Topics covered in this volume: 1. Metal ion transport in eukaryotic microorganisms: insights from Saccharomyces cerevisiae 2. Iron uptake by fungi: contrasted mechanisms with internal or external reduction 3. Dynamics of metabolism and its interactions with gene expression during sporulation in Saccharomyces cerevisiae 4. Carbon and nitrogen metabolism in rhizobium 5. Redundancy of aerobic respiratory chains in bacteria? Routes, reasons and regulations