Bacteria resemble Fungi in chitinous nature of cell wall, the absence of chlorophyll and mode of nutrition as saprophytes. Bacteria differ from fungi in their small size, unicellular nature, lack of definite nucleus in the cell and reproduction as a rule by fission. Due to last feature they are often referred to as Fission, fungi or schizomy cetes. On the basis of shape bacteria are classified in three groups.
(1) Coccus:- In these cells are spherical. They have one family coccaceae with three genera microcoaccus, streptocoaccus and saricina.
(2) Bacterium or Bacillus:- in these cells are elongated rod like or kidney shaped. They have family bacteriophyceae with genera like Bacterium, Bacillus and Psenomonas.
(3) Spirillum:- In these cells are in the form of spirals, curved or comma like. They have family spirillaceae with spirullum and microspores.
Bacteria are simplest unicellular, minute microscopic organisms grouped in schizomycetes. 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.
In 1676 leawachock first time observed Bacteria. Bacteria cell is very simple structure. It has tiny mass of dense protoplasm surrounded by a rigid cell wall and is colourless and homogenous. It has fatty granules and glycogen bodies.
There is no definiate nucleus but b y chromatin gramules or incipient nucleus. Bacteria may be motile or incipient nucleus. Bacteria may be motile or non motile. In motile condition they contain any flagella while in non motile condition they any flagella while is non motile condition they do not contain any flagella. Bacteria contain single or tuft of flagella at one pole. If tufts of cilia occur on both poles they are called as Amphiteichous. If flagella occur on all he surface bacteria are called pertinacious.
On the basis of form bacteria may be:
(1) Coccus:- These are spherical or ovoid e.g. micrococcus, streptococcus.
(2) Bacillus:- These are elongated rod like or kidney shaped eg. Bacterium, Bacillus, Pseudomonas.
(3) Spirilluim:- These are rigid and coiled eg: spirillus, spirochete.
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 are of two types.
(1) 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.
(2) Chemosynthesis 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.
(1) Vegetative reproduction:
(a) By Budding:- Bisset and Hale have reported vegetative reproduction by budding in bigidibacterium fibifus.
(b) 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.
(2) 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.
(3) 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. No further stages have been observed after fusion but it is thought that new cells arise as a result of such fusion.
Beneficial Bacteria:
(1) Samitation value: Some bacteria bring about decomposition of proteins, fats, carbohydrates and other complex organic compound in the bodies of plants and animals and in their waste products. In this way they clear the earth of organic debris and return to the soil and air, the simple substances which are necessary for manufacture of food by green plants and maintenance of soil fertility.
(2) Soil fertility: Some bacteria increase soil fertility. Nitrogen is an essential ingredient of all having protoplasm. All growing plants therefore require it in their metabolism. Nitrogen is most abundant of all minerals. It makes up about 80% of atmospheres composition. They are of two kinds:
(i) Nitrogen fixing bacteria: Some live free in soil and others in root modules of leguminous plants. These bacteria are able to make use of atmospheric nitrogen and change it into nitrogenous compounds. This process is called nitrogen fixation e.g. Bacillus radicicola.
(ii) Nitrifying bacteria: These bacteria covert free nitrogen into ammonium compounds. They are converted into nitrates.
Nitrogen Cycle: Cycle of changes by which nitrogen passes wing to activities of bacteria and other living organisms is called nitrogen cycle.
(3) Industrial Value: The metabolic process and products of bacteria are important in many industries like vinegar, Dairies, Alcohols, Tea, tobacco, textile and Tanneries.
(4) Medicinal Values: Antibiotics and Vitamins are obtained by bacterial activities. Stroptomycin is obtained from streptomyces grisens.
Harmful Bacteria:
Most harmful activities of bacteria include epidermis and ailment of human beings, animals and plants. They take highest tool of human life.
(1) Human Diseases: Bacteria causes many serious diseases of man e.g. Tuberculosis meningitis, pleumonia, lock jaw, typhoid, cholera, diphtheria, leprosy and dysentery.
(2) Animal diseases: Tuberculosis of cattle, anthrax of sheep, chicken, cholera, pneumonia, in horses, sheep and goats and various serious diseases are caused by bacteria.
(3) Plant diseases: Fire blight of pears, citrus canker, cotton root rot, potato blackleg, soft rot of carrot, cabbage and cucumber, plants. Pine apple rot and wild diseases of tomatoes, potatoes, cucumbers, squash, are serious plant diseases caused by bacteria.
(4) Food spoiling: Several species of bacteria infect food stuffs and spoil then by producing poisons. Most common poisoning bacteria are clostridium botulinum.
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