An example of a bacteria requiring low concentration of oxygen is?

Explanation

Option D: Campylobacter is the correct answer as it is a microaerophilic bacterium, requiring low levels of oxygen to survive and grow. This characteristic distinguishes it from the other options. Option A: Spirochetes can survive in a range of oxygen levels and are not exclusively microaerophilic. Option B: E. coli is a facultative anaerobe, adaptable to both oxygen-rich and oxygen-poor environments. Option C: Pseudomonas are versatile in their oxygen requirements and are not limited to low-oxygen conditions.