Improvement of the viability of Tetragenococcus halophilus under acidic stress by forming the biofilm cell structure based on RNA-Seq and iTRAQ analyses.

Background: Tetragenococcus halophilus is a halophilic lactic acid bacterium (LAB) isolated from soya sauce moromi. During the production of these fermented foods, acid stress is an inevitable environmental stress. In our previous study, T. halophilus could form biofilms and the cells in the biofilms exhibited higher cell viability under multiple environmental stresses, including acid stress.

Results: In this study, the effect of preformed T. halophilus biofilms on cell survival, cellular structure, intracellular environment, and the expression of genes and proteins under acid stress was investigated. The result showed that acid stress with pH 4.30 for 1.5 h reduced the live T. halophilus cell count and caused cellular structure damage. However, T. halophilus biofilm cells exhibited greater cell survival under acid stress than the planktonic cells, and biofilm formation reduced the damage of acid stress to the cell membrane and cell wall. The biofilm cells maintained a higher level of H -ATPase activity and intracellular ammonia concentration after acid stress. The RNA-Seq and iTRAQ technologies revealed that the genes and proteins associated with ATP production, the uptake of trehalose and N-acetylmuramic acid, the assembly of H -ATPase, amino acid biosynthesis and metabolism, ammonia production, fatty acid biosynthesis, CoA biosynthesis, thiamine production, and acetoin biosynthesis might be responsible for the stronger acid tolerance of T. halophilus biofilm cells together.

Conclusion: These findings further explained the mechanisms that allowed LAB biofilm cells to resist environmental stress. © 2023 Society of Chemical Industry.