Time of arrival during plant disease progression and humidity additively influenceSalmonella entericacolonization of lettuce

Abstract

ABSTRACTThe interplay between plant host, phytopathogenic bacteria, and enteric human pathogens in the phyllosphere have consequences for human health.Salmonella entericahas been known to take advantage of phytobacterial infection to increase its success on plants, but there is little knowledge of additional factors that may influence the relationship between enteric pathogen and plant disease. In this study, we investigated the role of humidity and the extent of plant disease progression onS. entericacolonization of plants. We found that high humidity was necessary for replication ofS. entericaon diseased lettuce, but not required forS. entericaingress into the UV-protected apoplast. Additionally, theXanthomonas hortorumpv. vitians (hereafter,X. vitians)-infected lettuce host was found to be a relatively hostile environment forS. entericawhen it arrived prior to the development of watersoaking or following necrosis onset, supporting the existence of an ideal window duringX. vitiansinfection progress that maximizesS. entericasurvival. In vitrogrowth studies in sucrose media suggest thatX. vitiansmay allowS. entericato benefit from cross-feeding during plant infection. Overall, this study emphasizes the role of phytobacterial disease as a driver ofS. entericasuccess in the phyllosphere, demonstrates how time of arrival during disease progress can influenceS. enterica’sfate in the apoplast, and highlights the potential for humidity to transform an infected apoplast into a growth-promoting environment for bacterial colonizers.Importance:Bacterial leaf spot of lettuce caused byX. vitiansis a common threat to leafy green production. The global impact caused by phytopathogens, includingX. vitians, is likely to increase with climate change. We found that even under a scenario where increased humidity did not enhance plant disease, high humidity had a substantial effect on facilitatingS. entericagrowth onXanthomonas-infected plants. High humidity climates may directly contribute to the survival of human enteric pathogens in crop fields or indirectly affect bacterial survival via changes to the phyllosphere brought on by phytopathogen disease.