Interactions of Pseudomonads with Mushroomsand Other Eukaryotic Hosts

摘要

Pseudomonads are ubiquitous Gram-negative bacteria with the potentialto interact with diverse organisms in the environment. We are investigating themolecular basis of pathogenesis in mushroom-pathogenic Pseudomonas (NZstrains) and also evaluating NZ interactions with other organisms found in themushroom environment, notably the nematode Caenorhabditis elegans and theamoeba Dictyostelium discoidium. Strain Pseudomonas sp. NZI7 is a tolaasin-producing mushroom pathogen that causes, lotch disease of Agaricus bisporus,inhibits nematode and Dictyostelium predation and inhibits the growth ofgram-positive and gram-negative bacteria. We have generated a collectionof miniTn5::gfp::lux transposon mutants of strain NZI7, which have been usedto identify genes and gene clusters whose loss of function alters one or more ofthese interactions. We are currently characterizing these in terms of their function,expression and regulation, and the effect that their disruption has upon bacterialfitness and colonization. Our screens have implicated tolaasin as a major factorin mushroom pathogenesis and antibacterial activity, but not in NZI7–nematodeinteractions. The two-component sensor kinase GacS plays a central role inregulating expression of tolaasin and other anti-microbial factors, includingnematode-inhibition genes. We have also shown that NZI7 and other mushroom-pathogenic Pseudomonas contain type III secretion (T3SS) genes similar to thosefound in plant pathogenic P. syringae.