CHST3 and infection: In addition to fatty acids, cholesterol has been suggested as a carbon source used by Mtb during infection (Pandey and Sassetti, 2008) but the role of cholesterol as an important carbon source in vivo has recently been challenged, as the hsd gene, encoding the first enzyme in cholesterol catabolism, has been shown to be dispensable for Mtb replication in guinea pigs (Yang et al., 2011).