Growth and pigmentation in Sphingobacterium antarcticus,a psychrotrophic bacterium from Antarctica

Sphingobacterium antarcticus, a yellow pigmented psychrotrophic bacterium from Antarctica exhibited enhanced pigmentation with increasing temperatures of incubation. This behavior was opposite to mesophilic Sphingobacterium in which pigmentation was reduced upon raising temperatures. The UV-visible spectrum of the crude pigment was characteristic of carotenoids and the pigment gave negative tests for flexirubins. Diphenylamine (DPA), a standard biochemical blocker of carotenoid biosynthesis reduced the growth of broth cultures when grown at extremes of the optimum temperature. Mutants defective in pigmentation were capable of growing between 1–31°C suggesting that pigmentation does not play any role in adapting the bacterium to the psychrotrophic growth temperature. On the other hand, our results suggest that DPA, which is known to block desaturation reactions in the carotenoid biosynthesis pathway may be affecting other desaturation reactions within the bacterium thereby causing reduced growth at extreme temperatures.