Effects of cations, temperature, and creosote on degradation of indole by Desulfobacterium indolicum (DSM 3383)

This work describes the activity of Desulfobacterium indolicum under different conditions. Hydroxylation of indole by the sulfate-reducing marine bacterium D. indolicum was related to the concentration of Na⁺ and Mg²⁺, whereas K⁺ and Ca²⁺ had no influence. Hydroxylation of indole by D. indolicum was possible in normal medium with cation concentrations corresponding to seawater at low temperatures (10-26°C). The effect of reduced cation concentrations was most pronounced at high temperatures (29 and 36°C) where only an incomplete hydroxylation was observed in the medium with reduced cation concentrations. Desulfobacterium indolicum was more sensitive to the presence of an artificial creosote mixture when depleted for cations. Sixty milligrams of artificial creosote per liter inhibited hydroxylation of indole by 30% in a normal growth medium compared to an 86% inhibition in a medium with low concentrations of cations. Indole and quinoline were the only compounds degraded from a creosote mixture consisting of 25 compounds. It was concluded that D. indolicum is active towards indole and quinoline under growth conditions quite distinct from its optimal laboratory conditions.