Thiamin and thiamine diphosphate act as a critical cofactor in many pathways such as carbohydrate and amino acid metabolism. Thiamin is essential to all living organisms, and in humans, its deficiency causes greater problems than its excess intake (thiamin toxicity is uncommon). Since humans cannot synthesize thiamin, thiamin synthesis by microorganisms is important. Biodegradation of thiamin is important for its recycling and de novo biosynthesis; therefore, thiamin biodegradation is also called thiamin salvage. Thiamin salvage is essential for the survival of bacteria when thiamin is limited. It also occurs in some archaea and eukaryotes. Jenkins et al. (2007) describe how formylaminopyrimidine and 5-hydroxy-3-sulfanylpentan-2-one are generated from thiamin hydrolysis in the presence of soil. Bacillus halodurans can then deformylate formylaminopyrimidine to aminopyrimidine using an amidohydrolase, and can further hydrolyze aminopyrimidine to toxopyrimidine using thiaminase II.