Isolation of a selective marker from Cephalosporium acremonium by complementation of an auxotrophic mutant of E. coli.

A Cephalosoporium acremonium gene library has been constructed using cosmid vector pYcl. After transformation of E. coli leuB strain JA221 with cosmids isolated from this gene library a cosmid (pCeleuB43) was isolated which complements the leucine auxotrophy of JA221. The same cosmid is also able to complement a leu2 strain of S. cerevisiae. The leuB and leu2 genes both code for β-isopropylmalate dehydrogenase. The complementation of a leuB E. coli strain and a leu2 S. cerevisiae strain strongly suggests that the analogous gene from C. acremonium has been isolated.