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Candidatus Liberibacter asiaticus’ bacteriophage search and the role of the OmpA protein in Liberibacter species

Marta Sena Velez: Florida State University

<div>‘<em>Candidatus</em> Liberibacter asiaticus’ (<em>C</em>Las), a phloem limited bacterium, causes citrus Huanglongbing (HLB), a psyllid-transmitted disease, which has put millions of citrus trees out of production in citrus growing areas, and for which no effective control method has been described. The lack of an axenic medium for culturing these bacteria is a major hurdle in the study and development of control strategies for HLB. Bacteriophages are highly infective pathogens of bacteria; they can be used as biocontrol agents as well as transduction vectors. Our main objective is to isolate <em>C</em>Las-infecting bacteriophages for the study, modification and control of <em>C</em>Las. <em>Liberibacter</em><em> crescens</em> (<em>Lcr</em>) is the only cultivable <em>Liberibacter</em> species. It has been widely used as a model for the study of <em>C</em>Las. In order to search for <em>C</em>Las-infecting bacteriophages, the <em>C</em>Las OmpA protein was expressed in <em>Lcr</em><em>.</em> OmpA is known to be a phage receptor in bacteria closely-related to <em>Liberibacter</em> spp. Extracts from <em>C</em>Las-free psyllids produced plaque-like zones of lysis on lawns of <em>Lcr</em> expressing <em>C</em>Las OmpA, but not on wild type <em>Lcr</em>. Our short term goals are focused on optimizing the yield and reproducibility of phage infection<em>.</em> In addition, the effect of the <em>C</em>Las OmpA protein on <em>Lcr</em> growth, stress sensitivity, and biofilm formation is being evaluated. Isolating bacteriophages able to infect <em>C</em>Las opens a new way to modify and study <em>C</em>. Liberibacter species, and possibly, more effective control methods.</div>