Strategy for the generation of a tap1 knockout strain. The tap1 open reading frame is shown in dark gray, flanking non-coding regions that are present in the knockout construct are given as white boxes, and adjoining regions not present in the knockout construct are shown in light gray. The Hygromycin B resistance cassette comprising the hph gene and the trpC promoter and 5' UTR is given in black. Positions of oligonucleotide primers d1 to d4 are indicated. For further information see text.