ELECTRON TRANSPORT-DEPENDENT TAXIS IN RHODOBACTER-SPHAEROIDES

Rhodobacter sphaeroides showed chemotaxis to the terminal electron acc epters oxygen and dimethyl sulfoxide, and the responses to these effec ters were shown to be influenced by the relative activities df the dif ferent electron transport pathways. R. sphaeroides cells tethered by t heir flagella showed a step-down response tea decrease in the oxygen o r dimethyl sulfoxide concentration when using them as terminal accepte rs. Bacteria using photosynthetic electron transport, however, showed a step down response to oxygen. addition, Addition of the proton ionop hore carbonyl cyanide 4-trifluoromethoxyphenylhydrazone did not cause a transient behavioral response, although it decreased the electrochem ical proton gradient (Delta p) and increased the rate of electron tran sport, However, removal of the ionophore, which caused an increase in Delta p and a decrease in the electron transport rate, resulted in a s tep-down response. Together, these data suggest that behavioral respon ses of R. sphaeroides to electron transport effecters are caused by ch anges in the rate of electron transport rather than changes in Delta p .