Project description:Giant viruses infecting amoebae are notable for their substantial particle sizes and expansive genomes. In this study, we collected water samples from 44 distinct locations along a river within Brazil's Pantanal biome. These samples were processed and subsequently inoculated into Vermamoeba vermiformis cultures. Observation of cytopathic effects led to the isolation of a novel virus, designated Naiavirus, distinguished by its unprecedented virion morphology and genomic organization. To elucidate the protein composition of Naiavirus particles, large-scale infections were conducted using 20 T175 flasks, each containing 10 million amoebae. Post-infection, viral particles were purified through two successive sucrose gradient centrifugations to achieve high purity. Proteomic analysis of these purified particles identified 254 associated viral proteins, a count exceeding those reported for all known giant viruses except for pandoraviruses. This dataset encompasses the raw mass spectrometry data, identification files, and associated metadata, offering valuable insights into the structural proteome of this unique giant virus.
Project description:Giant viruses infecting amoebae display remarkable structural and genomic complexity. In this study, we performed a comprehensive proteomic characterization of Cedratvirus particles purified from Acanthamoeba castellanii cultures to uncover their protein composition and organization. Approximately 100 million viral particles were purified through two consecutive sucrose cushion centrifugations to achieve high purity and homogeneity. The structural proteome was analyzed using LC-MS/MS, enabling the identification and quantification of both viral and potential host-derived proteins associated with the virion. This dataset includes raw mass spectrometry data, identification files, and metadata associated with the proteomic analysis
Project description:Legionella pneumophila are important opportunistic pathogens for which environmental reservoirs such as protists are crucial for the infection of humans. Free-living amoebae are considered key hosts providing nutrients and shelter for highly efficient intracellular proliferation of L. pneumophila, which eventually leads to lysis of the amoeba host cell. Yet, the significance of other bacterial players for L. pneumophila ecology is poorly understood. In this study we used a ubiquitous amoeba and their bacterial endosymbiont to investigate the impact of this common association on L. pneumophila infection. We demonstrate that Acanthamoeba castellanii harboring the chlamydial symbiont Protochlamydia amoebophila were able to erase L. pneumophila and, in contrast to symbiont-free amoebae, survived the infection and were able to resume growth. Environmental amoeba isolates harboring P. amoebophila were equally well-protected, and fresh environmental isolates of L. pneumophila were equally well-erased, suggesting ecological relevance of this symbiont-mediated protection. We further show that protection was not mediated by impaired L. pneumophila uptake. Instead, we observed reduced virulence of L. pneumophila released from symbiont-containing amoebae that is strongly supported by transcriptome data. Interference with transition to the transmissive phase is thus likely the basis for this protection. Finally, our data indicate that the defensive response of amoebae harboring P. amoebophila leaves the amoebae with superior fitness reminiscent of immunological memory. Given that mutualistic associations between bacteria and amoebae are widely distributed, P. amoebophila and potentially other amoeba endosymbionts could be key elements in shaping environmental survival, abundance and virulence of this important pathogen thereby affecting frequency of human infection.
Project description:Giant viruses are extraordinary members of the virosphere due to their structural complexity and high diversity in gene content. Haptophytes are ecologically important primary producers in the ocean, and all known viruses that infect haptophytes are giant viruses. Our in-depth electron microscopic, phylogenomic and virion proteomic analyses of two haptophyte-infecting giant viruses, Haptolina ericina virus RF02 (HeV RF02) and Prymnesium kappa virus RF02 (PkV RF02), unravel their large capacity for host manipulation and arsenals that functions during the infection cycle from virus entry to release. The virus infection induces significant morphological changes of host cell that are manipulated to build a virus proliferation factory. Both viruses’ genomes encode a putative nucleoprotein (dinoflagellate/viral nucleoprotein; DVNP), which was also found in the virion proteome of PkV RF02. Phylogenetic analysis suggests that DVNPs are widespread in marine giant metaviromes. Furthermore, the analysis shows that the dinoflagellate homologues were possibly acquired from viruses of the order Imitervirales.
Project description:High resolution Mass Spectrometry and Peptides identification uncovered ancestral giant insect viruses motifs within Histone-4 peptides in human liver cells. These peptides did not match any human sequence. This finding consolidates the dogma that molecular patterns are universal and suggests that metazoan cellular structures possibly share an evolutionary link with ancient giant viruses.
Project description:Viruses with large DNA genomes often carry auxiliary metabolic genes that reprogram host physiology, yet their contributions to host redox and membrane homeostasis remain poorly understood. Here we report the discovery and functional reconstitution of viral homologs of vitamin K epoxide reductase (VKOR) encoded by giant viruses. Using phylogenetic and genomic context analysis, we find that viral VKOR genes are frequently located adjacent to -carboxylase-like epoxidase and fatty acid desaturase domains, consistent with a putative modular redox pathway for membrane lipid modification. To investigate their function, we expressed viral VKORs in an Escherichia coli strain lacking disulfide bond–forming enzymes and examined both their membrane topology and activity. Remarkably, a minimal set of residue substitutions enabled proper membrane insertion and restored bacterial motility, demonstrating that viral VKORs are catalytically competent electron shuttles. Structural modeling supports their integration into the endoplasmic reticulum–like environment in the host. Finally, we show that VKORs and gamma-carboxylase-like epoxidase-desaturases from Fadolivirus and Yasminevirus giant viruses are expressed during infection of Vermamoeba vermiformis, where they may couple vitamin K epoxidation to desaturation-driven lipid remodeling. These findings expand the known functional repertoire of giant viruses and uncover a previously unrecognized viral strategy for manipulating host redox metabolism and membrane composition.
Project description:Nested parasitic chains are common schemes in nature, not limited to cellular organisms. Some giant viruses infecting protists are hyperparasitized by smaller viruses named virophages. Both can carry episomal plasmid-like DNA molecules known as transpovirons in their particles. They all share common transcriptional regulatory elements dictating the expression of their genes, which are transcribed within viral factories built by giant viruses in the host cytoplasm. This suggests close but as yet undetermined interactions between their respective transcriptional networks. Here, we studied the protein content of Megavirus chilensis virions produced in Acanthamoeba castellanii cells co-infected or not with the virophage Zamilon vitis.