An intracellular perspective of the metabolism of uropathogenic Escherichia coli

PROJECT DESCRIPTION

 
Extraintestinal pathogenic E. coli (ExPEC) are able to cause infections outside the intestines. Uropathogenic (UPEC) and Avian Pathogenic (APEC) E. coli are two ExPEC variants. They cause infection in the urinary tract system of human (UPEC) and in the salpinx and airways of birds (APEC), respectively. Genetically, these two ExPECs cannot be distinguished from one another. Previous studies have shown that APEC strains are able to infect in vivo models of human urinary tract infection (UTI), suggesting that they may be zoonotic. But no studies have shown that UPEC can infect in adult immonucompetent bird and examined a potential anthrozoonotic potential of UPEC.

ExPEC strains grow as commensals in the intestine, and to cause infections outside the intestine, they need to adapt their metabolism to a different environment. Therefore, a flexible metabolism is undoubtedly essential for ExPECs to cause infections and hence, enzymes of the metabolism may be a possible source of novel antimicrobial targets.

PROJECT PURPOSE

• Examine UPEC’s potential to cause infection in adult immonucompetent birds.
• Analyse the proteome of UPEC when growing in urine and intracellular in urinary bladder cells.
• Construct a genome scale mathematic model of UPEC metabolism to predict potential antimetabolic targets in specific environments.

RESULTS

UPEC were able to cause salpingitis in adult immonucompetent birds, and thus UPEC have a possible anthrozoonotic potential, and there is a risk that poultry can be infected with human derived UPEC strains. 

The proteome of UPEC grown in urine and intracellular in bladder epithelial cells was obtained.  This study is the first to report an intracellular proteome of UPEC and in connection to the study a novel protocol to determine proteins in bacteria in the intracellular environment was developed. Highly regulated enzymes involved in iron acquisition and arginine uptake and biosynthesis were observed during growth in both urine and in the intracellular environment. Specifically, during growth in urine, enzymes in biosynthesis of a variety of amino acids were upregulated, whereas enzymes involved in the sulphur compound biosynthetic processes were specifically upregulated in the intracellular environment.

A genome scale mathematic model of UPEC metabolism was constructed. The proteome was integrated into the model to adjust the modelling to the assumed environment in the urinary tract. By this approach, it was possible to identify important metabolic pathways during infection. Additionally, the genome scale metabolic model was used for prediction of potential antimetabolic targets in specific environments. Based on modelling, most targets of one reaction were involved with biosynthesis of certain amino acids together with chorismate and paraaminobenzoate (a precursor for tetrahydrofolate), whereas targets based on combinations of two inactive reactions, referred to as redundant reactions, were either involved with different reactions in the same pathway or different reactions in different pathways.

For more information, contact Sisse Mortensen: sissem@sund.ku.dk