In this blog Dr Marcio Custódio talks about the co-authored paper Reduction of RBL–2H3 cells degranulation by nitroaromatic compounds from a Bacillus strain associated to the Amazonian sponge Metania reticulata which featured in the New Frontiers in Sponge Science special issue from Journal of the Marine Biological Association.

Sea sponges (phylum Porifera) are already known as a rich source of new molecules. However, many are produced by a large and frequently specific associated microbiota. Several bioactivities were described for these compounds, antibiosis the most common; extracts from most species will show this characteristic in some degree. At the same time, it is also know that several antimicrobial agents can interfere with the vertebrate immune system, both at cell-mediated and/or humoral levels.

Based on these observations, we tested the possibility that these sponge antibiotics could have a similar immunomodulatory effects observed in common compounds such as tetracyclines or rifampicin. To do this, we used bacterial strains isolated from Metania reticulata, a freshwater sponge from the Brazilian Amazon.

Freshwater sponges are a relatively small group within Porifera but with an important presence in Brazil, with almost 50 from circa 250 species described worldwide. They can be quite abundant in some areas in the Amazon, growing attached to trees that become exposed during the dry season, leaving the dead sponge skeleton. As such, they are recognized as cauxi by the locals mainly due to the strong skin rash the contact with it causes, although most people do not know it is an animal. However, differently from its marine counterparts, limited knowledge is available about its bioactive compounds.

Using this sponge as source, we were able to isolate bacterial strains, whose extracts were first tested in antibiosis assays. The extract with the highest activity was then fractioned and tested regarding its capacity to inhibit the degranulation induced by fMLP in a neutrophil-like cell model. Two of these purified fractions, indentified as nitroaromatic compounds, showed inhibitory activity similar to that elicited by Cyclosporine A.

This immunosuppressive characteristic is not tested in many screenings, usually directed only to antibiosis. Performing such assays on newly isolated antibiotic compounds could reveal new and interesting molecules. In addition, this is the first report of bioactive molecules obtained from a sponge of the Amazon rainforest, an area that is under increasing pressure due to human occupation. As such, it could also raise the awareness for the preservation of this important biome and its biotechnological resources.

Read the article for free here until 1st August 2016.