Kingdom Prokayotae Overview
Prokaryotes were the earliest organisms and they lived and evolved all alone on Earth for 2 billion years. They have continued to adapt and flourish on an evolving Earth and in turn they have helped to change the Earth. After reading this article on Kingdom Prokaryotae also known as Monera, you will become more familiar with prokaryotes by studying their structure and function, their origins and evolution, their diversity and their ecological significance.
Kingdom Prokaryotae is a group of living organisms which are unicellular having prokaryotic or a primitive nucleus. Prokaryotes are unicellular organisms, called
bacteria, in which each cell contains a single DNA molecule coiled in a loop and not enclosed in a nucleus. They are almost everywhere, indispensable links in the recycling of chemical elements in ecosystem and human use them in research and technology.
Introduction to Bacteria
Bacteria are simplest and smallest living organisms. They are classified as one of the most primitive group of organism known as Kingdom Prokaryotae(Monera). The size of bacterial cell is 0.2 micron to 2 in breadth and 2 to 10 micron in length. Bacteria are unicellular but may form groups or colonies. A bacterial cell consists of following parts:
Flagella are thin hair like structures arise from basal body, a structure present beneath the cell membrane. Flagella are locomotory organs of bacteria i.e. help in the movement of the body
These are fine, hollow, filament like structures. These are not used in locomotion, but help in conjugation process of reproduction
It is an additional protective layer around the cell wall and found in some bacteria. It is composed of polysaccherides and proteins. In some bacteria slim-capsule is present, which is used for the protection of bacterial cell against phagocytosis and increases the activity of bacterial cell
- Cell wall
It is present around the bacterial cell. It is composed of amino acids, sugars and chitin. Cellulose is not present in bacterial cell. In some bacteria capsule is also present around the cell wall.
- Cell membrane
Internal to the cell wall, cell membrane or plasma membrane is present. The protoplasm of bacterial cell is bounded by cell membrane. It is composed of lipids and proteins.
The cytoplasm is a fluid material. It is dense and contains granules of glycogen, proteins and fat. Mitochondria and endoplasmic reticulum are absent. In the cytoplasm ribosomes are present. They are small minute granules composed of protein and R.N.A. and help in protein formation.
The plasma membrane of bacterial cell is folded inward to form a special structure, called mesosomes. The mesosomes take part in cell division, DNA-replication, secretion of certain enzymes, respiration and active transport of enzymes
- Nuclear material
There is a distinct nuclear region in the bacterial cell, but without nuclear membrane and nucleolus. The nuclear region contains the genetic material D.N.A. bacteria are haploid organisms with a single chromosome. The chromosome consists of a circular double helical DNA molecule. The single molecule of DNA contains several thousand genes. The genetic material replicate at the time of cell division and it is transferred to the daughter cell.
Gram Positive And Negative Bacteria
Certain bacteria are stained with a violet: dye during colouring procedure. They are called Gram positive bacteria. It was discovered by a Danish microbiologist Hans Christian Gram. Other bacteria do not stain with the violet dye, they are known as Gram negative bacteria.
This property of bacteria helps in the identification of unknown bacteria and also in the grouping of different kinds of bacteria.
Respiration in Bacteria
According to the respiration there are two types of bacteria.
These bacteria need oxygen for respiration. Aerobes bacteria are of two types:
- Obligate Aerobes
These bacteria require O2 and die in its absence.
- Facultative Aerobes
These bacteria used O2, but can also survive in it’s absence. The bacteria which require little amount of O2 are called microaerophilic bacteria.
These bacteria do not need O2 for respiration. Anaerobes bacteria are of different types:
- Obligate Anaerobes
Some bacteria are killed in the presence of O2. These are called obligate anaerobes.
- Facultative Anaerobes
The bacteria which use O2 but also can respire without it, they are called facultative anaerobes.
Growth in Bacteria
Growth is an increase in the number of cells and size of cells. Bacteria take their food from the environment by diffusion or active transport process. Oxygen is required for aerobe bacteria and it is not needed for anaerobe bacteria. The factors which affect the growth are:
- Available nutrients
- Ionic concentration
Stages OR Phases of Growth
In bacteria there are four phases of growth:
- Lag phase
This is inactive phase of bacteria. In this stage bacteria prepare themselves for growth. The cells accumulate essential substances such as water and proteins
- Log phase
The logarithmic phase (log phase) is the period in which bacteria grow very rapidly. Their metabolic activities are maximum. Their rate of reproduction is more and rate of death is very slow. So they increase their number rapidly.
- Stationary phase
After an active growth the bacteria face shortage of food, pH changes and energy is less, so they try to maintain themselves. They also start dying as a result of which their multiplication is equal to their death rate. The number of cells is almost unchanged, so it is called stationary phase
- Death phase or decline phase
When conditions are totally unfavorable, death occurs rapidly than growing cells. When death rate is faster than multiplication rate, it is called death phase
Importance of Bacteria
Bacteria have both positive and negative importance. They play very important role in the life of human being.
- Decaying of Dead Bodies(Decomposers)
Bacteria decompose the dead remains of plants, animals and human beings into simpler compounds. in this way they help to clean the world.
- Bacteria in Industries
Bacteria has so many important usages in the industry
- Bacteria are used in dairy industry. They change the milk into curd.
- They are used in the formation of butter and cheese from milk.
- They are used in the ripening of tobacco leaves.
- Bacteria are used in the preparation of alcohol and vinegar.
- Bacteria are also used in leather industry.
- Digestion in Alimentary Canal
Certain Bacteria are present in the intestine of man and help in the digestion of cellulose, by enzyme, called cellulose.
- Fertility of Soil
Bacteria increase the fertility of soil by adding organic substances due to the decomposition of dead bodies.
- Genetic Engineering or Bio Technology
Bacteria are used in genetic engineering. Escherichia coli bacteria are used to produce growth hormones, and production of insulin.
- Spoilage of Food
Bacteria spoil our food stuff in large amount by the chemical process. It is a great loss.
- Diseases in Man
Bacteria are responsible to cause various diseases in man and other animals, such as tuberculosis (T.B.), pneumonia, cholera, typhoid, tetanus, syphilis, Diphtheria etc.
- Diseases in Plants
Bacteria also cause diseases in various plants, such as citrus canker. Five blight of
apple, ring disease of potato, wilt of solanaceae plants etc.
Control of Bacteria
The different methods to control the infectious microorganisms are as follows:
- Infected persons should be properly treated by effective medicines.
- Persons in a population should be treated by immunization and vaccination.
- In epidemic condition the infected persons should be kept in quarantine to avoid the spread of infection to healthy persons.
- At different possible stages the life cycle of pathogen should be disrupted, so it can not cause further infection.
- The host bodies of pathogen should be identified and treated well to control the disease.
- By different ways knowledge and awareness about diseases and infection of pathogen should be provided to the public.
Many methods should be used to kill or inhibit the infection of pathogens, such as:
- High temperature treatment
- By ultraviolet rays
- By the use of antiseptics
- By the use of antibiotics
- By chemotherapy
Use and Misuse of Antibiotics
Antibiotics are the chemical substances which are used to kill micro-organisms that cause infectious diseases. These are produced by certain micro-organisms and prevent the activity of other micro-organisms.
Use of Antibiotics
- Antibiotics have their effect against the bacteria and kill them and control their infection.
- The antibiotics are used as vaccination to develop resistance in the body. They maintain immune system.
- Antibiotics are also used in agriculture to kill different organisms. These are also used in animal feeds to provide growth promoting substances.
Misuse of Antibiotics
- By the extensive use of antibiotics more resistance is developed in pathogenic micro-organisms, after that they cause more serious infection in the body.
- Antibiotics have many side-effects. Other organs of the body may be damaged such as liver cells and kidney cells.
- Antibiotics may react with human metabolism and in severe cases death of person may occur.
- Some antibiotics cause allergy in the body, such as penicillin.
Cyanobacteria (Blue-Green Algae)
- They are water living simple organisms.
- They are prokaryotes i.e. they do not have true nucleus. Like bacteria, so called cyanobacteria.
- They contain blue green pigments, chlorophyll a (green) and phycocyanin (blue), so they are also called blue green algae.
- They are unicellular or may be found in groups or colonies.
- They have double-layered cell wall.
- Asexual reproduction takes place by hormogonia, fragmentation, akinetes or zoospores.
- Sexual reproduction is absent.
Importance of Cyanobacteria
- These organisms take part in nitrogen fixation. Nostoc and anabaena are used as nitrogen fertilizer in agriculture to improve the soil fertility.
- During photosynthesis they use CO2 and H2O. They release oxygen as a byproduct. In this way they take part to change and flourish the environment.
- Many organisms of cyanobacteria are found in the form of phytoplankton. They are used as food by many aquatic animals.
- They also produce unpleasant smell in water and make it unable for drinking.