Proteomics of septicemic Escherichia coli

Virulent strains of Escherichia coli have become a major cause of infections, especially in hospitals and institutions, and result in high morbidity and mortality, due to the widespread antibiotic resistance. The infections usually start as complications of urinary tract infections or invasive medical procedures. Septicemic bacteria have to go through the blood stream, where they are exposed to a variety of stress conditions. The most difficult of these is the presence of the immune complement, which is strongly bactericidal. However, recently it has become clear that the nutritional immunity (metabolic stress) of serum is just as important. Thus, as shown by proteomic analyses, septicemic E. coli can cope with this latter stress condition by globally modifying the expression of a variety of metabolic genes. These include genes involved in amino acid metabolism and in metal homeostasis, whose robust regulation of expression appears to be critical for surviving the metabolic immunity of serum. Recognition of the nutritional immunity and the molecular mechanisms that enable septicemic bacteria to overcome it are the focus of this paper.