|
|
|
|
>>>> Scientific context |
|
|
|
|
|
|
|
|
|
|
|
|
 |
 |
 |
 |
|
Sinking particulate matter is the major vehicle for exporting carbon and energy from the sea surface to the intermediate and deep-sea waters until the final receptacle constituted by the sediments. During its transit towards the seafloor, most particulate organic carbon (POC) is returned to inorganic form. Attached bacteria play an important role in the degradation of aggregates, converting POC to dissolved organic carbon (DOC), bacterial carbon and carbon dioxide (CO2) through the preliminary step of ectoenzymatic hydrolysis Experiments devoted to the measurement of biodegradation rates of sinking particles are currently conducted under atmospheric pressure conditions.We used a new experimental strategy to simulate the particle sinking through the water column. Our preliminary results show that the increase of hydrostatic pressure affects the bacterially-mediated biodegradation and biodissolution of sinking particles. Yet, metabolic activities of surface-produced bacteria attached on particles sinking through the whole water column decrease in the twilight zone, and then in the deep-sea water. Hence, thanks to the we propose, we will be able to better understand a major step of the functioning of the global ocean, and to better quantify the role of attached bacteria on the transformation POC to DOC and recycling of biogenic elements (as silicate and carbonate biominerals). Molecular techniques based on culture-independent methods would permit us to better understand the role of heterotrophic bacteria in organic cycles and other biogeochemical processes. Whenever the metabolic potential of a community has been demonstrated, molecular techniques such as DGGE make it possible to know its structure without isolation. After DNA extraction of the community, PCR products of 16S rRNA V3-V5 gene fragments can be separated according to their electrophoretic mobility along a denaturating gradient. DGGE can sort DNA fragments of identical length but with different nucleotide sequences. DGGE can detect up to 95% of all possible single base substitutions among sequences of up to 1000 base pairs in length. After electrophoresis, major DGGE bands can be excised from the gel for subsequent phylogenic analysis or detected by genus probe after hybridization. However a number of studies has shown that bacteria attached to particles may be phylogenetically different from free-living bacteria. This project consists of multidisciplinary experimental studies devoted to biogeochemical processes of interest for the modeling of mater and energy flows through the whole water column. Experimental data obtained using the a specific equipment allowing to simulate increase in pressure conditions during the sink of particles through the water column will be related to field data obtained from sediment traps, and analysis of organic and inorganic compound concentrations in the water column. So, results will greatly enhance the possibility to quantify and qualify the pelagos – benthos relationships. |
|
Contact:
Christian Tamburini (tamburini@univmed.fr)
; Tel.: +33 4 91 82 90 53 - Fax : +33 4 91 82
90 51 |
Copyright
© 2003-2009 - Laboratoire de Microbiologie, Géochimie et Ecologie Marines
- Last update: April 20th 2006 |