Abstract
BackgroundPlant infection models provide certain advantages over animal models in the study of pathogenesis. However, current plant models face some limitations, e.g., plant and pathogen cannot co-culture in a contained environment. Development of such a plant model is needed to better illustrate host-pathogen interactions.Methodology/Principal FindingsWe describe a novel model plant system for the study of human pathogenic bacterial infection on a large scale. This system was initiated by co-cultivation of axenic duckweed (Lemna minor) plants with pathogenic bacteria in 24-well polystyrene cell culture plate. Pathogenesis of bacteria to duckweed was demonstrated with Pseudomonas aeruginosa and Staphylococcus aureus as two model pathogens. P. aeruginosa PAO1 caused severe detriment to duckweed as judged from inhibition to frond multiplication and chlorophyll formation. Using a GFP-marked PAO1 strain, we demonstrated that bacteria colonized on both fronds and roots and formed biofilms. Virulence of PAO1 to duckweed was attenuated in its quorum sensing (QS) mutants and in recombinant strains overexpressing the QS quenching enzymes. RN4220, a virulent strain of S. aureus, caused severe toxicity to duckweed while an avirulent strain showed little effect. Using this system for antimicrobial chemical selection, green tea polyphenols exhibited inhibitory activity against S. aureus virulence. This system was further confirmed to be effective as a pathogenesis model using a number of pathogenic bacterial species.Conclusions/SignificanceOur results demonstrate that duckweed can be used as a fast, inexpensive and reproducible model plant system for the study of host-pathogen interactions, could serve as an alternative choice for the study of some virulence factors, and could also potentially be used in large-scale screening for the discovery of antimicrobial chemicals.
Highlights
The study of human diseases requires the testing of microorganisms in model systems
By using the procedures described in Materials and Methods, different volumes of 2 to 100 ml P. aeruginosa strain PAO1 suspension of 16109 CFU/ml were inoculated and co-cultivated with duckweed
Our results demonstrated that duckweed was very sensitive to the addition of P. aeruginosa; a small amount caused detrimental effects
Summary
The study of human diseases requires the testing of microorganisms in model systems. Traditionally, pathogenesis of human pathogens has been studied in mammalian animal models. Mammalian animal models often do not fully resemble all aspects of human diseases caused by bacteria like Pseudomonas aeruginosa [2] To overcome these limitations, many laboratories have turned to analyzing host-pathogen interactions using alternative animal models such as Caenorhabditis elegans [3,4,5], Drosophila [6,7] and Danio rerio [8]. Many laboratories have turned to analyzing host-pathogen interactions using alternative animal models such as Caenorhabditis elegans [3,4,5], Drosophila [6,7] and Danio rerio [8] The use of these genetically tractable animal host systems have generated important information about host responses after pathogen infection and lead to a better understanding of the fundamental molecular mechanisms that underlie pathogenesis [2]. Development of such a plant model is needed to better illustrate host-pathogen interactions
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