Monday, 27 January 2014

Bacterial strains as sources of antioxidant, antimicrobial and antiplasmodial compounds in the marine sponge, Phorbas tenacior

Marine sponges are recognised as a rich source of biologically active compounds. Already, some of these compounds have been used as therapeutics and anticancer agents, another one hundred are currently under preclinical evaluation.

More than 30 different phyla of sponge-associated organisms have been recognised and can equate to as much as 37% of the sponges biomass. However, currently only 1% can be cultured in laboratory conditions. These species-specific micro-organisms may play a role in nutrient uptake, stability of the sponge skeleton, chemical defence or antibiofouling agents but these advantages remain poorly understood. It is thought that these bacteria provide a potential renewable source of biomedical agents. However, there are concerns about difficulties in ensuring production at an industrial level.

Transmission electron microscopy and scanning electron microscopy were used to assess the localisation of the bacteria within the sponge. Individual strains were isolated using serial dilutions cultured on various media. The bacterial community was determined by 16S rRNA gene sequencing then BLASTed against a database. Several assays were used to determine antiplasmodial, antioxidant and antimicrobial properties.

A great variety of bioactive molecules have been reported from the genus Phorbas, but this is the first report to describe antioxidant and antiplasmodial activities associated with the P. tenacior sponge.

Micro-organisms were found to be extracellular in the mesohyl of all different shapes and sizes. The two most common phyla associated with this sponge are Proteobacteria and Actinobacteria, including the genera Vibrio and Shewanella. Both of these genera have been shown to have antifouling, antioxidative or antibacterial properties.

It was also discovered that the sponge itself or its associated microbes can produce antioxidant compounds which prevent protein or lipid damage, ensuring the protection of the bacteria when the sponge host produces oxidative compounds. Vertical transmission of Pseudovibrio spp. bacterial larvae to the sponge has provided evidence of a possible symbiotic relationship.

Antiplasmodial activity from Vibrio strains was first reported in this study, with 45% inhibition of Plasmodium falciparum at 100 µg ml-1. No antimicrobial activity was detected against pathogenic environmental strains such as Vibrio harveyi and V. parahaemolyticus. A Citricoccus alkalitolerans strain was also first reported to be associated with a marine sponge. These microbes showed a moderate antimicrobial activity against many environmental stressors including V. parahaemolyticus, therefore could help in host defence against pathogens.

Bioactive compounds produced by the bacterial community of the marine sponge, P. tenacior, could be extremely beneficial to human health and marine organisms, depending on industrial production. Benefits for seafood industries could be a possibility, minimizing the outbreaks of harmful environmental pathogens.

 I thought this was an interesting new development and a good starting point for further research, acting as a wide overview of the bacterial community and its capabilities found within this sponge. Focusing on individual areas could provide a more in-depth knowledge and provide potential uses of these bioactive compounds in biomedical agents.

Dupont, S., Carre-Mlouka, A., Descarrega, F., Ereskovsky, A., Longeon, A., Mouray, E., Florent, I. and Bourguet-Kondracki, M.L. (2013) Diversity and biological activities of the bacterial community associated with the marine sponge Phorbas tenacior (Porifera, Demospongiae). Letters in Applied Microbiology. 58: 42-52

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