Search Results (34)

The greenbug aphid (Schizaphis graminum (Rondani)) is a major pest of wheat and an important vector of wheat viruses. An RNA-seq study was conducted to investigate the microbial effects of two greenbug genotypes, the presence or absence of cereal yellow dwarf virus, and the condition of the wheat host over a 20-day time course of unrestricted greenbug feeding. Messenger RNA reads were mapped to ca. 47,000 bacterial, 1218 archaeal, 14,165 viral, 571 fungal, and 94 protozoan reference or representative genomes, plus greenbug itself and its wheat host. Taxon counts were analyzed with QIIME2 and DESeq2. Distinct early (days 1 through 10) and late (days 15 and 20) communities differed in the abundance of typical enteric genera (Shigella, Escherichia, Citrobacter), which declined in the late community, while the ratio of microbial to greenbug read counts declined 50% and diversity measures increased. The nearly universal aphid endosymbiont, Buchnera aphidicola, accounted for less than 25% of the read counts in both communities. There were 302 differentially expressed (populated) genera with respect to early and late dates, while 25 genera differed between the greenbug genotypes and nine differed between carrier and virus-free greenbugs. The late community was likely responding to starvation as the wheat host succumbed to aphid feeding. Our results add to basic knowledge about aphid microbiomes and offer an attractive alternative method to assess insect microbiomes. Full article

Possible early detection of people at increased risk for severe COVID-19 clinical course is extremely important so that appropriate therapy can be initiated promptly to prevent numerous deaths. Our study included 45 patients treated for COVID-19 at Dubrava University Hospital, with clinical course analysed from medical records and stool samples collected for determination of the gut microbiota diversity using 16S rRNA analysis. Sequencing was successful for 41 samples belonging to four clinical course groups (WHO guidelines): 12 samples—critical, 12—severe, 9—moderate and 8—mild group. Microbial composition was assessed between groups using two approaches—ANCOM (QIIME2) and Kruskal–Wallis (MicrobiomeAnalyst). On the genus level, two taxa were found to be differentially abundant: archaeal Halococcus and Coprococcus (for both W = 37)—the two were most abundant in the critical group (10% and 0.94% of entire abundance, respectively). Coprococcus catus was the only species identified by both methods to be differentially abundant between groups and was most abundant in the critical group. Alpha diversity indicated greater evenness of features in the critical group. Beta diversity showed clustering of samples from the critical group. A relationship between gut microbiota composition and the clinical course of COVID-19 disease was indicated, pointing towards specific distinct features of the critical group. In a broader sense, our findings might be useful in combating potential future similar pandemics and emerging virus outbreaks. Full article

Ticks are blood-feeding ectoparasites that also transmit various pathogens, posing severe risks to human and animal health. DNA viruses play a crucial role in the microbial ecology of ticks, but their distribution and ecological significance remain largely undetermined. Here, we assembled an extensive catalog encompassing 4320 viral operational taxonomic units (vOTUs) from six main dominant tick species in China, of which 94.8% have not been found in any other environment. To bridge the knowledge gap in tick DNA virus research and provide a crucial resource platform, we developed the Tick DNA Virus Database. This database includes the vOTUs that are known to cause diseases. Most of the predicted vOTUs are associated with dominant bacterial and archaeal phyla. We identified 105 virus-encoded putative auxiliary metabolic genes (AMGs) that are involved in host metabolism and environmental adaptation, potentially influencing ticks through both top-down and bottom-up mechanisms. The identification of microbial communities and antibiotic resistance in wild tick species suggests that wild ticks are reservoirs of antibiotic resistance and potential spreaders of antibiotic resistance. These findings reveal the potential role of tick viruses in ecosystems, highlighting the importance of monitoring tick microbiomes to address global public health challenges. Full article

Viruses are nonliving biological entities whose host range encompasses all known forms of life. They are deceptively simple in description (a protein shell surrounding genetic material with an occasional lipid envelope) and yet can infect all known forms of life. Recently, due to technological advancements, viruses from more extreme environments can be studied through both culture-dependent and independent means. Viruses with thermophilic, halophilic, psychrophilic, and barophilic properties are highlighted in this paper with an emphasis on the properties that allow them to exist in said environments. Unfortunately, much of this field is extremely novel and thus, not much is yet known about these viruses or the microbes they infect when compared to non-extremophilic host–virus systems. With this review, we hope to shed some light on these relatively new studies and highlight their intrinsic value. Full article

Even though viruses and plasmids are both drivers of horizontal gene transfer, they differ fundamentally in their mode of transfer. Virus genomes are enclosed in virus capsids and are not dependent on cell-to-cell contacts for their dissemination. In contrast, the transfer of plasmids most often requires physical contact between cells. However, plasmid pR1SE of Halorubrum lacusprofundi is disseminated between cells, independent of cell-cell contacts, in specialized membrane vesicles that contain plasmid proteins. In this study, we searched for pR1SE-like elements in public databases and a metagenomics dataset from Australian salt lakes and identified 40 additional pR1SE-like elements in hypersaline environments worldwide. Herein, these elements are named apHPVs (archaeal plasmids of haloarchaea potentially transferred in plasmid vesicles). They share two sets of closely related proteins with conserved synteny, strongly indicating an organization into different functional clusters. We find that apHPVs, besides transferring themselves, have the potential to transfer large fragments of DNA between host cells, including virus defense systems. Most interestingly, apHPVs likely play an important role in the evolution of viruses and plasmids in haloarchaea, as they appear to recombine with both of them. This further supports the idea that plasmids and viruses are not distinct but closely related mobile genetic elements. Full article

N-glycosylation is a post-translational modification of proteins that occurs across all three domains of life. In Archaea, N-glycosylation is crucial for cell stability and motility, but importantly also has significant implications for virus–host interactions. While some archaeal viruses present glycosylated proteins or interact with glycosylated host proteins, the direct influence of N-glycosylation on archaeal virus–host interactions remains to be elucidated. In this study, we generated an N-glycosylation-deficient mutant of Halorubrum lacusprofundi, a halophilic archaeon commonly used to study cold adaptation, and examined the impact of compromised N-glycosylation on the infection dynamics of two very diverse viruses. While compromised N-glycosylation had no influence on the life cycle of the head-tailed virus HRTV-DL1, we observed a significant effect on membrane-containing virus HFPV-1. Both intracellular genome numbers and extracellular virus particle numbers of HFPV-1 were increased in the mutant strain, which we attribute to instability of the surface-layer which builds the protein envelope of the cell. When testing the impact of compromised N-glycosylation on the life cycle of plasmid vesicles, specialized membrane vesicles that transfer a plasmid between host cells, we determined that plasmid vesicle stability is strongly dependent on the host glycosylation machinery. Our study thus provides important insight into the role of N-glycosylation in virus–host interactions in Archaea, while pointing to how this influence strongly differs amongst various viruses and virus-like elements. Full article

Spatial and temporal distribution of lytic viruses in deep groundwater remains unexplored so far. Here, we tackle this gap of knowledge by studying viral infections of Altivir_1_MSI in biofilms dominated by the uncultivated host Candidatus Altiarchaeum hamiconexum sampled from deep anoxic groundwater over a period of four years. Using virus-targeted direct-geneFISH (virusFISH) whose detection efficiency for individual viral particles was 15%, we show a significant and steady increase of virus infections from 2019 to 2022. Based on fluorescence micrographs of individual biofilm flocks, we determined different stages of viral infections in biofilms for single sampling events, demonstrating the progression of infection of biofilms in deep groundwater. Biofilms associated with many host cells undergoing lysis showed a substantial accumulation of filamentous microbes around infected cells probably feeding off host cell debris. Using 16S rRNA gene sequencing across ten individual biofilm flocks from one sampling event, we determined that the associated bacterial community remains relatively constant and was dominated by sulfate-reducing members affiliated with Desulfobacterota. Given the stability of the virus-host interaction in these deep groundwater samples, we postulate that the uncultivated virus-host system described herein represents a suitable model system for studying deep biosphere virus-host interactions in future research endeavors. Full article

Coastal sediments in the proximity of wastewater and emergency outfalls are often sinks of pharmaceutical compounds and other organic and inorganic contaminants that are likely to affect the microbial community. The metabolites of these contaminants affect microbial diversity and their metabolic processes, resulting in undesirable effects on ecosystem functioning, thus necessitating the need to understand their composition and functions. In the present investigation, we studied the metagenomes of 12 coastal surface sediments through whole genome shot-gun sequencing. Taxonomic binning of the genes predicted about 86% as bacteria, 1% as archaea, >0.001% as viruses and Eukaryota, and 12% as other communities. The dominant bacterial, archaeal, and fungal genera were Woeseia, Nitrosopumilus, and Rhizophagus, respectively. The most prevalent viral families were Myoviridae and Siphoviridae, and the T4 virus was the most dominant bacteriophage. The unigenes further aligned to 26 clusters of orthologous genes (COGs) and five carbohydrate-active enzymes (CAZy) classes. Glycoside hydrolases (GH) and glycoside transferase (GT) were the highest-recorded CAzymes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) level 3 functions were subjugated by purine metabolism > ABC transporters > oxidative phosphorylation > two-component system > pyrimidine metabolism > pyruvate metabolism > quorum sensing > carbon fixation pathways > ribosomes > and glyoxalate and dicarboxylate metabolism. Sequences allying with plasmids, integrons, insertion sequences and antibiotic-resistance genes were also observed. Both the taxonomies and functional abundances exhibited variation in relative abundances, with limited spatial variability (ANOVA p > 0.05; ANOSIM-0.05, p > 0.05). This study underlines the dominant microbial communities and functional genes in the marine sediments of Kuwait as a baseline for future biomonitoring programs. Full article

Continuous viral evolution of SARS-CoV-2 has resulted in variants capable of immune evasion, vaccine breakthrough infections and increased transmissibility. New vaccines that invoke mucosal immunity may provide a solution to reducing virus transmission. Here, we evaluated the immunogenicity of intranasally administered subunit protein vaccines composed of a stabilized SARS-CoV-2 spike trimer or the receptor binding domain (RBD) adjuvanted with either cholera toxin (CT) or an archaeal lipid mucosal adjuvant (AMVAD). We show robust induction of immunoglobulin (Ig) G and IgA responses in plasma, nasal wash and bronchoalveolar lavage in mice only when adjuvant is used in the vaccine formulation. While the AMVAD adjuvant was more effective at inducing systemic antibodies against the RBD antigen than CT, CT was generally more effective at inducing overall higher IgA and IgG titers against the spike antigen in both systemic and mucosal compartments. Furthermore, vaccination with adjuvanted spike led to superior mucosal IgA responses than with the RBD antigen and produced broadly targeting neutralizing plasma antibodies against ancestral, Delta and Omicron variants in vitro; whereas adjuvanted RBD elicited a narrower antibody response with neutralizing activity only against ancestral and Delta variants. Our study demonstrates that intranasal administration of an adjuvanted protein subunit vaccine in immunologically naïve mice induced both systemic and mucosal neutralizing antibody responses that were most effective at neutralizing SARS-CoV-2 variants when the trimeric spike was used as an antigen compared to RBD. Full article

Saccharolobus spindle-shaped virus 1 (SSV1) was one of the first viruses identified in the archaeal kingdom. Originally isolated from a Japanese species of Saccharolobus back in 1984, it has been extensively used as a model system for genomic, transcriptomic, and proteomic studies, as well as to unveil the molecular mechanisms governing the host–virus interaction. The purpose of this mini review is to supply a compendium of four decades of research on the SSV1 virus. Full article

In eukaryotes, genomic DNA is bound with histone proteins and packaged into chromatin. The nucleosome, a fundamental unit of chromatin, regulates the accessibility of DNA to enzymes involved in gene regulation. During the past few years, structural analyses of chromatin architectures have been limited to evolutionarily related organisms. The amino acid sequences of histone proteins are highly conserved from humans to yeasts, but are divergent in the deeply branching protozoan groups, including human parasites that are directly related to human health. Certain large DNA viruses, as well as archaeal organisms, contain distant homologs of eukaryotic histone proteins. The divergent sequences give rise to unique and distinct nucleosome architectures, although the fundamental principles of histone folding and DNA contact are highly conserved. In this article, we review the structures and biophysical properties of nucleosomes containing histones from the human parasites Giardia lamblia and Leishmania major, and histone-like proteins from the Marseilleviridae amoeba virus family. The presented data confirm the sharing of the overall DNA compaction system among evolutionally distant species and clarify the deviations from the species-specific nature of the nucleosome. Full article

A small subset of acidic hot springs sampled in Yellowstone National Park yielded rod-shaped viruses which lysed liquid host cultures and formed clear plaques on lawns of host cells. Three isolates chosen for detailed analysis were found to be genetically related to previously described isolates of the Sulfolobus islandicus rod-shaped virus (SIRV), but distinct from them and from each other. Functional stability of the new isolates was assessed in a series of inactivation experiments. UV-C radiation inactivated one of the isolates somewhat faster than bacteriophage λ, suggesting that encapsidation in the SIRV-like virion did not confer unusual protection of the DNA from UV damage. With respect to high temperature, the new isolates were extremely, but not equally, stable. Several chemical treatments were found to inactivate the virions and, in some cases, to reveal apparent differences in virion stability among the isolates. Screening a larger set of isolates identified greater variation of these stability properties but found few correlations among the resulting profiles. The majority of host cells infected by the new isolates were killed, but survivors exhibited heritable resistance, which could not be attributed to CRISPR spacer acquisition or the loss of the pilus-related genes identified by earlier studies. Virus-resistant host variants arose at high frequency and most were resistant to multiple viral strains; conversely, resistant host clones generated virus-sensitive variants, also at high frequency. Virus-resistant cells lacked the ability of virus-sensitive cells to bind virions in liquid suspensions. Rapid interconversion of sensitive and resistant forms of a host strain suggests the operation of a yet-unidentified mechanism that acts to allow both the lytic virus and its host to propagate in highly localized natural populations, whereas variation of virion-stability phenotypes among the new viral isolates suggests that multiple molecular features contribute to the biological durability of these viruses. Full article

Viruses can infect members of all three domains of life. However, little is known about viruses infecting archaea and the mechanisms that determine their host interactions are poorly understood. Investigations of molecular mechanisms of viral infection rely on genetically accessible virus–host model systems. Euryarchaea belonging to the genus Haloferax are interesting models, as a reliable genetic system and versatile microscopy methods are available. However, only one virus infecting the Haloferax species is currently available. In this study, we tested ~100 haloarchaeal virus isolates for their infectivity on 14 Haloferax strains. From this, we identified 10 virus isolates in total capable of infecting Haloferax strains, which represented myovirus or siphovirus morphotypes. Surprisingly, the only susceptible strain of all 14 tested was Haloferax gibbonsii LR2-5, which serves as an auspicious host for all of these 10 viruses. By applying comparative genomics, we shed light on factors determining the host range of haloarchaeal viruses on Haloferax. We anticipate our study to be a starting point in the study of haloarchaeal virus–host interactions. Full article

Today, the number of known viruses infecting methanogenic archaea is limited. Here, we report on a novel lytic virus, designated Blf4, and its host strain Methanoculleus bourgensis E02.3, a methanogenic archaeon belonging to the Methanomicrobiales, both isolated from a commercial biogas plant in Germany. The virus consists of an icosahedral head 60 nm in diameter and a long non-contractile tail of 125 nm in length, which is consistent with the new isolate belonging to the Siphoviridae family. Electron microscopy revealed that Blf4 attaches to the vegetative cells of M. bourgensis E02.3 as well as to cellular appendages. Apart from M. bourgensis E02.3, none of the tested Methanoculleus strains were lysed by Blf4, indicating a narrow host range. The complete 37 kb dsDNA genome of Blf4 contains 63 open reading frames (ORFs), all organized in the same transcriptional direction. For most of the ORFs, potential functions were predicted. In addition, the genome of the host M. bourgensis E02.3 was sequenced and assembled, resulting in a 2.6 Mbp draft genome consisting of nine contigs. All genes required for a hydrogenotrophic lifestyle were predicted. A CRISPR/Cas system (type I-U) was identified with six spacers directed against Blf4, indicating that this defense system might not be very efficient in fending off invading Blf4 virus. Full article