Effects of temperature on rates and mineral products of microbial Fe(II) oxidation by Leptothrix cholodnii at microaerobic conditions

A comparison of Fe(III) reduction rates between fresh and aged biogenic iron oxides (BIOS) by Shewanella putrefaciens CN32

“…Impurities (e.g., Al, Si, and P) present in solution and/or adsorbed/incorporated by the iron oxide influence the rate of transformation and the secondary mineral products that form, and in some cases completely inhibit the transformation of ferrihydrite (Cornell and Schwertmann, 2003). It has been previously noted by several studies that bacterial cells and/or their exudates inhibit the transformation of ferrihydrite into crystalline phases (Banfield et al, 2000;Kennedy et al, 2004;Toner et al, 2009Toner et al, , 2012Vollrath et al, 2013). Our XRD and EXAFS results are in agreement with this notion, which show that 2-line ferrihydrite remains as the dominant mineral in our samples, even after~5 years of ageing.…”

“…For example, Kennedy et al (2004) subjected synthetic 2-line ferrihydrite and marine BIOS to aqueous heating at 80°C for 2 days, and found that synthetic 2-line ferrihydrite transformed into hematite, whereas BIOS did not transform into crystalline phases. In agreement with several studies (Banfield et al, 2000;Kennedy et al, 2003;Toner et al, 2009Toner et al, , 2012Vollrath et al, 2013), Kennedy et al (2004) concluded that the organic fraction associated with BIOS plays a role in inhibiting transformation. However, Chan et al (2009) showed that mineral transformation into akaganeite can occur in the immediate vicinity of bacterial exudates in naturally occurring BIOS.…”

Use of Iron Powder to Obtain High Yields of Leptothrix Sheaths in Culture

“…However, cell growth was not detected with more rapid agitations (180 rpm rotary and 140 rpm reciprocal) probably due to excessive oxygenation of the medium. This result was expected because low oxygen has been reported to favor growth and Fe(II) oxidation of aerobic Leptothrix [2,15,[18][19][20], consistent with their good growth at the natural air-water interface [17]. The present study confirmed that use of a proper amount of Fe powders in the medium did not adversely affect the cell growth under favorable shaking modes.…”

“…Intriguingly, natural Leptothrix sheaths were discovered to have a variety of the industrial functions: lithium-ion battery anode material [10], catalyst enhancer [11][12][13], and porcelain pigment [14]. The quality and quantity of the natural sheaths, however, are inevitably influenced by environmental changes such as temperature, quantity of supplied groundwater or spring water, concentrations of inorganics in water, as was noted by Vollrath et al [15]. For industrial applications, a constant supply system of qualitatively and quantitatively determinate material is critical.…”

Direct Adherence of Fe(III) Particles onto Sheaths of Leptothrix sp. Strain OUMS1 in Culture

“…In contrast, the inoculated SGP + Fe had gradually turned clear by 10 h as the cells multiplied and remained clear ( Figure 2A); the brownish colony clusters on the bottom and side wall of the flasks are considered to be colored by deposits of the turbid material (plausibly Fe-hydroxides and/or -oxyhydroxides formed by abiotic oxidation [22]) onto the sheaths. Vollrath and colleagues [36,37] reported that the rate of microbial Fe(II) oxidation by L. cholodnii Appels is significantly faster than that of abiotic oxidation. However, in the present study, the change in Fe(II) and/or Fe(II) + Fe(III) concentrations in the inoculated SGP + Fe over time were quite similar to that in the respective uninoculated medium ( Figure 1B,C), suggesting that abiotic oxidation of Fe(0) to Fe(III) via Fe(II) proceeded similarly regardless of the presence or absence of OUMS1.…”