The prokaryotic virus community is represented at the International Committee on Taxonomy of Viruses (ICTV) by the Bacterial and Archaeal Viruses Subcommittee. Since our last report [5], the committee composition has changed, and a large number of taxonomic proposals (TaxoProps) were submitted to the ICTV Executive Committee (EC) for approval.

1. Changes in subcommittee membership. During the past year we have lost two members. Dr. Hans-Wolfgang Ackermann, a life member of the ICTV, the father of caudovirus taxonomy [1] and an electron microscopist extraordinaire [2,3,4], lamentably died and will be gravely missed. In addition, Dr. Jens H. Kuhn, who, in spite of protestations about not being a genuine phage biologist, proved invaluable to our discussions and preparation of TaxoProps and manuscripts, resigned from the Subcommittee. Both Hans and Jens are acknowledged for their significant contributions to prokaryotic virus taxonomy. Furthermore, a number of current members have new responsibilities; and, in an effort to increase the geographical diversity of members, we appointed representatives from South America, Africa, and Asia (Table 1).

Table 1 List of current subcommittee members who have new responsibilities (*), along with new members of the subcommittee
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2. Changing the names of prokaryotic virus genera. A significant number of prokaryotic virus genera have either unpronounceable names (e.g., Pocjvirus, Rdjlvirus) or incorporated numerals (e.g., T4virus, D3112virus). In the first case, these names contravene The International Code of Virus Classification and Nomenclature (ICVCN, April 2017) Rule 3.12, which states “Names for taxa shall be easy to use and easy to remember. Euphonious names are preferred.” In the latter case, pronunciation is a problem. For example, is D3112virus pronounced “Dee+three thousand one hundred and twelve+virus” or “Dee+thirty one+twelve+virus” or “Dee+three+one+one+two+virus”? In addition, this nomenclature differs drastically from that for other virus taxa; and, would be incompatible with a Linnaean system of nomenclature [13]. We identified all prokaryotic taxon names that are problematic in the ICTV Master Species List (https://talk.ictvonline.org/files/master-species-lists/m/msl/6776) and suggested alternative names (Supplementary data file S1). These changes will be proposed officially at the next meeting of the ICTV EC in 2018.

3. Re-evaluation of the SPO1-like virus taxonomy. Over the past two years, members of the subcommittee have re-evaluated the taxonomy of a subset of myoviruses related to Bacillus phage SPO1. This group, made up of members of the subfamily Spounavirinae [10] and several genera of Bacillus-infecting viruses, was represented as a distinct module in various network analyses published recently [8, 9]. Using a combination of genomic, proteomics, and phylogenetic approaches, we have shown that this group of phages represents a new family, comprising five subfamilies and 13 genera [7]. We therefore suggest that these viruses be moved from their current taxonomic position in the family Myoviridae to a new family included in the order Caudovirales.

4. New taxa. Table 2 lists of all new taxa proposed at the ICTV EC49 meeting in Singapore in 2017. In total, two new families, eight new subfamilies, 34 new genera, and 91 new species were proposed. Two significant items are on this list. The first item is the introduction of two new families of prokaryotic viruses: Ackermannviridae and Portogloboviridae. With the acceptance of changes to ICVCN Rule 3.11, the second item is the application of the names of eminent phage scientists, specifically Hans-Wolfgang Ackermann (Université Laval) and Charles Shelton McCleskey (Louisiana State University) as prefixes for taxon name stems.

Table 2 Taxonomy proposals (TaxoProps) proposing new taxa (families, subfamilies, genera, species) submitted to the ICTV Executive Committee in 2017
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5. Updates to taxonomy. As the readership may be aware, “Virus Taxonomy: The Classification and Nomenclature of Viruses - The Online (10th) Report of the ICTV” is freely accessible at http://ictv.global/report. We would like to acknowledge the hard work of Hanna M. Oksanen (Corticoviridae), Dennis H. Bamford (Pleolipoviridae), and Minna M. Poranen (Cystoviridae) for completing updates to their sections. The family Pleolipoviridae is now recognized as the first virus taxon in the newly established ICTV category for ssDNA/dsDNA Viruses. The summaries of the ICTV Report chapters are published in The Journal of General Virology [6, 11, 12].