grown in 16x100 mm test tubes containing 5 ml of appropriate medium. Cultures were incubated as described for the aerobic growth except the tubes were held in place at an angle of 45'. Cell growth was monitored by measuring optical density at 600 nm using a Spectronic 20D+ spectrophotometer. When cultures were supplemented with CO2 they were grown in a Forma Scientific CO2 Water Jacketed Incubator Model 3110 at 37'C and 5% CO2 on a New Brunswick Gyratory Shaker ModelG2 at 275 RPM.

     Inocula for the growth experiments were prepared as follows: bacterial strains were grown overnight at 37'C with shaking at 275 RPM in LB medium; cells from 1.5 ml of an overnight culture were pelleted by centrifugation and resuspended in 1 ml of growth medium, and 0.125 ml was used to inoculate 5 ml cultures or 0.250 ml for 10 ml cultures.

Cloning of pduA for High-Level Expression

     The following primers were used for PCR amplification of pduA DNA using pVJ70 (RT 1679) as template: forward, 5'GGAATTCCATATGCAACAAGCACTAGGAATGG-3' and reverse, 5'CACCGATGGATCCTCATTGGCTAATTCCCTTCG-3'. The PCR product was gel purified, restricted with NdeI and BamHI and ligated to similarly restricted plasmid pET15b. The ligation reaction was heated to 700 C for 15 minutes and used to transform E. coli ER1992 by electroporation. The DNA sequence of the cloned DNA was shown to be in agreement with the previously reported pduA DNA sequence (Bobik et al. 1999). For protein expression, E. co/i BL21 (DE3)/pSJS1240 was used as the host strain. Cloning ofpduJ for High-Level Expression

     The following primers were used for PCR amplification of pduJ using pMGS2

(BE1l) as template: forward, 5'-GGAATTCATATGAATAACGCACTGGGACTGG-3'