Effect of Temperature on Gene Expression of Escherichia marmotae
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Increased temperature is one of the first environmental cues encountered by bacteria upon entering a mammalian host. Here, we investigated the effects of two incubation temperatures on the transcriptome and proteome of E. marmotae and E. coli . As previous studies demonstrated that temperature affects motility in E. marmotae , our goal was to determine how temperature alters global gene expression at 37 °C versus 28 °C, and whether this response is conserved in E. coli . To do this, we grew strains of each species in static conditions at 28 °C and 37 °C and assessed gene expression by RNA transcriptome analysis and protein abundance by global proteomics.
Temperature altered the expression of 111 genes (2.7% of the genome analyzed) in E. marmotae and 99 genes (2.5%) in E. coli (adjusted p < 0.05, ≥2-fold change), with differential expression concentrated within specific functional pathways rather than reflecting global transcriptome-wide shifts. Comparable proportions of each proteome were similarly affected. In E. marmotae , genes spanning the class II and class III flagellar hierarchy and chemotaxis genes, along with operons for cellulose-dependent biofilm formation and nitrate respiration, were markedly downregulated at 37 °C. In contrast, genes associated with fimbrial adhesion and immune evasion, including fimA/fimB , ompT , and prophage-associated loci, were upregulated. Proteomic analysis corroborated these trends, showing coordinated loss of flagellar and chemotaxis proteins at 37 °C and increased abundance of stress-adaptation and host-interaction proteins, including OmpT. E. coli showed a partially overlapping but distinct response, with stronger enrichment of metabolic and amino-acid biosynthesis pathways and minimal changes in motility regulation. Together, our studies demonstrate that motility in E. marmotae is temperature-dependent and may represent a mechanism for immune evasion within the host.
Importance
Escherichia marmotae is an emerging member of the genus Escherichia that has increasingly been associated with human infections, yet the mechanisms that enable its transition from environmental reservoirs to the mammalian host remain poorly understood. This study provides the first transcriptomic and proteomic characterization of the temperature response of E. marmotae and demonstrates that growth at host temperature (37 °C) selectively alters pathways associated with bacterial lifestyle and virulence. Most notably, the coordinated repression of flagellar motility and chemotaxis, together with increased expression of factors associated with adhesion, stress adaptation, and host interaction, suggests that temperature serves as an environmental signal that promotes adaptation to the host. Comparison with E. coli further revealed that this response is not broadly conserved, highlighting distinct temperature-dependent regulatory strategies in E. marmotae . These findings expand our understanding of the biology of this understudied pathogen and suggest that reduced motility at mammalian body temperature may contribute to host adaptation and immune evasion.
