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SUMMARYThe particulate fraction of disrupted Chromobacterium violaceum grown under cyanide-evolving conditions was unable to oxidize ascorbate plus N, N, ","-tetramethyl-p-phenylenediamine (TMPD), but oxidized NADH and succinate by a linear respiratory pathway which was very resistant to inhibition by cyanide. When the bacteria were grown under conditions where little cyanide evolution occurred, particulate fractions developed the ability to oxidize ascorbate-TMPD by a pathway highly sensitive to cyanide inhibition; respiratory activity with NADH and succinate proceeded via both the cyanide-sensitive and -resistant pathways. Studies with respiratory inhibitors, and the cytochrome compositions of the fractions derived from cultures grown under both conditions, are presented. A soluble, carbon monoxide-binding cytochrome c was found, and this appears similar to those found recently in Beneckea natriegens, methylotrophic bacteria and the marine pseudomonad B16.

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S U M M A R YAMP is catabolized by cell-free extracts of Benecked natriegens to inosine via adenosine by AMP nucleotidase and adenosine deaminase. In the presence of ATP, the AMP nucleotidase is inhibited and an AMP deaminase is activated, resulting in formation of IMP. When low concentrations of ATP are used, the IMP is converted, simultaneously with ATP consumption, to inosine by IMP nucleotidase, which is presumably ATP-sensitive. Since 5'-nucleotidases from various organisms are known to catabolize several ribonucleoside monophosphates, the AMP and IMP nucleotidase activities of B. natriegens may be due to the same enzyme. CTP, GTP and UTP inhibit AMP nucleotidase from B. natriegens without stimulating AMP deaminase, thus severely decreasing the rate of AMP breakdown.