Oblique incidence reflection imaging of live cells: improving contrast and image quality with an objective mask.

Dry 40x and 60x microscope objectives were fitted with opaque black masks in order to eliminate reflection and scattering of light off the objective front lens assembly during oblique incidence reflection (OIR) microscopy. The reflection and scattering are shown to induce background glare that leads to degradation in the quality of the OIR images. Mask prototypes were designed and machined to snap onto the spring-loaded retractable front lens assembly of each objective.

The bactericidal effect of ultraviolet and visible light on Escherichia coli.

The bactericidal radiation dosages at specific wavelengths in the ultraviolet (UV)-visible spectrum are not well documented. Such information is important for the development of new monochromatic bactericidal devices to be operated at different wavelengths. In this study, radiation dosages required to cause mortality of an Escherichia coli strain, ATCC 25922, at various wavelengths between 250 and 532 nm in the UV and visible spectrum were determined.

Visible laser and UV-A radiation impact on a PNP degrading Moraxella strain and its rpoS mutant.

The role of stationary phase sigma factor gene (rpoS) in the stress response of Moraxella strain when exposed to radiation was determined by comparing the stress responses of the wild-type (WT) and its rpoS knockout (KO) mutant. The rpoS was turned on by starving the WT cultures for 24 h in minimal salt medium. Under non-starved condition, both WT and KO planktonic Moraxella cells showed an increase in mortality with the increase in duration of irradiation.

Monitoring live cell viability: Comparative study of fluorescence, oblique incidence reflection and phase contrast microscopy imaging techniques.

The relative performances of fluorescence, oblique incidence reflection and phase contrast imaging techniques have been studied for the purpose of monitoring long-term cellular activity and cell viability of several types of normal and cancerous cells in cultures. Time-lapse movies of live cell imaging of untagged and green fluorescent protein (GFP) tagged cell lines are presented. Oblique incidence reflection microscopy is the simplest and least expensive method to implement, appears to be the least phototoxic to cells, and is recommended for use in long-term optical monitoring of cell viability.