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Updated: Jun 27, 2026
Evaluation of Microbial Safety of Dairies using Bacterial Proteomic Profiling via MALDI Approach
Published on: October 7, 2025
Proteomic changes in Escherichia coli when grown in fresh milk versus laboratory media
John D Lippolis1, Darrell O Bayles, Timothy A Reinhardt
1Periparturient Diseases of Cattle Research Unit, USDA-ARS, National Animal Disease Center, Ames, Iowa 50010, USA. john.lippolis@ars.usda.gov
Abstract:
To establish an infection, bacteria must first adapt to the host environment and grow. For mastitis, the media in which bacteria must adapt to is milk. Mammary pathogenic Escherichia coli may express factors that are important for these bacteria to grow in milk and establish both acute and chronic infections of the mammary gland. We have used shotgun expression proteomics to determine the changes in protein expression when E. coli were grown in laboratory media compared to bacteria grown in whole fresh bovine milk. We report the expression data of approximately 1000 proteins. We found many proteins involved in the metabolism of lactose and various amino acids were up-regulated when bacteria were grown in milk. In addition, the LuxS protein was up-regulated when bacteria were grown in milk; this protein is associated bacterial quorum sensing as well as the expression of mobility proteins, such as flagellar components, and a number of genes associated with virulence. Growth of a mammary pathogenic E. coli in milk results in the up- and down-regulation of hundreds of proteins, some of which may be important to the pathogenesis of this organism.
Insights
Mammary pathogenic Escherichia coli adapt to bovine milk by altering protein expression. This adaptation involves changes in metabolism, virulence factors, and quorum sensing, crucial for establishing mastitis infections.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Proteomics
Background:
- Bacterial adaptation to host environments is critical for infection establishment.
- Mammary pathogenic Escherichia coli (E. coli) must adapt to bovine milk to cause mastitis.
- Understanding E. coli's milk adaptation is key to controlling mammary gland infections.
Purpose of the Study:
- To investigate protein expression changes in E. coli grown in bovine milk versus laboratory media.
- To identify proteins involved in E. coli's adaptation to the milk environment.
- To elucidate potential virulence factors expressed by E. coli during milk growth.
Main Methods:
- Shotgun expression proteomics was employed to analyze protein expression profiles.
- E. coli strains were cultured in both whole fresh bovine milk and standard laboratory media.
- Quantitative proteomic analysis identified differentially expressed proteins.
Main Results:
- Approximately 1000 proteins were quantified, revealing significant expression changes.
- Proteins associated with lactose and amino acid metabolism were upregulated in milk.
- The LuxS protein, linked to quorum sensing and virulence, was also upregulated in milk.
Conclusions:
- Bovine milk significantly alters the proteome of mammary pathogenic E. coli.
- Upregulated proteins, including LuxS and metabolic enzymes, may play roles in E. coli mastitis pathogenesis.
- These findings provide insights into bacterial adaptation strategies during infection.
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