When anaerobes encounter oxygen: mechanisms of oxygen toxicity, tolerance and defence

In this Review, we explore the molecular mechanisms by which oxygen impairs anaerobes and the degree to which bacteria protect their metabolic pathways from it

Zheng Lu; James A. Imlay

2021

Scholarcy highlights

  • The defining trait of obligate anaerobes is that oxygen blocks their growth, yet the underlying mechanisms are unclear
  • A popular hypothesis was that these microorganisms failed to evolve defences to protect themselves from reactive oxygen species such as superoxide and hydrogen peroxide, and that this failure is what prevents their expansion to oxic habitats
  • The hypoxic environments in which these organisms dwell — including the mammalian gut, sulfur vents and deep sediments — experience episodic oxygenation. In this Review, we explore the molecular mechanisms by which oxygen impairs anaerobes and the degree to which bacteria protect their metabolic pathways from it
  • The emergent view of anaerobiosis is that optimal strategies of anaerobic metabolism depend upon radical chemistry and low-potential metal centres
  • Such catalytic sites are intrinsically vulnerable to direct poisoning by molecular oxygen and ROS
  • Observations suggest that anaerobes have evolved tactics that either minimize the extent to which oxygen disrupts their metabolism or restore function shortly after the stress has dissipated

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