microaerotolerant

Edge evidence

• limited oxygen exposure tolerated by microaerotolerant

  Microaerotolerant organisms survive limited oxygen exposure.

  • DOI:10.1016/j.biortech.2011.02.011 microaerotolerant or aerotolerant anaerobes can survive Supports low-oxygen survival as the defining trait context.
• microaerotolerant does not require limited oxygen exposure

  Microaerotolerance differs from microaerophily because oxygen is tolerated rather than required.

  • DOI:10.1038/nrmicro2970 Many obligate anaerobes tolerate transient or low levels of O2 Supports low oxygen tolerance without implying oxygen requirement.
• limited oxygen exposure can generate reactive oxygen species

  Oxygen exposure can create ROS stress that tolerant organisms must manage.

  • DOI:10.1038/s41579-021-00583-y molecular oxygen and ROS Review links oxygen exposure with ROS stress.
• oxidative stress defense enzymes mitigates reactive oxygen species METPO:2007407

  ROS detoxification enzymes contribute to oxygen tolerance.

  • DOI:10.1128/iai.16.1.20-25.1977 oxygen tolerance of anaerobes is usually related to their level of SOD Supports antioxidant defense as a mechanism for oxygen tolerance.
• microaerotolerant compatible with anaerobic growth

  Microaerotolerant organisms can remain anaerobic while surviving limited oxygen exposure.

  • DOI:10.1016/j.biortech.2011.02.011 microaerotolerant or aerotolerant anaerobes Supports microaerotolerance as an anaerobe oxygen-tolerance subtype.
• intermediate oxygen level maximizes growth of microaerotolerant

  Maximal growth of microaerotolerant cells often occurs at intermediate oxygen levels.

  • DOI:10.1128/CMR.00110-14 Growth occurs in the presence or absence of oxygen; however, maximal growth occurs at intermediate oxygen levels.
• superoxide reductase reduces superoxide METPO:2000017

  Superoxide reductase reduces superoxide (to hydrogen peroxide) using reduced electron donors.

  • DOI:10.1128/IAI.00502-24 Review notes SOR reduces superoxide using electrons from donors like NADH.
• superoxide reductase produces hydrogen peroxide METPO:2000202

  Reduction of superoxide by SOR yields hydrogen peroxide.

  • DOI:10.1128/IAI.00502-24 SOR reduces superoxide to H2O2 as part of the anaerobe oxygen-defense backbone.
• rubrerythrin/peroxidase reduces hydrogen peroxide METPO:2000017

  Rubrerythrin/peroxidases reduce hydrogen peroxide to water.

  • DOI:10.1128/IAI.00502-24 Review states Rbr/peroxidases reduce H2O2 to water.
• reduced electron donors (NADH) enables function of oxidative stress defense enzymes

  Protection by SOR/Rbr defenses depends on available reduced electron donors.

  • DOI:10.1128/IAI.00502-24 The protection conferred by SOR/Rbr depends on available reduced electron donors.
• gut lumen oxygen gradient creates selection for low-oxygen defense systems

  Host gut oxygen gradients expose anaerobes to low O2, selecting for low-O2 defense systems.

  • DOI:10.1128/IAI.00502-24 Gut O2 gradients (colon lumen 0.1-0.4% to ~5% in tissues) expose anaerobes to low O2 during colonization/inflammation.