John M. Turner

Occurrence, biochemistry and physiology of phenazine pigment production.

Publisher Summary This chapter describes the structural features, nomenclature, origin, metabolism, and some properties of phenazines. Naturally occurring phenazines are pigments formed exclusively by bacteria. The absorption spectra of phenazines are characteristic, with an intense peak in the range 250 to 290 nm and a weaker peak at 350 to 400 nm. Unlike the various carotenoid and other pigments that color many bacteria, the phenazine pigments are mostly water soluble and are excreted into the medium. The chapter discusses the biosynthetic origins of phenazine compounds followed by the metabolism of phenazines. The immediate precursors of the long-known products—namely, pyocyanine, chlororaphine and iodinin, attracted early attention. In addition, phenazines, along with most other secondary metabolites, are of uncertain physiological significance. There is little information on the physiological factors that regulate the initiation of phenazine biosynthesis and cause its cessation. Although many phenazines participate in redox reactions, there is no generally accepted evidence that any phenazine functions physiologically in a respiratory chain.

Interrelationships Between the Enzymes of Ethanolamine Metabolism in Escherichia coli

The activities of the enzymes ethanolamine ammonia-lyase, CoA-dependent and CoA-independent aldehyde dehydrogenases, and isocitrate lyase were assayed in Escherichia coli which had been grown on various sources of carbon and nitrogen. Induction of ethanolamine ammonia-lyase and of maximal levels of both aldehyde dehydrogenases required the concerted effects of ethanolamine and vitamin (or coenzyme) B12. Molecular exclusion chromatography revealed that, in the absence of one or both co-inducers, two repressible isoenzymes of CoA-dependent aldehyde dehydrogenase (mol. wts 900000 and 120000) were produced, these being replaced by two inducible isoenzymes (mol. wts 520000 and 370000) in the presence of both co-inducers. A similar inducible repressible series of isoenzymes was also observed for CoA-independent aldehyde dehydrogenase. No evidence was found for structural relationships between ethanolamine ammonia-lyase, CoA-dependent aldehyde dehydrogenase and CoA-independent aldehyde dehydrogenase, but mutant and physiological studies demonstrated that the induction of the first two enzymes is under common control. Evidence is presented for the operation of a previously unreported pathway of ethanolamine metabolism in E. coli.

Effect of Growth Conditions on Phenazine Production by Pseudomonas phenazinium

SUMMARY: Phenazine production by Pseudomonas phenazinium was not reduced by high concentrations of phosphate during batch culture (cf. Pseudomonas aeruginosa) but was inhibited by high concentrations of (NH4)2SO4 (1 to 10 g 1-1). In carbon-, sulphate-, magnesium- and potassium-depleted medium phenazine production paralleled growth. In continuous culture, phenazine production occurred over a wide range of growth rates under various nutrient-limiting conditions. At low growth rates cell resources were conserved and cell mass was maintained at the expense of secondary metabolite production. Low oxygen tensions and the addition of phenylalanine (0.1 g 1-1) each inhibited phenazine production.