gram-negative bacteria.

INTERCELLULAR(INTERNAL)STRUCTURES:

DNA is not enclosed inside of a membrane bound nucleus but instead resides inside the bacterial cytoplasam.

DNA is not associated with histone protein.

All cell organelles are absent except 70s ribosomes is made up of a 50s and 30s sub units.

They group together and attached to Mrna molecules so they are called as polysomes and polyribosomes.

There is no well organised chloroplast but contain chlorophyll called bacterial chlorophyll and it is present within the cytoplasm.

The cytoplasm contain the reserved food material called polyhydroxybutyrate.

Plasmid-extra cellular chromosomal double standard circular,naked dna is called palsmid.

It contains genes which are inheritable and some contains antibiotic resistance genes.

Aquatic bacteria contains gas vacuoles ex:-hallow bacterium.