Scheda di dettaglio – i prodotti della ricerca
| Dato | Valore |
|---|---|
| Title | Extracellular enzyme activity and dynamics of bacterial community in mucilaginous aggregates of the northern Adriatic Sea |
| Abstract | Bacterial degradation of mucilaginous aggregates (creamy layers, stringers and macroflocs) collected during two summer events (2001-2002) was tested. The objective was to describe the temporal trend of the bacterial activity, abundance and composition in the aggregated and dissolved organic matter under different trophic conditions. In the native aggregates proteins and organic phosphorous were actively hydrolyzed as aminopeptidase and alkaline phosphatase activities represented up to 87% and 25% of total activity, respectively; polysaccharides were less hydrolyzed and the highest activities were observed for h-glucosidase (5% of the total). This hydrolysation pattern tends to a progressive accumulation of long persistent polysaccharides. During short term incubations nutrient addition (P, N and Glucose) differently stimulated bacterial growth in the seawater: P played the main role in stimulating bacterial production from 3 to 6 folds higher than in the control, whereas a secondary Climitation was observed only for bacteria growing on seawater from macroflocs. This scarce dissolved organic carbon (DOC) bioavailability was confirmed by the lower DOC removal (13% macroflocs, 36% stringers). The total amount of carbon incorporated by bacteria living on aggregates was similar (0.58 mg C L1) both in the control and under P enrichments showing a more balanced condition with respect to the seawater. Hence the well-known P limitation in the Northern Adriatic Sea affects only dissolved organic carbon uptake without influencing the uptake of aggregated organic matter. Organic matter limitation was observed only on stringers--total C incorporated raised to 0.96 mg C L1 after PNG addition. Macroflocs release of refractory compounds leads to DOC accumulation (73 AM DOC) contributing to inflate the pool of refractory DOC in the surrounding waters. Several evidences, including different monosaccharide composition of stringers and macroflocs (glucose 15% and 56% on stringers and macroflocs, respectively), bring to the conclusion that stringers are in an older stage in comparison with macroflocs. Community composition described by fluorescence in situ hybridization did not show significant differences between free-living and attached bacteria but it was modified by the different enrichment conditions: Cytophaga- Flavobacteria increased after inorganic nutrients enrichments while organics advantaged g-Proteobacteria. |
| Source | Science of the total environment 353, pp. 270–286 |
| Keywords | MucilageEnzymatic activityBacterial activityCommunity compositionOrganic matter |
| Journal | Science of the total environment |
| Editor | Elsevier, Lausanne ;, Paesi Bassi |
| Year | 2005 |
| Type | Articolo in rivista |
| DOI | 10.1016/j.scitotenv.2005.09.019 |
| Authors | Annamaria Zoppini (a); Alberto Puddu (a); Stefano Fazi (a); Michela Rosati (a); Paola Sist (b) |
| Text | 179912 2005 10.1016/j.scitotenv.2005.09.019 ISI Web of Science WOS 000234421900023 Mucilage Enzymatic activity Bacterial activity Community composition Organic matter Extracellular enzyme activity and dynamics of bacterial community in mucilaginous aggregates of the northern Adriatic Sea Annamaria Zoppini a ; Alberto Puddu a ; Stefano Fazi a ; Michela Rosati a ; Paola Sist b a Water Research Institute, National Research Council, Rome, Italy; b Department of Biochemistry, Biophysics and Macromolecular Chemistry University of Trieste, Italy Bacterial degradation of mucilaginous aggregates creamy layers, stringers and macroflocs collected during two summer events 2001 2002 was tested. The objective was to describe the temporal trend of the bacterial activity, abundance and composition in the aggregated and dissolved organic matter under different trophic conditions. In the native aggregates proteins and organic phosphorous were actively hydrolyzed as aminopeptidase and alkaline phosphatase activities represented up to 87% and 25% of total activity, respectively; polysaccharides were less hydrolyzed and the highest activities were observed for h glucosidase 5% of the total . This hydrolysation pattern tends to a progressive accumulation of long persistent polysaccharides. During short term incubations nutrient addition P, N and Glucose differently stimulated bacterial growth in the seawater P played the main role in stimulating bacterial production from 3 to 6 folds higher than in the control, whereas a secondary Climitation was observed only for bacteria growing on seawater from macroflocs. This scarce dissolved organic carbon DOC bioavailability was confirmed by the lower DOC removal 13% macroflocs, 36% stringers . The total amount of carbon incorporated by bacteria living on aggregates was similar 0.58 mg C L1 both in the control and under P enrichments showing a more balanced condition with respect to the seawater. Hence the well known P limitation in the Northern Adriatic Sea affects only dissolved organic carbon uptake without influencing the uptake of aggregated organic matter. Organic matter limitation was observed only on stringers total C incorporated raised to 0.96 mg C L1 after PNG addition. Macroflocs release of refractory compounds leads to DOC accumulation 73 AM DOC contributing to inflate the pool of refractory DOC in the surrounding waters. Several evidences, including different monosaccharide composition of stringers and macroflocs glucose 15% and 56% on stringers and macroflocs, respectively , bring to the conclusion that stringers are in an older stage in comparison with macroflocs. Community composition described by fluorescence in situ hybridization did not show significant differences between free living and attached bacteria but it was modified by the different enrichment conditions Cytophaga Flavobacteria increased after inorganic nutrients enrichments while organics advantaged g Proteobacteria. 353 Extracellular enzyme activity and dynamics of bacterial community Bacterial degradation of mucilaginous aggregates creamy layers, stringers and macroflocs collected during two summer events 2001 2002 was tested. The objective was to describe the temporal trend of the bacterial activity, abundance and composition in the aggregated and dissolved organic matter under different trophic conditions. Zoppini_et_al_STOTEN_05.pdf Articolo in rivista Elsevier 0048 9697 Science of the total environment Science of the total environment Sci. total environ. stefano.fazi FAZI STEFANO alberto.puddu PUDDU ALBERTO annamaria.zoppini ZOPPINI ANNAMARIA |