Abstract
AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 57:343-350 (2009) - DOI: https://doi.org/10.3354/ame01365 AME Special: 'Rassoulzadegan at Villefranche-sur-Mer: 3 decades of aquatic microbial ecology' Addition of monomeric and polymeric organic substrates alleviates viral lytic pressure on bacterial communities in coastal seawaters Chiaki Motegi1,2,3,*, Toshi Nagata1,2 1Ocean Research Institute, The University of Tokyo, 1-15-1 Minamidai, Nakano-ku, Tokyo 164-8639, Japan 2Center for Ecological Research, Kyoto University, 2-509-3 Hirano, Otsu, Shiga 520-2113, Japan 3Present address: Université Pierre et Marie Curie-Paris 6 and CNRS, Laboratoire d’Océanographie de Villefranche, 06234 Villefranche-sur-Mer, Cedex, France *Email: motegi@obs-vlfr.fr ABSTRACT: We examined the effect of growth conditions on the fraction of bacterial production lysed by viruses (Flysed). Time-course changes in bacterial and viral variables were determined in coastal seawater cultures with and without the addition of monomeric (glucose or amino acids) or polymeric (protein) substrates. Substrate-induced enhancement of bacterial production was much more pronounced than that of viral production during the incubation period of 60 to 90 h. Estimates of Flysed were highest in non-addition controls (range = 0.3 to 1.0), followed by the monomer addition treatment (0.1 to 0.2), and lowest in the protein addition treatment (0.04 to 0.1). These data are consistent with the proposition that bacterial communities grown under substrate-rich conditions are less subject to viral attacks. Low Flysed values in the protein addition treatment were associated with high activities of leucine aminopeptidase, indicating a role of extracellular proteases in alleviating viral lytic pressure. Our data support the notion that supplies of dissolved organic matter affect the magnitude of bacteria–virus couplings in marine environments. KEY WORDS: Virus–bacteria interactions · Lytic viral production · Dissolved organic matter · Marine environments Full text in pdf format PreviousNextCite this article as: Motegi C, Nagata T (2009) Addition of monomeric and polymeric organic substrates alleviates viral lytic pressure on bacterial communities in coastal seawaters. Aquat Microb Ecol 57:343-350. https://doi.org/10.3354/ame01365Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 57, No. 3. Online publication date: November 24, 2009 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2009 Inter-Research.
Highlights
Lytic viral production associated with destruction of host bacterial cells accounts for a significant, albeit highly variable (10 to 50%), fraction of bacterial mortality in marine environments (Weinbauer 2004, Breitbart et al 2008)
Bacterial production displayed a substantial (100-fold) increase after 15 h incubation in the glucose addition treatment, which was accompanied by a peak in viral production at 21 h (Figs. 1C, D)
Protein addition resulted in the enhancement of bacterial production (Fig. 1C), there was no concomitant increase in viral production (Fig. 1D)
Summary
Lytic viral production associated with destruction of host bacterial cells accounts for a significant, albeit highly variable (10 to 50%), fraction of bacterial mortality in marine environments (Weinbauer 2004, Breitbart et al 2008). Factors that may affect viral production and the extent of viral-induced bacterial mortality include the activity of host cells (Middelboe 2000). This proposition is consistent with the observation that viral production increases with increasing bacterial production or growth in response to the addition of nutrients and organic substrate (Tuomi et al 1995, Williamson & Paul 2004, Motegi & Nagata 2007). There is experimental evidence of viral loss rates increasing with increasing bacterial production from a study on nutrient enriched seawater cultures (Motegi & Nagata 2007); one possible explanation proposed was the destruction of viral capsids by extracellular proteases released by rapidly growing bacteria Few studies have systematically examined the magnitude of the enhancement of bacterial and viral production in response to the addition of organic sub-
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