Bacteria can reproduce by two methods like the
- Asexual reproduction
- Sexual reproduction.
Bacteria reproduce very fast that a colony of bacteria can double in bacterial population in just half an hour.
Hence they can perform non-stop tasks, like scavenging the dead and waste material, fermenting the molasses, and producing beneficial yields in biotechnology.
In fact, they are considered immortal organisms on the earth as they do not die unless forced to.
Despite rapid reproduction, they maintain genetic diversity and robustness.
In times of harsh conditions, they convert to spores.
When the times are favorable, from these spores, new bacteria.
Thus they rarely die and are considered immortal.
Hence we can notice the development of resistance to drugs by some parasitic bacteria.
Types of Bacterial Reproduction
Unlike other organisms, bacteria reproduction occurs in multiple ways.
l. Asexual reproduction.
- Binary fission.
- Spore formation.
2. Sexual reproduction
- This happens by simple cleavage of the cell.
- This is of two types binary fission and endospores.
- Here a single bacteria undergo division into two new bacterial cells.
a) Binary fission
- This is the most common method of reproduction.
- This occurs during favorable conditions.
- Here each bacteria reproduce by binary fission, and the parent cell is split into two identical daughter cells.
- This process involves many intermediate steps.
- It occurs every 20 minutes once.
- Hence we can notice that bacteria double their population every half hour.
- During unfavorable conditions like drought, bacteria undergo spore formation.
- They cover themselves with a hard coat that is rigid and resistant to extreme conditions.
- When the conditions are favorable, spores break open to release bacteria.
Example: Clostridium tetani bacteria follow this method.
- There is no true sexual reproduction. But then, reproduction happens by mutual exchange of gametes.
- In doing so, their chromosomes get interchanged.
- This interchange is considered helpful in developing healthier offspring than that of asexual reproduction.
- The combination of gametes occurs by three methods.
- Here, the bacteria take up the naked DNA strands from the surrounding.
- Then it is incorporated into its genome.
- Griffith discovered the phenomenon in 1928 in diplococcus pneumonia bacteria.
- This transformation occurs inside the body, in the soil and in marine environments.
It is seen in bacteria like streptococcus, Bacillus, azotobacter, and Pseudomonas.
- Lederberg and Tatum discovered this in Escherichia coli.
- The donor-type bacteria F+ binds with recipient-type bacteria F- with the help of pili.
- Pili are the sexual appendages of bacterial cells.
- A conjugation tube is formed between two bacteria through pili.
- A part of the chromosome of one bacteria cell reaches the other.
- Sometimes entire chromosome of F+ passes into F-.
- The donor bacteria do not die and go for natural multiplication, while the recipient bacteria acquire new characters due to recombination.
Thus the genetic exchange occurs. Ex: E.Coli
- Here, the genetic material from one bacteria is transferred to another with the help of a bacteriophage.
- Bacteriophages are viruses that use bacterial genetic machinery to synthesize their own genetic material.
- So when this virus transfers from one bacteria to another, transduction occurs.
Ex: in Salmonella Typhi bacteria.
- When the virus multiplies inside a bacterial cell, bacterial DNA fragments are incorporated into the newly formed virus particles.
- When these virus particles or phages infect another bacteria, the DNA of the first bacteria is transferred here.
- This transferred DNA gets incorporated into the chromosome of the second bacteria. Thus the DNA gets transferred between bacteria by a virus.
- Because of the above reproduction methods, antibiotics can kill disease-causing bacteria.
These antibiotics intervene in some parts of the reproductive cycle and arrest their growth and multiplication.
What is responsible for genetic variation in bacteria
Plasmids are responsible for genetic variation in bacteria in asexual reproduction.
Plasmids are circular-shaped structures containing single-stranded DNA that can move from one bacteria to another and cause genetic variation.
In sexual reproduction, gene alteration from two sets of bacteria occurs, leading to variation.
Antibiotic resistance is one of the phenomena where bacteria acquire the genetic character from others due to plasmid transfer.
Is bacterial sporulation a reproductive process
Bacterial sporulation is a survival process that is needed for bacteria to sustain harsh conditions.
But as new bacteria emerge from spores; it looks like a reproductive process.