Bacteria metal assimilation

The importance of metal assimilation for bacteria is perhaps best illustrated by the correlation between the efficacy of iron uptake systems and virulence in many strains of pathogenic... 

Since in mammalian species metals first need to be assimilated from dietary sources in the intestinal tract and subsequently transported to the cells of the different organs of the body through the bloodstream, we will restrict ourselves in this section to the transport of metal ions across the enterocytes of the upper part of the small intestine (essentially the duodenum), where essentially all of the uptake of dietary constituents, whether they be metal ions, carbohydrates, fats, amino acids, vitamins, etc., takes place. We will then briefly review the mechanisms by which metal ions are transported across the plasma membrane of mammalian cells and enter the cytoplasm, as we did for bacteria, fungi and plants. The specific molecules involved in extracellular metal ion transport in the circulation will be dealt with in Chapter 8. 

As in Chapter 7, we successively consider the transport, storage and metal ion homeostasis in prokaryotes, plants and animals. Since the assimilation of metals in unicellular bacteria does not require their transport to other cell types, we confine our discussion only to storage and homeostasis. 

We therefore discuss in succession the assimilation of metal ions by bacteria, by plants, and fungi, and finally by mammals, with a particular focus on man. In most cases, we consider systems involved in iron uptake and then those involving copper and zinc. This is based on the simple logic that these are the three metals for which the assimilation systems are the best characterized. We begin with a brief outline of inorganic biogeochemistry and then discuss a few other metals where sufficient information is available. The specific cases of Na" ", K, and will be dealt with in Chapters 9 and 11. We remind the reader that uptake systems for the essential metalloids B and Si and their toxic homologues As and Sn were already discussed in Chapter 1. 

Isotopic compositions of Mo and Fe measured by MC-ICP-MS indicate that during assimilation of Mo and Fe via nitrogen fixation by Azotobacter vindandii, the lighter isotope of Mo ( Mo versus Mo) is preferentially assimilated by the bacteria with a fractionation factor between assimilated and dissolved Mo of0.9997 [2]. In contrast, the heavier isotope of Fe ( Fe versus Fe) was removed from solution by the bacteria with a fractionation factor of 1.0011. Fractionation of Mo isotopes results from kinetic effects involving metal-binding ligands, whereas Fe... 

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