[Coral-List] Paper on Bleaching-Induced Outbreak of Viruses in Corals

[Rebecca Vega Thurber]

Hello everyone,
  Please see our recent open access paper published in *Frontiers in
Microbiology* on viral infections of Acropora corals during a bleaching
event. On behalf of the authors I hope you find it interesting, and should
you have any questions please don't hesitate to ask. -Becky

http://journal.frontiersin.org/article/10.3389/fmicb.2016.00127/abstractAbstract

*Title:* Viral outbreak in corals associated with an in situ bleaching
event: atypical herpes-like viruses and a new megavirus infecting
*Symbiodinium*

*Abstract*
Previous studies of coral viruses have employed either microscopy or
metagenomics, but few have attempted to comprehensively link the presence
of a virus-like particle (VLP) to a genomic sequence. We conducted
transmission electron microscopy imaging and virome analysis in tandem to
characterize the most conspicuous viral types found within the dominant
Pacific reef-building coral genus *Acropora*. Collections for this study
inadvertently captured what we interpret as a natural outbreak of viral
infection driven by aerial exposure of the reef flat coincident with heavy
rainfall and concomitant mass bleaching. All experimental corals in this
study had high titers of viral particles. Three of the dominant VLPs
identified were observed in all tissue layers and budding out from the
epidermis, including viruses that were ~70 nm, ~120 nm, and ~150 nm in
diameter; these VLPs all contained electron dense cores. These
morphological traits are reminiscent of retroviruses, herpesviruses, and
nucleocytoplasmic large DNA viruses (NCLDVs), respectively. Some 300-500 nm
megavirus-like VLPs also were observed within and associated with
dinoflagellate algal endosymbiont (*Symbiodinium*) cells. Abundant sequence
similarities to a gammaretrovirus, herpesviruses, and members of the
NCLDVs, based on a virome generated from five *Acropora aspera* colonies,
corroborated these morphology-based identifications. Additionally sequence
similarities to two diagnostic genes, a MutS and (based on re-annotation of
sequences from another study) a DNA polymerase B gene, most closely
resembled *Pyramimonas orientalis* virus, demonstrating the association of
a cosmopolitan megavirus with *Symbiodinium*. We also identified several
other viral particles in host tissues, along with sequences
phylogenetically similar to circoviruses, phages, and filamentous viruses.
This study suggests that viral outbreaks may be a common but previously
undocumented component of natural bleaching events, particularly following
repeated episodes of multiple environmental stressors.

-- 
Dr. Rebecca Vega Thurber
Assistant Professor of Microbiology
Oregon State University
454 Nash Hall
Corvallis OR  97331-3804, U.S.A
541-737-1851 (office) 541-737-0496 (FAX)
rvegathurber at gmail.com;Rebecca.Vega-Thurber at oregonstate.edu
<Rebecca.Vega.Thurber at oregonstate.edu>