Relation between denitrification and biodegradation of n-heptadecane in a marine bacterium

The marine denitrifying bacterium Pseudomonas nautica sp. 617 was cultivated on n-heptadecane under various conditions of oxygenation in presence of nitrate. In aerobiosis, when the partial pressure of dissolved oxygen (ppO(2)) was upper than 0.34 parts per million (ppm), Ps. nautica used the molecular oxygen as terminal electron acceptor to grow on n-heptadecane, but without denitrification. When the ppO(2) value became lower than 0.34 ppm, nitrate and molecular oxygen were used simultaneously as electron acceptors. In absence of molecular oxygen, Ps. nautica did not oxidise the n-heptadecane but grew on the oxygenated derivates produced during the aerobical phase of growth, using nitrate as sole electron acceptor These results confirm the possibility of denitrification in presence of molecular oxygen and show the way used by a denitrifying bacterium for the biodegradation of the n-alkanes in the marine sediments submitted to variations of ppO(2).