Jezbera J, Hornak K, Simek K.. Prey selectivity of bacterivorous protists in different size fractions of reservoir water amended with nutrients. Environ Microbiol 8: 1330-1339

Hydrobiological Institute of the Academy of Sciences of the Czech Republic, Na Sádkách 7, CZ-37005, Ceské Budejovice, Czech Republic.
Environmental Microbiology (Impact Factor: 6.2). 08/2006; 8(8):1330-9. DOI: 10.1111/j.1462-2920.2006.01026.x
Source: PubMed


An experiment designed to examine food preferences of heterotrophic nanoflagellates (HNF) grazing on bacterioplankton was performed in the freshwater Rímov reservoir (Czech Republic). Water samples were size-fractionated to obtain < 5 microm filtrate containing bacteria and HNF. To manipulate resource availability, < 5 microm treatments were incubated in dialysis bags submerged in the barrels filled with the unfiltered reservoir water amended with either orthophosphate or glucose or combination of both. We employed rRNA-targeted probes to assess HNF prey preferences by analysing bacterial prey in HNF food vacuoles compared with available bacteria. Actinobacteria (the HGC69a probe) were avoided by HNF in all treatments. Cytophaga-Flavobacterium-Bacteroidetes bacteria (the CF319a probe) were positively selected mainly in treatments in which bacteria were heavily grazed, the < 5 microm treatments, but this trend was less pronounced towards the end of the study. The members of a small subcluster of Betaproteobacteria (the R-BT065 probe) were mostly positively selected. The nutrient amendments differentially affected bacterioplankton dynamics in almost all treatments, and together with the size fractionation, altered HNF overall bacterivory as well as prey selection. Analyses of bacterivores in unfiltered treatments allowed to detect the effect of different protists on shifts in HNF selectivity observed in < 5 microm compared with unfiltered treatments.

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    • "proportions of HGC in spring and/or autumn (Allgaier and Grossart, 2006; Salcher et al., 2010). These microbes seem to be better protected from bacterivorous flagellates due to their minute cell sizes and gram-positive cell walls (Pernthaler et al., 2001; Jezbera et al., 2006; Tarao et al., 2009), and they profit from organic carbon sources released by the consumption of their grazing-vulnerable competitors (Eckert et al., 2013). However, HGC never reached high densities in our predator-free dilution cultures (Fig. 3), hinting at competitive disadvantages to opportunistic bacterial taxa (Burkert et al., 2003). "
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    • "Betaproteobacteria and Actinobacteria have apparently different life strategies. Whereas AcI Actinobacteria have been qualified as defence specialists (Salcher, 2014) due to their small cell size that protects them from grazing (Jezbera et al., 2006; Šimek et al., 2006), Betaproteobacteria and particularly the fast-growing R-BT subgroup were associated to an opportunistic lifestyle with resource specialization and high vulnerability to predation (Salcher, 2014). However, recently Thingstad and colleagues (2014) pointed out that the key to numerical success might just be an intermediate strategy, in which the right balance between defensive and competitive capabilities is reached. "
    Dataset: EMR14

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    • "Different studies focussed on the microbial plankton communities conducted both in marine and freshwater ecosystems have highlighted the importance of different factors (e.g. transparency, geographic region, DOC content and quality, grazing) in shaping their structure (Lindström et al., 2005; S ˇ imek et al., 2005; Jezbera et al., 2006). Planktonic food web structure also changes according to the prevailing equilibrium regimes (Jeppesen et al., 1997). "
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