Abstract
Xylella fastidiosa is a bacterial pathogen causing severe diseases and asymptomatic colonization in more than 600 plants worldwide. Copper (Cu) is a widely used antimicrobial treatment for various plant diseases, including those affecting X. fastidiosa hosts. Cu homeostasis among X. fastidiosa strains from different geographical locations and host species has not been characterized. Here, we assessed minimum inhibitory concentration (MIC) of Cu for 54 X. fastidiosa strains. We observed strain-level variation in MIC values within each subspecies. We hypothesized that these differences could be explained by sequence variation in Cu homeostasis genes. Phylogenies based on copA, copB, copL, and cutC were created using 74 genomes (including 43 strains used in vitro) of X. fastidiosa, showing that the phylogenetic clustering of Cu homeostasis associated with clustering was based on core genome phylogenies, rather than on pattern of MIC. No association was found among Cu MIC, subspecies classification, and host and location of isolation, probably due to uneven and limited group of strains whose genomes are available. Further analysis focused on a subgroup of isolates from Georgia’s vineyards that shared similar Cu-related phenotypes. Further research is needed to better understand the distribution of Cu homeostasis for this pathogen.
Highlights
Xylella fastidiosa, a gram-negative bacterial pathogen, can colonize and infect ~600 different host species, including agricultural crops, landscape trees, and weeds [1,2]
The in vitro minimum inhibitory concentration (MIC) of CuSO4 of X. fastidiosa was used as numerical estimator of Cu tolerance among X. fastidiosa strains
The results showed that Cu MIC in X. fastidiosa strains was not markedly different amongst subspecies, the mean rank scores from the test of the Cu MIC data in others, subsp. fastidiosa and subsp. multiplex were 35, 28, and 24, respectively (Figure 3A)
Summary
A gram-negative bacterial pathogen, can colonize and infect ~600 different host species, including agricultural crops, landscape trees, and weeds [1,2]. The spread of X. fastidiosa causes great damage to agricultural production and has a significant economic impact. The spread of X. fastidiosa in Europe would lead to future economic impact in the billions of Euros [8]. A study of X. fastidiosa isolates from different locations in CA suggested the importance of environmental factors on the adaption of the pathogen [9]. Xylella fastidiosa colonizes plants living in environments with history of Cu-based antimicrobial compounds application, like those used in vineyards and orchards [10,11,12].
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