Influence of light on the infection of Aureococcus anophagefferens CCMP 1984 by a “giant virus”

Abstract

The pelagophyte Aureococcus anophagefferens has caused recurrent brown tide blooms along the northeast coast of the United States since the mid-1980's, and more recently spread to other regions of the globe. These blooms, due to the high cell densities, are associated with severe light attenuation that destroys the sea grass beds which provide the basis for many fisheries. Data collected by transmission electron microscopy, PCR, and metatranscriptomic studies of the blooms, support the hypothesis that large dsDNA viruses play a role in bloom dynamics. While a large (~140 nm) icosahedral virus, with a 371 kbp genome, was first isolated more than a decade ago, the constraints imposed by environmental parameters on bloom infection dynamics by Aureococcus anophagefferens Virus, (AaV) remain unknown. To investigate the role light plays in infection by this virus, we acclimated A. anophagefferens to light intensities of 30 (low), 60 (medium) or 90 μmol photons m-2 s-1 (high) and infected cultures at these irradiance levels. Moreover, we completed light shift experiments where acclimated cultures were exposed to even lower light intensities (0, 5, and 15 μmol photons m-2 s-1) consistent with irradiance found during the peak of the bloom when cell concentrations are highest. The abundance of viruses produced per lytic event (burst size) was lower in the low irradiance acclimated cultures compared to the medium and high acclimated cultures. Transferring infected cultures to more-limiting light availabilities further decreased burst size and increased the length of time it took for cultures to lyse, regardless of acclimation irradiance level. A hypothetical mechanism for the reduced efficiency of the infection cycle in low light due to ribosome biogenesis was predicted from preexisting transcriptomes. Overall, these studies provide a framework for understanding light effects on infection dynamics over the course of the summer months when A. anophagefferens blooms occur.

A single-cell view on alga-virus interactions reveals sequential transcriptional programs and infection states

“…in agreement with the recent finding that viral infection depends on light in both the coccolithophore E. huxleyi (32) and the pelagophyte alga Aureococcus anophagefferens (33). Consistent with protein immunoblot analysis showing significant decrease in the level of RbcL [RuBisCO (ribulose-1,5-bisphosphate carboxylase-oxygenase) large subunit] compared with PsbD (photosystem II protein D2) at 24 hpi (32), the transcript encoding PsbD persisted until the late phase of infection while most transcripts, including the one for RbcL, were shut down earlier (Fig.…”

Internal Nitrogen Pools Shape the Infection of Aureococcus anophagefferens CCMP 1984 by a Giant Virus

“…It is therefore possible this could account for some of the differences. Burst sizes determined in this study are similar to those determined by qPCR in laboratory studies using ASP 12 A (Gann et al, 2020). Differences caused by culturing in different growth media on the infection cycle should be determined.…”

“…Uninfected controls were also done in five biological replicates. A high multiplicity of infection was used as only a small fraction of AaV are infectious and infecting cultures with m.o.i's between ∼20 and 100 allows for lysis of the majority of cells (>99%) within 3 days (Gann et al, 2020). Cultures were infected at the start of the light cycle.…”

Infection cycle and phylogeny of the Polinton-like virus Phaeocystis globosa virus virophage-14T

“…We compared the virulence of PgV with and without PgVV, in our setup only ~10% of infections ended in lysis, regardless of PgVV (Fig. 2b, Supplementary File 2), similarly to reports for other giant viruses [31][32][33] . In mixed lysates, successful co-infections of PgV and PgVV are rare: less than 20% of successful PgV infections are co-infections with PgVV (Supplementary File 2).…”