[Respiratory resistance of methylotrophic bacteria to formate and cyanide]

Whole cells and cell-free preparations of the methylotrophic bacteria, Pseudomonas sp. AM 1 and Achromobacter parvulus, can oxidize formate at tis concentration in the reaction medium up to 1 M. The respiration of whole cells is registered at a concentration of formate greater than 10(-2) M, while that of cell-free extracts at a formate concentration greater than 5 X 10(-5) M. This seems to be due to the presence of a permeability barrier in cells for formate. The oxidation of reduced TMPD and exogenous cytochrome c by the membrane preparations of the two bacteria is inhibited by formate and cyanide; Ki50% = 2.5 X 10(-2) and 10(-6) M, respectively. The oxidation of NADH by the membrane preparations of the bacteria is not inhibited by 1 M formate and 5 X 10(-4) M cyanide but is inhibited by formaldehyde with Ki50% = 3 X 10(-2) M. Formaldehyde has no effect on the oxidation of reduced TMPD and cytochrome c at concentrations greater than 2 X 10(-1) M. These data indicate that respiration of the studied methylotrophic bacteria in the presence of high formate concentrations should be attributed in the presence of a branched electron transport chain in them; one branch of the chain is resistant to formate and cyanide, but is sensitive to formaldehyde.