Microbiology

Phage Invaders

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Science  22 Apr 2011:
Vol. 332, Issue 6028, pp. 398
DOI: 10.1126/science.332.6028.398-a
CREDIT: (GRAPHIC) N. KEVITIYAGALA/SCIENCE (IMAGES) YAU ET AL., PROC. NATL. ACAD. SCI. U.S.A. 108, 6163 (2011)

Aquatic viruses play important roles in regulating the abundance of marine cyanobacteria and eukaryotic algae. They do this by lysing marine primary producers but, by releasing organic carbon matter, they also stimulate secondary production. To determine the contribution of viruses in planktonic communities, Yau et al. performed a metagenomic survey of the simple microbial loop system of a stratified Antarctic lake and found abundant evidence for Sputnik-like virophages. Virophages infect amoebas but can only replicate in the presence of other double-stranded DNA viruses, which act as “helpers” by supplying essential proteins and exchanging genes. Sputnik virophages damage the ability of the helper virus to replicate successfully itself, and it appears, from modeling of the microbial loop dynamics, that by damping the virulence of the helper viruses to their algal hosts, virophages may be instrumental in maintaining the stability of the microbial food web during the prolonged light-dark cycles in the Antarctic and elsewhere.

Proc. Natl. Acad. Sci. U.S.A. 108, 6163 (2011).

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