Monitoring microbial diversity and natural product profiles of the sponge<Emphasis Type="Italic"> Aplysina cavernicola</Emphasis> following transplantation

In order to assess the stability of the microbial community of the sponge Aplysina cavernicola under in situ conditions, sponges were transplanted from their original location (>40 m depth) to shallower, more light-exposed sites (7-15 m depth). Transmission electron microscopy revealed that the microbial community remained visually unchanged and free of cyanobacteria over the experimental time period of 3 months. Denaturing gradient gel electrophoresis (DGGE) of PCR-amplified partial 16S rRNA gene sequences allowed a distinction between the variable and permanent fraction of the bacterial community. Comparative sequence analysis of four variable DGGE bands revealed high sequence similarity to representatives of the Alpha- and Gammaproteobacteria and the phylum Bacteroidetes, which have been recovered previously from Mediterranean seawater as clone sequences or by cultivation. Seven (out of 12) permanent DGGE bands showed high sequence similarity to a sponge-specific, monophyletic 16S rRNA gene sequence cluster within the Acidobacteria division, and to a sequence cluster of uncertain affiliation. These sequence clusters represent members of a common microbial community that is shared among distantly related sponges from different, non-overlapping geographic regions. Four additional permanent DGGE bands showed high sequence similarity to a Betaproteobacterium, Burkholderia cepacia, which is not typically known as a marine bacterium. High-performance liquid chromatography analyses of sponge tissues revealed no changes in metabolite pattern, indicating that these compounds are expressed constitutively irrespective of the variations resulting from the transplantation experiment.