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Acinetobacter calcoaceticus BD413 was examined for production of siderophores and iron-repressible outer membrane proteins following growth in iron-restricted media. The iron-scavenging phenotype was associated with the secretion of iron-repressible catechol and the induction of a group of six outer membrane proteins with molecular weights ranging from 34 to 85 kDa. The amount of catechol produced was dependent on medium composition and iron stringency. The relation between iron limitation and lipase production was studied at the level of lipA transcription and extracellular lipase activity. In minimal medium, iron limitation slightly affected lipA expression but decreased exo-lipase activity significantly. However, if iron limitation and rich nitrogen sources were simultaneously present in the culture media, the production of lipase was increased approximately 4 times.

Mg2+ level affected growth, xylitol and ethanol production by P. stipitis grown under microaerophilic conditions. Low Mg2+ level (1 mM) directed the C flux from ethanol to xylitol, with no effect on xylose consumption rate. The addition of pyrazole, an alcohol dehydrogenase (ADH) inhibitor, had the same effect, even in conditions of Mg2+ excess (4 mM), indicating a negative interaction between ADH and Mg2+ ions (p << 0.01). Cells grown either with pyrazole or Mg limitation increased their intracellular NADH concentration about 3 times, but displayed no significant differences in ADH specific activities (1,000 U/mg protein, +/- 10%). In contrast, no interaction was measured between Mg and antimycin A, excluding the possibility that Mg2+ limitation interferes with respiration.