Isolation of an Aptamer that Binds Specifically to E. coli

Area of Science:

• Molecular Biology
• Biotechnology
• Microbiology

Background:

• Escherichia coli (E. coli) is a common bacterium, with pathogenic strains posing significant public health risks.
• Aptamers, short DNA or RNA molecules, offer high specificity and affinity for molecular targets, making them promising for diagnostics and therapeutics.

Purpose of the Study:

• To isolate and characterize DNA aptamers with high binding affinity and specificity for E. coli.
• To evaluate the potential of these aptamers for the detection of pathogenic E. coli, including Meningitis/sepsis associated E. coli (MNEC).

Main Methods:

• Cell-based Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) was employed to identify E. coli-binding aptamers.
• Four single-stranded DNA (ssDNA) aptamers were isolated and characterized for their binding affinity (Kd values in nanomolar range).
• Specificity was assessed against twelve different bacterial species, and aptamer binding was visualized using fluorescent microscopy.

Main Results:

• Four ssDNA aptamers demonstrated strong binding to E. coli (ATCC generic strain 25922) with nanomolar affinity.
• One aptamer, designated P12-31, exhibited high specificity for E. coli compared to other bacterial species tested.
• P12-31 effectively labeled the surface of E. coli cells and demonstrated binding to clinical isolates of MNEC.

Conclusions:

• The study successfully identified novel ssDNA aptamers that bind specifically to E. coli.
• The aptamer P12-31 is the first described aptamer with demonstrated potential for diagnosing MNEC-associated infections.
• These findings highlight the utility of aptamers in developing sensitive and specific diagnostic tools for bacterial pathogens.