THESE Anne POSTEC Diversité de populations microbiennes ...

Résultats - Chapitre 3
Summary
The microbial diversity of the thermophilic communities inhabiting deep-sea hydrothermal
vents was analysed using batch enrichment cultures, in vials, and a continuous enrichment
culture, in a gas-lift bioreactor. Experiments were conducted at 60°C and pH 6.5, using a
complex medium containing carbohydrates, peptides, and sulfur, and inoculated with a
hydrothermal black chimney sample. Cultures were examined by molecular analyses to
assess their microbial composition and to evaluate the relevance of both culture methods.
Molecular analyses were undertaken through 16S ribosomal RNA (rRNA) gene cloning and
sequencing, DGGE, and whole-cell hybridization. Sequences related to the archaeal genus
Thermococcus and the bacterial genera Caminicella, Marinitoga and Thermosipho were
obtained from batch cultures in vials and from the continuous culture in the bioreactor.
Interestingly, sequences affiliated to the autotrophic genera Deferribacter and
Thermodesulfatator were detected only in the culture in bioreactor, indicating that a larger
microbial diversity was observed using this enrichment process. As the presence of novel
microorganisms in the bioreactor was supported by phylogenetic information retrieved by
molecular techniques, attempts to isolate new strains were undertaken. In this respect, we
successfully subcultivated in vials autotrophs belonging to the genera Deferribacter and
Thermodesulfatator, and heterotrophs belonging to the genera Thermococcus, Thermosipho
and Marinitoga, all originating from the bioreactor. Continuous enrichment culture in a gas-lift
bioreactor might be helpful to better assess the microbial diversity at deep-sea hydrothermal
vents.
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