BACTERIAL REPRODUCTION

Bacteria can reproduce through binary fission and by exchanging their genetic material. Binary fission produces the daughter cells having the same characteristics as that of the parent cell. In the conjugation and transformation methods, two organisms are involved in the reproduction process.

Binary fission

Binary fission is the division of one parent organisms into two daughter bodies. This process takes place in two steps, i.e., replication of genetic material and division of parent body into two. The process takes place through following steps:

1. At the spot of origin, the DNA of bacteria started to replicate. In this process, the two parts moves towards the opposite ends of the cell, due to which, chromosome is also pulled. For adding the separation of the newly formed chromosomes, the cell gets longer.
2. On the completion of the division of the genetic material, the newly formed chromosome shifts to the opposite end of the cell and it begins the cytoplasm division process.
3. Cell membrane pinches inwards and the new dividing cell wall is formed in the middle of the cell.
4. The septum splits down in the middle to give rise to two individual cells.

Fig: Binary fission in bacteria

The above image is taken only for educational purpose from [1]

Conjugation

DNA is transferred from on bacteria to another through a structure called pilus. DNA in the form of plasmid is transferred from the donor (F⁺) cell to the recipient (F^–) cell. Donor cell has an additional F factor or fertility factor which can code for protein that can make the sex pilus. The following steps are involved in the process of conjugation:

1. Pilus is produced by The F+ or donor cell which starts to contact with the F- or Recipient cell.
2. There is direct contact between donor and recipient with the help of Pilus.
3. The T-strand is transferred to the recipient cell through the pilus.
4. In the final step, both donor and recipient cells replicate the single stranded DNA and forms double-stranded F-plamid.

Fig: Conjugation in bacteria

The above image is taken only for educational purpose from [1]

Transformation

In this process, the bacteria takes the DNA from the environment. When the DNA taken is in circular form, then it is called plasmid, which can be passed to the other generations. This technique in also used in laboratories for introducing new DNA fragments into the bacterial cells.

The process of bacterial transformation is very useful  in the molecular cloning. Multiple copies of recombinant DNA molecule can be formed by using transformation process.

Transduction

In this, the carrier for the DNA transfer is viruses. Viruses which infects the bacteria can carry small fragments of DNA from one bacterial cell to another. Viruses which can infect the bacterial cell are known as bacteriophages.

Fig: Transduction in bacteria

The above image is taken only for educational purpose from [1]

MCQs

1. Daughter cells produced from binary fission in bacteria have?

a. Same characteristics as that of the parent cell

b. Different characteristics as that of the parent cell

c. May have same of different characteristics as that of the parent cells

d. Bacteria cannot reproduce from binary fission

2. Genetic material is transferred from one bacteria to another bacteria in Bacterial conjugation with the help of?

a. Cilia

b. Flagella

c. Pilus

d. Mitochondria

3. Molecular cloning of recombinant DNA can be done by the help of?

a. Binary fission

b. Conjugation

c. Transformation

d. Transduction

4.Which Viruses are involved in the Bacterial Transduction process?

a. Animal viruses

b. Plant viruses

c. Bacteriophages

d. All of the above

5. Bacteria can reproduce through which method?

a. Binary fission

b. Conjugation

c. Transduction

d. All of the above

6. Transfer of genetic material can take place in bacteria through which method?

a. Transformation

b. Transduction

c. Conjugation

d. All of the above

7. Pilus is formed by which type of cell?

a. F⁺ 

b. F^–

c. Bacteriophages

d. Both a. and b.

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ANSWERS

1-a

2-c

3-c

4-c

5-d

6-d

7-a

RFERENCES