Grazing of heterotrophic nanoflagellates on marine picophytoplankton presents a major mortality factor for this important group of primary producers. However, little is known of the selectivity of the grazing process, often merely being thought of as a general feature of cell size and motility. In this study, we tested grazing of two heterotrophic nanoflagellates, Paraphysomonas imperforata and Pteridomonas danica, on strains of marine Synechococcus. Both nanoflagellates proved to be selective in their grazing, with Paraphysomonas being able to grow on 5, and Pteridomonas on 11, of 37 Synechococcus strains tested. Additionally, a number of strains (11 for Paraphysomonas, 9 for Pteridomonas) were shown to be ingested, but not digested (and thus did not support growth of the grazer). Both the range of prey strains that supported growth as well as those that were ingested but not digested was very similar for the two grazers, suggesting a common property of these prey strains that lent them susceptible to grazing. Subsequent experiments on selected Synechococcus strains showed a pronounced difference in grazing susceptibility between wild-type Synechococcus sp. WH7803 and a spontaneous phage-resistant mutant derivative, WH7803PHR, suggesting that cell surface properties of the Synechococcus prey are an important attribute influencing grazing vulnerability.
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http://dx.doi.org/10.1111/j.1462-2920.2009.01902.x | DOI Listing |
ISME J
January 2024
Physical and Life Science Directorate, Lawrence Livermore National Laboratory, 7000 East Ave, Livermore, CA, 94550, United States.
Microorganisms
October 2024
Laboratoire Microorganismes: Génome et Environnement, UMR CNRS 6023, Université Clermont-Auvergne, 63000 Clermont-Ferrand, France.
To investigate the hypothesis of top-down control by viruses and heterotrophic nanoflagellates on bacterial-mediated carbon fluxes in freshwater systems, a year-long study (2023-2024) was conducted in the pelagic zone of Lake Saint-Gervais (France). The variability in BGE (9.9% to 45.
View Article and Find Full Text PDFMar Pollut Bull
September 2024
Instituto Universitario de Investigación Marina (INMAR), Campus de Excelencia Internacional del Mar (CEI·MAR), Departamento de Biología, Facultad de Ciencias del Mar y Ambientales Universidad de Cádiz, Campus Universitario de Puerto Real, Puerto Real, Cádiz, Spain.
Large nutrient levels and herbivory stress, particularly when acting together, drive a variety of responses in seagrass communities that ultimately may weaken their carbon balance. An in situ three-months experiment was carried out in two contrasting seasons to address the effects of two levels of nutrient load and three levels of artificial clipping on Cymodocea nodosa plants. Nutrient enrichment shifted the community from autotrophic to heterotrophic and reduced DOC fluxes in winter, whereas enhanced community carbon metabolism and DOC fluxes in summer.
View Article and Find Full Text PDFAppl Environ Microbiol
August 2024
Department of Marine Sciences, University of Georgia, Athens, Georgia, USA.
Oil spills are a frequent perturbation to the marine environment that has rapid and significant impacts on the local microbiome. Previous studies have shown that exposure to synthetic dispersant alone did not enhance heterotrophic microbial activity or oxidation rates of specific hydrocarbon components but increased the abundance of some taxa (e.g.
View Article and Find Full Text PDFFEMS Microbiol Ecol
July 2024
Marine and Freshwater Solutions, Finnish Environment Institute, Latokartanonkaari 11, 00790 Helsinki, Finland.
The phosphorus (P) concentration is increasing in parts of the Baltic Sea following the spring bloom. The fate of this excess P-pool is an open question, and here we investigate the role of microbial degradation processes in the excess P assimilation phase. During a 17-day-long mesocosm experiment in the southwest Finnish archipelago, we examined nitrogen, phosphorus, and carbon acquiring extracellular enzyme activities in three size fractions (<0.
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