Characterization of anti-Xylella endolysins from genomic data. A preliminary insight into the identification of novel antimicrobial molecules

Xylella fastidiosa is an emerging problem among infective agents threatening crops of commercial interest in the Mediterranean region, most notably Eastern Spain and Southern Italy. Infections determined by X. fastidiosa subspecies multiplex and X. fastidiosa subspecies pauca, affect respectively almond and olive trees, and represent a major concern in these two countries. Ecological and economic damages that Xylella spp. can cause, therefore, recommend measures aimed at preventing further spreading across different plants and areas of agricultural interest. 
Among molecules with intrinsic antimicrobial activity, phage-encoded endolysins constitute a natural tool which may be used in the biological warfare against pathogenic microbes. Lytic and lysogenic phages express endolysins at the late stage of the infection in order to degrade the host cell wall and favor the dispersal of viral particles in the environment. A number of phages capable of infecting Xylella spp. have been already sequenced, and lysogenic phages can be identified from available Xylella spp. pure culture genomes.  Thus far, we have identified hundreds putative endolysins from genomic data with the aim of exploring their efficiency as antimicrobial agents against X. fastidiosa. We found 159 candidate anti-Xylella endolysins belonging to four mayor clades with possible differential specificity against X. fastidiosa subspecies. Among these proteins, we selected a subset of interest for biotechnology application based on distinctive features of their sequences and predicted protein structures. 
Clearly, new genomic data from further isolates of X. fastidiosa and relative phages will extend the information regarding spreading and diversity of this plant pathogen. At the same time, this information will also increase the available database of endolysins for the identification and testing of novel candidate anti-microbial molecules.