Pseudomonas donghuensis HYS virulence towards Caenorhabditis elegans is regulated by the Cbr/Crc system.

Pseudomonas donghuensis HYS is the type strain of a recently identified species, P. donghuensis, which has pathogenic potential with an unclear virulence mechanism. In this study, we used Caenorhabditis elegans as a host to explore the virulence mechanism of P. donghuensis HYS. Based on a correlation between P. donghuensis HYS virulence and its repellence property, we identified 68 potential virulence-related genes, among them the Cbr/Crc system, which regulates the virulence of prokaryotic microorganisms. Slow-killing assays indicated that cbrA, cbrB, or specific sRNA-encoding genes all affected P. donghuensis virulence positively, whereas crc affected it negatively. Transcriptome analyses demonstrated that the Cbr/Crc system played an important role in the pathogenesis of P. donghuensis. In addition, experiments using the worm mutant KU25 pmk-1(km25) showed a correlation between P. donghuensis HYS virulence and the PMK-1/p38 MAPK pathway in C. elegans. In conclusion, our data show that Crc plays a novel role in the Cbr/Crc system, and the P. donghuensis virulence phenotype therefore differs from that of P. aeruginosa. This process also involves C. elegans innate immunity. These findings significantly increase the available information about Cbr/Crc-based virulence mechanisms in the genus Pseudomonas.

Pseudomonas donghuensis sp. nov., exhibiting high-yields of siderophore.

A strain giving high-yields of siderophores, designated HYS(T), was isolated from the water of East Lake (also called Donghu Lake) of Wuhan in China. Strain HYS(T) is Gram-stain negative, non-spore-forming and rod-shaped with polar flagella. Phylogenetic analysis based on 16S rRNA gene and the other three housekeeping genes (gyrB, rpoD and rpoB) indicated that strain HYS(T) belongs to the genus Pseudomonas. Genomic DNA comparison experiments including DNA-DNA hybridization and whole-genome sequence similarities were performed between HYS(T) and its phylogenetically most closely related type strains, all of the relatedness values are lower than the threshold to ascribe strain HYS(T) to a known species. The major cellular fatty acids of strain HYS(T) are C16:0, C17:0 cyclo, Summed feature 3 (C16:1 ω7c or/and C16:1 ω6c) and Summed feature 8 (C18:1 ω7c or C18:1 ω6c). Its predominant isoprenoid quinone was identified as Q-9, and the minor isoprenoid quinone was Q-8. Phylogenetic analysis together with genomic DNA comparison, phenotypic metabolic tests and chemotaxonomic analysis justified the proposal of strain HYS(T) as a representative of a novel species, for which the name Pseudomonas donghuensis sp. nov. is proposed. The type strain is HYS(T) ( = CCTCC AB 2012141(T) = NRRL B-59108(T)).