Insight into the transcriptome profile of mature biofilm produced by Brochothrix thermosphacta at 25 and 8 °C

Brochothrix thermosphacta is a psychrotrophic Gram-positive bacterium frequently associated with food spoilage and commonly found in food-processing environments. Its ability to persist at low temperatures (e.g., 8 °C), notably through biofilm formation, raises important questions about its adaptive strategies under cold stress. In this study, we performed a transcriptomic analysis of B. thermosphacta strain CD337(2), comparing gene expression profiles between biofilm and planktonic cells at 25 °C and 8 °C. RNA-Seq analysis revealed 300 differentially expressed genes (DEGs) at 25 °C (236 upregulated and 64 downregulated) and 137 DEGs at 8 °C (27 upregulated and 110 downregulated). At 25 °C, genes involved in sugar metabolism, particularly the iol, lev, and bgl operons, were upregulated in biofilm, whereas these operons were downregulated at 8 °C. In addition, pathways related to iron uptake, amino acid metabolism, and stress responses were differentially expressed between the two conditions. These findings provide new insights into the temperature-dependent regulatory mechanisms underlying biofilm lifestyle of B. thermosphacta, highlighting its transcriptional plasticity and suggesting new perspectives for improving spoilage control strategies in chilled food products.