Effects of iron limitation on growth and carbon metabolism in oceanic and coastal heterotrophic bacteria

We investigated the metabolic response to iron (Fe) limitation of two bacterial strains of Alteromonas macleodii, isolated from a coastal and an oceanic marine environment. Bacteria were grown under Fe-limited and Fe-replete conditions, and comparative analyses of cellular properties and total proteomes were conducted. Respiration was reduced by a factor of two in both strains, but the growth rate of the oceanic strain was less affected by Fe limitation (reduced by 1.2-fold) than the coastal strain (reduced by 2-fold). Fe limitation led to significant changes in the expression of several key enzymes associated with carbon catabolism, specifically those involved in the citric acid cycle, glycolysis, and oxidative phosphorylation. The strain-specific overall responses to Fe limitation were in part reflected in different metabolic strategies of the carbon metabolism and energy acquisition. Our study provides novel insights on how Fe limitation can affect bacterial heterotrophic metabolism, and how this could influence the coupling of the Fe and carbon cycles in the ocean.