Anti-protease and immunomodulatory activities of bacteria associated with Caribbean sponges

Abstract

Marine sponges and their associated bacteria have been proven to be a rich source of novel secondary metabolites with therapeutic usefulness in cancer, infection, and autoimmunity. In this study, 79 strains belonging to 20 genera of the order Actinomycetales and seven strains belonging to two genera of the order Sphingomonadales were cultivated from 18 different Caribbean sponges and identified by 16S rRNA gene sequencing. Seven of these strains are likely to represent novel species. Crude extracts from selected strains were found to exhibit protease inhibition against cathepsins B and L, rhodesain, and falcipain-2 as well as immunomodulatory activities such as induction of cytokine release by human peripheral blood mononuclear cells. These results highlight the significance of marine sponge-associated bacteria to produce bioactive secondary metabolites with therapeutic potential in the treatment of infectious diseases and disorders of the immune system.

Fig. 1

Neighbor-joining trees of isolates and representative species of the order Actinomycetales (a) and Sphingomonadales (b) based on nearly complete 16S rRNA gene sequences. Numbers at the nodes indicate the levels of the bootstrap support based on 1,000 resampled data sets. Only values greater than 50% are shown. The arrow points to the outgroup consisting of four species belonging to Methanosarcinaceae. The scale bar indicates 0.05 substitution per nucleotide position

Fig. 2

Cytokine responses of precultured human peripheral blood mononuclear cells to crude extracts from bacterial isolates. a TNF, b IFN-γ, c IL-2, and d IL-10. Crude extracts were tested in triplicates at three different concentrations (preparations from liquid cultures—25, 2.5, and 0.25 μg/ml, from solid cultures—10, 1, and 0.1 μg/ml), and the most active one is shown. The isolates A. jenensis strain BA22, A. oxydans strain BA30, A. oxydans strain BA34a, and M. coxensis strain CO164 were grown on M1 agar plates for 7–10 days. Crude extract from isolate A. oxydans strain BA34b was obtained after 4 days of liquid culture, and active extracts from strains Lapillicoccus sp. BA53, S. shandongensis strain CO86 and Sphingobium sp. CO132 were prepared after 7 days of liquid culture

Fig. 3

PBMC proliferation, measured as radioactivity incorporated into DNA from tritiated thymidine, in response to stimulation with crude extract from strain Sphingobium sp. CO105. Crude extract was tested in triplicates at a concentration of 65 ng/ml