title: Effects of myxothiazol and 5-undecyl-6-hydroxy-4,7-dioxobenzothiazole on the respiratory pathways of the phytopathogenic fluorescent bacteria Pseudomonas cichorii and Pseudomonas aptata.
abstract: Myxothiazol inhibited the electron transport in the cytochrome b/c segment of membrane particles from Pseudomonas cichorii. A residual NADH-oxidation due to the presence of an alternative pathway via cytochrome o (Em, 7 = +250 mV) was sensitive to the quinone analog 5-undecyl-6-hydroxy-4,7-dioxobenzothiazole (UHDBT). This latter inhibitor was equally effective in blocking the linear respiratory chain of Pseudomonas aptata, a strain deficient in cytochromes of c type and Rieske iron-sulphur centre. The analysis of the oxido-reduction kinetic patterns of cytochromes indicated that, among the b type haems present in P. aptata, only cyt. o could be reduced by ubiquinol-1 in a reaction insensitive to both antimycin A and myxothiazol but inhibited by UHDBT. This latter finding has been correlated to the fact that P. aptata exhibits a defective b/c complex. In membranes from P. cichorii, in which the absorption maximum of dithionite reduced cytochrome(s) b shifted by 2-3 nm in the presence of antimycin A and/or myxothiazol, the electron flow through the b/c oxidoreductase complex has tentatively been arranged in a proton motive "Q-cycle" like mechanism.
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology*; D005453:Fluorescence; D007700:Kinetics; D008689:Methacrylates; D010101:Oxygen Consumption / Q000187:drug effects*; D011549:Pseudomonas / Q000187:drug effects / Q000378:metabolism*; D013045:Species Specificity; D013844:Thiazoles / Q000494:pharmacology*
chemical_list: C025993:5-n-undecyl-6-hydroxy-4,7-dioxobenzothiazole; D000935:Antifungal Agents; D008689:Methacrylates; D013844:Thiazoles; C030517:myxothiazol