Table 1.
The NCLDV families and their representation in marine metagenomic samples
| Virus family | Known host range | Genome size (kb)a | Number and percentage of NCLDV-related sequences b | |
|---|---|---|---|---|
| Sargasso Sea metagenome | GOS metagenome | |||
| Poxviridae | Animals (vertebrates and insects) | 134–360 | 0 | 0 |
| Asfarviridae | Animals (mammals) | 170 | 1 (0.4%) | 20 (1%) |
| Iridoviridae | Animals (vertebrates and insects) | 103–191 | 7 (3%) | 74 (5%) |
| Ascoviridae | Animals (insects) | 119–186 | 0 | 0 |
| Mimiviridae | Amoebozoa (Acanthamoeba) | 1181 | 50 (22%) | 279 (20%) |
| Phycodnaviridae | Chlorophyta (green algae), Haptophyta, stramenopiles | 155–407 | 160 (71%) | 1032 (72%) |
Data from the NCBI genome database.
The amino acid sequences of the following three core NCLDV proteins were used as queries to search the metagenomic nucleotide sequences using the TBLASTN program [63]: the major capsid protein (ortholog of vaccinia virus D13 protein), a transcription factor (ortholog of vaccinia virus A2 protein) and the disulfide oxidoreductase (ortholog of vaccinia virus E10 protein). Metagenomic sequences with the similarity to the NCLDV proteins above the chosen cut-off value (expectation value <10−5) were pooled and searched against the non-redundant protein database (NCBI) using the BLASTX program [63], and the taxonomic affiliation of the most similar sequences were determined using BLAST taxonomy reports.