The diversity of bacteria,eukaryotic cells and viruses in an oligotrophic lake |
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Authors: | W A Corpe T E Jensen |
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Institution: | (1) Department of Biological Sciences, Columbia University, New York, NY 10027, USA, US;(2) Department of Biological Sciences, Lehman College, City University of New York, Bronx, New York, NY 10468, USA, US |
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Abstract: | An in situ transmission electron microscopic study of biomass samples concentrated from oligotrophic lake water revealed
a variety of virus-infected microbial cells and many free viruses and virus-like particles. The most abundant group of microorganisms
in screened and filtered water-column samples were 2 μm or less in diameter, and included representatives of several oligotrophic
genera, Prosthecomicrobium, Ancyclobacter, Caulobacter and Hyphomicrobium. Among the prokaryotic host cells, which included both heterotrophs and autotrophs, on the basis of electron microscope observations,
approximately 17% were infected with bacteriophage or bore adherent phage particles on their surfaces. Several bacterial morphotypes
were observed among the prokaryotic hosts. Water samples passed through a 20-μm Nitex screen allowed us to concentrate and
examine the larger host cells as well, including several species of single-celled algae and two amoeba species. The infected
algal cells included those Chlorella-like in appearance, photosynthetic flagellates and others that could not be positively identified. About one-third of the
eukaryotic cells were infected by viruses that were larger (150–200 nm) and structurally more complex than bacteriophages
(50–60 nm). None of the viruses have been isolated, but when 0.2 μm filtrate from a biomass sample was spotted onto lawns
of four representative heterotrophs and a Chlorella, the clearing observed was taken as evidence of lysis. Cyanobacterial lawns showed no plaques. Thin sections of two amoeba
showed food vacuoles containing what appeared to be virus particles of a type seen in certain prokaryotic and eukaryotic cells
in the biomass.
Received: 26 January 1996 / Received revision: 10 July 1996 / Accepted: 5 August 1996 |
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