Team:Tokyo Tech/Iron-oxidizing bacteria

Achievement

 * We cultured iron-oxidizing bacteria (Acidithiobacillus ferrooidans).



Introduction ~Why do we need to use Iron-oxidizing bacteria for terraforming of Mars?~
Heterotrophic bacteria cannot live in native Martian environment because there are no organic matters on the Martian surface, however autotrophic bacteria can live without organic matters. Iron-oxidizing bacteria is a kind of autotrophic bacteria. Iron-oxidizing bacteria get energy by oxidizing Fe(Ⅱ) and grow with CO2. To grow on Mars, iron-oxidizing bacteria require only energy injection by human beings because of composition of the Martian surface, crust and atmosphere.  Martian surface and crust contains carbonate(Bandfield,2003 et al.) and FeO(Fe(Ⅱ)). In addition, Martian atmosphere contains much CO2.(For detail, see here)  We propose culturing iron-oxidizing bacteria on Mars to produce organic matters. Accumulation of organic matters provides habitable environment for heterotrophic bacteria (for instance, E.coli). We plan to culture iron-oxidizing bacteria on the Martian surface in early stage of terraforming to accumulate enough organic matters for heterotrophic bacteria to live.

Iron-oxidizing bacteria
Iron-oxidizing bacterium is a kind of autotrophic bacteria. Iron-oxidizing bacteria reduce NAD+ to NADH by oxidizing Fe(Ⅱ). Iron-oxidizing bacteria grow with dissolved CO2 as carbon source, not organic matters. In laboratory, iron-oxidizing bacteria are cultured in 9K medium which contains Fe(Ⅱ) and no organic matters.

Preparation of 9K medium (for iron-oxidizing bacteria)
We Prepared following A and B solution. We sterilized A solution by autoclaving. We sterilized B solution by using filter. We Mixed A and B solution before use.

Cultivation of Acidithiobacillus ferrooxidans
We cultured in 9K medium at 30℃ with vigorous shaking. We used the microscope when confirmed the growth.

Cultivation of A.ferrooxidans
We succeeded in culturing Acidithiobacillus ferrooxidans (iron-oxidizing bacteria). The medium for A.ferrooxidans was blue before cultivation owing to Fe(Ⅱ). The presence of A.ferrooxidans changed the medium into brown one after culturing for two days. We confirmed the growth by using microscope of 200 magnifications. This experiment was conducted by Shinya Tahara (student member).<br\><br\><br\><br\><br\>

Discussion
We cultured iron-oxidizing bacteria in 9K medium. This experimental result means that iron-oxidizing bacteria require only dissolved CO2 as carbon source. Therefore, iron-oxidizing bacteria is useful to terraform Mars, where lacks organic matters and contains Fe(Ⅱ). Iron-oxidizing bacteria require us only to heat the surface to control the surface temperature.<br\><br\> To apply to terraform Mars, we have to introduce genes to iron-oxidizing bacteria. However, there are few methods for selecting iron-oxidizing bacteria with introduced genes, because antibiotics are deactivated in culture conditions of iron-oxidizing bacteria. Some researchers succeeded in introducing genes to iron-oxidizing bacteria in their previous researches. They introduced mercury-resistance gene to iron-oxidizing bacteria and selected in the medium that contains mercury ion.

Reference

 * Joshua L. Bandfield,* Timothy D. Glotch, Philip R. Christensen (2003) Spectroscopic Identification of Carbonate Minerals in the Martian Dust, science 22 August 2003 Vol. 301. no. 5636, pp. 1084 - 1087
 * TOMONOBU KUSANO, KAZUYUKI SUGAWARA, CHIHIRO INOUE, TOSHIYUKI TAKESHIMA, MASAHIKO NUMATA, AND TOSHIKAZU SHIRATORI2 (1992) Electrotransformation of Thiobacillus ferrooxidans with Plasmids Containing a mer Determinant, JOURNAL OF BACTERIOLOGY, Oct. 1992, p. 6617-6623
 * MEDIA FOORMULATIONS http://wdcm.nig.ac.jp/catalogue/ncim/document/Ncim_media.pdf <br\>

Acknowledgement

 * Chihiro Inoue (Tohoku university, Graduate School of Environmental Studies Department of Environmental Studies )