Exocellular and intracellular accumulation of lead in Pseudomonas fluorescens ATCC 13525 is mediated by the phosphate content of the growth medium

: Pseudomonas fluorescens appears to elicit disparate lead detoxification mechanisms in phosphate‐rich and phosphate‐deficient media. When grown in the presence of 0.1 mM Pb2+ complexed to citrate, the sole source of carbon, only a slight diminution in cellular yield was observed in the former medium. However, in a phosphate‐deficient milieu, lead imposed approximately a 30% reduction in bacterial multiplication. At stationary phase of growth, 72% of the metal was found in the bacterial cells from the phosphate‐deficient medium, while that from phosphate‐rich broth contained only 12.5% The latter medium was characterised by an insoluble pellet that accounted for 73.5% of the lead. Although no citrate was detected in the phosphate‐rich media after 40 h of incubation, only 72% of citrate was consumed even after 70 h of growth in the phosphate‐deficient cultures. The inclusion of lead did not appear to enhance the production of either extracellular proteins or carbohydrates.