The bacterium Pseudomonas syringae pv syringae B728a (PsyB728a) uses a type III secretion system (T3SS) to inject effector proteins into plant cells, a process that modulates the susceptibility of different plants to infection. Analysis of GREEN FLUORESCENT PROTEIN-expressing PsyB728a after spray inoculation without additives under moderate relative humidity conditions permitted (1) a detailed ...

In prokaryotes, flagellar biogenesis is a complicated process involving over 40 genes. The phytopathogen Xanthomonas campestris pv. campestris possesses a single polar flagellum, which is essential for the swimming motility. A sigma54 activator, FleQ, has been shown to be required for the transcriptional activation of the flagellar type III secretion system (F-T3SS), rod, and hook proteins. One...

Genes localized at Salmonella pathogenicity island-1 (SPI-1) are involved in Salmonella enterica invasion of host non-professional phagocytes. Interestingly, in macrophages, SPI-1-encoded proteins, in addition to invasion, induce cell death via activation of caspase-1 which also cleaves proIL-1β and proIL-18, precursors of 2 proinflammatory cytokines. In this study we were therefore interested ...

Harpins are a subset of type III secretion system (T3SS) substrates found in all phytopathogenic bacteria that utilize a T3SS. Pseudomonas syringae pv. tomato DC3000 was previously reported to produce two harpins, HrpZ1 and HrpW1. DC3000 was shown here to deploy two additional proteins, HopAK1 and HopP1, which have the harpin-like properties of lacking cysteine, eliciting the hypersensitive res...

Plant associations by bradyrhizobia have been detected not only in leguminous plants, but also in non-leguminous species including rice. Bradyrhizobium sp. SUTN9-2 was isolated from Aeschynomene americana L., which is a leguminous weed found in the rice fields of Thailand. This strain promoted the highest total rice (Oryza sativa L. cultivar Pathum Thani 1) dry weight among the endophytic brady...

Erwinia amylovora causes a devastating disease called fire blight in rosaceous plants. The type III secretion system (T3SS) is one of the important virulence factors utilized by E. amylovora in order to successfully infect its hosts. By using a green fluorescent protein (GFP) reporter construct combined with a high-throughput flow cytometry assay, a library of phenolic compounds and their deriv...

The type III secretion system (T3SS) is a principal virulence determinant of the model bacterial plant pathogen Pseudomonas syringae T3SS effector proteins inhibit plant defense signaling pathways in susceptible hosts and elicit evolved immunity in resistant plants. The extracytoplasmic function sigma factor HrpL coordinates the expression of most T3SS genes. Transcription of hrpL is dependent ...

Fis is a versatile DNA binding protein in bacteria. It has been demonstrated in multiple bacteria that Fis plays crucial roles in regulating bacterial virulence factors and optimizing bacterial adaptation to various environments. However, the role of Fis in Pseudomonas aeruginosa virulence as well as gene regulation remains largely unknown. Here, we found that Fis was required for the virulence...

Type III secretion systems (T3SSs) are protein injection devices essential for the interaction of many Gram-negative bacteria with eukaryotic cells. While Shigella assembles its T3SS when the environmental conditions are appropriate for invasion, secretion is only activated after physical contact with a host cell. First, the translocators are secreted to form a pore in the host cell membrane, f...

Gram-negative bacteria, including Salmonella enterica serovar Typhimurium, exploit type III secretion systems (T3SSs) through which virulence proteins are delivered into the host cytosol to reinforce invasive and replicative niches in their host. Although many secreted effector proteins and membrane-bound structural proteins in the T3SS have been characterized, the functions of many cytoplasmic...