Leptospirillum ferrooxidans

Bacteria may catalyze and considerably enhance the oxidation of pyrite and Fe(II) in water, especially under acidic conditions (Welch et al., 2000, 597). Many microbial species actually oxidize only specific elements in sulfides. With pyrite, Acidithiobacillus thiooxidans is important in the oxidation of sulfur, whereas Leptospirillum ferrooxidans and Acidithiobacillus ferrooxidans (formerly Thiobacillus fer-rooxidans) oxidize Fe(II) (Gleisner and Herbert, 2002, 140). Acidithiobacillus ferrooxidans obtain energy through Reaction 3.45 (Gleisner and Herbert, 2002, 140). The bacteria are most active at about 30 °C and pH 2-3 (Savage, Bird and Ashley, 2000, 407). Acidithiobacillus sp. and Leptospirillum ferrooxidans have the ability to increase the oxidation of sulfide minerals by about five orders of magnitude (Welch et al., 2000, 597). 

Colmer and Hinkle (14) identified T. ferrooxidans in acidic mine waters. Subsequent studies by Silverman et al. (15,16) confirmed that T. ferrooxidans could be utilized to oxidize FeSo in coal in 3 to 4 days, and the rate of oxidative dissolution was a function of the particle size and rank of the coal. Dugan and Apel (4,5) showed that a mixed culture of T. ferrooxidans and T. thiooxidans was most effective at a pH of 2 to 2.5 when the nutrient was enriched with NH " -. They reported 97% removal of pyritic sulfur from a coal sample with 3.1 weight percent sulfur. Norris and Kelly (17) reported that other acidophilic bacteria, Leptospirillum ferrooxidans in mixed cultures with T. thiooxidans, was effective for FeS2 removal. ... 

Rusticyanin is found in Thiobacillus ferrooxidans, an acidophilic, chemolithotrophic sulfur bacterium utilizing Fe + and reduced sulfur compounds as its sole energy source. T. ferrooxidans does not produce rusticyanin when grown on reduced sulfur. Similar to other substrate-inducible cupredoxms, the msticyanin gene is activated when soluble iron is present in the media. Little is known about its redox partners and it should be noted that rusticyanin itself does not carry out Fe + oxidation. Other iron-oxidizing bacteria, for example, Leptospirillum ferrooxidans, prodnce a cytochrome which substitutes rusticyanin functionally. To date T. ferrooxidans remains the only source for rusticyanin. 

Among the acidophilic iron-oxidizing bacteria, Acidithiobacillus ferrooxidans (Kuenen, 1989) and Leptospirillum ferrooxidans (Eccleston et al., 1985) are well... 

The Fe(II)-cytochrome c oxidoreductase catalyzes the reduction of cytochrome c-552 with ferrous ion but does not catalyze the direct reduction of rusticyanin. This agrees with the finding of Hazra et al. (1992) that rusticyanin is reduced via cytochrome c. Blake and Shuts (1994) have claimed that the oxidation of ferrous ion occurs by the catalysis of Fe(II)-rusticyanin oxidoreductase. However, as their enzyme preparation probably contained cytochrome c as a contaminant, its catalysis could be the reduction of rusticyanin by Fe(II)-cytochrome c oxidoreductase mediated by cytochrome c. It has been reported that rusticyanin is not present in Leptospirillum ferrooxidans (Blake et al., 1993). This may mean that rusticyanin is not necessarily required for the oxidation of ferrous ion by the iron-oxidizing bacteria. 

A cytochrome having the a peak at 579 nm is obtained from Leptospirillum ferrooxidans DSM 2706 (Hart et al., 1991). The cytochrome has 1 atom of zinc in addition to heme iron. Its molecular mass is 17.9 kDa and its Emj5 is +0.68 V (Blake et al., 1993). From L. ferrooxidans P3A, a cytochrome with the molecular mass of 12 kDa is obtained, while the 17.9 kDa cytochrome is not obtained. In any case, nothing is known about the function of the L. ferrooxidans cytochromes. Moreover, Metallosphaera sedula and Acidianus brierleyi have a membrane-bound yellow cytochrome which is reduced by ferrous ion (Blake and McGinness, 1993 Blake et al., 1993). However, the description here about cytochromes c will be limited to the proteins that have been purified from A. ferrooxidans and well characterized. 

The growth of the bacterium is inhibited by benzoic acid, sorbate, and sodium laurylate (Onysko et al., 1984), and nitrate at 50 mM inhibits completely the oxidation of ferrous ion by the bacterium (Eccleston et al., 1985). Although the bacterium is sensitive to chloride ion, it becomes resistant to 140 pM chloride ion by training (Shiratori and Sonta, 1993). The bacterium is fairly resistant to heavy metal ions its activity to oxidize ferrous ion is scarcely inhibited in the presence of 65 mM cupric ion, 100 mM nickel ion, 100 mM cobalt ion, 100 mM zinc ion, 100 mM cadmium ion, and 0.1 mM silver ion (Eccleston et al., 1985). The bacterium acquires the ability to grow even in the presence of 2 mM uranyl ion (Martin et al., 1983). Furthermore, it becomes resistant to arsenate and arse-nite by training a strain of the bacterium has been obtained which oxidizes ferrous ion in the presence of 80 mM arsenite and 287 mM arsenate (Collinet and Morin, 1990 Leduc and Ferroni, 1994). The resistant ability of the bacterium to arsenite and arsenate is important when they are applied for the solubilization of arsenopyrite (FeAsS) [reactions (5.8) and (5.9)]. Leptospirillum ferrooxidans is generally more sensitive to heavy metal ions than A. ferrooxidans (Eccleston et al., 1985). 

From the shape (rods) of the bacteria, they appear to be Acidithiobacillus ferro-oxidans but not Leptospirillum ferrooxidans. Finally, when the mixture of the mudstone and the medium for the sulfur-oxidizing bacteria (pH 6.5) supplemented with powdered pyrite is shaken in air, the pH of the culture medium is lowered over time. When the pH is lowered to below 4, the amount of ferrous ion plus ferric ion in the medium increases rapidly together with a parallel increase of sulfate ion (Yamanaka et al., 2002b). These phenomena are not observed with the mudstone heated at 121°C for 20 min. The results show that the acidophilic iron-oxidizing bacteria (growing at pH lower than about 4) oxidize pyrite but the usual sulfur-... 

Hart A, Murrel JC, Poole RK, Norris PR (1991) An acid-stable cytochrome in iron-oxidizing Leptospirillum ferrooxidans. FEMS Microbiol Lett 81 89-94 Hatch MD, Slack CR, Johnson HS (1967) Further studies on a new pathway of photosynthetic carbon dioxide fixation in sugar-cane and its occurrence in other plant species. Biochem J 102 417-422... 

Acuna, J., Rojas, J., Amaro, A.M., Toledo, H. and Jerez, C.A. (1992). Chemotaxis of Leptospirillum ferrooxidans and other acidophilic chemohthotrophs comparison with the Escherichia coli chemosensory system. FEMS Microbiol. Lett. 96, 37-42. 

Stoytcheva M, Zlatev R, Magnin JP, Ovalle M, Valdez B (2009) Leptospirillum ferrooxidans based Fe2-t sensor. Biosens Bioelectron 25(2) 482-487. doi 10.1016/j.bios.2009.08.019... 

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