How does streptococci tolerate 02?

Streptococci are facultative anaerobes, meaning they can grow in both the presence and absence of oxygen. They tolerate oxygen by using fermentation pathways to generate energy, producing lactic acid as a byproduct. Additionally, some species possess enzymes like superoxide dismutase and catalase, which help mitigate oxidative stress by neutralizing harmful reactive oxygen species. This allows them to survive and thrive in environments with fluctuating oxygen levels.