Modulation by copper of the products of nitrite respiration in Pseudomonas perfectomarinus

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Abstract
A synthetic growth medium was purified with the chelator 1,5-diphenylthiocarbazone to study the effects of Cu on partial reactions and product formation of nitrite respiration in P. perfectomarinus. This organism grew anaerobically in a Cu-deficient medium with nitrate or nitrite as the terminal electron acceptor. Cu-deficient cells had high activity for reduction of nitrate, nitrite and NO, but little activity for N2O reduction. High rates of N2O reduction were observed only in cells grown on a Cu-sufficient (1 .mu.M) medium. Cu-deficient cells converted nitrate or nitrite initially to N2O instead of N2, the normal end product of nitrite respiration in this organism. In agreement with this was the finding that anaerobic growth of P. perfectomarinus with N2O as the terminal electron acceptor required Cu. This requirement was not satisfied by substitution of Mo, Zn, Ni, Co or Mn for Cu. Reconstitution of N2O reduction in Cu-deficient cells was rapid on addition of a small amount of Cu, even though protein synthesis was inhibited. Cu protein(s) are apparently involved in the last step of nitrite respiration in P. perfectomarinus. NO, a presumed intermediate of nitrite respiration, inhibited N2O reduction.