50 years of the International Committee on Taxonomy of Viruses: progress and prospects

We mark the 50th anniversary of the International Committee on Taxonomy of Viruses (ICTV) by presenting a brief history of the organization since its foundation, showing how it has adapted to advancements in our knowledge of virus diversity and the methods used to characterize it. We also outline recent developments, supported by a grant from the Wellcome Trust (UK), that are facilitating substantial changes in the operations of the ICTV and promoting dialogue with the virology community. These developments will generate improved online resources, including a freely available and regularly updated ICTV Virus Taxonomy Report. They also include a series of meetings between the ICTV and the broader community focused on some of the major challenges facing virus taxonomy, with the outcomes helping to inform the future policy and practice of the ICTV

Characterization and genomic analyses of two newly isolated Morganella phages define distant members among Tevenvirinae and Autographivirinae subfamilies

Morganella morganii is a common but frequent neglected environmental opportunistic pathogen which can cause deadly nosocomial infections. The increased number of multidrug-resistant M. morganii isolates motivates the search for alternative and effective antibacterials. We have isolated two novel obligatorily lytic M. morganii bacteriophages (vB_MmoM_MP1, vB_MmoP_MP2) and characterized them with respect to specificity, morphology, genome organization and phylogenetic relationships. MP1s dsDNA genome consists of 163,095bp and encodes 271 proteins, exhibiting low DNA (10kb chromosomal inversion that encompass the baseplate assembly and head outer capsid synthesis genes when compared to other T-even bacteriophages. MP2 has a dsDNA molecule with 39,394bp and encodes 55 proteins, presenting significant genomic (70%) and proteomic identity (86%) but only to Morganella bacteriophage MmP1. MP1 and MP2 are then novel members of Tevenvirinae and Autographivirinae, respectively, but differ significantly from other tailed bacteriophages of these subfamilies to warrant proposing new genera. Both bacteriophages together could propagate in 23 of 27M. morganii clinical isolates of different origin and antibiotic resistance profiles, making them suitable for further studies on a development of bacteriophage cocktail for potential therapeutic applications.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, COMPETE 2020 (POCI-01-0145-FEDER-006684) and the Project PTDC/BBB-BSS/6471/2014 (POCI-01-0145-FEDER-016678). RL contributed to the genome sequencing analysis, supported by the KU Leuven GOA Grant ‘Phage Biosystems’. JP acknowledges the project R-3986 of the Herculesstichting.info:eu-repo/semantics/publishedVersio

Ortervirales: A new viral order unifying five families of reverse-transcribing viruses

Reverse-transcribing viruses, which synthesize a copy of genomic DNA from an RNA template, are widespread in animals, plants, algae and fungi (1, 2).

Microviridae Goes Temperate: Microvirus-Related Proviruses Reside in the Genomes of Bacteroidetes

The Microviridae comprises icosahedral lytic viruses with circular single-stranded DNA genomes. The family is divided into two distinct groups based on genome characteristics and virion structure. Viruses infecting enterobacteria belong to the genus Microvirus, whereas those infecting obligate parasitic bacteria, such as Chlamydia, Spiroplasma and Bdellovibrio, are classified into a subfamily, the Gokushovirinae. Recent metagenomic studies suggest that members of the Microviridae might also play an important role in marine environments. In this study we present the identification and characterization of Microviridae-related prophages integrated in the genomes of species of the Bacteroidetes, a phylum not previously known to be associated with microviruses. Searches against metagenomic databases revealed the presence of highly similar sequences in the human gut. This is the first report indicating that viruses of the Microviridae lysogenize their hosts. Absence of associated integrase-coding genes and apparent recombination with dif-like sequences suggests that Bacteroidetes-associated microviruses are likely to rely on the cellular chromosome dimer resolution machinery. Phylogenetic analysis of the putative major capsid proteins places the identified proviruses into a group separate from the previously characterized microviruses and gokushoviruses, suggesting that the genetic diversity and host range of bacteriophages in the family Microviridae is wider than currently appreciated

Numerous cultivated and uncultivated viruses encode ribosomal proteins

Viruses modulate ecosystems by directly altering host metabolisms through auxiliary metabolic genes. However, viral genomes are not known to encode the core components of translation machinery, such as ribosomal proteins (RPs). Here, using reference genomes and global-scale viral metagenomic datasets, we identify 14 different RPs across viral genomes arising from cultivated viral isolates and metagenome-assembled viruses. Viruses tend to encode dynamic RPs, easily exchangeable between ribosomes, suggesting these proteins can replace cellular versions in host ribosomes. Functional assays confirm that the two most common virus-encoded RPs, bS21 and bL12, are incorporated into 70S ribosomes when expressed in Escherichia coli. Ecological distribution of virus-encoded RPs suggests some level of ecosystem adaptations as aquatic viruses and viruses of animal-associated bacteria are enriched for different subsets of RPs. Finally, RP genes are under purifying selection and thus likely retained an important function after being horizontally transferred into virus genomes