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TitleCompetition and protist predation are important regulators of riverine bacterial community composition and size distribution
AbstractAmong the bacterivorous protists, heterotrophic nanoflagellates (HNFs) are considered to be the main grazers of bacteria in freshwaters due to their size-selective grazing. In this work, we assessed the change of a riverine bacterial community in controlled incubations, where HNFs' predation pressure was initially released through filtration. Filtration did not prevent the passage of cysts, which grew in the enrichments afterwards. Data on the composition of the bacterial community were gathered by Catalyzed Reporter Deposition Fluorescent In situ Hybridization (CARD-FISH) using 16S probes targeting phylogenetic groups. Bacterial cell size was also examined using image analysis. Overall, the initial filtration directly (through release of predation pressure) or indirectly (through competition among bacterial groups) affected the bacterial community composition. When nanoflagellate abundance rose, a reduction of bacterial abundance and changes in cell size distribution were observed. Gamma-Proteobacteria and Actinobacteria were the groups showing the greatest reduction in abundance. Beta-Proteobacteria showed a reduction of cell size and were found in aggregates. Alpha-Proteobacteria and Actinobacteria developed two distinct filamentous morphotypes: short, segmented rods and long chains of rods. Our results showed that the release of the predation pressure and the successive rise of the nanoflagellates changed the bacterial community in terms of composition at large phylogenetic scale. HNF grazing is highly group-specific and seems to reconstruct the community based on cell size, and thus, not only drastically changing the bacterial community composition, but also increasing its functional diversity.
SourceJournal of freshwater ecology 31 (4), pp. 609–623
KeywordsBacteriananoflagellatesaggregatesfilamentsfunctional diversityriver ecology
JournalJournal of freshwater ecology
EditorOikos Publishers,, La Crosse, Wis., Stati Uniti d'America
Year2016
TypeArticolo in rivista
DOI10.1080/02705060.2016.1209443
AuthorsBatani, Giampiero; Perez, German; Martinez de la Escalera, Gabriela; Piccini, Claudia; Fazi, Stefano
Text372307 2016 10.1080/02705060.2016.1209443 ISI Web of Science WOS 000387166100011 Bacteria nanoflagellates aggregates filaments functional diversity river ecology Competition and protist predation are important regulators of riverine bacterial community composition and size distribution Batani, Giampiero; Perez, German; Martinez de la Escalera, Gabriela; Piccini, Claudia; Fazi, Stefano Natl Res Council Italy IRSA CNR; Inst Investigaciones Biol Clemente Estab Among the bacterivorous protists, heterotrophic nanoflagellates HNFs are considered to be the main grazers of bacteria in freshwaters due to their size selective grazing. In this work, we assessed the change of a riverine bacterial community in controlled incubations, where HNFs predation pressure was initially released through filtration. Filtration did not prevent the passage of cysts, which grew in the enrichments afterwards. Data on the composition of the bacterial community were gathered by Catalyzed Reporter Deposition Fluorescent In situ Hybridization CARD FISH using 16S probes targeting phylogenetic groups. Bacterial cell size was also examined using image analysis. Overall, the initial filtration directly through release of predation pressure or indirectly through competition among bacterial groups affected the bacterial community composition. When nanoflagellate abundance rose, a reduction of bacterial abundance and changes in cell size distribution were observed. Gamma Proteobacteria and Actinobacteria were the groups showing the greatest reduction in abundance. Beta Proteobacteria showed a reduction of cell size and were found in aggregates. Alpha Proteobacteria and Actinobacteria developed two distinct filamentous morphotypes short, segmented rods and long chains of rods. Our results showed that the release of the predation pressure and the successive rise of the nanoflagellates changed the bacterial community in terms of composition at large phylogenetic scale. HNF grazing is highly group specific and seems to reconstruct the community based on cell size, and thus, not only drastically changing the bacterial community composition, but also increasing its functional diversity. 31 Published version Competition and protist predation are important regulators of riverine bacterial community composition and size distribution Batani et al. 2016.pdf Articolo in rivista Oikos Publishers, 0270 5060 Journal of freshwater ecology Journal of freshwater ecology J. freshw. ecol. Journal of freshwater ecology. stefano.fazi FAZI STEFANO