Bacterial fruit blotch, caused by seed-borne pathogen Acidovorax citrulli, poses a serious threat to the production of cucurbits globally. Although the disease can cause substantial economic losses, limited information is available about the molecular mechanisms of virulence. This study identified that, a random transposon insertion mutant impaired in the ability to elicit a hypersensitive response on tobacco. The disrupted gene in this mutant was determined to be Aave_0638, which is predicted to encode a YggS family pyridoxal phosphate-dependent enzyme. YggS is a highly conserved protein among multiple organisms, and is responsible for maintaining the homeostasis of pyridoxal 5′-phosphate and amino acids in cells. yggS deletion mutant of A. citrulli strain XjL12 displayed attenuated virulence, delayed hypersensitive response, less tolerance to H2O2 and pyridoxine, increased sensitivity to antibiotic β-chloro-D-alanine, and reduced swimming. In addition, RNA-Seq analysis demonstrated that yggS was involved in regulating the expression of certain pathogenicity-associated genes related to secretion, motility, quorum sensing and oxidative stress response. Importantly, YggS significantly affected type III secretion system and its effectors in vitro. Collectively, our results suggest that YggS is indispensable for A.citrulli virulence and expands the role of YggS in the biological processes.

This study revealed the bacterial community structure and the effects of carbon and nitrogen on the distribution pattern of bacterial community in the sediments of the Chang’an section of the Zao River in Xi’an. And we expect to provide a theoretical basis for the biological monitoring and bioremediation of the Zao River by this study. Therefore, based on 16SrRNA high-throughput sequencing technology, we analyzed the characteristics of carbon, nitrogen and bacterial community structure in Chang’an section of Zaohe River. The results showed that in the Chang’an section of Zaohe River Basin, Proteus and firmicum were tolerant bacteria, and the dominant bacteria were Proteus (24%∼45%). At the gate level, the difference of bacterial community composition was significantly correlated with pH, TN, NO2 − and TOC.