MARINE INGREDIENTS
The quest for biodiversity Prospection
Accessing the potential of the microbial communities in marine ecosystems is heavily challenged by the difficulties in culturing most of these microorganisms in the laboratory. Estimates on our capacity of culturing marine bacteria and fungi range from 0.1% to 0.01% of the microorganisms in water being able to grow in laboratory conditions, a number that could be even lower according to the data obtained by Craig Venter after his environmental genome sequencing in the Sargasso sea.6 While there is debate on the reasons for this low culturability, from lack of required growth signals to the toxic effect of the rich media used in the lab, it is clear that it represents a serious barrier for the discovery of novel bioactive products. The efforts made to resolve this problem have focused on the design of specific isolation and fermentation media, as well as the construction of metagenomic libraries expressing DNA isolated from the marine sample into well known laboratory microorganisms. The latter approach provides very powerful tools for the isolation of new enzymatic activities and secondary metabolites7
that could be used for the
development of novel cosmetic ingredients. The limits that the genetic manipulation involved in constructing a metagenomic library will impose in the direct use of this technology will not impact the incorporation of new types of enzymes into the production of innovative ingredients, a line of research that seems endless based on the diversity of biochemical processes that are part of the microbial life in the oceans. In any case, depending on the type of application sought, different sampling sites should be selected. If the interest is in novel enzymatic activities, the water column or some of the extreme environments are the best places to look, but if we want secondary metabolites, the rich bottom sediment, or filtrating invertebrates are a better option. A key step in promoting biodiversity in a microbial collection is strong taxonomical de-replication. Due to the intensity of horizontal transfer of DNA in the microbial communities,8
de-replication
should be carried out for each collection point independently. An example of the power of gene transfer among bacteria is our own data on samples analysed from a location in the South Atlantic, where a novel compound not previously described in the scientific literature was found in two totally unrelated species of bacteria. Our quest for maximum diversity has resulted in a collection of samples from very different marine locations; from intertidal zones to 800 m depth sediments, and from the water surface to submarine
76 PERSONAL CARE April 2012
caves. In all these locations we have isolated a great variety of microorganisms, and when sampling the same area at different times in the year, a strong seasonal variation has been observed, suggesting that microbial diversity in the sea is a very important component of general marine biodiversity. In summary, even though culturable bacteria represents a very small fraction of the total microbial diversity, those microorganisms that can grow in the laboratory represent a formidable reservoir of novel products for cosmetic applications.
Strain isolation and fermentation How marine are marine microorganisms? From a scientific point of view, bacteria and fungi will have to be strictly marine to be considered a marine microorganism, and therefore require salt for survival. However, when we look for microorganisms with properties applicable to the cosmetic industry (or any other), a more pragmatic view can be taken, as the ability to grow in a marine environment (whether it can also grow on terrestrial conditions) potentially confers distinct structural and biochemical properties that can be the basis for a product of industrial relevance. A collection of more than 50,000 marine microorganisms, mainly isolated from invertebrates and sediments, was established, containing actinobacteria, fungi and microalgae.
Analysis of this collection revealed that application of strong dereplication methods based in HPLC and Mass Spectrometry, led to the isolation of compounds with high chemical diversity, and where more than 30% have not been previously described in the scientific literature. In addition, the potential for some of these strains to
produce secondary metabolites is highlighted by the wide array of compounds that they produce during fermentation, with some fungi and actinomycetes displaying more than 20 different metabolites when their fermentation broths are analysed by high pressure liquid chromatography (HPLC). As different conditions stimulate the production of different metabolites, a decision has to be taken regarding the old debate of ‘one strain many culture conditions’ versus ‘many strains, one standard culture condition’. A reasonable approach is the construction of an initial library of wide taxonomic diversity, and its fermentation in different types of media, aimed at different final applications (production of secondary metabolites, biotransformations, enzyme production, etc.)
Chemical nature of marine microbial products
Natural products, either structural components or secondary metabolites, reflect the peculiarities of the marine environment, although our knowledge of the association between marine conditions and structural characteristics of microorganisms is still scant. Production of toxins by marine invertebrates as a defence mechanism against predators is a widespread ecological event, and some of the first active compounds of marine origin described were among this class. Secondary metabolites produced by microorganisms have ecological functions and an impact in community relations that go far beyond the concept of chemical warfare initially proposed as the function of antibiotics.
The effect of the marine environment in the chemical structure of secondary metabolites can be seen in the higher than usual presence of halogenated
Penicillium fungus, coremial type, showing characteristic blue-green synnemata.
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