Kingdom Monera and Eubacteria

 

KINGDOM MONERA 

Bacteria are sole member of kingdom monera. They are unicellular and prokaryotic and most abundant micro-organism. They also live in extreme habitats like hot springs, desert, snow and deep ocean. Where very few live from can survive . Many of them live in or on other organism as parasites.
Cell wall of prokaryotes made up of peptidoglycan or murein composed of polysaccharides and amino acids, which is a type of mucopeptide. Cell membrane of prokaryotes made up of lipoprotein (Lipid + Protein)  The space between cell wall and cell membrane is known as periplasmic space. This space is, analogous  (functionally same) to lysosome because in this space the digestion of complex substances is done. The cytoplasm of prokaryotes lack of membrane bound organelles. The nucleus of prokaryotic cell is primitive and also known as incipient nucleus or nucleoid . Nuclear membrane is absent around nucleus and also lack the true chromosome . Instead of of it, a false chromosome is present , which is made up of DS circular naked DNA  and polyamines. In prokaryotic ribosome are of 70s type . Ribosome are the site of protein synthesis.

Example of prokaryotes :- Eubacteria (True bacteria) , Blue green algae , Archaebacteria , Mycoplasma  

(         (A)     EUBACTERIA

There are thousands of different eubacteria or true bacteria . They are characterized by the presence of rigid cell wall , and motile , a flagellum. Bacteria have variations in their shape . Bacteria are grouped under four categories on the basis of shape.

(A)         Coccus – smallest bacteria and spherical shape and most resistant bacteria.

(B)         Bacillus- These are rod shaped.

(C)         Spirillum- These are spiral shaped bacteria.

(D)         Vibrio-  These are comma shaped bacteria.

Bacteria cells are motile as well as non motile . If motile they have thin filamentous extensions from their cell wall called flagella . Movements in bacteria takes place by means of flagella . Bacteria show range in number and arrangement of flagella. Bacterial flagellum is made up of three parts. ( A) Basal body (B) Hook (C) Filament 

STRUCTURE OF EUBACTERIAL CELL 

Though the bacterial structure is very simple. They are very complex in behaviour . The organisation of prokaryotic cell is fundamentally similar even though prokaryotes exhibits a wide variety in shape and function. Bacterial cell has chemically complex cell envelope. The cell envelope consists of a tight bound three layered structure.

(A)   Glycocalyx   (B)  Cell wall     (C)  Cell membrane 

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

(A)             GLYCOCALYX  

Capsule- Thick, tough , regular and smooth layer.

Slime layer- Thin , loose , irregular and rough layer.

Glycocalyx differ in composition and thickness among bacteria. When bacteria are surrounded by capsule called capsulated bacteria . Formation of capsule is performed by cell membrane . Mostly pathogenic bacteria are capsulated. It  is made up of polysaccharides and polypeptide. When the molecules of polysaccharides are very loosely arranged they form thin and sticky layer known as slime layer.

Glycocalyx protects the bacteria from W.B.C. and also help in colony formation. And the cytoplasm from this bacteria is fluid matrix and no organelle, like the ones in eukaryotes, are found in prokaryotic cells except for ribosomes. Bacterial cytoplasm does not streaming of cyclosis. Mesosome is a special membranous structure formed by the extension or infoldings or invaginations of plasma membrane into the cell. These extension are in in the form of vesicles, tubules and lamellae. They help in cell respiration and cell wall secretion processes to increase surface area of the plasma membrane and enzymatic content . They help in DNA replication and distribution to daughter cell during cell division.

Reserve material in prokaryotic cells are stored in the form of inclusion body . These are not bound by any membrane and lie free in cytoplasm.

Glycogen granules- They store carbohydrate.

Phosphate granules – These are phosphate polymer and function as storage reservoir for phosphate.

Some eubacteria ( purple bacteria and green sulphur bacteria ) have capacity of photosynthesis. In bacterial cytoplasm many photosynthetic pigments are present in purple bacteria ( sulphur & non sulphur ) : Bacteriochlorophyll a & b in green sulphur bacteria : Bacteriochlorophyll a, Bacterioviridin.

There is no well defined nucleus. The genetic material is double stranded circular DNA which is basically naked, ( without histone) and not surrounded by a nuclear membrane but non histone protein is present. In addition to genomic DNA many bacteria have small circular DNA outside the genomic DNA. These DNA are known as plasmid . These plasmid DNA confers certain unique phenotypic characters to bacteria . e.g. Antibiotic resistance.

On the basis of their function or phenotypic character plasmids are of many types

F- plasmid – If present F positive/ male /donor .
                      If absent F negative/ female / recipient  .
R – plasmid – provide resistance towards the antibiotics.

MODE OF NUTRITION 

The vast number of bacteria  are show heterotrophic mode of nutrition. They depend on other organisms or on dead organic matter for food, but some are autotrophic. Autotrophic bacteria synthesize their own food from inorganic substances.

On the basis of nutrition bacteria are classified into following three categories :-

(     (A)                  AUTOTROPHS :- These bacteria use light or chemical energy for their own food synthesis. There are two types photoautotrophs and chemoautotrophs.

The bacteria use light energy for formation of their food are called as photoautotrophs. Bacteria use H2S instead of H2O as hydrogen donor, hence during photosynthesis in bacteria instead of oxygen sulphur liberates. 

Example-  Green sulphur bacteria = Chlorobium
                   Purple sulphur bacteria = Chromatium
               Purple non sulphur bacteria = Rhodospirillum

 The bacteria use chemical for formation for their food are called as chemoautotrophs .

E.G. – Nitrifying bacteria – They oxidise nitrogenous compounds and obtain energy.

Chemosynthetic bacteria play a great role in recycling nutrients like nitrogen, phosphorus, iron and sulphur.

    (B)                  HETEROTROPHS :-  Most of the bacteria are heterotrophic. They cannot make their own food it can be depend on other organisms. They are useful in making curd from milk, production of antibiotics, fixing nitrogen in legumes plants ( pea, gram, bean ) .

Saprotrophic bacteria – These bacteria obtain food from dead and decaying organic matter.

e.g. Clostridium botulinum

Parasitic bacteria – They obtain their food from living organism.

e.g. Mycobacterium tuberculosis 

Symbiotic bacteria – They form symbiotic relation with other organisms. These bacteria convert atmospheric nitrogen into ammonia and then into nitrogenous compounds like amino acids, NO3_ or salts of ammonia .

e.g. Rhizobium – Rhizobium bacteria forms nodule in the root of legume plants.

RESPIRATION

On the basis of respiration bacteria are of two types

Aerobic bacteria :- They use oxygen in respiration.

e.g. Azotobacter , Acetobacter aceti

Anaerobic bacteria :- They do not use oxygen in respiration.

e.g. Clostridium botulinum, Fermentation bacteria ( Lactobacillus ) except Acetobacter aceti.

Lactobacillus causes souring of milk

REPRODUCTION

Bacteria in two type of reproduction method present asexual and genetic recombination. In bacteria true type of sexual reproduction absent but transfer of genetic material from one to another bacterium present called genetic recombination.

Asexual reproduction:- Following methods of asexual reproduction are found in bacteria. 

(1  (1)              Binary fission

      Most common method ,Occurs in favourable conditions and bacterial cell divide by amitosis which is faster process than mitosis or meiosis.

(1      (2)               By Endospore  formation

Occurs in unfavourable conditions

It is highly resistant structure to high temperature, radiations, antibiotics and chemicals.

It is made up of a calcium dipicolinate in its thick wall.

Genetic recombination:-  Bacteria also reproduces by a sort of sexual reproduction by adopting primitive type of DNA transfer from one bacterium to another with the help of conjugation tube.