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To improve the ultraviolet (UV) water disinfection process and to better understand the impact of the harmful effects of germicidal radiation on the DNA molecule, we have developed a reliable biological monitoring system based on PCR 16S ribosomal DNA (rDNA) and terminal restriction fragment length polymorphism analysis. The PCR analysis was performed using the bacteria-specific 27F and 905R primers to replicate a fragment of the rDNA gene. This new and versatile method can be used to evaluate the effects of direct UV radiation on DNA (UV dose/response) and to estimate the potential of bacteria to mitigate UV lethal effects via photoreactivation and dark repair. [ABSTRACT FROM AUTHOR]

The infectivity rates of Salmonella typhi's phage was used as a bio-indicator to detect the presence of viable but non cultivable bacteria after irradiation by an increasing number of pulsed UV light. Indeed, the combination of a conventional method used to measure colony-forming ability of UV-irradiated bacteria, and the study of relationship between host bacteria and a suitable phage can reveal the existence of active bacteria which lose the cultivability in usual culture media, but keep viability and phage susceptibility. [ABSTRACT FROM AUTHOR]