Morphological, Bacterial, and Secondary Metabolite Changes of Aplysina aerophoba upon Long-Term Maintenance Under Artificial Conditions

The aim of this study was to analyze successional changes in the bacterial community over a period of 6 months of cultivation of Aplysina aerophoba sponges under different artificial cultivation conditions by use of denaturing gradient gel electrophoresis (DGGE). The cultivation conditions varied concerning the water temperature (20 +/- 2 A degrees C and 25 A +/- 2 A degrees C) of the aquaria, additional illumination of one aquarium, and feeding of the sponges. Amplicons from DGGE separation of dominant colonizing or variably appearing bacteria were sequenced and aligned for taxonomical identification. In addition, secondary metabolites typically found in A. aerophoba were analyzed to investigate changes in the natural product profile during cultivation. The cultivation of sponges under any given condition did not lead to a depletion of their bacterial community in the course of the experiment. On the contrary, the distinctive set of associated bacteria was maintained in spite of a dramatic loss of biomass and morphological degradation during the cultivation period. Generally, all sequences obtained from the DGGE gels were related to bacteria of five phyla: Actinobacteria, Cyanobacteria, alpha-Proteobacteria, gamma-Proteobacteria, and Chloroflexi. Despite the overall stability of the bacterial community in A. aerophoba, an unambiguous variability was detected for the Cyanobacteria A. aerophoba clone TK09. This variability was ascribed to the predominant light conditions. The analysis of the metabolic pattern revealed that the concentration of a class of characteristic-brominated compounds typically found in A. aerophoba, like aeroplysinin-1, aerophobin-1, aerophobin-2, and isofistularin-3, increased over the 6 months of cultivation.