As heard mentioned on Radio 4: Snottites (SNOT-ites)

Snottites or snotties are colonies of single-celled extremophilic bacteria that hang from the walls and ceilings of caves (similar to small stalactites, but with the consistency of “snot”, or mucous). They digest sulfur compounds in warm water in the cave, and slowly drip down from above. Because of this, they are highly acidic, some with the corrosive properties of battery acid.

Snottites were recently brought to attention by a researcher, Penny Boston, studying them (and other organisms) in a toxic sulfur cave called Cueva De Villa Luiz (Cave of the Lighted House), in Tabasco, Mexico.

…from [en.wikipedia.org] ; see also snottites and [www.nasa.gov] and [www.i-pi.com]