A model for the generation of low level chemiluminescence from microbiological growth media and its depletion by bacterial cells

Water assessment using ultra-weak bioluminescence

In this paper a method to evaluate the presence of microorganisms of the coliform group in water samples using the ultra-weak bioluminescence (UWB) is proposed. A series of UWB measurements and optical density measurements from cultures of both a set of standard E. coli strain samples, and a set of water samples from a river near Curitiba City in Brazil were performed. All samples were previously incubated at 37°C for 11h in nutritive medium before the temporal UWB emission profiles data were acquired for a period of 24h inside a dark chamber of an especially implemented instrumentation capable of doing photon counting measurements. For the optical density measurements, a spectrophotometer was used to acquire the growth kinetics of those cultures for a period of 13h, and the results compared to the UWB profiles. Periodic time-components analysis of the UWB data from both the set of standard E. coli samples and the set of the river's water samples were performed and compared to each other. The results have shown that the UWB temporal profiles resemble in some way the growth kinetics curve and the periodic time-components analysis is an effective way to discriminate between contaminated and non-contaminated samples, therefore the method may be viable for detecting coliforms in water samples in less time than usual methods.

Imaging localized horseradish peroxidase on a glass surface with scanning electrochemical/ chemiluminescence microscopy

Scanning electrochemical/chemiluminescence microscopy (SECM/SCLM) was developed for simultaneous imaging of chemiluminescence and topography of immobilized horseradish peroxidase (HRP) on a glass substrate. When the SECM tip for electrochemical generation of H2O2 scanned over the immobilized spot in an aqueous luminol solution, the immobilized enzymes catalyzed the oxidation of luminol to emit chemiluminescence, which was detected by a photon counter. The photon-counting intensity was plotted against the position of the tip to give a two-dimensional image, indicating the activity of immobilized enzymes. Since the current was sensitive to the topography of substrate, the topography image was also obtained by mapping the oxygen reduction current.