A naphthalene-degrading plasmid from a psychrotolerant pseudomonad

Abstract

Pseudomonas strain MC1 was isolated from the waste water treatment facilities at the Korea's King Sejong station (62°13′S 58°47′W) on King George Island for the ability to grow on naphthalene as the sole carbon and energy source. MC1 was also found to grow well on phenanthrene and biphenyl. Growth substrate range experiments coupled with the ring-cleavage enzyme assay data suggest that MC1 initially metabolizes naphthalene to salicylate with subsequent degradation through meta-ring cleavage pathway. One interesting aspect of the MC1 growth is that growth temperature optima are different for different growth substrates. Namely, on succinate, MC1 showed optimal growth at the temperature of 15-30°C whereas its growth on salicylate is significantly inhibited above 27°C with accumulation of brownish-colored compound in the medium. This observation indicates that a certain enzyme(s) responsible for metabolizing salicylate is more thermo-unstable than the ones involved in the metabolism succinate. This hypothesis is in good agreement with the fact that when grown on salicylate MC1 reaches higher growth peaks, with the highest at 5°C, as the culture temperature decreases.