Mediación salino-alcalina de la quimiotaxis en la bacteria promotora del crecimiento vegetal Enterobacter cloacae

The biomass, pH changes, and chemotaxis of Enterobacter cloacae (E. cloacae) DJ strain were assessed under various conditions using liquid culture and semi-solid agar plate. Concurrently, GABA concentration, GAD activity, and chemotactic gene expression were measured. The results demonstrated that DJ strain exhibited adaptability to saline-alkaline environments. After 4 h of culture, the pH value decreased, with more pronounced pH changes observed in the saline-alkaline groups. Semi-solid agar plate assays revealed that the DJ strain exhibited the strongest chemotaxis toward the saline-alkaline environment. The average migration radius of the DJ strain reached 1.64 ± 0.09 cm in the saline-alkaline environment after a 24-h cultivation, significantly exceeding the control group's value of 0.88 ± 0.097 cm. The DJ strain exhibited strong positive taxis toward the saline-alkaline environment. Na+ concentration was identified as the primary factor influencing the chemotactic behavior of DJ strain. The GABA content in the saline-alkali group and salt group was 13±0.38 µmol/l and 10.5±1.12 µmol/l, respectively. GAD enzyme activity peaked after 4 h of cultivation, then decreased progressively. qPCR results indicated that the expression of tsr and che-Y genes was up-regulated under saline-alkaline conditions. We propose a model whereby environmental Na+ activates GAD enzyme activity in the DJ strain, leading to increased GABA production that alters the bacterial microenvironment. In response, the DJ strain up-regulates chemotaxis-related gene expression, thereby modifying its behavior to adapt to the saline-alkaline environment.