**Core Concept**
Anaerobic bacteria are microorganisms that cannot survive in the presence of oxygen. They thrive in environments with low or no oxygen levels, such as deep within the gut, soil, or decaying matter. Anaerobes have unique metabolic pathways and enzyme systems that allow them to function in the absence of oxygen.

**Why the Correct Answer is Right**
Anaerobic bacteria, such as Clostridium species (e.g., C. difficile), Bacteroides species, and Fusobacterium species, lack the enzymes necessary for oxidative phosphorylation and electron transport. Instead, they rely on fermentation to generate energy, producing compounds like lactic acid, ethanol, and carbon dioxide as byproducts. This anaerobic metabolism is essential for their survival in low-oxygen environments.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because there are many types of bacteria that can survive in the presence of oxygen, including aerobic bacteria like Staphylococcus aureus and Escherichia coli.
**Option B:** This option is incorrect because while some bacteria may be facultative anaerobes, meaning they can grow with or without oxygen, they are not completely unable to survive in the absence of oxygen.
**Option C:** This option is incorrect because while some bacteria may be microaerophilic, meaning they require a low oxygen environment to grow, they are not necessarily unable to survive in the absence of oxygen.

**Clinical Pearl / High-Yield Fact**
Anaerobic infections often present with gas production, tissue necrosis, and a foul odor, making them distinct from aerobic infections. Recognizing the clinical features of anaerobic infections is crucial for accurate diagnosis and treatment.

**Correct Answer: C. Fusobacterium species.