Sequencing the genomes of LPP-1, the first isolated cyanophage, and its relative LPP-2 reveal different integration mechanisms in closely related phages

In the early 1960s, the first cyanophage was isolated. The description of this phage, named LPP-1, led to the extensive investigation of various cyanophages and to the study of their interactions with their cyanobacterial hosts towards controlling blooms. Here, the genomes of LPP-1 and its putative relative, LPP-2 were sequenced. Sequencing these genomes revealed that LPP-1 and LPP-2 are members of a group of short-tailed cyanophages, which are distantly related to the T7-like cyanophages. Most of the phages in this group have the ability to lysogenize their hosts. Their ability to switch between lytic and lysogenic infection may explain the formation of cyanobacterial blooms despite the persistence of their phages. This lysogenic capacity of the LPP-1-like phages occurs despite the lack of an obvious integrase gene within their genomes. Interestingly, we show that LPP-2 integrates into the host genome through an integration site in high proximity to a recombination endonu-clease that may have integrase activity. Further understanding of cyanobacterial-phage relationships may pro-vide insight into their population dynamics and suggest novel approaches for control of destructive cyanobacterial blooms.

Automated summary

In the 1960s, the first cyanophage, LPP-1, was isolated, leading to the study of various cyanophages and their interactions with cyanobacterial hosts to control blooms. Sequencing the genomes of LPP-1 and its relative, LPP-2, revealed that they belong to a group of short-tailed cyanophages distantly related to T7-like cyanophages. These phages have the ability to switch between lytic and lysogenic infection, which may explain the persistence of cyanobacterial blooms despite their phages.