In vitro assembly of Haemophilus influenzae adhesin transmembrane domain and studies on the electrostatic repulsion at the interface

Transcriptome Analysis Reveals the Molecular Mechanism of Pseudomonas with Different Adhesion Abilities on Tilapia Decay

This study aimed to investigate the molecular mechanism of Pseudomonas with varying adhesion capabilities to Tilapia's intestinal mucus influence the spoilage potential of Tilapia. Sodium chloride(NaCl) was used as an environmental factor to regulate Pseudomonas' adhesion ability. After being exposed to 3.5% NaCl stress, the PS01 strain with low adhesion showed an enhancement in adhesion ability, while the LP-3 strain with high adhesion exhibited a decrease. Correspondingly, the expression of critical adhesion genes, such as flgC, fliC, and cheB, was found to be altered. LP-3, with high adhesion ability, was observed to promote a relative increase in Nocardioides and Cloacibacterium in fish intestines. This led to the production of more volatile compounds, including 2-octen-1-ol Z, 2,3-Octanedione, and Eicosane, thus deepening the spoilage of tilapia. LP-3, with reduced adhesion ability after NaCl regulation, showed a diminished capacity to cause fish spoilage. Transcriptomics analysis was used to examine two Pseudomonas strains that exhibited different adhesion abilities, leading to the identification of an adhesion regulatory network involving flagellar assembly regulation, bacterial chemotaxis, quorum sensing, two-component systems, biofilm formation, and bacterial secretion systems. This study identified the Pseudomonas adhesion regulatory pathway and determined 10 key adhesion-related genes.

BamA is required for autotransporter secretion

BACKGROUND

In Gram-negative bacteria, type Va and Vc autotransporters are proteins that contain both a secreted virulence factor (the "passenger" domain) and a β-barrel that aids its export. While it is known that the folding and insertion of the β-barrel domain utilize the β-barrel assembly machinery (BAM) complex, how the passenger domain is secreted and folded across the membrane remains to be determined. The hairpin model states that passenger domain secretion occurs independently through the fully-formed and membrane-inserted β-barrel domain via a hairpin folding intermediate. In contrast, the BamA-assisted model states that the passenger domain is secreted through a hybrid of BamA, the essential subunit of the BAM complex, and the β-barrel domain of the autotransporter.

METHODS

To ascertain the models' plausibility, we have used molecular dynamics to simulate passenger domain secretion for two autotransporters, EspP and YadA.

RESULTS

We observed that each protein's β-barrel is unable to accommodate the secreting passenger domain in a hairpin configuration without major structural distortions. Additionally, the force required for secretion through EspP's β-barrel is more than that through the BamA β-barrel.

CONCLUSIONS

Secretion of autotransporters most likely occurs through an incompletely formed β-barrel domain of the autotransporter in conjunction with BamA.

GENERAL SIGNIFICANCE

Secretion of virulence factors is a process used by practically all pathogenic Gram-negative bacteria. Understanding this process is a necessary step towards limiting their infectious capacity.