ÿþ<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <html> <head> <title>Role of bacterial phenotypic traits in selective feeding of the heterotrophic nanoflagellate Spumella sp.</title> <LINK REL="SHORTCUT ICON" href="http://www.medealab.de/medealab.ico"> <meta name="Author" content="medea AV GmbH"> <meta name="keywords" lang="en" content="medeaLAB, software, image analysis, image analysis system, count, classify, measurement, motion analysis, tracking, application"> <meta name="description" content="heterotrophic nanoflagellate Spumella - The nanoflagellate Spumella sp. was used as a model interception-feeding predator in short-term grazing experiments. High-resolution video microscopy allowed to observe distinct stages of the feeding process (contact, capture, ingestion). 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High-resolution video microscopy allowed to observe distinct stages of the feeding process (contact, capture, ingestion). High swimming speed of bacteria increased contact rates but also decreased flagellate capture efficiency. <br><br> <table cellspacing="2" cellpadding="2" border="0"> <tr> <td> <!-- <img src="../images/content/" alt=""></img><br> --> </td> </tr> <tr> <td> <!-- <img src="../images/content/" alt=""></img><br> --> </td> </tr> </table> <br> Reference:<br> Matz, C., Boenigk, J., Arndt, H., Jürgens, K., "Role of bacterial phenotypic traits in selective feeding of the heterotrophic nanoflagellate Spumella sp.." <u>Aquatic Microbial Ecology</u> 27(2002): 137-148. <br><br> Abstract:<br> The influence of different bacterial phenotypic traits on the feeding selectivity of a bacterivorous nanoflagellate was investigated in laboratory experiments. Twelve bacterial isolates from freshwater habitats were characterized in terms of cell size, morphology, capsule formation, surface hydrophobicity and charge, and swimming behavior. Mechanisms of differential flagellate feeding on these isolates were studied in short-term grazing experiments by high-resolution video microscopy using the nanoflagellate Spumella sp. as a model interception-feeding predator. The differentiation into distinct stages of the feeding process (contact, capture, ingestion) revealed a complex selection behavior illustrated by the relatively small proportion of ingested bacteria over cell contacts. We found that bacterial swimming speed increased contact rates but also decreased flagellate capture efficiency, which had a compensating effect on overall ingestion rates. Bacterial cell size revealed no correlation with flagellate contact rates but an effective inhibition of ingestion rates when exceeding a critical size limit. Correlation analysis presented no bacterial property to account for the residual variability of flagellate ingestion efficiencies. Experiments with specifically coated artificial particles provided evidence for the relative importance of the biochemical surface composition in flagellate food selection compared to physicochemical interaction forces. Only extreme charges beyond  45 mV reduced flagellate ingestion rates. Our results reinforce the idea that bacterial cell size strongly affects the feeding success of bacterivorous flagellates, and further implicates size-independent bacterial traits such as swimming speed and biochemical surface composition in this feeding success </td> <!-- Ende des INHALTSTEILS--> </tr> </table> <script type="text/javascript">var gaJsHost = (("https:" == document.location.protocol) ? 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