The tetrathionate effector pathway enables facultative anaerobic bacteria to use tetrathionate (S₄O₆²⁻) as a terminal electron acceptor during anaerobic respiration, particularly in the gut or other low-oxygen environments where alternative electron acceptors are available. This pathway is regulated by the TtrSR two-component system, with TtrR functioning as the response regulator. Upon sensing tetrathionate through the sensor kinase TtrS, TtrR becomes phosphorylated and activates transcription of the ttr operon, which encodes the tetrathionate reductase complex. Key genes in the TtrR regulog include: ttrA – Encodes the catalytic molybdopterin-containing subunit of the tetrathionate reductase, responsible for the reduction of tetrathionate to thiosulfate. ttrB – Encodes the iron-sulfur cluster subunit, which facilitates electron transfer within the reductase complex. ttrC – Encodes the membrane anchor subunit, which likely helps stabilize the complex and supports electron transfer from the quinone pool.

Tetrathionate References