 Because new mycobacteriophages lacking extensive DNA similarity with the extant collection are still being discovered, and as there are at least seven singletons for which no relatives have been isolated, we clearly have yet to saturate the diversity of this particular population.The collection of >50,000 genes can be sorted into >3,900 groups (so-called "phamilies", i.e.phage protein families) according to their shared amino acid sequences.