Question

Following features belong to A. Complete lacking of cell wall B. Anaerobic C. Smallest living cell D. Many of them are pathogenic to plant and animals (a) Chrysophytes (b) Prions (c) Viroids (d) Mycoplasma

Short answer

The option that fits all the features A, B, C and D is Mycoplasma.

Step-by-step solution

Analyze the options

Each of the options need to be analyzed based on the provided features. In general, Chrysophytes have cell walls, live in aquatic environments, and are not typically pathogenic, thus they do not fit the given features. Prions are protein particles, so they are not cells and do not possess a cell wall, but they are pathogenic - however, they cannot be the correct answer as they are not the smallest living cells. Viroids are infectious plant pathogens comprising a short stretch of highly complementary, circular, single-stranded RNA - thus, they might not match the descriptions accurately either.

Determine the Correct Option

Mycoplasma is a genus of bacteria that lack a cell wall (Feature A). They can live in both anaerobic and aerobic conditions so we can consider them as anaerobic (Feature B). Amongst all living cells, they are the smallest (Feature C), and they are pathogenic to plants and animals (Feature D). This makes Mycoplasma match all the given features appropriately.

Conclusion

Judging by the presented features, the correct answer is Mycoplasma, since this is the only option that fits all the given characteristics.

Key concepts

Smallest Living Cell

Mycoplasma is renowned for being the smallest living cell. Unlike typical bacterial cells that possess a rigid cell wall, Mycoplasmas are devoid of one and thus exhibit a more flexible and tiny structure.
This unique feature allows them to pass through filters that normally trap bacteria, showcasing their minute size. Their cell size ranges from 150-300 nanometers, which is significantly smaller than other bacteria.

Due to their small size, they have limited genetic material and rely heavily on their host for essential nutrients. This dependency on a host contributes to their parasitic lifestyle. By understanding their minimalistic cell structure, scientists have gained insights into the basic components necessary for life.

Pathogenic Organisms

Mycoplasmas are notorious for their role as pathogenic organisms. They cause numerous diseases in humans, animals, and plants.
A well-known example of a human disease caused by Mycoplasma is Mycoplasma pneumoniae, which leads to respiratory infections.

Key characteristics of pathogenic Mycoplasma include:

• Adherence: They attach firmly to the host's cells to initiate infection.
• Immune Evasion: Due to the lack of a cell wall, they can easily evade typical immune responses.
• Host Dependence: Dependence on hosts provides them with essential nutrients.

In animals, Mycoplasma is responsible for mastitis in cows and arthritis in pigs. In plants, they can cause diseases like aster yellows. This versatility in affecting different hosts highlights their adaptive pathogenic nature.

Cell Wall Structure

One of the defining traits of Mycoplasmas is their lack of a typical cell wall. In other bacteria, the cell wall provides shape, support, and protection.
Without this structure, Mycoplasmas exhibit a more pliable and variable shape, referred to as pleomorphism.

Key impacts of lacking a cell wall include:

• Resistance to antibiotics that target cell wall synthesis, like penicillin.
• An increased ability to attach to and invade host tissues, leading to infection.
• Enhanced mobility through narrow spaces in the host organism.

Due to these features, treating infections caused by Mycoplasmas requires antibiotics that affect other cellular targets, such as protein synthesis inhibitors.

Anaerobic Bacteria

Mycoplasma can thrive in both anaerobic and aerobic environments, making them adaptable to different living conditions.

In anaerobic settings, Mycoplasmas survive without oxygen, although they can also utilize oxygen when it's available, demonstrating their flexible metabolic pathways.
This adaptability enables Mycoplasmas to colonize diverse environments within the host, from surface tissues to internal organs.

The ability to function under anaerobic conditions is essential in areas of the host where oxygen might be limited, such as deep within tissues. Understanding these traits can help in devising strategic treatments and predicting infection sites.