STRUCTURE OF EUBACTERIAL CELL

STRUCTURE OF EUBACTERIAL CELL

Through the bacteria structure is very simple, they are very complex in behavior 

Bacteria cell has a chemically complex cell envelope. The cell envelope  consists of a tightly bound three layered structure 

(1) Outer glycocalyx  

(2) Cell wall              

(3) Cell membrane 

Although each layer of the envelope performs distinct function  they act as a single protective unit.

                                                           

I) Glyococalyx:-

Capsule- Thick,nonsticky, regular and smooth layer

Slime Layer-Thin, sticky, irregular and rough layer

A) When bacteria are surrounded by capsule, called encapsulated bacteria. Formation of capsule is performed by cell membrane. Capsulated bacteria are mostly pathogenic.

B) Capsule is made up of polysaccharides and polypeptides.

C) Capsule protests the bacteria from w.b.c. and also helps in colony formation.

D) When the molecules of polysaccharides are very loosely arranged they form a thin and sticky layer known as slime layer.

2. Cell wall:-

Bacterial cell wall is made up of mainly peptidoglycan and murein which is a type of muco-peptide Gram(+) and Gram(-) bacteria :

In Gram (+) bacteria cell wall is single layered are thick. It is made up of peptidoglycan. Lipids are also present but in less quantity.

While in Gram (-) bacteria cell  well is double layered inner layer is thin and composed of peptidoglycan while outer layer is thick and made up of lipop-polysaccharide. Some quantity of lipoproteins and phospholipids are also present in outer layer.

 Note:-Bacterial cell wall can be removed by lysozyme enzyme. When bacterial cell wall is removed artificially then these bacteria are called L-forms (Lister form)

3) Cell membrane or plasmalemma:-

A.This is the inner most layer

B. Bacteria cell membrane is made up of lipoprotein like the eukaryotic membrane.

4) Cytoplasm:-

In bacteria Cytoplasm membrane bound cell organelles viz. Mitochondria, Chloroplast E.R. Lysosome, Golgibody, Microbodies are absent.

Cytoplasmic organelles:-

1.Mesosome

A. Mesosome was discovered by F. James. Mesosome is a special membrane structure found by the the extension or infolding  of plasma  membrane  into the cell. These extensions  are in the form of vesicles ,tubules, and lamellae.

B.These are functionally mitochondria like structures. Oxidative enzymes are found in mesosome. 

Functions-

I. They help in cell respiration and cell well secretion processes to increase surface area of the plassmamembrane and enzymatic content 

II. Help in DNA replication and distribution to doughter cell during cell division.

2.Storage granules-

A. Glycogen granules- They store carbohydrates 

B. Evolution granules- These are also known as meta chromatic granules. They are made up of RNA. They store RNA as a source of nitrogen and phosphorus.

3. Photosynthetic structure:-

some eubacteria (purple bacteria and green sulphur bacteria) have capacity of photosynthesis.

In photosynthesis eubacteria, no special type of structure is found photosynthesis. In bacterial cytoplasm many photosynthesis pigments are scattered

Pigments:-

(a) In purple bacteria (sulphur and non sulphur bacteria) - bacteriochlorophyll 'a' & 'b'.

(b) In green sulphur bacteria- bacteriochorophyll 'a' Chlorobium chlorophyll or bacterioviridin.

Chromatin Material (nucleoid)-

1. Nucleus of bacterial cell is called nucleoid or Genophore or Incipient nucleus .Nuclear membrane and nucleolus are absent.
2. True chromosomes are also absent in bacterial cells.