Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria | INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

Twitter

Aller au compte twitter

  Extracellular Iron Biomineralization by Photoautotrophic Iron-Oxidizing Bacteria

Publication Type:

Journal Article

Source:

Applied and Environmental Microbiology, Volume 75, Issue 17, p.5586-5591 (2009)

ISBN:

0099-2240

Accession Number:

WOS:000269344200021

URL:

http://aem.asm.org/content/75/17/5586

Keywords:

UMR 7154 ; Minéralogie ; N° Contribution : 2536

Abstract:

Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (alpha-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy analyses performed at the C K-edge suggest that these fibers are composed of a mixture of lipids and polysaccharides or of lipopolysaccharides. The iron and the organic carbon contents of these fibers are linearly correlated at the 25-nm scale, which in addition to their texture suggests that these fibers act as a template for mineral precipitation, followed by limited crystal growth. Moreover, we evidence a gradient of the iron oxidation state along the mineralized fibers at the submicrometer scale. Fe minerals on these fibers contain a higher proportion of Fe(III) at cell contact, and the proportion of Fe(II) increases at a distance from the cells. All together, these results demonstrate the primordial role of organic polymers in iron biomineralization and provide first evidence for the existence of a redox gradient around these nonencrusting, Fe-oxidizing bacteria.