POSSIBLE ORIGIN OF ZEAXANTHIN IN THE MARINE SPONGE, RENIERA-JAPONICA

As part of a study to clarify the origins of biologically active subst ances in marine sponges, the carotenoids produced by two species of ma rine bacteria, Flexibacter sp. strain number DK30213 and DK30223, asso ciated with the marine sponge, Reniera japonica, were investigated. Bo th bacteria were found to produce zeaxanthin [(3R,3'R)-dihydroxy-beta, beta-carotene] which is widely distributed in marine organisms. This c arotenoid was also detected in the host sponge, suggesting the transpo rt of zeaxanthin from the microorganisms to the host. As zeaxanthin pl ays the role of a quencher and scavenger for active species of oxygen, it is presumed that the sponge accumulates the bacterial product as a defense substance against the active oxygen species produced under ir radiation by strong sunlight. It is thought that the bacteria are symb ionts of the host sponge and act by obtaining the solid substrate and medium needed for settlement and growth from the host, and by producin g and transmitting the biologically active substance to the host. Zeax anthin-producing bacteria are also considered to have potential for pr actical uses by the aquacultural, pharmaceutical and food industries.