Leptothrix

Fig. 6. Thin section of Leptothrix sp. which is precipitating manganese oxide on its outermost structure called a sheath (McLean et al. 2002). The arrows point to the manganese mineral phase identified by EDS. Scale bar = 150 nm. 

Nelson YM, Lion LW, Ghiorse WC, Shuler ML (1999) Production of biogenic Mn oxides by Leptothrix discophora SS-1 in a chemically defined growth medium and evaluation of their Pb adsorption characteristics. Appl Environ Microbial 65 175-180... 

Metal oxidation Fe V Mn + O2, possibly NO CO2 2Fe2 + O.5O2 + 2H 2Fe + + H2O Mesophilic bacteria putative Gallionella, Leptothrix... 

Bacteria which oxidize ferrous iron (Fe2+) to ferric iron (Fe3+) such as Gallionella and Leptothrix species are termed metal-depositing bacteria. The result of this metabolic process is the formation of ferric hydroxide. 

Iron bacteria Filamentous, aerobic bacteria Examples are Crenothrix polyspora and Gallionella ferrugine. Also Leptothrix ochracea, Sidero-capsa and Ferrobacillus sp., and ThiobaciUus ferroxidans. 

The oxidation rate of As(III) in the presence of manganese and water may be substantially enhanced by manganese-oxidizing bacteria, such as Leptothrix ochracea (Katsoyiannis, Zouboulis and Jekel, 2004). Katsoyiannis, Zouboulis and Jekel (2004) found that the bacteria are important in oxidizing Mn(II) to Mn(IV), Fe(II) to Fe(III), and As(III) to As(V). The oxidation of Mn(II) leads to the precipitation of Mn(IV) (oxy)(hydr)oxides, which then abiotically oxidize additional As(III) and significantly sorb the As(V) that results from both abiotic and biotic oxidation. 

It should be noted that the kinetic rate law described above is quantitatively applicable only to the strain of L. discophora used in the experiments described. Different Mn-oxidizing bacteria and even different stains of L. discophora would be expected to exhibit different rates of catalysis of Mn oxidation. For example, recent investigations in a wetland in New York State found many different genetic strains of Leptothrix, each exhibiting different rates of catalysis of Mn oxidation (Verity, 2001). However, the general form of the rate law could be expected to be similar for different species of Mn oxidizers. 

Adams, L.F. and Ghiorse, W.C., Characterization of extracellular Mn2+-oxidizing activity and isolation of an Mn2+-oxidizing protein from Leptothrix discophora SS-1, J. Bacteriol., 169, 1279, 1987. 

Brouwers, G.J. et al., Stimulation of Mn2+ oxidation in Leptothrix discophora SS-1 by Cu2+ and sequence analysis of the region flanking the gene encoding putative multicopper oxidase mofA, Geomicrobiol. J., 17, 25, 2000a. 

Zhang, J. et al., Kinetics of Mn oxidation by Leptothrix discophora SSI, Geochim. Cosmochim. Acta, 65, 773, 2002. 

Leptothrix ochracea, whereas chemohthoautotrophic iron bacteria reduce CO rather than oxidize ambient organic material by means of Fe(III), yet assuming the same C/N ratio... 

Fig. 2.12 A colony of Leptothrix ochracea (some 15 cm across) in a small spring (producing 1-2 L water/min) among roots of a tree does locally control access to Fe (and probably Mn, Al, REEs) by this tree and nearby plants. Oxygen is...

Bacillus sp. SG-1) (Leptothrix discophora SS-1) (Pseudomonas putida GB-1) (plants)... 

Because Mn(II) is stable at pH <8, significant contributions from microorganisms to Mn(II) oxidation has been relatively easy to demonstrate, and a number of Mn(II) oxidizing bacteria have been isolated. Microbial oxidation is considered the primary mechanism of Mn(II) oxidation in circumneutral freshwater (Ghiorse, 1984 Nealson et al., 1988). The sheathed bacterium Leptothrix discophora is perhaps the most-studied species of Mn(II)-oxidizing bacteria, and rate laws have been developed to describe Mn(II) oxidation as a function of pH, temperature, dissolved O2, and Cu concentration (Zhang et al., 2002). Bacillus sp. 

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