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
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?
ReplyDeleteThanks 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.
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