Experimental setup and image processing method for automatic enumeration of bacterial colonies on agar plates.

Automated colony counting methods have long been known in Microbiology. Numerous methods for automated image analysis have been described and a wide range of commercial products exists. Known advantages are saving cost by reducing enumeration time, automatic documentation, reproducibility, and operator independence. Still, even today the realization of all advantages of automated image analysis makes it necessary to either invest in an expensive, high performance commercial system, or to acquire expert knowledge in image processing. This is a considerable obstacle for many laboratories, and the reason why manual colony counting is still done frequently. This article describes an easy to apply automatic colony counting system-including suggestions for sample preparation-that can be put into operation with basic knowledge of image processing and low budget.

Actinometric and biodosimetric evaluation of UV-C dose delivery in annular, Taylor-Coutte and coiled tube continuous systems.

In this study, the evaluation of the performance of two thin-film UV-C reactors (annular and Taylor-Couette) and a coiled tube system is presented using actinometry and biodosimetry methods. The iodide/iodate actinometry method was found suitable for comparison of the efficiency of UV-C dose delivery of the UV-C continuous flow systems. Inactivation kinetics of Escherichia coli ATCC 8739 in quarter-strength Ringer's solution (absorption coefficient α254 nm ∼ 0 cm-1) at various flow conditions at Reynolds numbers in the range of 26 to 3000 showed a good correlation between the different reactor types. In high UV-C absorbing liquids, the inactivation efficiency increases due to the improved radial mixing. The inactivation performance of the Taylor-Couette system correlates to the annular reactor when no rotation force is applied. The residence time distributions showed the narrowest distribution with the coiled tube system at comparable flow rates. The results indicate that, despite the laminar flow conditions, the performance of the Taylor-Couette unit becomes equal to the turbulent flow conditions of the coiled tube reactor by rotation of the inner cylinder.