Catovirus naegleriensis strain 1, genome sequencing and assembly. null

Giant viruses (belonging to the Nucleocytoviricota) are significant lethality agents of various eukaryotic hosts. Metagenomic studies showed that giant viruses are key players in virtually every environment. However, available giant virus isolates are limited to a minuscule number of protist and algae hosts. Here we report on the first viral isolate replicating in the amoeboflagellate Naegleria. This genus includes the infamous human pathogen Naegleria fowleri, the causative agent of the rare but lethal disease primary amoebic meningoencephalitis. We revealed the structure and infection cycle of Catovirus naegleriensis strain 1 (CatNiV1), and show its unique adaptations to its Naegleria host by fluorescence in situ hybridization, electron microscopy, genomics, and proteomics. CatNiV1 is only the fourth isolate of the subfamily Klosneuvirinae, a diverse group of viruses known mainly from metagenomic studies. Like other Klosneuviruses, the genome of CatNiV1 contains an unusually high amount of translation genes, yet it lacks tRNAs. CatNiV1 acquired genes from its Naegleria host, which code for heat shock proteins and apoptosis inhibiting factors, presumably for host interactions. Notably, CatNiV1 infection was lethal for all tested Naegleria species, including the human pathogen N. fowleri. This study extends our experimental framework for investigating giant viruses and could represent a first step toward the biological control of Naegleria fowleri.