Bacteria

Bacteria

In 1676 Anton Von Leeuwenhoek  first time observed Bacteria. Bacteria cell is very simple structure. It has small mass of  protoplasm surrounded by a rigid cellwall . It has fat granules and glycogen bodies as reserve food in protoplasm.

 Bacteria lies in phylum Monera.they are prokaryotes and they don't contain well developed nucleus. dna of bacteria lacks of histone protein and RNA is of 70s type. 

 They are cosmopolitan in distribution and occur in every place i.e. they are omnipresent. They occur in air, water, soil plants and animal bodies.

On the basis of shape bacteria may be:

 Coccus:- These are spherical or ovoid e.g. micrococcus, streptococcus.

 Bacillus:- These are elongated rod like or kidney shaped eg. Bacterium, Bacillus, Pseudomonas.

 Spirilluim:- These are rigid and coiled eg: spirillus, spirochete.

  vibrio:- they are comma shaped. e.g -vibrio cholera

Nutrition:-

Bacteria lack chlorophyll and are heterotrophic in nutrition. There is small group of Bacteria which are autotrophic. Bacteria are able to synthesize carbohydrate food from CO2 and water like green plants.

Autotrophic bacteria ;

 Phototrophic Autotrophic Bacteria:- They build carbon of CO2 into carbohyderates in the presence of sunlight and use light energy in preparation of food. They are purple and red bacteria. 

 Chemosynthetic Bacteria:- They obtain energy required for synthesis of organic compounds from the oxidation of certain chemicals. No light is involved in this reaction. Important chemosynthetic bacteria are:-

(a) Sulphur Bacteria:- They occur in sulphur spring, soils rich in sulphur, savage. They oxidize hydrogen sulphide (H2S) to free sulphur and then to sulphuric acid, obtaining energy which they utilize in synthesizing food.

(b) Iron Bacteria:- They live in water rich in iron salts and convert ferric compounds.

(c) Hydrogen Bacteria:- These convert hydrogen into water. They get oxygen from oxides of nitrogen and are aerobic in nature.

(d) Nitrifying bacteria:- These oxidize simple ammonium compounds into nitrates and then oxidize nitrites into nitrates eg. Nitrobacteria. These are aerobic

Heterotrophic Bacteria:- These bacteria obtain their food ready made from external agency. They are of following types:-

(i) Parasitic Bacteria:- They live on or in the bodies of living organism both plants and animals. They obtain their organic food from the host on which they grow. Parasitic bacteria may be harmless to their hosts or cause serious diseases in them. Former are called non pathogenic and latter are pathogenic. Cholera, parrmonia, diphtheria, tuberculosis, typhoid are common diseases caused by bacteria.

(ii) Saprophytic Bacteria:- they get their food from dead organic matter. Bacteria break down complex organic compounds into simple products with the help of enzymes. Conversion of milk into lactic acid and sugar in vinegar is done by such bacteria. They are also used in ripening of cheese curing of tobacco, setting of flox and jute.

Reproduction:-

It takes place by vegetative asexual and sexual methods.

Vegetative reproduction:

 By Budding:- Bisset and Hale have reported vegetative reproduction by budding in bigidibacterium fibifus.

 By fission:- It is common method in all bacteria cell divides across the long axis. In spherical coccus bacteria division may occur in any plane. In favourable conditions, the bacterial cell divides amitotically into two equal daughter cells each of which leads separate life. This type of division of mother cell is called binary fission.

 Asexual Reproduction:-

(a) BY Conidia:- Some filamentous bacteria like streptomycetes produce spore like structure in chains called coindiospores or conidia. Each conidia develop into new bacterial cell.

(b) By Zoospores:- Under unfavourable conditions of environment bacteria from small motile spores. This is rare process eg. Rhyzobium azotobacter.

(c) By Endospores:- The endospore is formed by condensation of protoplasm into spherical ovoid mass which develops its own wall and becomes spore. When the spore is mature old cell wall breaks down to form spore under favourable conditions the spore absorbs water, germinates and grown into an active bacterial cell.

 Sexual Reproduction:

It takes place in gram negative bacteria. In this case two fuses over a narrow area, their contents unite and zygostore like structure is formed. it takes place by transduction and conjucation.