Coping with Environmental Eukaryotes; Identification of Pseudomonas syringae Genes during the Interaction with Alternative Hosts or Predators

Abstract

Understanding the molecular mechanisms underpinning the ecological success of plant pathogens is critical to develop strategies for controlling diseases and protecting crops. Recent observations have shown that plant pathogenic bacteria, particularly Pseudomonas, exist in a range of natural environments away from their natural plant host e.g., water courses, soil, non-host plants. This exposes them to a variety of eukaryotic predators such as nematodes, insects and amoebae present in the environment. Nematodes and amoeba in particular are bacterial predators while insect herbivores may act as indirect predators, ingesting bacteria on plant tissue. We therefore postulated that bacteria are probably under selective pressure to avoid or survive predation and have therefore developed appropriate coping mechanisms. We tested the hypothesis that plant pathogenic Pseudomonas syringae are able to cope with predation pressure and found that three pathovars show weak, but significant resistance or toxicity. To identify the gene systems that contribute to resistance or toxicity we applied a heterologous screening technique, called Rapid Virulence Annotation (RVA), for anti-predation and toxicity mechanisms. Three cosmid libraries for P. syringae pv. aesculi, pv. tomato and pv. phaseolicola, of approximately 2000 cosmids each, were screened in the susceptible/non-toxic bacterium Escherichia coli against nematode, amoebae and an insect. A number of potential conserved and unique genes were identified which included genes encoding haemolysins, biofilm formation, motility and adhesion. These data provide the first multi-pathovar comparative insight to how plant pathogens cope with different predation pressures and infection of an insect gut and provide a foundation for further study into the function of selected genes and their role in ecological success.

Identification of the Genes of the Plant Pathogen Pseudomonas syringae MB03 Required for the Nematicidal Activity Against Caenorhabditis elegans Through an Integrated Approach

“…Pseudomonas syringae has been generally annotated as the “most notorious plant pathogen” ( Mansfield et al, 2012 ), however, little information is available regarding its interaction with C. elegans ( Ali et al, 2016 ; Dorati et al, 2018 ; Manan et al, 2018 ; Bashir et al, 2020 ). Previous attempts to investigate its pathogenic potential against C. elegans showed that the strain B728a and DC3000 did not possess nematicidal activity on NGM medium ( Burlinson et al, 2013 ).…”

Genomic Characterisation of Mushroom Pathogenic Pseudomonads and Their Interaction with Bacteriophages

“…agarici of a third, quite different T3SS (RS22985–23120) resembling the Inv-Spa gene cluster found in human pathogens [ 90 , 91 ]. This would also be a good target to examine whether the cluster plays a role in the drippy gill disease or is involved in its wider ecology such as interactions with alternative hosts [ 92 ].…”

A predation assay using amoebae to screen for virulence factors unearthed the first W. chondrophila inclusion membrane protein

“…Resistance to grazing by protists has thus been widely used to identify virulence factors especially for extracellular bacteria 41–43,61 . However, to our knowledge, only a few studies report the use of E.coli transduced with a cosmid library as prey for amoebae 44,62 . Our partial screening of a W. chondrophila 1600 clones library resulted in the identification of 28 putative virulence proteins.…”