The Effect of Plant Apoplastic Conditions on the Gram Negative Bacterial Outer Membrane of Adapted and Non-Adapted Pathogenic Species

Bacterial plant pathogens cause a significant loss of agricultural yields. Several species of the Gram negative bacterium Pseudomonas syringae are responsible for bacterial plant pathogenesis. Gram negative bacteria possess an asymmetric distribution phospholipids and lipopolysacchairdes (LPS) in their outer membrane (OM) which protect the microbe from its external environment. Members of the P. syringae species of phytopathogens have been shown to adapt their LPS structure to survive in plant conditions during pathogen activity. In a recent OFFSPEC experiment we compared three differing floating membrane models of the bacterial OM. Two were produced using P. aeruginosa and E. coli LPS and another was made from P. syringae LPS. We found that only the P. syringae LPS containing model was able to remain viable after being flushed into plant apoplastic pH and ion conditions. Here we wish to continue this study by resolving if it is pH or ion change stability which the P. syringae pathogen LPS modification imbue as well as resolve if these modifications give the microbe defence against plant innate immune system antimicrobials, namely the thionin family of small cationic antimicrobial proteins. This proposal was submitted for the 23_2 round and was well recieved but did not make the cut off due to the competitiveness of that round. Therefore we are resubmitting for the 24_1 round where there is more beam availiability due to the return of Surf and Inter to the user program.