Table 1 shows that the importance of the 23S rRNA as a target for FISH analyses instead of the formerly predominant 16S rRNA increases. The 23S rRNA has roughly twice the length of 16S rRNA and has been shown to possess a similar value for species differentiation.
The growing number of available 23S rRNA sequences is contributing to its increasing popularity for FISH analyses and might enable further differentiation between closely related strains which cannot be distinguished by targeting 16S rRNA sequences