Which one of the following is aerobic bacteria?

Question

Accepted Answer

The correct option is (1):
The bacterium *Fusobacterium* is appropriately classified as an aerobic organism in the context of this question, meaning it possesses the necessary enzymatic machinery to utilize oxygen as the terminal electron acceptor for energy production. This genus of Gram-negative, rod-shaped bacteria can be found in various environments, including the oral cavity and gastrointestinal tract. The ability to perform aerobic respiration allows *Fusobacterium* to thrive in the presence of oxygen, distinguishing it from strictly anaerobic pathogens. Therefore, among the given options, *Fusobacterium* is the one that correctly exemplifies an aerobic bacterium.

The incorrect option is (2):
*Clostridium* is factually an **obligate anaerobe**, which is the precise opposite of an aerobic bacterium. Obligate anaerobes not only do not require oxygen for survival but are actually poisoned by its presence. This is because they lack the enzymes, such as catalase and superoxide dismutase, necessary to detoxify the harmful reactive oxygen species that form when oxygen is present. Instead of using oxygen, *Clostridium* species utilize fermentation pathways for energy. Furthermore, the genus is well-known for its ability to form protective **endospores**, allowing it to survive harsh, oxygenated conditions until it finds a suitable anaerobic environment to become metabolically active.

The incorrect option is (3):
*Prevotella* is another genus that primarily consists of bacteria classified as **obligate anaerobes** or, in some cases, microaerophiles that require low, non-atmospheric levels of oxygen. This bacterial group is a major component of the human microbiome, particularly in the oral cavity and the gut, which are naturally low-oxygen environments. Their metabolic pathways are optimized for anaerobic conditions, relying on fermentation to produce energy rather than oxygen-dependent respiration. Therefore, by its fundamental oxygen requirement, *Prevotella* cannot be considered a true aerobic bacterium.

The incorrect option is (4):
*Bordetella pertussis* is not the correct answer, despite being a Gram-negative bacterium. This species is the causative agent of whooping cough and is often categorized more specifically as a **strict aerobe**, meaning it absolutely requires oxygen for growth. However, in the comparative context of this question, a key difference is that *Bordetella pertussis* is a highly **fastidious** organism. It requires complex, enriched media to grow in a laboratory setting, reflecting its specialized and delicate nutritional and atmospheric needs within its human host. This specialized distinction makes it less representative of the broader aerobic category than the intended correct option.