title: Ecological Dynamics of Two Distinct Viruses Infecting Marine Eukaryotic Decomposer Thraustochytrids (Labyrinthulomycetes, Stramenopiles).
abstract: Thraustochytrids are cosmopolitan osmotrophic or heterotrophic microorganisms that are considered as important decomposers in coastal ecosystems. However, because of a lack of estimation method for each genus or systematic group of them, relatively little is known about their ecology in situ. Previously, we reported two distinct types of virus infecting thraustochytrids (AuRNAV: reported as SssRNAV, and SmDNAV) suggesting they have wide distributions in the host-virus systems of coastal environments. Here we conducted a field survey from 2004 through 2005 to show the fluctuation pattern of thraustochytrids and their viruses in Hiroshima Bay, Japan. During the field survey, we monitored the dynamics of the two types of thraustochytrid-infecting virus: small viruses causing lysis of Aurantiochytrium sp. NIBH N1-27 (identified as AuRNAV) and the large viruses of Sicyoidochytrium minutum NBRC 102975 (similar to SmDNAV in physiology and morphology). Fluctuation patterns of the two distinct types of virus were different from each other. This may reflect the difference in the preference of organic substrates; i.e., it may be likely the host of AuRNAV (Aurantiochytrium sp.) increases utilizing algal dead bodies or feeble cells as the virus shows a large increase in abundance following raphidophyte blooms; whereas, the trophic nutrient supply for S. minutum may primarily depend on other constantly-supplied organic compounds because it did not show any significant change in abundance throughout the survey. Further study concerning the population composition of thraustochytrids and their viruses may demonstrate the microbial ecology (especially concerning the detrital food web) of marine environments.
authors.affiliation: Department of Marine Bioscience, Fukui Prefectural University, 1-1 Gakuencho, Obama, Fukui, 917-0003, Japan.
authors.forename: Yoshitake
authors.initials: Y
authors.lastname: Takao
authors.affiliation: National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tomaru
authors.affiliation: National Research Institute of Fisheries and Environment of Inland Sea, Fisheries Research Agency, 2-17-5 Maruishi, Hatsukaichi, Hiroshima, 739-0452, Japan.
authors.forename: Keizo
authors.initials: K
authors.lastname: Nagasaki
authors.affiliation: Department of Biology, Faculty of Science and Engineering, Konan University, 8-9-1 Okamoto, Higashinada, Kobe, 658-8501, Japan.
authors.forename: Daiske
authors.initials: D
authors.lastname: Honda
mesh_terms: D004463:Ecology; D017753:Ecosystem; D012623:Seawater / Q000821:virology*; D058009:Stramenopiles / Q000821:virology*; D014780:Viruses