Methylophaga thiooxydans is a methylotrophic bacterium that requires high salt concentrations for growth.

It was originally isolated from a culture of the algae Emiliania huxleyi, where it grows by breaking down dimethylsulfoniopropionate from E. hexleyi into dimethylsulfide and acrylate.

Most bacteria that degrade dimethylsulfide (including some Methylophaga strains) as a source of carbon leave the sulfur behind in the fully oxidised form of sulfate, whereas Methylophaga sulfidovorans forms thiosulfate as the end-product of growth.

The respiratory chain of this species contains a bc1 complex, unlike Escherichia coli and the flavoprotein succinate dehydrogenase, which is not always present in methylotrophic or autotrophic bacteria since they do not have the complete Krebs cycle, and instead have the partial cycle dubbed Smith's horseshoe - in the case of Methylophaga species, the fumarase and succinate dehydrogenase that are often missing are present and permit growth on a limited range of carbohydrates rather than just one-carbon compounds such as methanol or dimethylsulfide, which are metabolised not via Krebs cycle but via the ribulose monophosphate pathway (RuMP pathway, also known as the Quayle pathway).

M. thiooxydans was isolated in 2010 from a culture of the coccolithophore Emiliania huxleyi after enrichment culture using dimethylsulfide as the sole source of carbon and the sole electron donor, with molecular oxygen as the terminal electron acceptor.