Methylacidiphilum fumariolicum is an autotrophic bacterium first described in 2007 growing on volcanic pools near Naples, Italy.

[1] No biotic interactions between M. fumariolicum and other organisms are known, probably due to the extreme environment the bacteria needs in order to grow.

The genome of M. fumariolicum is 2.36 Mbp in size with a GC-content of 40.9% and 2,283 protein encoding genes.

It generally uses lanthanum as an essential cofactor but it has been shown that it can be replaced with other lanthanides such as cerium, praseodymium, or neodymium without negative effects and with samarium, europium, or gadolinium only slowing down the growth speed of the bacteria.

[4] M. fumariolicum was found to be more oxygen sensitive than most Pseudomonadota methanotrophs, probably due to the fact that it uses nitrogenase during nitrogen fixation which is known to be oxygen sensitive.