Stinky problem

The article on the human microbiome ( January) is a nice overview of our relationship to microorganisms, but it contains a significant error. When discussing the role of these organisms in the human gut, it states that methane is the smelly component of farts. Sorry, methane is odourless. It is for this reason that methyl mercaptan, an organosulphur compound that is easily smelled, is added to methane used as a fuel. The smell of farts is largely due to hydrogen sulphide, along with other odour contributors. Kenneth Koutz, California

You’re absolutely right and we apologise for this error. Methane is a component of the gases released by gut bacteria that make up farts, but natural methane is indeed odourless and NOT the smelly component of farts. The pungent smell of farts comes from other gases in the mix, hydrogen sulphide being one of the smelliest along with methanethiol. – Mun Keat Looi, science writer