Sulfated vizantin suppresses mucin layer penetration dependent on the flagella motility of Pseudomonas aeruginosa PAO1

Design and Synthesis of Aryl Amide Derivatives Containing Thiazole as Type III Secretion System Inhibitors against Pseudomonas aeruginosa

To identify potent inhibitors of the type III secretion system (T3SS) in the foodborne pathogen Pseudomonas aeruginosa, we synthesized 35 thiazole-containing aryl amides by merging salicylic acid with various heterocycles through active splicing. Screening for exoS promoter activity led to the discovery of a highly effective T3SS inhibitor from these 35 compounds. Through subsequent experiments, it was confirmed that compound II-22 specifically targeted the T3SS of P. aeruginosa. Additionally, compound II-22 inhibited the secretion of the effector protein ExoS by modulating the CyaB-cAMP/Vfr-ExsA and ExsCED-ExsA regulatory pathways. Furthermore, compound II-22 suppressed the transcription of genes involved in the needle complex assembly, leading to reduced bacterial virulence. Further validation through inoculation tests using Galleria mellonella larvae demonstrated the strong in vivo efficacy of compound II-22. The study also revealed that compound II-22 enhanced the bactericidal activity of antibiotics, such as CIP (ciprofloxacin) and TOB (tobramycin). These results could help develop novel antimicrobial drugs to reduce bacterial resistance.

Structure and functional analysis of the Legionella pneumophila chitinase ChiA reveals a novel mechanism of metal-dependent mucin degradation

Chitinases are important enzymes that contribute to the generation of carbon and nitrogen from chitin, a long chain polymer of N-acetylglucosamine that is abundant in insects, fungi, invertebrates and fish. Although mammals do not produce chitin, chitinases have been identified in bacteria that are key virulence factors in severe respiratory, gastrointestinal and urinary diseases. However, it is unclear how these enzymes are able to carry out this dual function. Legionella pneumophila is the causative agent of Legionnaires' disease, an often-fatal pneumonia and its chitinase ChiA is essential for the survival of L. pneumophila in the lung. Here we report the first atomic resolution insight into the pathogenic mechanism of a bacterial chitinase. We derive an experimental model of intact ChiA and show how its N-terminal region targets ChiA to the bacterial surface after its secretion. We provide the first evidence that L. pneumophila can bind mucins on its surface, but this is not dependent on ChiA. This demonstrates that additional peripheral mucin binding proteins are also expressed in L. pneumophila. We also show that the ChiA C-terminal chitinase domain has novel Zn2+-dependent peptidase activity against mammalian mucin-like proteins, namely MUC5AC and the C1-esterase inhibitor, and that ChiA promotes bacterial penetration of mucin gels. Our findings suggest that ChiA can facilitate passage of L. pneumophila through the alveolar mucosa, can modulate the host complement system and that ChiA may be a promising target for vaccine development.