Possible involvement of Pseudomonas sphingolipid ceramide N-deacylase in red spot disease of eels

Strain TK4 capable of producing sphingolipid ceramide N-deacylase (SCDase) was isolated from pond in which eel culture was conducted. TK4 was assigned to the genus Pseudomonas on the basis of morphological, physiological and biochemical characteristics and found to be very similar to P. anguilliseptica, a known pathogen for red spot disease in eels. 16S rDNA sequence analysis revealed that TK4 and P. anguilliseptica should be classified into Group I of the genus Pseudomonas. Interestingly, not only TK4 but also P. anguilliseptica had the ability to produce SCDase which hydrolyzes glycosphingolipids and sphingomyelin to generate lyso-forms of sphingolipids. Since lyso-sphingolipids are toxic to many cell lines, SCDase-producing Pseudomonas spp. are suspected to be a potential virulence factor for fish disease including red spot disease (Sekiten-byo) in eels.