Question

Sex pili are present in
A. Male Escherichia coli
B. Female Escherichia coli
C. Diplococcus
D. All bacteria

Answer 1

Hint: Bacteria are the microorganisms which are not visible through naked eyes. They are unicellular prokaryotic organisms and contain the simplest type of cell structure. The bacterial cells do not contain cell organelles such as mitochondria, golgi and their genetic material lies free in the cytoplasm. However, bacterial cells are known to contain certain specialized structures which are needed to survive and reproduce.

Complete answer:
The bacterial cells contain several hair-like short or long structures present on the cell surface. These hair-like structures are known as pili. The pili are less rigid and straight in structure and are found evenly distributed over the surface of the bacterial cells. In some cases, the pili can be located to either one or both the poles. The pili are typically present in the Gram-negative bacteria but in some cases, can be also found in Gram-positive as well as other bacteria also.
The main function of pili is in the bacterial cell adhesion and in the transfer of genetic material. They have an important role in bacterial infection. Pili do not act as the organs of locomotion rather it acts as a sensory and sex structure. They are used during the process of conjugation in which genetic materials are exchanged.
The pili are known to consist of single or multiple kinds of protein subunit. These subunits are known as pilins or fimbres. The genes which are responsible for the encoding of the pili are located in the bacterial chromosomes, which are known as the plasmids. The pili can be of two types which are the conjugative pili and type IV pili.
The conjugative pili are used during the transfer of genetic material or DNA between the bacterial cells. They are referred to as sex pili as they allow the flow or exchange of genetic material or genes between the cells. This process occurs by the formation of pairs and is also called as sexual reproduction in bacteria. The pili of Escherichia coli are the most well studied pilus. The pili is encoded by the fertility factor F sex factor. During conjugation between the mating pairs, a pilus arises from the donor cells and draws the other cell known as the recipient cell. This triggers the formation of a connection-like structure known as the mating bridge and it causes direct contact between the cells. The process then allows the transfer of the DNA from the donor to the recipient cells.
The bacterial cells that are known to contain the sex pili are referred to as the male types of cells while in the other types of cells where the sex pili are absent are known as the female types of cells. The pili are also called the fertility plasmid.

Therefore, the correct option is option A.

Note:
The pili are specialised structures present on the surface of the bacteria and are associated in the process of conjugation and mating. The pili are often called as sex pili because the pili acts to transfer the DNA material between two bacterial cells during the process of conjugation. In E.coli, the presence of sex pili in the male bacterial cell is important for reproduction. In addition to reproduction, pili are also used as a mode of adhesion and bacterial infection to other cells.