AUTHOR=Ali Muhammad , Sun Yu , Xie Li , Yu Huafu , Bashir Anum , Li Lin 

TITLE=The Pathogenicity of Pseudomonas syringae MB03 against Caenorhabditis elegans and the Transcriptional Response of Nematicidal Genes upon Different Nutritional Conditions

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.00805

DOI=10.3389/fmicb.2016.00805

ISSN=1664-302X

ABSTRACT=<p>Different species of the <italic>Pseudomonas</italic> genus have been reported for their pathogenic potential against animal cells. However, the pathogenicity of <italic>Pseudomonas syringae</italic> against <italic>Caenorhabditis elegans</italic> has never been reported. In this study, the interaction of <italic>P. syringae</italic> MB03 with <italic>C. elegans</italic> was studied. Different bioassays such as killing assay, lawn leaving assay, food preference assay, L4 growth assay and newly developed “secretion assay” were performed to evaluate the pathogenic potential of <italic>P. syringae</italic> on different growth media. The results of the killing assay showed that <italic>P. syringae</italic> MB03 was able to kill <italic>C. elegans</italic> under specific conditions, as the interaction between the host and the pathogen varied from non-pathogenic (assay on NGM medium) to pathogenic (assay on PG medium). The lawn leaving assay and the food preference assay illustrated that <italic>C. elegans</italic> identified <italic>P. syringae</italic> MB03 as a pathogen when assays were performed on PG medium. Green fluorescent protein was used as the reporter protein to study gut colonization by <italic>P. syringae</italic> MB03. Our results suggested that MB03 has the ability to colonize the gut of <italic>C. elegans.</italic> Furthermore, to probe the role of selected virulence determinants, qRT-PCR was used. The genes for pyoverdine, <italic>phoQ/phoP, phoR/phoB</italic>, and flagella were up regulated during the interaction of <italic>P. syringae</italic> MB03 and <italic>C. elegans</italic> on PG medium. Other than these, the genes for some proteases, such as <italic>pepP</italic>, <italic>clpA</italic>, and <italic>clpS</italic>, were also up regulated. On the other hand, <italic>kdpD</italic> and <italic>kdpB</italic> were down regulated more than threefold in the NGM – <italic>C. elegans</italic> interaction model. The deletion of the <italic>kdpD</italic> and <italic>kdpE</italic> genes altered the pathogenicity of the bacterial strain against <italic>C. elegans</italic>. Overall, our results suggested that the killing of <italic>C. elegans</italic> by <italic>P. syringae</italic> requires a prolonged interaction between the host and pathogen in an agar-based assay. Moreover, it seemed that some toxic metabolites were secreted by the bacterial strain that were sensed by <italic>C. elegans</italic>. Previously, it was believed that <italic>P. syringae</italic> could not damage animal cells. However, this study provides evidence of the pathogenic behavior of <italic>P. syringae</italic> against <italic>C. elegans</italic>.</p>