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Applied and Environmental Microbiology, September 2000, p. 3790-3797, Vol. 66, No. 9
University of Southern California, Los
Angeles, California 90089-0371
Received 22 March 2000/Accepted 7 July 2000
Pelagic marine viruses have been shown to cause significant
mortality of heterotrophic bacteria, cyanobacteria, and phytoplankton. It was previously demonstrated, in nearshore California waters, that
viruses contributed to up to 50% of bacterial mortality, comparable to
protists. However, in less productive waters, rates of virus production
and removal and estimates of virus-mediated bacterial mortality have
been difficult to determine. We have measured rates of virus production
and removal, in nearshore and offshore California waters, by using
fluorescently labeled viruses (FLV) as tracers. Our approach is
mathematically similar to the isotope dilution technique, employed in
the past to simultaneously measure the release and uptake of ammonia
and amino acids. The results indicated overall virus removal rates in
the dark ranging from 1.8 to 6.2% h
0099-2240/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Rapid Virus Production and Removal as Measured with
Fluorescently Labeled Viruses as Tracers
1 and production
rates in the dark ranging from 1.9 to 6.1% h
1,
corresponding to turnover times of virus populations of 1 to 2 days,
even in oligotrophic offshore waters. Virus removal rates determined by
the FLV tracer method were compared to rates of virus degradation,
determined at the same locations by radiolabeling methods, and were
similar even though the current FLV method is suitable for only dark
incubations. Our results support previous findings that virus impacts
on bacterial populations may be more important in some environments and
less so in others. This new method can be used to determine rates of
virus degradation, production, and turnover in eutrophic, mesotrophic,
and oligotrophic waters and will provide important inputs for future
investigations of microbial food webs.
*
Corresponding author. Mailing address: Southern
California Coastal Water Research Project, 7171 Fenwick Ln.,
Westminster, CA 92683. Phone: (714) 372-9228. Fax: (714) 894-9699. E-mail: racheln{at}sccwrp.org.
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