Oceanic ecosystems are dominated by minute microorganisms that play a major role in food webs and biogeochemical cycles 1 . Many microorganisms thrive in the dilute environment due to their capacity to locate, attach to, and use patches of nutrients and organic matter 2,3 . We propose that some free-living planktonic bacteria have traded their ability to stick to nutrient-rich organic particles for a non-stick cell surface that helps them evade predation by mucous filter feeders. We used a combination of in situ sampling techniques and next-generation sequencing to study the biological filtration of microorganisms at the phylotype level. Our data indicate that some marine bacteria, most notably the highly abundant Pelagibacter ubique and most other members of the SAR 11 clade of the Alphaproteobacteria, can evade filtration by slipping through the mucous nets of both pelagic and benthic tunicates. While 0.3 μm polystyrene beads and other similarly-sized bacteria were efficiently filtered, SAR11 members were not captured. Reversed-phase chromatography revealed that most SAR11 bacteria have a much less hydrophobic cell surface than that of other planktonic bacteria. Our data call for a reconsideration of the role of surface properties in biological filtration and predator-prey interactions in aquatic systems.
Bibliographical noteFunding Information:
We thank S. Giovannoni for providing strains HTCC1062, HTCC2506 and HTCC2143, and L. Gomez-Consarnau for providing strains MED134 and DLF12 and D. Roth-Rosenberg and D. Sher lab for providing strain PRO9312. M. Landry for useful discussion and help with HIC application. M. Gilboa and staff of the School of Marine Science, Ruppin for technical assistance. BSF grant 2012089 to K.S, Y.T. and G.Y. ISF grant 1280/13 to G.Y. ECOGELY ANR-10-PDOC-005-01 to F.L. and ANR RHOMEO 11-BSV7-0021 to M.T.S. We thank the Bio2Mar, and Cytometry-Imaging platforms of the OOB and EMBRC-zooplankton of OOV for access to instrumentation. Support provided to A.D.P by the Mediterranean Sea Research Center of Israel and IUI PhD award.
© 2017 The Author(s).
ASJC Scopus subject areas
- Applied Microbiology and Biotechnology
- Microbiology (medical)
- Cell Biology