Implications of benzoate induced alterations in cell morphology and physiology in Pseudomonas aeruginosa TMR2.13 for potential application in bioremediation and monitoring approaches

Abstract

The aromatic hydrocarbon sodium benzoate induced significant alterations in cell morphology with parallel changes in physiological processes like denitrification and pigment formation during growth of a bacterial strain TMR2.13 in denitrification medium. The isolate obtained from a low nutrient level ecosystem (coastal sand dunes) was identified as Pseudomonas aeruginosa. The culture was capable of growing in up to 3 percent benzoate as the sole carbon source. The culture, a strong denitrifier, showed changes in nitrite levels in response to benzoate. Presence of benzoate induced a 50 percent reduction in intermediate nitrite accumulation under well aerated conditions. High benzoate levels caused a delay in growth rate, nitrate reduction activity and prominent decrease in transitional nitrite levels from 1528 mu M (without benzoate) to 508 mu M (with 1 percent benzoate). Further, the intensity of pigment production was also enhanced in presence of sodium benzoate indicated by a significant increase in absorbance at 380 nm (pyoverdin peak) and 680 nm (pyocyanin peak). The impact of benzoate was greater on pyoverdin production than on pyocyanin. The alterations depicted by TMR2.13 at high benzoate concentrations in nitrite and pigment levels can be projected with potential application in bioremediation and monitoring studies.