Tufa is a variety of limestone, formed by the precipitation of carbonate minerals from ambient temperature water bodies. Geothermally heated hot springs sometimes produce similar (but less porous) carbonate deposits known as travertine. Tufa is sometimes referred to as (meteogene) travertine; care must be taken when searching through literature to prevent confusion with hot spring (thermogene) travertine. Calcareous tufa should not be confused with tuff, a porous volcanic rock with parallel etymological origins that is sometimes called "tufa".

EF-Tu (elongation factor thermo unstable) is one of the prokaryotic elongation factors. Elongation factors are part of the mechanism that synthesizes new proteins by translation at the ribosome. Individual amino acid links are added to the protein chain by transfer RNA (t-RNA). Messenger RNA (mRNA) carries a codon that codes for each amino acid. t-RNA carries the amino acid and an anticodon for that amino acid. The ribosome creates a protein chain by following the mRNA code and selecting the next t-RNA and its amino acid.