In many of the stories about Titanic, there are regular mentions of bacteria that are eating the iron and steel that make up the ship, sometimes saying the wreck loses a couple of hundred pounds a day.
What kind of bacteria are they talking about? Seems odd that there would be a type of bacteria at the bottom of the ocean that has evolved to eat iron and steel?
There is plenty of iron-oxidizing bacteria on the surface. A wreck like Titanic would be like an all-you-can-eat buffet.
Not a detailed answer(sorry, about to start work, but I know a teeny smidge about this) mostly it’s microbes in an oxygen poor environment. Iron, and manganese too, are used as “electron sinks” in chemical reactions (and sometimes supplies of electrons) bacteria use to generate energy.
I’m sure someone will be along shortly to give a better, more detailed answer
Is this because you think there isntusually any iron for them to eat there?
Microbially Induced Corrosion (MIC) is sometimes a problem in the pipeline industry, usually in the gas gathering or gas storage areas. Some companies will inject biocides into the gas stream to control MIC.
Controlling microbiologically influenced corrosion in pipelines (ampp.org)
Ancient metallurgy depended to a degree on iron-eating bacteria.
Iron-bearing groundwater typically emerges as a spring and the iron in it forms ferric hydroxide upon encountering the oxidizing environment of the surface. Bog ore often combines goethite, magnetite, and vugs or stained quartz. Oxidation may occur through enzyme catalysis by iron bacteria.
Bog iron was some of the earliest iron ore worked by early blacksmiths, since it’s easy to find (look for a bog with reddish-stained water and poorly growing bog grass), easy ro extract (cut and peel soft peat), and easy to refine (doesn’t have to be complete molten to purify to iron).
Thank you, iron-eating bacteria!
It wasn’t just bog iron that came from the bacteria…
Australia’s Iron ore, a giant deposit in the Pilbara region, was made by bacteria…
Only indirectly.
Most Pilbara iron ore is banded ironstone, and that’s a precipitate caused by oxygenation of the oceans by cyanobacteria doing normal photosynthesis, not a direct catalyzed precipitation by chemotrophes, like in bog iron.
Most of the early ironworks in the New World were bog iron. In Europe, pretty much all the bog iron had already been exploited, but America still had plenty of it. Furthermore, if the bog was near seashell deposits, they could use crushed shells as flux in the smelter. New Jersey happened to have them in close proximity, so NJ was an early iron working region.
This has been a fascinating discussion. I learnt new things. Thanks, all.
Great discussion, I loved it!
I feel like we had a thread on how much “blood of my enemies” it would take to forge a sword.
In the case of the bacteria responsible for bog deposits, they’re using Fe(II) as an electron source. The resulting Fe(III) precipitates. In the case of ship hulls, we’re starting with metallic iron, Fe(0). What I don’t know, and which may have already been addressed by the links I’m still working through, is at what stage(s) the bacteria are involved and how. But this will again result in iron being used as an electron source.
You mean like this one?
Along with the salt air I mentioned (and on which I was educated)) in another thread, my part of New Jersey was once a hotbed for bog iron. I’ve often seen the sheen mentioned in this thread and always thought it was some kid of ground water pollution. I’m getting less ignorant by the day!
Seems to me there’s a real chicken-and-egg, or is it blood-and-sword problem here. I need the sword to extract blood from my enemies, and I need enemy blood to forge my sword. 
More seriously, great cite. Thank you.