Re: Does rusting of iron commonly involve bacteria?

To: William Beaty

Major modes of nutrition of bacteria are:

1. Photoautotrophy -- photosynthetic prokaryotes (bacteria), e.g.
2. Chemoautotrophy -- need only CO2 as a carbon source, but instead of using light for energy, they obtain energy by oxidizing inorganic substances.
3. Photoheterotrophy -- prokaryotes which use light to generate ATP (adenosine tri-phosphate, the energy 'currency' of the cell) but must obtain the carbon in organic form.
4. Chemoheterotrophy -- must consume organic molecules for both energy and carbon.

Chemoautotrophs extract chemical energy by oxidizing inorganic substances: from hydrogen sulfide, amonia, ferrous ions or some other chemicals. That is why they need ferrous ions (human subjects need ferrous ions for many important substances as hemoglobin etc.) When steel is getting rusty this process needs mainly oxygen but no prokaryotes.

Atmospheric oxygen is, however, produced by living organisms. Oxygen has been in atmosphere for 2.4 billion years thanks to living organisms such as cyanobacteria (bluegreen algae = cyanophyta). Therefore, rusting is not significantly produced by organisms (incl. bacteria), but oxygen produced by photosynthetic organisms is needed for our life as well as for rusting.

Warmest personal regards Josef Berger

Admin note:
In addition, many bacteria secrete acids as they grow (lactic acid, and others, e.g.). In the sense that acids accelerate the process of corrosion, microbes present on iron-containing surfaces could enhance the ability of material to rust.