Regulation of iron transport related genes by boron in the marine bacterium Marinobacter algicolaDG893

While there has been extensive interest in the use of boron isotope ratios as a surrogate of pH in paleoclimate studies in the context of climate change-related questions, the high (0.4 mM) concentration and the depth-independent (conservative or non-nutrient-like) concentration profile of this element have led to boron being neglected as a potentially biologically relevant element in the modern ocean. Here we report that boron affects the expression of a number of protein and genes in the "algal-associated" Gram-negative marine bacterium Marinobacter algicolaDG893. Most intriguingly, a number of these proteins and genes are related to iron uptake. In a recent separate publication we have shown that boron regulates one such iron transport related protein, i.e.the periplasmic iron binding protein FbpA viaa direct interaction of the metalloid with this protein. Here we show that a number of other iron uptake related genes are also affected by boron but in the opposite way i.e.they are up-regulated. We propose that the differential effect of boron on FbpA expression relative to other iron transport related genes is a result of an interaction between boron and the global iron regulatory protein Fur.