Bacteria, Their Structure, Types and Their Importance
Mainly there are four types of bacteria based on their shape. They are of following types
1: Round shaped bacteria:
The bacteria whose body structure or shape is of round type they are called as round - shaped bacteria. For example, coccus.
2:Rod shaped bacteria:
The bacteria whose body shape or structure is of rod type are known as rod - shaped bacteria. For example; Bacillus, diplococcus.
3:Comma shaped bacteria:
The bacteria whose body structure or shape is of comma type they are known as Comma-shaped bacteria. For example; Vibrio bacteria.
4:Spiral - shaped bacteria:
The bacteria whose body shape is of the spiral type they are known as the spiral-shaped bacteria.
Bacteria consist of an incipient nucleus which is not bounded by the nuclear membrane. Here, the hereditary material is DNA, which is scattered in the cytoplasmic mass, which means that the rest of the other material are also not bounded by the membrane, Bacteria are the prokaryotic organism so their nucleus is not of primitive type. The size of the bacteria varies from 0.02mm to 1mm so they can only be seen under the microscope of highly resolving power.
General structure of Bacteria:
In some of the bacteria, there is the presence of slime, gelatinous viscous mass outside the cell wall while these are absent in other bacteria. In bacteria, if there is the continuous presence of slime then it is termed as a capsule. But this kind of slime layer is not continuous in other bacteria so they lack capsule. Those bacteria which consist of the continuous layer of slime they are called slimy bacteria. This slimy layer is highly resistant to antibody and protective in nature. The slime has the refractive index similar to the water and made by the peptidoglycan material. That material is made of protein and amino acid.
2: Cell wall:
In some of the bacteria, the cell wall is multilayer this kind of bacteria are called gram- positive bacteria. But some of the species of bacteria there is the presence of only 30% peptidoglycan they are known as gram negative. In gram-positive bacteria, the cell membrane is in folded and that form the mesosome. But this kind of organs is absent in gram- negative bacteria. Only the sex pili or fimbriae is present in the gram- negative bacteria.
Cytoplasm is the viscous mass where there is the presence of genetic material and other cell organelles. Circular DNA which does not consist of a nuclear membrane which performed as the heredity transformation as well as protein synthesis. This all happens with the help of polyribosomes and messenger RNA. Messenger RNA synthesized all the essential proteins.
Gram-negative bacteria are those bacteria that do not retain violet color in the gram staining protocol. In a gram stain test, a counter stain which is commonly called safranin is added after the crystal violet, coloring all gram- negative bacteria with a red or pink color. If this kind of test is useful, it helps to differentiate the gram positive and gram negative bacteria based on the structure of bacterial cell wall. Here the gram positive bacteria will retain the crystal violet color when it is washed by the decolorizing solution.
Process of gram staining:
Take a smear of bacteria in a slide then go on doing the following steps:
1: Take crystal violet
2: Add small amount of distilled water
3: Then add few drops of iodine solution
4: Again add distilled water
5: Now see under the microscope
If the bacteria are seen colorless, then
6: Add safranin
If pink color appears then it is known as gram - negative bacteria
If purple color appears then it is known as gram - positive Bacteria:
Types of Bacteria:
1: Aerobic and Anaerobic Bacteria:
Some bacteria are aerobic and some bacteria anaerobic. Aerobic type of bacteria are those bacteria which need oxygen to survive or to live their life while anaerobic bacteria are those types of bacteria which do not need oxygen to survive or to live their life. Aerobic bacteria helps in the process of biodegradation process which is the decay of organic matter by bacteria in the presence of oxygen. While some of the other bacteria can decompose the organic matter in the absence of the oxygen they are called as anaerobic bacteria.
2: Autotropic, Heterotrophic, Phototrophic, and Chemotropic:
Autotrophic bacteria are those bacteria who can prepare their own food by the use of Carbon dioxide and oxygen. Heterotrophic bacteria are those bacteria who obtain their food from other bacteria that means they depend on other bacteria for their food. Phototrophic bacteria are those bacteria who utilize the radiant energy to prepare their food. Chemotrophic bacteria are those bacteria who utilized the inorganic salts such as nitrates ,phosphates, nitride, ammonium to prepare their food.
Heterotrophic bacteria are further divided into three, types they are:
1: Saprophytic bacteria:
That microorganism which obtains their food energy by degradation of organic matter is known as saprophytic bacteria.
Degradation process that is performed by the microorganism are two types:
If the degradation of carbohydrates is done by the microorganism this process is called fermentation process. And the bacteria are termed as fermentative bacteria. However, this fermentation process always takes place in an anaerobic condition that’s why carbohydrates are either changed into ethanol or methane gas.
The process of degradation of protein by the microorganism is called as purification.
2: Parasitic bacteria:
That microorganism which fully depend on the host for their survival is known as parasitic bacteria.
Parasitic bacteria are also of two types they are:
*: Ectoparasitic bacteria:
Those bacteria which affects the host by living outside the body of the host they are known as ectoparasitic bacteria.
*: Endoparasitic bacteria:
Those bacteria which affects the host by remaining inside the body of the host they are known as endoparasitic bacteria.
Generally, all the pathogenic bacteria are parasitic in nature. Sometimes if the host cell dies then the microorganism also die along with the host but sometimes the microorganism survives even the host cell dies.
3: Symbiosis bacteria:
The different leguminous plant consists of the root noodles where it consists the symbiotic bacteria which help in the fixation of nitrogen. Example: Rhizobium, Clostridium, Spirillum are the bacteria which fixes the molecular atmospheric nitrogen as in the form of nitrite and nitrate. Where nitrites are absorbed by the plants as in the form of fertilizer and nitrates also increases the fertility of the soil. Some of the free bacteria like Azobacteria also fixes or convert the atmospheric nitrogen into the nitrates.
Importance of bacteria:
1: Bacteria are used for waste water treatment.
2: They are also used for water treatment.
3: Bacteria are used in bakery and brewery industries.
4: Bacteria help in the process of nitrification.
5: They are also used in the dairy and medicine industries.
6:Bacteria helps in the process of Ensilage.
Harmful activities of bacteria:
1: Bacteria causes different kinds of disease to the plants and animal. Example: anthrax, leaf blight disease of wild rice.
2: Bacteria cause spoilage of food like milk, vegetables.
3: Some of the bacteria releases the toxic substances and causes the food poisoning. Example: Clostridium bacillium
Miller, Jr. G.T. Living in the Environment. Wadsworth Publication, 2003.
S.C., Santee. Environmental Science. India, New Center: New Center Book Agency (P) Ltd, 2004.
T., Richard. Environmental Science Towards a Sustainable Future. India: PHI (P) Ltd., 2008.
- Mainly there are four types of bacteria based on their shape.
- Bacteria structure consists of a capsule, cell wall, and cytoplasm.
- Bacteria helps in the process of Ensilage.
- Bacteria causes different kinds of disease to the plants and animal. Example: anthrax, leaf blight disease of wild rice.
- Bacteria cause spoilage of food like milk, vegetables.
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