Dip in the gene pool: metagenomic survey of natural coccolithovirus communities

Abstract

Despite the global oceanic distribution and recognised biogeochemical impact of coccolithoviruses (EhV), their diversity remains poorly understood. Here we employed a metagenomic approach to study the occurrence and progression of natural EhV community genomic variability. Analysis of EhV metagenomes from the early and late stages of an induced bloom led to three main discoveries. First, we observed resilient and specific genomic signatures in the EhV community associated with the Norwegian coast, which reinforce the existence of limitations to the capacity of dispersal and genomic exchange among EhV populations. Second, we identified a hyper-variable region (approximately 21kbp long) in the coccolithovirus genome. Third, we observed a clear trend for EhV relative amino-acid diversity to reduce from early to late stages of the bloom. This study validated two new methodological combinations, and proved very useful in the discovery of new genomic features associated with coccolithovirus natural communities.

Keywords: Algae virus; Bloom dynamics; Coccolithovirus; EhV; Emiliania huxleyi; Emiliania huxleyi virus; Genomic hyper-variable region; Giant virus; Marine metagenomics; Metagenome; Viral genomic diversity; Virome.