If you are a student of microbiology, you must have heard of F+ and Hfr cells. Both of these cells are bacterial cells, but they have some differences. In this article, we will discuss the differences between F+ and Hfr cells.
What is an F+ Cell?
An F+ cell is a bacterial cell that contains an F plasmid. The F plasmid is a circular DNA molecule that carries genes for the production of sex pilus. The sex pilus is a structure that helps the cell to transfer genetic material to another bacterial cell during conjugation.
The F plasmid can replicate independently of the bacterial chromosome. During conjugation, the F plasmid is transferred from the F+ cell to the F- cell. The F- cell then becomes an F+ cell.
What is an Hfr Cell?
An Hfr cell is a bacterial cell that has the F plasmid integrated into its chromosome. The term Hfr stands for high-frequency recombination. The integration of the F plasmid into the bacterial chromosome happens through a process called homologous recombination.
During conjugation, the Hfr cell transfers a part of its chromosomal DNA along with the F plasmid to the F- cell. The transferred chromosomal DNA can recombine with the recipient DNA to form a recombinant cell. However, the F plasmid usually remains with the Hfr cell, and the F- cell does not become an Hfr cell.
Differences Between F+ and Hfr Cells
Now that we have discussed what F+ and Hfr cells are let's look at their differences:
F Plasmid
The F plasmid in an F+ cell is a circular DNA molecule that replicates independently of the bacterial chromosome. In contrast, the F plasmid in an Hfr cell is integrated into the bacterial chromosome and can only replicate along with the chromosome.
Transfer of Genetic Material
In an F+ cell, only the F plasmid is transferred to the recipient cell during conjugation. On the other hand, in an Hfr cell, a part of the chromosomal DNA along with the F plasmid is transferred to the recipient cell during conjugation.
Formation of Recombinant Cells
In an F+ cell, the recipient cell does not acquire any new chromosomal DNA, and therefore, no recombinant cells are formed. However, in an Hfr cell, the transferred chromosomal DNA can recombine with the recipient DNA to form a recombinant cell.
Stability of the F Plasmid
The F plasmid in an F+ cell is relatively stable and can be easily transferred to the recipient cell during conjugation. However, the F plasmid in an Hfr cell is less stable and is rarely transferred to the recipient cell during conjugation.
Conclusion
In conclusion, F+ and Hfr cells are two types of bacterial cells that differ in the presence and integration of the F plasmid. While F+ cells only transfer the F plasmid during conjugation, Hfr cells transfer a part of their chromosomal DNA along with the F plasmid. This difference leads to the formation of recombinant cells in Hfr cells but not in F+ cells.
