Novel marine diatom ssRNA virus NitRevRNAV infecting Nitzschia reversa

Abstract

Background and aims – Diatoms are one of the most species rich groups of organisms on Earth. They are fundamental in supporting the biomass of the natural environment. The presence of marine viruses can greatly influence diatom diversity in their natural environment and has attracted interest from multi-disciplinary research teams after a diatom infected virus was reported for the first time in the 21st century. As initial research in this field demonstrated, for the acquisition of a new virus it is important to learn about their infect hosts. Therefore, we have been searching for new viruses that infect diatoms.
 Methods – A clonal host species Nitzschia reversa was isolated from natural sea water. Aliquots of the filtrates obtained from this sea water were inoculated to yield the exponentially-growing isolated host species. The resultant lysate was used as a clonal lysate and treated as a clonal virus suspension. The suspension was then used for further analysis of various biochemical studies.
 Key results – We discovered and isolated a new virus that infected the pennate diatom Nitzschia reversa. Since this newly discovered virus was a single strand RNA virus, it has capsid proteins with 30 nm size icosahedron without an envelope. The species epithet is NitRevRNAV.
 Conclusions – In this study, we described the morphology, genome type and partial sequences, as well as lytic activities, of the new species NitRevRNAV. Of note, the virus harbours a positive-sense single-stranded RNA genome. These features were highly similar to those of previously known diatom RNA viruses therefore NitRevRNAV is a new member of the genus Bacillarnavirus in the Order Picornavirales.

Virome Variation during Sea Star Wasting Disease Progression in Pisaster ochraceus (Asteroidea, Echinodermata)

“…Previous work has revealed the presence of presumably fungal viruses and a wide richness of protistan rRNAs in metagenomes prepared from material purified from <0.2 µm filtered tissue homogenates [ 17 ]. Picornaviruses have been recovered in stressed marine metazoa [ 43 , 44 ], cause mortality in protists (e.g., diatom viruses [ 45 , 46 ]) and disease in marine arthropods (e.g., Taura syndrome virus [ 47 ]). However, the wide diversity of picornaviruses recovered from grossly normal specimens in field surveys [ 22 ] suggests that their role in disease, especially in mass mortality settings, is unclear for most hosts.…”

RNA Viruses in Aquatic Unicellular Eukaryotes

“…The size of these virus particles, in diameter, was 30 nm, as shown by transmission electron microscopy (TEM) after negative staining. The NitRevRNAV genome is a linear +ssRNA with a poly(A) tail (Table 1) [77]. It has four major polypeptides at 36, 32, 30, and 28 kDa.…”

“…It has four major polypeptides at 36, 32, 30, and 28 kDa. Phylogenetic analysis of amino acid sequences of RdRp placed NitRevRNAV as a member of the genus Bacillarnavirus [77]; however, the reclassification could be required (Figures 1 and 2).…”

“…Nitzschia reversa RNA virus (NitRevRNAV) was isolated from surface seawaters of Sagami Bay, Japan, with the pennate diatom Nitzschia reversa (Figure 3) [77]. The host specificity of this virus was revealed by inoculating various diatom species, such as Nitzschia spp., Cylindrotheca spp., Chaetoceros spp., Skeletonema spp., and Achnanthes spp., with virus suspensions.…”

Virome Temporal Variation During Sea Star Wasting Disease Progression in Pisaster ochraceus (Asteroidea, Echinodermata)

“…Picornaviruses have been recovered in stressed marine metazoa [42,43], cause mortality in protists (e.g. diatom viruses [44,45]) and disease in marine arthropods (e.g. Taura syndrome virus [46]).…”