Geobacter sulfurreducens

A Microbial Biorealm page on the genus Geobacter sulfurreducens

Classification

Higher order taxa

Bacteria ; Proteobacteria ; delta/epsilon subdivisions ; Deltaproteobacteria ; Desulfuromonadales ; Geobacteraceae

Species

Geobacter sulfurreducens

Description and significance

Geobacter sulfurreducens are comma shaped gram-negative, anaerobic bacteria that are found below the surface and are one of the predominant metal-reducing bacteria. G. sulfurreducens can oxidize organic compounds and couple that to the reduction of metals.

The Geobacter sulfurreducens PCA strain was discovered in a sample of soil contaminated by hydrocarbons in Norman, Oklahoma. G. sulfurreducens oxidizes acetate to carbon dioxide and water while reducing compounds such as sulfur, fumarate, and some metals including iron oxides.

Genome structure

Geobacter sulfurreducens has a genome of about 3.8 million base pairs. This is a medium size for bacteria. A citrate synthase gene previously found only in eukaryotes was identified as well as enzymes in the acetyl co-enzyme A pathway involved in acetate and carbon metabolism.

Cell structure and metabolism

G. sulfurreducens has enzymes involved in energy capture. It encodes over 100 cytochromes which contain c-type hemes. They are seen to bear flagella mostly on one side and short pili on the other side.

Ecology

Geobacter sulfurreducens is of considerable ecological importance due to its wide range of biotechnologically exploitable bioremediation capabilities. The organism is involved in carbon cycling, can precipitate soluble metals, and has the ability to generate electricity.

Insoluble materials like iron, magnesium, and uranium oxides, that cant be broken down into soluble subunits can be metabolized by Geobacter. Geobacter is capable of an anaerobic respiration using one or another of these solid oxides as the terminal electron acceptor.

Pathology

Organism is not pathogenic.

Application to Biotechnology

Geobacter sulfurreducens can attach to electrodes and remain viable for long periods of time while completely oxidizing organic substrates with quantitative transfer of electrons to an electrode. This ability can be used to increase the effectiveness of microbial fuel cells by adding G. sulfurreducens. In other words, G. sulfurreducens can be used to generate electricity when attached to electrodes.

References

Ueki and Lovley. “Heat-shock sigma factor RpoH from Geobacter sulfurreducens” Microbiology.2007; 153: 838-846

Cathy Holding. “Perfidious proteobacterium” Science, December 12, 2003. 302:1967-1969

Edited by Frank Nguyen, student of Rachel Larsen and Kit Pogliano