Bacteria, iron metabolism

This overview illustrates that in bacteria, the two protein families Fur and DtxR are the main regulators of iron metabolism and transport. Both repressors are also... 

Figure 18.4 Effects of cytokines on fate of iron during an infection. Transferrin is the form in which iron is transported in the blood (Chapter 15). Cytokines increase the number of ferritin receptors in proliferating lymphocytes, to facilitate the uptake of iron by lymphocytes. They also stimulate synthesis of apofer-ritin in the liver, which removes iron from the blood to reduce that available for bacteria. (See Chapter 15 for discussion of iron metabolism)...

Ferrihydrite is the iron oxide with the most widespread distribution in living organisms. In the form of ferritin, an iron storage protein, it is found in all organisms from bacteria through to man (in heart, spleen and liver). It occurs in plants as phytoferritin (review by Seckback, 1982). Ferritin plays a key role in iron metabolism it maintains... 

The CleanOX process is limited in saturated matrices possessing very low permeabilities and high calcium carbonate levels, as well as in groundwater with high total organic carbon content. In addition, the presence of iron-metabolizing bacteria can reduce the effectiveness of the iron catalyst, resulting in operations and maintenance problems for the system. 

Ratledge C, Dover LG. Iron metabolism in pathogenic bacteria. 

One striking similarity between iron metabolism in animals and bacteria is that both contain ferritin (63). Bacterial ferritin, or bacfer, resembles ferritin in a number of respects (Section IV), but a key difference is that bacfer is also a 6-type cytochrome (129), cytochrome bi (126). Thus the question arises Is it primarily a cytochrome or primarily an iron storage protein This question opens up a large number of avenues of research, some of which are described in Section IV, that we believe will help define further how animal ferritin functions. One important area is that of genetic control of bacfer expression. 

Lundgren, D.G., Vestal, J.R. and Tabita, F.R., 1974. The iron-oxidizing bacteria. In J.B. Neilands (Editor), Microbial Iron Metabolism, Academic, New York, NY, Ch. 18,... 

We might turn an argument around to substantiate the hypothesis that, especially in acute oral intoxications, the animals do not die from the toxin but from secondary effects to the GIT It has been documented in at least three major attempts, that cytotoxicity correlates pretty well with acute oral toxicity (see Halle register, MEIC study and the more recent ICCVAM/NICEATM/ECVAM validation study). Actually, this makes little sense if we assume that the substances are taken up, distributed and metabolized with complex kinetics and can affect more than 400 different tissues with various sensitivities. Might it be that the animal experiment simply measures cytotoxicity to the GIT epithelium, which results in translocation of bacteria Ironically, this would mean that we can pretty well predict this animal test in vitro, because the animal test measures a phenomenon (cytotoxicity to the intestine) that is irrelevant for humans (we would vomit—which rodents cannot do—or remove the intoxication before it reaches the intestine, supply intensive care treatment, etc.). Instead of our 9 million effort of A-Cute-Tox (http //www.acutetox.org/), a well-designed series of animal experiments might demonstrate that the reference method is meaningless. 

The phenomenon of attenuation of translation of the trp operon in bacteria is provided as an example of posttranscriptional gene regulation. This mechanism, which is used by several amino acid biosynthetic operons, relies on alternative RNA secondary structures and on the coupling of transcription and translation in prokaryotes. The regulation of iron metabolism in animals is presented to show how RNA secondary structures can by bound specifically by proteins and thereby regulate translation. 

Albomycin an antibiotic synthesized by Actinomyces subtropicus. A. is a cyclic polypeptide containing a pyrimidine base (cytosine) and 4.16% Fe in the form of a hydroxamate-Fe(IIl) complex (Fig.). It is one of the sideromycins (similar to, and possibly identical to, grisein), and it interferes with iron metabolism as an antimetabolite of the sideramines. A. is effective against both Gram-positive and Gram-negative bacteria, and inhibits the aerobic metabolism of Staphylococcus aureus and E. colt... 

In the United States it is common medical practice to supplement infant formula with iron sometime during the first year of life because human milk is virtually devoid of iron. Given what is now known about iron metabolism by bacteria, many research workers in nutrition believe that iron supplementation is not generally justified or wise. 

Manganese and iron oxidation are coupled to cell growth and metabolism of organic carbon. Microbially deposited manganese oxide on stainless and mild steel alters electrochemical properties related to the potential for corrosion. Iron-oxidizing bacteria produce tubercles of iron oxides and hydroxides, creating oxygen-concentration cells that initiate a series of events that individually or collectively are very corrosive. 

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