Scheda di dettaglio – i prodotti della ricerca
| Dato | Valore |
|---|---|
| Title | Effects of Small-Scale Turbulence on Bacteria: A Matter of Size |
| Abstract | We examined the influence of small-scale turbulence and its associated shear on bacterioplankton abundance and cell size. We incubated natural microbial assemblages and bacteria-only fractions and subjected them to treatments with turbulence and additions of mineral nutrients and/ or organic carbon. Bacterial abundance was not affected directly by turbulence in bacteria-only incubations. In natural microbial assemblage incubations, bacterial concentrations were higher under turbulence than in stillwater controls when nutrients were added. In general, in the turbulence treatments bacteria increased significantly in size, mainly due to elongation of cells. The addition of inorganic nutrients had a negative effect on bacterial size, but a significantly positive effect on abundance independently of other factors such as turbulence and the presence of predators. Flagellate grazing did not trigger an increase in bacterial size as a grazing resistance response in unmixed containers. With the addition of organic carbon, bacteria elongated and partly settled to the bottom of the containers, in both the turbulent and still treatment, but bacterial abundance did not further increase. Furthermore, bacteria aggregated in the turbulence treatments after the second day of incubation even in the absence of other components of the microbial community. We found that turbulence and the associated shear increase bacterial size and change bacterial morphology, at least under certain nutrient conditions. This might be due to a physiological response (enhanced growth rate and/or unbalanced growth) or due to the selection of opportunistic strains when organic carbon is in excess compared to mineral nutrients. We suggest that shear associated with turbulent flow enhances the DOM flux to bacteria directly as well as indirectly through enhanced grazing activity and photosynthetic release. The formation of bacterial aggregates and filaments under turbulence might give selective advantage to bacteria in terms of nutrient uptake and grazing resistance. |
| Source | Microbial ecology 48, pp. 287–299 |
| Keywords | bacterioplanktoncell sizegrazingturbulenceseawater |
| Journal | Microbial ecology |
| Editor | Springer-Verlag,, New York,, Stati Uniti d'America |
| Year | 2004 |
| Type | Articolo in rivista |
| DOI | 10.1007/s00248-004-0133-4 |
| Authors | A. Malits (1); F. Peters (1); M. Bayer-Giraldi (1); C. Marrasé (1); A. Zoppini (2); O. Guadayol (1); M. Alcaraz (1) |
| Text | 179949 2004 10.1007/s00248 004 0133 4 ISI Web of Science WOS 000225869200001 bacterioplankton cell size grazing turbulence seawater Effects of Small Scale Turbulence on Bacteria A Matter of Size A. Malits 1 ; F. Peters 1 ; M. Bayer Giraldi 1 ; C. Marrase 1 ; A. Zoppini 2 ; O. Guadayol 1 ; M. Alcaraz 1 1 Institut de Ciencies del Mar, CMIMA CSIC , Passeig Mar tim de la Barceloneta 37 49, 08003 Barcelona, Spain; 2 Istituto di Ricerca Sulle Acque CNR , Via Reno l, 00198 Rome, Italy We examined the influence of small scale turbulence and its associated shear on bacterioplankton abundance and cell size. We incubated natural microbial assemblages and bacteria only fractions and subjected them to treatments with turbulence and additions of mineral nutrients and/ or organic carbon. Bacterial abundance was not affected directly by turbulence in bacteria only incubations. In natural microbial assemblage incubations, bacterial concentrations were higher under turbulence than in stillwater controls when nutrients were added. In general, in the turbulence treatments bacteria increased significantly in size, mainly due to elongation of cells. The addition of inorganic nutrients had a negative effect on bacterial size, but a significantly positive effect on abundance independently of other factors such as turbulence and the presence of predators. Flagellate grazing did not trigger an increase in bacterial size as a grazing resistance response in unmixed containers. With the addition of organic carbon, bacteria elongated and partly settled to the bottom of the containers, in both the turbulent and still treatment, but bacterial abundance did not further increase. Furthermore, bacteria aggregated in the turbulence treatments after the second day of incubation even in the absence of other components of the microbial community. We found that turbulence and the associated shear increase bacterial size and change bacterial morphology, at least under certain nutrient conditions. This might be due to a physiological response enhanced growth rate and/or unbalanced growth or due to the selection of opportunistic strains when organic carbon is in excess compared to mineral nutrients. We suggest that shear associated with turbulent flow enhances the DOM flux to bacteria directly as well as indirectly through enhanced grazing activity and photosynthetic release. The formation of bacterial aggregates and filaments under turbulence might give selective advantage to bacteria in terms of nutrient uptake and grazing resistance. 48 Effects of Small Scale Turbulence on Bacteria A Matter of Size We examined the influence of small scale turbulence and its associated shear on bacterioplankton abundance and cell size. We incubated natural microbial assemblages and bacteria only fractions and subjected them to treatments with turbulence and additions of mineral nutrients and/ or organic carbon. We suggest that shear associated with turbulent flow enhances the DOM flux to bacteria directly as well as indirectly through enhanced grazing activity and photosynthetic release. The formation of bacterial aggregates and filaments under turbulence might give selective advantage to bacteria in terms of nutrient uptake and grazing resistance. Malits_et_al_ME_05.pdf Articolo in rivista Springer Verlag, 0095 3628 Microbial ecology Microbial ecology Microb Ecol Microbial ecology. annamaria.zoppini ZOPPINI ANNAMARIA |