Biotin (vitamin H or B7) is an important micronutrient that func-
tions as a cofactor for biotin-dependent enzymes. 1 These include
the biotin-dependent carboxylases, decarboxylases and
transcarboxylases, all of which are found in the microbial world. In
the prototypical bacteria Escherichia coli, there is a single biotin-
dependent enzyme, namely acetyl CoA carboxylase, that catalyzes
the first committed step in the fatty acid biosynthesis pathway. 2,3
Other examples of biotin-dependent enzymes commonly found
in prokaryotes include pyruvate carboxylase responsible for
replenishing the TCA cycle with oxaloacetate, 4 and propionyl CoA
carboxylase required for the metabolism of certain amino acids and