| Summary: | <i>Xylella fastidiosa</i> (<i>Xf</i>) is a plant pathogen causing significant losses in agriculture worldwide. Originating from America, this bacterium caused recent epidemics in southern Europe and is thus considered an emerging pathogen. As the European regulations do not authorize antibiotic treatment in plants, alternative treatments are urgently needed to control the spread of the pathogen and eventually to cure infected crops. One such alternative is the use of phage therapy, developed more than 100 years ago to cure human dysentery and nowadays adapted to agriculture. The first step towards phage therapy is the isolation of the appropriate bacteriophages. With this goal, we searched for phages able to infect <i>Xf</i> strains that are endemic in the Mediterranean area. However, as <i>Xf</i> is truly a fastidious organism, we chose the phylogenetically closest and relatively fast-growing organism <i>X. albineans</i> as a surrogate host for the isolation step. Our results showed the isolation from various sources and preliminary characterization of several phages active on different <i>Xf</i> strains, namely, from the <i>fastidiosa</i> (<i>Xff</i>), <i>multiplex</i> (<i>Xfm</i>), and <i>pauca</i> (<i>Xfp</i>) subspecies, as well as on <i>X. albilineans</i>. We sequenced their genomes, described their genomic features, and provided a phylogeny analysis that allowed us to propose new taxonomic elements. Among the 14 genomes sequenced, we could identify two new phage species, belonging to two new genera of the <i>Caudoviricetes</i> order, namely, <i>Usmevirus</i> (<i>Podoviridae</i> family) and <i>Subavirus</i> (<i>Siphoviridae</i> family). Interestingly, no specific phages could be isolated from infected plant samples, whereas one was isolated from vector insects captured in a contaminated area, and several from surface and sewage waters from the Marseille area.
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