Using PCR on these strains, we also found that short, 2.4 kb, and long, 2.7 kb, versions of both the MTT1 and the MAL31 genes are present (Dietvorst et al., 2005). We have extended these studies by cloning and sequencing long and short versions from two more lager strains and testing their ability to restore the growth of the A15 lager strain on maltotriose with antimycin A. Escherichia coli XL1-Blue (Bullock et al., 1987) was used for plasmid amplification. Standard methods were used for E. coli transformation (Inoue et al., 1990). Four lager

strains, A15 (Dr J. Londesborough, VTT Biotechnology, Finland), WS34/70 (Weihenstephan brewery, Freising, Germany), BS01 and BS07 (Heineken Supply Chain), were used in this study. Standard methods were used for yeast transformation (Gietz et al., 1995). Plasmid pRUL409 was constructed BYL719 by inserting ARS1 from plasmid pNatCre (Steensma

& Ter Linde, 2001) into the XbaI and EcoRI sites of vector pHSS6 (Seifert et al., 1986), thereby introducing a NotI site next to the EcoRI site flanking the ARS. Plasmid pRUL409 was provided with a KanMX cassette (Wach et al., 1994) from pUG6 by inserting it as a BamHI–BglII fragment into its BamHI site yielding pRUL409(KanMX). This plasmid was digested with BamHI and Vemurafenib XbaI to clone the various MALx1 and MTT1 genes. To convert the resulting plasmids from a multicopy plasmid into a single copy plasmid, CEN4 from plasmid YCplac33 (Gietz & Sugino, 1988) was amplified using the primers CEN4SacI and CEN4EcoRV and inserted into the EcoRV and SacI sites of pRUL409(KanMX) containing one of the various

MALx1 and MTT1 genes. Yeast cells were grown in YP (Difco peptone 2%, Difco yeast extract 1%) containing 2%d(+)−glucose (Merck), maltose (Merck) or maltotriose (Fluka, 96% pure HPLC). When required, G418 (Duchefa) Chlormezanone was added to the medium at a concentration of 200 μg mL−1, and antimycin A (Fluka) at a concentration of 3 mg L−1. Escherichia coli (XL1-Blue) was grown in Luria–Bertani broth and, if necessary, kanamycin was added to a concentration of 40 μg mL−1. For solid medium, 15 g L−1select agar (Gibco) was added to the liquid media. The primers used for PCR are listed in Table 1. PCR amplifications were performed with 50–100 ng genomic DNA. The amplification conditions were as follows: 5 min at 94 °C, 30 cycles of 1 min at 94 °C, 1 min at 5 °C below Tm of the primers and 1 min kb−1 to be amplified at 74 °C, followed by 10 min at 74 °C. The reactions were performed in a total volume of 50 μL and, per reaction, 0.5 μL Vent polymerase (New England BioLabs) was used with the buffer supplied. All PCR products were cloned into the pCR®-Blunt II-TOPO® vector (Invitrogen) before they were recloned into pRUL409(KanMX). For each of the four strains, 11 independent PCRs were performed. The sequences of the MTT1 and MAL31 gene isolates from strains BS01, BS07, WS34/70 and A15 cloned into vector pRUL409(KanMX) were determined commercially (Baseclear).