Responses of Clostridia to oxygen: from detoxification to adaptive strategies

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Morvan, Claire | Folgosa, Filipe | Kint, Nicolas | Teixeira, Miguel | Martin-Verstraete, Isabelle

Edité par CCSD ; Society for Applied Microbiology and Wiley-Blackwell -

International audience. Clostridia comprise bacteria of environmental, biotechnological and medical interest and many commensals of the gut microbiota. Because of their strictly anaerobic lifestyle, oxygen is a major stress for Clostridia. However, recent data showed that these bacteria can cope with O 2 better than expected for obligate anaerobes through their ability to scavenge, detoxify and consume O 2 . Upon O 2 exposure, Clostridia redirect their central metabolism onto pathways less O 2 ‐sensitive and induce the expression of genes encoding enzymes involved in O 2 ‐reduction and in the repair of oxidized damaged molecules. While Faecalibacterium prausnitzii efficiently consumes O 2 through a specific extracellular electron shuttling system requiring riboflavin, enzymes such as rubrerythrins and flavodiiron proteins with NAD(P)H‐dependent O 2 ‐ and/or H 2 O 2 ‐reductase activities are usually encoded in other Clostridia. These two classes of enzymes play indeed a pivotal role in O 2 tolerance in Clostridioides difficile and Clostridium acetobutylicum . Two main signalling pathways triggering O 2 ‐induced responses have been described so far in Clostridia. PerR acts as a key regulator of the O 2 ‐ and/or reactive oxygen species–defence machinery while in C . difficile , σ B , the sigma factor of the general stress response also plays a crucial role in O 2 tolerance by controlling the expression of genes involved in O 2 scavenging and repair systems.

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