Influence of Iron on Yields of Extracellular Products in Pseudomonas aeruginosa Cultures

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Abstract
The effect of the Fe content of the medium on the yields of extracellular products by 7 distinct strains of P. aeruginosa was examined. All strains showed at least an 85% decrease in toxin A yields when grown in medium containing 5.0 .mu.g of Fe/ml (high Fe) as compared to 0.05 .mu.g/ml (low Fe), whereas bacterial growth increased about 2-fold. During the course of examining extracellular products produced by P. aeruginosa, many strains that produced an extracellular factor which agglutinated [sheep] erythrocytes were found. This hemagglutinin was nondialyzable, heat stable and resistant to Pronase and trypsin. The effect of Fe on extracellular yields of hemagglutinin was strain dependent; 4 of 7 strains showed decreases in hemgglutinin yields in high-Fe medium. Similarly, the effect of increasing the Fe concentration of the growth medium on yields of total extracellular proteases or on elastase was strain dependent. The amount of total extracellular protein was decreased by at least 31% in the high-Fe medium for all strains of P. aeruginosa examined. Detailed studies on 1 strain (WR-9) showed that, in the presence of increasing amounts of Fe in the medium, the extracellular yields of toxin A, protease and hemagglutinin were decreased in a similar manner. The kinetics of release of these extracellular products were similar at a given Fe concentration. The yields of other extracellular products of P. aeruginosa besides toxin A are apparently influenced by the concentration of Fe in the growth medium.