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Root Internalization and Temperature-Dependent Regulation of Persistence and Virulence Genes in Pseudomonas aeruginosa PAO1 on Oak Leaf Lettuce

ABSTRACT: Increasing evidence of Pseudomonas aeruginosa on fresh plant-based foods raises food safety concerns. While internalization of pathogens such as Salmonella enterica in vegetables such as lettuce is well documented, corresponding data for P. aeruginosa are lacking. Moreover, climate change-associated temperature shifts may influence the plant microbiota and the presence of human pathogens. This study investigates the internalization and temperature-dependent gene expression of P. aeruginosa PAO1 on green oak leaf lettuce as a model system. For this purpose, oak leaf lettuce was cultivated in soil inoculated with P. aeruginosa PAO1_sfGFP_UHH07, and internalization was analyzed using confocal laser scanning microscopy. Temperature-dependent transcriptomic changes of P. aeruginosa PAO1 were assessed by analyzing differentially expressed genes following plant inoculation and incubation at 18 and 22 °C, respectively. P. aeruginosa PAO1 is capable of internalizing into the roots of oak leaf lettuce, but a translocation into leaves was not detected. Transcriptomic analyses showed that a moderate temperature increase shifts bacterial gene expression, with virulence genes upregulated at 22 °C and persistence-associated genes predominating at 18 °C. These results show that temperature influences the persistence and pathogenic potential of P. aeruginosa present on oak leaf lettuce, highlighting potential impacts of climate change on food safety.

ORGANISM(S): Pseudomonas aeruginosa PAO1

PROVIDER: GSE324477 | GEO | 2026/03/15

REPOSITORIES: GEO

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Project description:Although Pseudomonas aeruginosa is an opportunistic pathogen that does not often naturally infect alternate hosts such as plants, the plant-P. aeruginosa model has become a widely recognized system for identifying new virulence determinants and studying pathogenesis of this organism. Here we examine how both host factors and P. aeruginosa PAO1 gene expression are affected in planta after infiltration into incompatible and compatible cultivars of tobacco (Nicotiana tabacum L.) Nicotiana tabacum has a resistance gene (N) against tobacco mosaic virus; and although resistance to PAO1 infection correlated to the presence of a dominant N-gene, our data suggests that it is not a factor in resistance against Pseudomonas. We did observe that the resistant tobacco cultivar had higher basal levels of salicylic acid, and a stronger salicylic acid response upon infiltration of PAO1. Salicylic acid acts as a signal to activate defense responses in plants, limiting the spread of the pathogen and preventng access to nutrients. It has also been shown to have direct virulence modulating effects on P. aeruginosa. We also examined host effects on the pathogen by analyzing global gene expression profiles of bacteria removed from the intracellular fluid of the two plant hosts. We discovered that the availability of micronutrients, particularly sulfate and Pi, are important factors in in planta pathogenesis, and that the amounts of these nutrients made available to the bacteria may in turn have an effect on virulence gene expression. Indeed, there are several reports suggesting that P. aeruginosa virulence is influenced in mammalian hosts by the availability of iron and by levels of O2. Experiment Overall Design: Pseudomonas aeruginosa cells were removed from leaf tissue 24 hours post-infiltration and RNA was directly extracted from these cells. Comparisons are between cells removed from a susceptible cultivar of Nicotiana tabacum (cv. Samsun) and a resistant cultivar (cv. Xanthi). Three biological replicates per cultivar were analyzed.

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Root Internalization and Temperature-Dependent Regulation of Persistence and Virulence Genes in Pseudomonas aeruginosa PAO1 on Oak Leaf Lettuce

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