Failure of complex supplementation of minimal cultures to elicit a shift-up response in Pseudomonas putida.

The addition of complex supplements (particularly amino acids) to cultures of Pseudomonas putida growing on a good carbon source did not result in a substantial increase in the growth rate. Amino acids entered the cells within 30 s of addition and reached significant internal pool concentrations. Endogenous amino acid biosynthesis was quickly inhibited (about 75%), with a substantial sparing of the original carbon source. Within 20 min of supplementation significant respiration of added amino acids was detected, yet the ATP pool size did not increase and the bacteria did not grow faster. The RNA content of P. putida growing in complex medium differed from that of enteric bacteria in that, although it varied with growth rate, it was not substantially larger than the RNA content of bacteria grown in a minimal medium with a good carbon and energy source. The rate of RNA accumulation on shift-up remained substantially unchanged on supplementation if the minimal medium had a carbon source producing fast growth, and did not increase for about 30 min if the carbon source was relatively poor. In other respects RNA synthesis was similar to that of the enteric bacteria, being stringently controlled, inhibited by trimethoprim and continuing in the presence of chloramphenicol. It is proposed that growth of P. putida in complex media is limited by the rate of synthesis of stable RNA.