Tuesday, 22 October 2013

Investigating the Photoprotective Capacities of Bacteria collected from Deep Sea Hydrothermal Vents in the Mid-Atlantic Ridge

Overexposure to Ultraviolet (UV) radiation is harmful to organisms and can result in skin cancer. Therefore some form of photoprotection is needed to block this damage, so some natural compounds in organisms are known to act as a natural sunscreen, such as melanin, and there has been high commercial interest from several industries in the bioactive compounds present in marine microorganisms. The extreme conditions found in the marine environment has led to the development of a wider range of compounds in organisms  and there is high demand to exploit this, as there aren’t yet any available natural anti-UV sunscreens on the market.

To obtain the highest diversity of these compounds, scientists are looking for marine microbial resources from the most extreme sources, such as hydrothermal vents. Marine prokaryotes were collected at four vents in the Mid-Atlantic Ridge (MAR) to discover more about the diversity of functional taxonomic groups of free-living microorganisms, and their biotechnological potential.

New Marine Prokaryotes Isolates from MAR Vents:
289 marine prokaryotes were successfully isolated from the sites and grown in standardised culturing conditions, even though it was previously thought that complex culturing methods were needed for microorganisms, particularly in the deep sea (Alain & Querellou, 2009). These prokaryotes were categorised into three phenotypic operational groups (Groups I, II and III) depending on oxygen demand and temperature for optimum growth.

MAR Vents Prokaryotic Biodiversity
A polyphasic characterisation approach was applied in conjunction with a strain clustering strategy for the 246 marine prokaryotes isolated to investigate biodiversity, and used methods such as PCR fingerprinting, which involved whole-cell protein profiling. Shannon (J’) and Simpson (D’) biodiversity indices were also obtained for each of the phenotypic groups. The authors used two molecular techniques to obtain a more robust dataset, which led to 23 clusters of phonetically similar isolates being identified, and the observation that phenetic diversity decreases from groups I to III. A subset of isolates from the clusters were also identified by 16S rRNA gene sequencing, and the results was suggested that almost half of the collected samples were composed of new species.

MAR Vents Bacteria Extract Possess Photoprotective Capacity
A yeast-based assay was exposed to either UV-A or UV-C lethal radiation doses and  it was found that the yeast cells injected with extracts with a photoprotective capacity were able to proliferate and form colonies, but those without didn’t grow. Two extracts, MGMS241O2 and RBRS241O2 isolates, were also found to possess protective capacity under UV-B as well. Further gene sequencing identified MGMS241O2 as a new strain belonging to the species Shewanella algae, which is known to produce melanin for multiple roles, potentially for photoprotection. RBRS251O2 was also found to be a new strain that belonged to Vibrio fluvialis, although this work was the first to identify photoprotection in this species.

The attraction to the study of bioactive compounds in marine microorganisms is due to their already established photoprotective ability, and many industries are keen to exploit this trait and develop anti-UV natural sunscreen products. Considering the high commercial value of these microorganisms, the authors have managed to portray the importance of biological products in marine prokaryotes, which allow them to tolerate stressful conditions in extreme marine environments, by developing a novel and industrial-suited marine bacteria collection, as well as managing to grow these microorganisms under standard cultivation methods, which is controversial to previous work.

Martins, A., Tenreiro, T., Andrade, G., Gadanho, M., Chaves, S., Abrantes, M., Calado, P., Tenreiro, R., & Vieira, H. (2013) Photoprotective Bioactivity Present in a Unique Marine Bacteria Collection from Portuguese Deep Sea Hydrothermal Vents. Marine Drugs, 11, 1506-1523


  1. It seems fascinating that these bacteria from the deep sea produce photoprotective pigments, suggesting to me that the compounds probably have another natural function. Maybe they have general antioxidant properties?

  2. Thanks Colin, I’m glad you made that point. That particular idea was also mentioned briefly in the conclusion- they suggest that the metabolites that cause photoprotection actually have different roles in their natural environment, but under certain, favourable, conditions (i.e. exposed to light in the lab) may also act as photoprotectives. It’s widely known that many microorganisms in hydrothermal vents are highly thermotolerant to the extreme temperatures, but now that they have found evidence for mechanisms even in the absence of the stressful conditions, it opens new possibilities for other underlying or secondary roles. Maybe future work could look into how these particular metabolites, or other similar compounds, cope with other types of stressors. This isn’t a brand new concept, but I think it would be fascinating to exploit the multiple purposes of these compounds as they could potentially have an even greater biotechnological potential than the role they play in sunscreens. Because the authors have also found new techniques to cultivate these bacteria, in spite of several complex methods being widely used previously, this provides new and more effective techniques to other deep-sea microbiologists, and could make this type of work easier to undertake in the future.