Subfamily: Gammarhabdovirinae
Genus: Margarhavirus
Distinguishing features
Viruses assigned to the genus Margarhavirus form a distinct monophyletic group based on well-supported Maximum Likelihood or Maximum Clade Credibility trees inferred from complete L sequences. Chemarfal virus 1 (CHMFV1; species Margarhavirus chemarfal), currently the only virus assigned to the genus, was detected in a freshwater mussel.
Virion
Morphology
Virion morphology is unknown.
Nucleic acid
The CHMFV1 genome consists of a single molecule of negative-sense, single-stranded RNA of approximately 15.4 kb (Goldberg et al., 2023).
Proteins
The CHMFV1 N, P, M, G and L proteins share sequence homology and/or structural characteristics with the cognate proteins of other rhabdoviruses.
Genome organisation and replication
The CHMFV1 genome includes the five canonical rhabdovirus structural protein genes (N, P, M, G and L). and two consecutive additional genes (U1 and U2) encoding small proteins between the M and G genes (Figure 1 Margarhavirus).
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| Figure 1 Margarhavirus. Schematic representation of the chemarfal 1 genome shown in reverse (positive-sense) polarity. The genome contains long open reading frames (ORFs) in the N, P, M, G and L genes (open arrows) along with two additional ORFs (U1 and U2) between M and G. |
Biology
CHMFV1 was discovered by viral metagenomic sequencing of hemolymph from freshwater mussels collected in Washington, USA in 2018 (Goldberg et al., 2023). No isolate of the virus has yet been reported.
Species demarcation criteria
There is only one species in the genus. For viruses to be assigned to additional species in the genus, several of the following characteristics would have to be observed: A) minimum amino acid sequence divergence of 10% in the N proteins; B) minimum amino acid sequence divergence of 10% in the L proteins; C) minimum amino acid sequence divergence of 15% in the G proteins; D) significant differences in genome organisation as evidenced by numbers and locations of ORFs; E) they can be distinguished in virus neutralisation tests; and F) they occupy different ecological niches as evidenced by differences in vertebrate hosts and or arthropod vectors.