Chapter 26, Problem 1TYK

Summary Introduction

Introduction:

Bacterial cells can be classified as gram-positive or gram-negative, depending upon the ability to retain the stain. The gram-positive bacteria have a thick layer of peptidoglycan, while the gram-negative bacteria have a thin layer of peptidoglycan cell-wall. The crosslinking of a peptidoglycan in gram-positive bacteria helps it retain the crystal violet stain (gram stain). Gram-negative bacteria have a slime layer outside their plasma membrane that is also known as a capsule in certain cases. The human gut and excretory system are often colonized by a huge range of microbiota.

Answer to Problem 1TYK

Correct answer:

Pili keep them attached to the urethral walls.

Explanation of Solution

Explanation/justification for the correct answer:

Option (d) is pili. Pili are the hair-like structures that arise from the cell walls of the bacteria. Pili are mostly present in gram-negative bacteria and help them adhere to a surface like other prokaryotic cells or tissue membranes like the urethral lining in humans. Hence, option (d) is the correct answer.

Explanation for incorrect answer:

Option (a) is sex pili. The sex pili are extended for conjugation, in which the one bacterium exchanges genetic material with another, under adverse conditions. Sex pili do not help in adherence to the host tissues. So, it is an incorrect option.

Option (b) is flagella. Flagella are hair-like extensions that help in the locomotion of a microbe. The flagella move with the help of motor proteins, allowing the bacteria to move from one location to another. So, it is an incorrect option.

Option (c) is capsule. The capsule is a diffused glycocalyx present in the gram-negative bacteria. It protects the bacteria from antibiotic effects. The peptidoglycan of cell-wall protects the bacteria from adverse environments. So, it is an incorrect option.

Conclusion

Therefore, it can be concluded that the bacterial cells that are present in the urethra are gram-negative as their surface is covered with pili that help them adhere to the urethral walls.