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Molecular Ecology of the
Photosynthetic Procaryote Prochlorococcus, a Key Organism of Oceanic
Ecosystems
EU MAST III program, coordinated by Frédéric Partensky
Project summary
The application of molecular biology to oceanography
is still little developed, especially in Europe. However, it is a very
promising field for marine biologists, who have become able to address
key ecological questions with a level of resolution never attained by
previous methods. It is now possible to directly use molecular probes
on field samples either to assess the extent of genetic diversity in
genetically related marine organisms or to determine their nutrient
status.
The present project is centered on an important and recently discovered genus of marine photosynthetic microorganism: Prochlorococcus. This prokaryote proliferates in oligotrophic areas, including the Mediterranean and
Red Seas, is the tiniest and numerically the most abundant
photosynthetic organism on Earth (see Figure below) and accounts for a
large part (up to 50%) of the photosynthetic biomass and primary
production in these areas.
Moreover, Prochlorococcus has the advantages of being easily
discriminated and counted by flow cytometry and of possessing a unique
pigment signature (divinyl-chlorophylls a and b). In addition, natural
isolates from a variety of sites and depths are available under
laboratory conditions. Prochlorococcus therefore constitutes an
outstanding biological model for ecological studies.
In the framework of the Promolec project, we will:
1) study the intrageneric diversity of
Prochlorococcus in the laboratory and in the field, with an effort to
correlate the phenotypical and genotypical characters,
2) characterize the genes encoding cellular
components responsible for ecologically significant functions
(photosynthesis, growth, responses to nitrogen and phosphorus
limitation) and study their regulation,
3) develop a set of molecular probes and screen these functions in natural Prochlorococcus populations.
Because of the remarkable ecological importance of
Prochlorococcus, which can be considered as a biological tracer of
oligotrophy, this project is expected:
1) to improve the knowledge of the actual status of oligotrophic areas
2) to provide means to monitor biological changes
that may occur in response to variations in short or long-term
hydrological conditions (including the global man-induced increase in
carbon dioxide in the atmosphere)
3) to help identify key factors controlling the genetic diversity in picophytoplankton. |
