“…The trp mutant hosts are mostly E. coli derivatives, as used in the cloning of Bacillus stearothermophilus trpBA (Ishiwata et al, 1989), Brevibacterium lactofermentum trpE (Matsui, Miwa and Sano, 1987), Caulobacter crescentus trpF (Winkler et al, 1984), Clostridium thermocellum trpEG (Sato et al, 1989), Lactobacillus casei trpDCFBA (Natori, Kano and Imamoto, 1990), Methanococcus voltae trpFBA (Sibold and Henriquet, 1988), Streptomyces griseus trpCBA (Rivero-Lezcano et al, 1990) and Thermus thermophilus trpEG (Sato et al, 1988). In cases where problems with an E. coli host were anticipated or encountered, other hosts were used.…”