Siderophore production of fluorescent pseudomonads is sensitive to fluctuations in the levels of oxygen and carbon dioxide

Abstract

Four strains of the fluorescent pseudomonads were studied to determine the effect of controlled atmospheres on the growth and fluorescent siderophore production at pH 6.0 and 7.8. Bacterial strains were grown in Liquid King's Medium B for 48 hr in the presence of O2/CO2 combination percentages of 21.0/0.03, 18.3/3.0, 15.0/6.0, 12.0/9.0, and 9.0/12.0. The bacterial biomass was determined after centrifugation and the siderophores were isolated, partially purified, and quantified spectrophotometrically. Results showed a steady decline in growth and in siderophore production per unit biomass with decreases in the O2/CO2 ratio at pH 7.8 and to a lesser extent at pH 6.0. The average percentage changes in siderophore production levels, relative to control were +0.8, -1.2, -18.2, and -40.6 at pH 6.0; -33.0, -50.4, -66.8, and -64.1 at pH 7.8 in the presence of O2CO2 levels of 18.0/3.0, 15.0/6.0, 12.0/9.0, and 9.0/12.0, respectively.