Role of the R349 Gene and Its Repeats in the MIMIVIRE Defense System

MIMIVIRE is a defense system described in lineage A Mimivirus (Mimiviridae family) that mediates resistance against Zamilon virophage. It is composed of putative helicase and nuclease associated with a gene of unknown function called R349, which contains four 15 bp repeats homologous to the virophage sequence. In a previous study, the silencing of such genes restored virophage susceptibility. Moreover, the CRISPR Cas-4 like activity of the nuclease has recently been characterized. In this study, a recently isolated Mimivirus of lineage A with R349 gene lacking 3 of 4 repeats was demonstrated to be susceptible to Zamilon. To reinforce the importance of the R349 gene in the MIMIVIRE system, we developed and presented, for the first time to our knowledge, a protocol for Mimivirus genomic editing. By knocking out R349 gene in a Mimivirus lineage A, we observed the replication of Zamilon, indicating that this gene is critical in the resistance against this specific group of virophages

A Student\u27s Guide to giant Viruses Infecting Small Eukaryotes: From Acanthamoeba to Zooxanthellae

The discovery of infectious particles that challenge conventional thoughts concerning “what is a virus” has led to the evolution a new field of study in the past decade. Here, we review knowledge and information concerning “giant viruses”, with a focus not only on some of the best studied systems, but also provide an effort to illuminate systems yet to be better resolved. We conclude by demonstrating that there is an abundance of new host–virus systems that fall into this “giant” category, demonstrating that this field of inquiry presents great opportunities for future research

Guarani Virophage, a New Sputnik-Like Isolate From a Brazilian Lake

Virophages are critical regulators of viral population dynamics and potential actors in the stability of the microbial networks. These small biological entities predate the replicative cycle of giant viruses, such as the members of the Mimiviridae family or their distant relatives, which produce within the cytoplasm of their host cells a viral factory harboring a complex biochemistry propitious to the growth of the smaller parasites. In this paper, we describe the isolation and the characterization of a new virophage, the eighth, that we named Guarani. We observed that Guarani exhibits a late replication cycle compared to its giant virus host. In addition, like all Sputnik strains, Guarani is able to infect the three lineages A, B and C of the Mimiviridae family, and affects the replication and the infectivity of its host virus. In terms of genetic content, Guarani has a 18,967 bp long double-stranded DNA genome encoding 22 predicted genes very similar to Sputnik genes, except for ORF19 and ORF12. The former is more related to Zamilon while the latter seems to be novel. The architecture of the Guarani genome is closely related to Sputnik and Zamilon strains, suggesting a common origin for all these virophages

Replication strategies of newly discovered giant viruses of amoebas

Giant viruses are a group of viruses with genome composed of double-stranded DNA molecule. They are characterized by the creation of giant viral particles, the size of which varies between 150-1500 nm. Also, their genomes are huge reaching sizes of up to 2,5 Mbp. The viruses replicate either in the cytoplasm or they exploit for their replication both nucleus and cytoplasm. Therefore, they are called, nucleocytoplasmic large DNA viruses (NCLDVs). During their replication cycle, the giant viruses induce the creation of viral factories, which provide morphogenesis of new virions. The aim of this thesis is to summarise current knowledge of selected representatives of the giant viruses, and to describe their replication strategies. Furthemore, this work aims to discuss discoveries made in relation to this particular group if viruses. Thanks to the discovery of giant viruses, another group of small viruses was identified - the so-called virophages (viruses of viruses). Virophages have the ability to take advantage of the giant virus infecting an amoeba to realize their own replication strategy. In some members of the Mimiviridae family there was described a presence of an genome element providing a unique way of immunoprotection of giant viruses from being infected by the Zamilon virophage. Key words:...Gigantické viry jsou skupinou virů, jejichž genom je tvořen dvouvláknovou molekulou DNA. Vyznačují se tvorbou obrovských virových částic, jejichž velikost se pohybuje v rozmezí 150-1500 nm. Stejně tak i jejich genomy jsou obrovské a dosahují velikosti až 2,5 Mbp. Obrovské DNA viry se replikují buď v cytoplazmě, nebo využívají obou buněčných kompartmentů - jádra i cytoplazmy. Proto byly pojmenovány jako jaderno-cytoplazmatické viry (nucleocytoplasmic large DNA viruses, NCLDVs). V průběhu replikační cyklu indukují tvorbu virových továren, které zajišťují morfogenezi nových virionů. Cílem této práce je shrnout dosavadní poznatky o vybraných zástupcích gigantických virů a popsat jejich replikační strategie. Dále budou diskutovány objevy učiněné ve spojitosti s touto skupinou virů. Díky objevu gigantických virů byly také identifikovány menší DNA viry, tzv. virofágy (viry virů), jež mají schopnost využívat infekce améby gigantickými viry pro realizaci své vlastní replikační strategie. U zástupců čeledi Mimiviridae byla popsána přítomnost úseku genů MIMIVIRE, který zajišťuje unikátní způsob imunitní ochrany virů před infekcí virofágem Zamilon. Klíčová slova: gigantické viry, Mimivirus, virofág, MIMIVIRE, amébaKatedra genetiky a mikrobiologieDepartment of Genetics and MicrobiologyPřírodovědecká fakultaFaculty of Scienc

Emerg Infect Dis

28518044PMC544344

Emerg Infect Dis

We report a case of a 54-year-old Moroccan woman living in France diagnosed with eosinophilic meningitis caused by Angiostrongylus cantonensis. Diagnosis was based on clinical symptoms and confirmed by testing of serum and cerebrospinal fluid samples. Physicians should consider the risk for A. cantonensis infection outside of endemic areas.28518042PMC544344

The Impact of CRISPR-Cas System on Antiviral Therapy

Clustered regularly interspaced short palindromic repeats (CRISPR)-associated protein nuclease (Cas) is identified as an adaptive immune system in archaea and bacteria. Type II of this system, CRISPR-Cas9, is the most versatile form that has enabled facile and efficient targeted genome editing. Viral infections have serious impacts on global health and conventional antiviral therapies have not yielded a successful solution hitherto. The CRISPR-Cas9 system represents a promising tool for eliminating viral infections. In this review, we highlight 1) the recent progress of CRISPR-Cas technology in decoding and diagnosis of viral outbreaks, 2) its applications to eliminate viral infections in both pre-integration and provirus stages, and 3) various delivery systems that are employed to introduce the platform into target cells

Ancestrality and Mosaicism of Giant Viruses Supporting the Definition of the Fourth TRUC of Microbes

Giant viruses of amoebae were discovered in 2003. Since then, their diversity has greatly expanded. They were suggested to form a fourth branch of life, collectively named ‘TRUC’ (for “Things Resisting Uncompleted Classifications”) alongside Bacteria, Archaea, and Eukarya. Their origin and ancestrality remain controversial. Here, we specify the evolution and definition of giant viruses. Phylogenetic and phenetic analyses of informational gene repertoires of giant viruses and selected bacteria, archaea and eukaryota were performed, including structural phylogenomics based on protein structural domains grouped into 289 universal fold superfamilies (FSFs). Hierarchical clustering analysis was performed based on a binary presence/absence matrix constructed using 727 informational COGs from cellular organisms. The presence/absence of ‘universal’ FSF domains was used to generate an unrooted maximum parsimony phylogenomic tree. Comparison of the gene content of a giant virus with those of a bacterium, an archaeon, and a eukaryote with small genomes was also performed. Overall, both cladistic analyses based on gene sequences of very central and ancient proteins and on highly conserved protein fold structures as well as phenetic analyses were congruent regarding the delineation of a fourth branch of microbes comprised by giant viruses. Giant viruses appeared as a basal group in the tree of all proteomes. A pangenome and core genome determined for Rickettsia bellii (bacteria), Methanomassiliicoccus luminyensis (archaeon), Encephalitozoon intestinalis (eukaryote), and Tupanvirus (giant virus) showed a substantial proportion of Tupanvirus genes that overlap with those of the cellular microbes. In addition, a substantial genome mosaicism was observed, with 51, 11, 8, and 0.2% of Tupanvirus genes best matching with viruses, eukaryota, bacteria, and archaea, respectively. Finally, we found that genes themselves may be subject to lateral sequence transfers. In summary, our data highlight the quantum leap between classical and giant viruses. Phylogenetic and phyletic analyses and the study of protein fold superfamilies confirm previous evidence of the existence of a fourth TRUC of life that includes giant viruses, and highlight its ancestrality and mosaicism. They also point out that best evolutionary representations for giant viruses and cellular microorganisms are rhizomes, and that sequence transfers rather than gene transfers have to be considered

The discovery of CRISPR in archaea and bacteria

CRISPR-Cas are self-/nonself-discriminating systems found in prokaryotic cells. They represent a remarkable example of molecular memory that is hereditarily transmitted. Their discovery can be considered as one of the first fruits of the systematic exploration of prokaryotic genomes. Although this genomic feature was serendipitously discovered in molecular biology studies, it was the availability of multiple complete genomes that shed light about their role as a genetic immune system. Here we tell the story of how this discovery originated and was slowly and painstakingly advanced to the point of understating the biological role of what initially was just an odd genomic feature.FJMM is funded by the Spanish Ministerio de Economía y Competitividad (BIO2014-53029P) and the European Commission/Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (291815 Era-Net ANIHWA). FR-V is funded by projects MEDIMAX BFPU2013-48007-P from the Spanish Ministerio de Economía y Competitividad, MaCuMBA Project 311975 of the European Commission FP7 and PROMETEO II/2014/012 project AQUAMET from the Generalitat Valenciana