Question

A distinctive feature of spirochetes is the presence of: A. fimbriae. B. endoflagella. C. helically arranged pili. D. nucleosomes. E. variable surface antigens.

Short answer

The distinctive feature of spirochetes is B. endoflagella.

Step-by-step solution

Understand the Question

The question is asking to find out a special structural feature of spirochetes which distinguishes them from other bacteria. These features could include any structural elements or molecular arrangements. Therefore, it requires knowledge in microbiology, particularly about the bacterial families and their special features.

Understanding Spirochetes

Spirochetes are a phylum of distinctive gram-negative bacteria, which have long, spiral-shaped structures. By far, the most significant feature of spirochetes is the presence of endoflagella (also called axial filaments), which are located in the periplasmic space, between the outer membrane and the cell wall. Endoflagella give spirochetes their unique motility.

Analyzing Other Options

Let's look at the other options: A. Fimbriae - these are bristle-like fibers on the surface of bacteria, not unique to spirochetes. C. Helically arranged pili - this option may seem similar to endoflagella but pili are not exactly the same. D. Nucleosomes - these are in eukaryotes, not bacteria. E. Variable surface antigens - while spirochetes like Borrelia do change surface antigens, this is not a distinctive feature of spirochetes only.

Key concepts

Endoflagella

Spirochetes possess a unique form of locomotion, thanks to the presence of endoflagella. Unlike typical bacterial flagella that protrude externally, endoflagella are found within the outer membrane of spirochetes.
They are also known as axial filaments. These structures run longitudinally along the spirochete body, allowing the bacterium to move in a corkscrew-motion through its environment.

• Endoflagella are nestled in the periplasmic space, located between the outer membrane and the cell wall.
• This unique arrangement provides spirochetes with their distinctive spiral shape.

This internal flagella setup grants them incredible motility, allowing them to efficiently penetrate viscous environments such as mucus or dense tissue.
This characteristic is particularly significant for pathogenic spirochetes, aiding in their ability to invade host tissues.

Gram-negative bacteria

Spirochetes belong to the class of gram-negative bacteria. This classification is based on their cell wall structure, which is composed of a thin layer of peptidoglycan situated between two membranes.
This double-layer arrangement contributes to several notable traits:

• Their structural integrity, allowing them to withstand environmental pressures.
• An outer membrane that contains lipopolysaccharides, contributing to their pathogenicity in certain varieties by evoking strong immune responses from hosts.

One of the features of gram-negative bacteria, which includes spirochetes, is their resistance to certain antibiotics that target the peptidoglycan layer.
Understanding this classification helps in appreciating the complexity and adaptive nature of spirochetes in diverse environments.

Bacterial motility

One of the most fascinating aspects of bacterial life is their ability to move. Spirochetes exhibit a distinctive form of motility that is different from many other bacteria. This is predominantly due to their endoflagella.
The spiral motion afforded by the endoflagella allows for:

• Effective navigation through viscous substances, such as mucus or host connective tissues.
• Enhanced capability to locate nutrients or evade hostile environments.

This corkscrew movement is highly efficient and sets spirochetes apart, enabling them to cover distances swiftly, promoting their survival and proliferation in their respective niches.
Understanding their mechanism of motility is crucial for grasping how they interact with their environments and host organisms, aiding both in pathogenesis and survival.

Bacterial structure

The structural complexity of spirochetes is remarkable, as they display a unique anatomical configuration that supports their motility and survival. Similar to other bacteria, spirochetes possess a cell wall and membranes, but with some distinct differences.
Key features include:

• A flexible, helically-shaped cell body owing to their unique morphological setup.
• Inner and outer membranes with a periplasmic space where endoflagella reside, contribute to the bacterial structure.

These characteristics not only ensure structural integrity but also play a vital role in their motility and interaction with environments.
Additionally, the presence of specific proteins and sugars on their surfaces aids in protection and interactions with hosts, often dictating their roles in bacterial pathogenesis.

Axial filaments

Axial filaments, synonymous with endoflagella in spirochetes, play a key role in their unique spiral motion. Unlike surface flagella found on many bacteria, axial filaments are embedded within the periplasmic space of spirochetes. This unique arrangement facilitates their corkscrew motion, enabling them to `swim` through viscous environments with ease.
Some important points about axial filaments:

• The rotation of these filaments results in the whole-cell twisting, propelling it forward.
• This mechanism reduces friction and enhances mobility in dense matrices where other bacteria might struggle.

This efficient movement is not just about mobility; it aids in the pathogenic success of certain spirochetes by enabling them to penetrate host tissues effectively.
Thus, axial filaments are integral both to the lifestyle and the pathogenic potential of spirochetes, playing a pivotal role in their biology.