Evolution of β-lactam biosynthesis genes and recruitment of trans-acting factors

β-Lactam antibiotics are produced by some filamentous fungi, Gram-negative and Gram-positive bacteria. There were arguments in favour of horizontal gene transfer of β-lactam biosynthesis genes from bacteria to fungi. This hypothesis was further supported by the recent identification of cis-/trans-elements involved in the regulation of the β-lactam biosynthesis genes.