Nitrogen and Phosphorus for Growth of Oil-Degrading Microorganisms in Seawater

Abstract

Seawater was supplemented with NH4 + and P to determine concentrations of N and P adequate for supporting exponential growth of bacteria utilizing crude oil, and to determine maximum rates of N and P uptake. Oil-degrading microorganisms were obtained by enrichment culture of indigenous oil-utilizing microorganisms in seawater. NH4 + at a concentration of 5.5 µM was limiting to growth of bacteria on crude oil. Exponential growth occurred at concentrations higher than 30 µM NH4 +. The P concentration of 0.13 µM was limiting to growth of bacteria on crude oil. Exponential growth occurred at 1.8 |J,M P. The maximum NH4+ consumption rate was 426 ± 30 |J,g NH4 + L−1 hr−1, and the maximum uptake rate of P was 48±4 µg P L−1 hr−1. Uptake of N and P with time showed zero-order kinetics, likely due to substrate solubility limitations. The uptake ratio of N:P was approximately 7:1 on a weight basis. Natural concentrations of N and P in marine and estuarine systems after hydrocarbon spillage initially may not limit oil biodegradation but may become limiting if adequate flux does not occur to replenish N and P depleted by microbial consumption.