Giant phage genome assembled from metagenomic data obtained from a decaying Trichodesmium bloom with prominent Alteromonas. Trichodesmium decaying bloom metagenome sequencing

The globally important marine diazotrophic cyanobacterium Trichodesmium is abundant in the New Caledonian lagoon (Southwestern Pacific ocean) during austral spring/summer. We sampled biomass from a Trichodesmium surface aggregation, rinsed and resuspended it in filtered seawater, and incubated in in 4.5 L bottles for ~24h. Samples were taken after 0h, 8h, and 22h by filtration, and preserved. DNA was extracted, mixed in equal amounts from all three samples, and sequenced (Illumina HiSeq). Metagenomic data was assembled using different assembly tools, and the here reported giant phage genome was the largest contig, obtained independently with multiple tools. PCR confirmed a likely circular genome and confirmed the presence of this phage in a replicate incubation bottle. 16S sequencing showed that while Trichodesmium cell numbers declined, Alteromonas became the dominant bacterial component of the bloom biomass.