shown experimentally, just predicted from model results.
Fig. 5.14 Diagram illustrating “kill the winner” dynamics. Although the total
concentration of bacteria and viruses remains relatively stable over time, the
concentration of individual bacterial and viral strains changes dramatically. As a
bacterial species becomes abundant (Bacterium 1), viruses that can infect those
bacteria (Virus 1) will specifically lyse that host. This will lead to a decrease in the
population size of Bacterium 1 and an increase in the population size of Virus 1.
However, as the host population declines, there will no longer be hosts to produce
more Virus 1, leading to a subsequent decrease in its population size. The virally
mediated decline of the host population creates an open niche, allowing another
bacterium to become abundant (Bacterium 2). A virus that can infect Bacterium 2 then
becomes abundant, and the cycle continues. Selective virally induced mortality is a
driving force for fluctuations in the structure of bacterial communities and contributes
to maintaining high bacterial diversity.
(^) (After Breitbart et al. 2008.)
(^) Viral lysis results in release of new virus particles (a range of 20–50 per cell) plus
other cellular contents consisting mostly of dissolved organic material, and as much as
25% of primary production may flow through the viral shunt. The cellular
components are rich in nitrogen and phosphorus, and may enhance rates of cycling of
carbon and nutrients. Wilhelm and Suttle (1999) estimated that viral lysis could
supply 80–95% of the bacterial carbon demand in waters of the Strait of Georgia
(Western Canada), and that on a global scale virally mediated DOM release is
approximately 3–20 GtC per year. Middleboe and Jorgensen (2006) conducted
experiments with a marine bacterium (Cellulophaga sp.) and a virus specific to it, and
quantified the amounts of dissolved free and combined amino acids released (DFAA
and DCAA). The DCAA constituted 51–86% of the total DOC released. Glucosamine
and DFAA each accounted for 2–3% of the total. Most of the released material (83%)
was reassimilated by the remaining live bacteria. Given the high N content of this
released material, it is reasonable to assume that a large fraction of the amino N could