Download Insight into the ecology of aquatic Archaea

RESUME DU DOSSIER DE CANDIDATURE POUR
L’HABILITATION A DIRIGER DES RECHERCHES
Présenté par Pierre E. GALAND, CR 1 CNRS
Insight into the ecology of aquatic Archaea
Archaea were first delineated as a separate lineage based on 16S rRNA sequences from
methanogens and originally contained only representative organisms isolated from
environments considered as extreme by humans, with high temperatures, very high salt
concentrations or without oxygen. They were later defined as a new domain of life,
containing two main kingdoms later named the two phyla Crenarchaeota and
Euryarchaeota, in the classification proposed by Carl Woese in 1990, which separated
Eukaryotes, Bacteria and Archaea as three distinct domains of life. With the application
of molecular tools to target natural environments, Archaea considered originally as
extremophiles were soon found to inhabit all possible ecosystems on earth.
Interestingly, it all began with the sea, in which, for exactly 20 years ago, Archaea were
first discovered as free-living mesophilic organisms. This finding opened the way to new
research that rapidly detected Archaea in soils, sediments, lakes and associated with
metazoan species. Archaea appeared soon to be as ubiquitous as Bacteria, but were
though to have a lower diversity, in the sea and also in other environments.
This HDR thesis presents a summary of the work I conducted on Archaea,
microorganisms that have been classified and named only recently, that have potentially
a great impact globally but that remain mysterious. The report is divided into
paragraphs that reflect the scientific context in which the studies were conducted. It
covers (i) the diversity of aquatic Archaea, (ii) the spatial and temporal dynamics of
marine Archaea and (iii) Archaea as ammonium oxidizers.