Ecological and functional biodiversity in a marine algal-virus system: genotypes, phenotypes and their ecological significance

• Main Author: Nissimov, Jozef I.
• Format: Thesis
• Language: English
• Published: 2013
• Subjects: Norway; North Atlantic
• Online Access: http://eprints.nottingham.ac.uk/13776/; https://eprints.nottingham.ac.uk/13776/1/PhD_thesis_Jozef_Nissimov_Jozefs_papers_modified_28.03.2014.pdf

Coccolithoviruses are large dsDNA viruses infecting the cosmopolitan calcifying marine phytoplankton Emiliania huxleyi. Therefore they are instrumental components of algal bloom demise and thus agents contributing significantly to biogeochemical cycling in the oceans. Several coccolithovirus strains exist in culture and have been used so far to study the co-evolutionary arms-race between them and their unicellular host in naturally occurring or induced blooms in the North Atlantic Ocean and the fjords of Norway. However, little is known of their distribution in non-bloom conditions, their natural diversity in times of reduced infectivity rates, and the role of functionally important genes found in natural coccolithovirus communities. Even less is known about their genetic differences and the phenotypic consequences of these differences on their infection dynamics. Hence here a three dimensional approach was undertaken, during which the genomes of several coccolithovirus strains were analysed, their diversity in the global ocean characterised, and their phenotypic properties as seen from their infection dynamics with their host established. It was revealed that although coccolithoviruses share a common subset of core genes, they differ in a large proportion of their genomic material, as seen from the presence and/or absence of large sub-clusters of functionally unknown genes. Moreover, a gene that encodes for a phosphate scavenging mechanism (phosphate permease) was truncated from the genome of the Norwegian isolate EhV-99B1 but not from any other strain, while a gene encoding for the virulence factor sialidase was truncated only in the genomes of the English Channel strains isolated in 2001. The discovery of an additional gene that is potentially involved in the regulation of sphingosine and ceramide intermediates during the de novo virus encoded sphingolipid biosynthesis pathway was also intriguing, and the extent of gene homology to host genes (i.e. almost 13% of the analyzed genomes) highlighted the ...