Detection of Escherichia coli using luminometer with pyruvate kinase.

Portable and quantitative detection of Escherichia coli (E. coli) has the potential to reform clinical diagnostics, food safety, and environmental monitoring. At present, most commercial devices used for pathogen detection have disadvantages such as expensive, highly complex operations, or limited detection specificity. Using the common luminometer and the properties of pyruvate kinase utilizing phosphoenolpyruvate to generate adenosine triphosphate (ATP), we have developed a method that could specifically quantify E. coli. The system is based on a sandwich hybridization procedure wherein both oligonucleotide probes recognize each end of the target of pathogenic 16S rRNAs segment. The detection probe DNA-conjugated pyruvate kinase can link ATP production to the detection of pathogenic nucleic acid in the samples. The luminometer-based system is capable of detecting E. coli with single bacteria resolution. The platform should be easily used to the detection of many other toxic analytes through the application of suitable functional-DNA recognition elements.

Oxygen Reduction Reaction Affected by Sulfate-Reducing Bacteria: Different Roles of Bacterial Cells and Metabolites.

Sulfate-reducing bacteria (SRB) were found to be capable of tolerating a certain amount of oxygen (O2), but how they affect oxygen reduction reaction (ORR) has not been clear. The present work investigated the impact of SRB on ORR in 3.5 wt% sodium chloride solution with the cyclic voltammetry method. The addition of SRB culture solution hampered both the reduction of O2 to superoxide (O2·-) and hydrogen peroxide (H2O2) to water (H2O), and the influence of SRB metabolites was much larger than that of bacterial cells. Sulfide and extracellular polymeric substances (EPS), typical inorganic and organic metabolic products, had great impact on ORR. Sulfide played an important role in the decrease of cathodic current for H2O2 reduction due to its hydrolysis and chemical reaction activity with H2O2. EPS were sticky, easy to adsorb on the electrode surface and abundant in functional groups, which hindered the transformation of O2 into O2·- and favored the reduction of H2O2 to H2O.