#FEMSmicroBlog: New viruses discovered in 2023


As the year 2023 comes to an end, we want to welcome the new viral members of our microbial world. As the viral world keeps expanding, choosing a few interesting viruses to present becomes quite difficult. In this #FEMSmicroBlog, Sarah Wettstadt introduces a few new viruses identified in 2023. #FascinatingMicrobes


Fungi-infecting viruses

Mycoviruses, those infecting fungi, can have hypo-virulent effects on their hosts. Especially for plant pathogenic fungi, mycoviruses are promising candidates for the application as a biocontrol to prevent fungal spread.

A new study isolated mycoviruses from edible mushrooms from a Botanical Garden in Tsukuba, Japan. They identified seven novel RNA viruses, with three of them clustering into the Alphapartitivirus genus, and one each into the Betapartitivirus, Orthocurvulavirus, Alphaendornavirus and Tulasvirus genus. While the ecological effect of the viruses on the mushrooms was not investigated, this study helped broaden the knowledge of the diversity of viruses in fungal samples.


Protists-infecting viruses

In comparison to viruses affecting fungi, knowledge of viruses infecting protists is rather limited, which is what another study aimed to tackle. The authors analysed a culture of the protist Haloplacidia with its unspecified prey bacteria.

They identified a novel RNA virus named Haloplacidia narnavirus 1 from the family Narnaviridae. The researchers assumed that the host of the virus is the protist instead of the bacteria as all known narnaviruses have eukaryotic hosts.


Fish-infecting viruses

Viruses infecting cartilaginous fish are fascinating due to the complex immune system of the fish. As cartilaginous fish are the oldest group of existing vertebrates, their relationships with viruses can provide deep insights into the evolutionary mechanisms of viruses and immune systems.

Researchers found a novel foamy virus, termed “cartilaginous fish endogenous foamy virus”, in the genomes of sharks and rays. Leading to a vacuolisation of infected cells in vitro, foamy viruses belong to the Spumaretrovirinae subfamily (Retroviridae family). They are complex non-pathogenic retroviruses present in various vertebrates, including land-based mammals.

Based on genomic and phylogenetic analysis, the researchers hypothesised that foamy viruses switched their hosts several times within the past 250 million years. During this process, they both gained and lost extensive genetic sequences, allowing them to adapt to new hosts, thus eventually settling in terrestrial animals.

From the spleen tissue of a thornback skate, an endemic ray species in Australia, researchers isolated and identified the Raja clavata polyomavirus. This small, non-enveloped DNA virus belongs to the Polyomaviridae family and has a circular genome of approximately 4,000-7,000 nucleotides. The researchers did not detect any sign of infection in the collected sample, suggesting also a potential co-evolution.


Mulberry-infecting virus

Viruses infecting plants and trees can result in the loss of fruit and crop yields, which is why understanding phytoviruses is necessary. In China, the Mulberry tree has been cultivated for centuries mainly for its fruit which is consumed directly or as jam, juice or dessert. Several viruses are already known to cause mosaic symptoms in Mulberry trees, yet, a study isolated another one from mulberry leaves collected at a temple in Fujian, China.

Mulberry viruses infecting Mulberry leaves.
Mulberry viruses infecting Mulberry leaves. From Wei et al. (2023).

Transcriptome sequencing allowed researchers to identify the Quanzhou mulberry virus in the Ribovirus family. The virus consists of a genome of 9,000 nucleotides, five open reading frames and icosahedral particles. The researchers infiltrated Mulberry and Nicotiana benthamiana leaves with recombinant Agrobacterium tumefaciens containing viral genetic material, resulting in visible virion particles only in the cytoplasm of the Mulberry, suggesting host specificity.

If you’ve read this far it seems you have an interest in viruses! Make sure to check out the latest research in Pathogens and Disease to learn even more.

About the author of this blog

Dr Sarah Wettstadt is a microbiologist-turned science writer and communicator publishing for professional associations and life science organisations. She runs the blogs BacterialWorld, to share the diverse and colourful activities of microbes and bacteria, and Sunny Scientist, to support researchers in their busy scientific days. As science communication manager for the Scientific Panel on Responsible Plant Nutrition and blog post commissioner for the FEMSmicroBlog, Sarah writes about microbiology and plant nutrition research for expert and non-expert audiences. To coach and mentor scientists in science communication, she co-founded the Partnership Business SciComm Society. Previous to her science communication career, Sarah did a PhD at Imperial College London, UK, and a postdoc at the CSIC in Granada, Spain. In her non-scicomm time, she travels the world or enjoys the sunny beaches in Spain playing beach volleyball.

About this blog section

The section #FascinatingMicrobes for the #FEMSmicroBlog explains the science behind a paper and highlights the significance and broader context of a recent finding. One of the main goals is to share the fascinating spectrum of microbes across all fields of microbiology.

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The #FEMSmicroBlog welcomes external bloggers, writers and SciComm enthusiasts. Get in touch if you want to share your idea for a blog entry with us!

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