Comparative transcriptome analysis explored the molecular mechanisms of a luxR-type regulator regulating intracellular survival of Aeromonas hydrophila.

Aeromonas hydrophila is not a traditional intracellular bacterium. However, previous studies revealed that pathogenic A. hydrophila B11 could temporarily survive for at least 24 h in fish phagocytes, and the regulation of intracellular survival in bacteria was associated with regulators of the LuxR-type. The mechanisms of luxR 08110 on the A. hydrophila's survival in macrophages were investigated using comprehensive transcriptome analysis and biological phenotype analysis in this study. The results showed that after luxR 08110 was silenced, the intracellular survival ability of bacteria was significantly diminished. Comparative transcriptome analysis revealed that luxR 08110 was a critical regulator of A. hydrophila, which regulated the expression of over 1200 genes, involving in bacterial flagellar assembly and chemotaxis, ribosome, sulphur metabolism, glycerolipid metabolism, and other mechanisms. Further studies confirmed that after the inhibition of expression of luxR 08110 , the motility, chemotaxis and adhesion of A. hydrophila significantly decreased. Moreover, compared with the wild-type strain, the survival rates of silencing strain were all considerably reduced under both H 2 O 2 and low pH stress conditions. According to both transcriptome analysis and phenotypic tests, the luxR 08110 of A. hydrophila could act as global regulator in bacteria intracellular survival. This regulator regulated intracellular survival of A. hydrophila mainly through two ways. One way is to regulate bacterial flagellar synthesis and further affects the motility, chemotaxis and adhesion of bacteria. The other way is to regulate sulphur and glycerolipid metabolisms, thus affecting bacterial energy production and the ability to resist environmental stress.