Gary Woodnutt – Diversa Corp., San Diego, CA, USAAnti-bacterial phages have been used successfully for many years in the treatment of infectious disease in some parts of the world. However, the effectiveness and convenience of broad-spectrum anti-bacterials have prevented the more widespread use of phage therapy. The spread of anti-microbial resistance has necessitated re-analysis of alternate therapy and interest in phage is now on the increase. In particular, there is increased interest in understanding the potential for phage lytic enzymes as this can reduce production difficulties by heterologous expression in suitable fermentation hosts. As highlighted by this review, there are clear advantages for this type of therapy, including rapid killing and lysis of bacterial strains. Lopez et al. also discuss the potential advantages of combination therapy with mixtures of enzymes. However, it is probable that the specificity of these lysins for particular bacteria could be a significant issue (phage are perfectly adapted to infect particular species or even sub-sets of species) but there is potential for construction of chimeric enzymes that might increase both activity and anti-bacterial spectrum. If this proves possible, phage lysins have a very exciting future.