Bacteria – Types of bacteria, Structure, Feeding, Reproduction and Transformation, Essential Bacteria
Bacteria are single celled organisms that lack in nucleus that are few micrometers in size and are neither animals nor plants .
One million of bacterial cells are present in one milliliter of water. A gram of soil usually holds millions of bacterial cells.
Types of bacteria:
Bacteria are generally differentiated on the basis of their structure and shape.
Bacteria have three basic shapes:
- Rod shaped: They are called as bacilli.Rod shaped bacteria that are curved are called vibrio.
Example: Bacillus anthracis
- Spherical: Ball shaped bacteria are called cocci. Also a single bacterium is called coccus.
Example: Streptococcus group.
- Spiral: They are called as spirilla. If they have a very tight coil they are called spirochetes. These types of bacteria cause diseases such as syphilis and Leptospirosis.
Structure:
Bacterial cells differ from animal and plant cells. Bacteria are prokaryotic organisms which means the absence of nucleus.
Structure of bacterial cell includes:
Capsule: This is the outer layer of the cell wall present in some bacteria.
Cell wall: Cell wall is the outer layer of plasma membrane which is made up of peptidoglycan(a polymer). Gram Positive bacteria have a thick cell wall in comparison to Gram Negative bacteria.
Plasma membrane: It is the permeable inner layer of cell wall that transport the chemicals.
Cytoplasm: Cytoplasm is present in the plasma membrane. It is a gelatinous material containing ribosomes and genetic material.
Ribosome: Ribosomes are made of RNA rich granules and this is where proteins are synthesized.
DNA: It is present in the cytoplasm and is responsible for function and development of bacteria as it has all the genetic information .
Flagellum: Bacteria uses flagellum for movement. Some bacteria can also have more than one flagellum.
Pilli: Outer surface of the cell has hair like appendages that allows it to stick to other cell surfaces and transfer genetic material .
Feeding:
Depending upon the feeding pattern bacteria are differentiated in many categories:
Heterotrophic bacteria:
Bacteria that consume organic carbon as energy source are called heterotrophic organisms or heterotrophs. Some bacteria kill their host while other absorb dead organic material .
Autotrophic bacteria:
Bacteria that are capable of making their own food through chemosynthesis or photosynthesis are autotrophic bacteria.
Depending on this they are subdivided into Chemoautotrophs(uses chemicals like nitrogen, sulfur as food source)and Photoautotrophs(uses sunlight, carbon dioxide and water as food source)respectively.
Bacteria is present in soil, water, deep in earth’s crust, radioactive waste, hot springs and glaciers.
Presence of oxygen in the environment is favourable for growth of Aerobic bacteria(also called aerobes). They cause problems for human environment such as water clarity, corrosion, fouling, etc.
Anaerobic bacteria or anaerobes can only grow in absence of oxygen.These organisms can cause infections in gastrointestinal tract.
They also cause dental infections, gas, gangrene, etc.
Anaerobic bacteria are further subdivided into facultative anaerobic bacteria which means they can live either with or without oxygen. They are generally found in vegetation , normal human flora, soil, etc. Ex: Salmonella
They have the capability to survive in extreme environments . They are called Extremophiles.
They are classified as:
- Thermophiles
- Halophiles
- Acidophiles
- Alkaliphiles
- Psychrophiles
Bacteria that are responsible for causing infections in human body are called Mesophilic bacteria or mesophiles. They thrive in human body temperature.
Examples: Staphylococcus aureus, Citrobacterkoseri, Pseudomonas aeruginosa, Thiobacillusnovellus.
The human intestine or gut contains beneficial mesophiles such as Lactobacillus acidophilus.
Reproduction and Transformation:
1.) Binary fission:
This is asexual form of reproduction. In this type of reproduction the cells grow until the formation of a new cell wall through center that forms two cells. The two cells separate but holds same genetic material.
2.) Transfer of genetic material:
New genetic material is acquired by the bacterial cell through processes such as transformation, conjugation or transduction. These processes help the bacterial cells to ressist the lethal stress and also make them stronger.
3.) Spores:
Some bacteria, when low on resources form spores that contain enzymes required for germination. Spores also contain the DNA material of the organism. As spores can remain inactive for ages they cansurvive through periods of chemical exposure, gamma radiation, environmental stress, starvation and extreme temperature conditions.
Example of endospore forming organism is Clostridiumbotulinim.
This organism is responsible for causing food poisoning.
Essential Bacteria:
It is estimated by researchers that human body has 10 times more bacteria than human cells. Majority of these bacteria are present in gut and helps in the process of break down of food. People consume probiotics regularly to support the gut health. These probiotics contain some strains of beneficial bacteria like Lactobacillus or Bifidobacterium.
These organisms are also used in production of yogurt and fermented foods.
The ecosystem relies on bacteria to function properly. Ex Certain bacteria breaks down the dead matter like dead leaves and releases nutrients and carbon dioxide in this process.
Harmful bacteria:
When harmful bacteria are either consumed or come in contact with human body, they reproduce and release toxins damaging the tissues causing illnesses. These bacteria are called pathogenic bacteria.
Examples:
- Vibro cholera causescholera
- Clostridium tetani responsible for causing tetanus.
- Salmonella typhicauses typhoid.
- Brucellaand Pastrurela cause bacterial infections in pets and animals.
Antibiotics are used to treat infections caused by pathogenic bacteria. But also it is important to receive proper diagnosis as antibiotics only can be used against bacteria and cannot treat fungal and viral infections.
Antibiotic resistance is anemerging concern. This may reduce the efficiency of antibiotics.
This problem can be reduced by:
- Completing your dosage even id you are feeling good.
- Never use someone else’s prescription
- Avoid skipping the doses
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