Differential Response of Cafeteria roenbergensis to Different Bacterial and Archaeal Prey Characteristics
In the marine environment, the abundance of Bacteria and Archaea is either controlled bottom-up via nutrient availability or top-down via grazing. Heterotrophic nanoflagellates (HNF) are mainly responsible for prokaryotic grazing losses besides viral lysis. However, the grazing specificity of HNF on specific bacterial and archaeal taxa is under debate. Bacteria and Archaea might have different nutritive values and surface properties affecting the growth rates of HNF. In this study, we offered different bacterial and archaeal strains with different morphologic and physiologic characteristics to Cafeteria roenbergensis, one of the most abundant and ubiquitous species of HNF in the ocean. Two Nitrosopumilus maritimus-related strains isolated from the northern Adriatic Sea (Nitrosopumilus adriaticus, Nitrosopumilus piranensis), two Nitrosococcus strains, and two fast growing marine Bacteria (Pseudoalteromonas sp. and Marinobacter sp.) were fed to Cafeteria cultures. Cafeteria roenbergensis exhibited high growth rates when feeding on Pseudoalteromonas sp., Marinobacter sp., and Nitrosopumilus adriaticus, while the addition of the other strains resulted in minimal growth. Taken together, our data suggest that the differences in growth of Cafeteria roenbergensis associated to grazing on different thaumarchaeal and bacterial strains are likely due to the subtle metabolic, cell size, and physiological differences between different bacterial and thaumarchaeal taxa. Moreover, Nitrosopumilus adriaticus experienced a similar grazing pressure by Cafeteria roenbergensis as compared to the other strains, suggesting that other HNF may also prey on Archaea which might have important consequences on the global biogeochemical cycles.
KeywordsCafeteria roenbergensis Bacteria Archaea Flagellate grazing Bacterivory
We thank B. Bayer for providing the two archaeal strains and F.W. Valois for providing the two Nitrosococcus strains.
Laboratory work was supported by the Austrian Science Fund (FWF) projects Z194-B17 and P28781-B21 and by the European Research Council under the European Community’s Seventh Framework Program (FP7/2007-2013)/ERC grant agreement No. 268595 (MEDEA project) to GJH. DDC was supported by the Marie Curie Fellowship (PIEF-GA-2011-299860) and by overseas researcher under the Postdoctoral Fellowship of Japan Society for Promotion of Science (P16085), and ES was supported by Austrian Science Fund (FWF) project P27696-B22.
- 3.Weitz JS, Wilhelm SW (2012) Ocean viruses and their effects on microbial communities and biogeochemical cycles. F1000 Biol Rep 4:17Google Scholar
- 11.Sherr BF, Sherr EB, Fallon RD (1987) Use of monodispersed, fluorescently labeled bacteria to estimate in situ protozoan bacterivory. Appl Environ Microbiol 53:958–965Google Scholar
- 19.Ballen-Segura M, Felip M, Catalan J (2017) Some mixotrophic flagellate species selectively graze on archaea. Appl Environ Microbiol 83Google Scholar
- 23.Sherr BF, Sherr EB, Rassoulzadegan F (1988) Rates of digestion of bacteria by marine phagotrophic protozoa: temperature dependence. Appl Environ Microbiol 54:1091–1095Google Scholar
- 24.Gonzalez JM, Iriberri J, Egea L, Barcina I (1990) Differential rates of digestion of bacteria by freshwater and marine phagotrophic protozoa. Appl Environ Microbiol 56:1851–1857Google Scholar
- 33.Hahn MW, Höfle MG (1999) Flagellate predation on a bacterial model community: interplay of size-selective grazing, specific bacterial cell size, and bacterial community composition. Appl Environ Microbiol 65:4863–4872Google Scholar