Phage production is blocked in the adherent-invasive Escherichia coli LF82 upon macrophage infection
Abstract
The prototype adherent-invasive Escherichia coli (AIEC) strain LF82, hosting five predicted prophages, was isolated from a patient with Crohn's disease. It can adhere to and invade intestinal epithelial cells. In addition, its uptake by the first line of defense, the macrophages, does not lead to its lysis, as LF82 is able to multiply within macrophages. This leads to an amplification of the inflammation process, which is characteristic of Crohn's disease. The macrophage is a genotoxic environment that induces the lytic cycle of prophage lambda in a lysogenized laboratory E. coli strain, thereby helping the macrophage to eliminate the bacteria. This raises the question of the activity of LF82 prophages and the control of their lytic cycle when LF82 grows in macrophages.
By combining virome sequencing, qPCR, electronic and fluorescent microscopy analyses, we showed that all LF82 prophages form viral particles in vitro. The most active of them, Gally, spontaneously produces more than 108 virions per mL of culture. Its production further increases upon exposure of LF82 cells to the SOS inducer ciprofloxacin, leading to the clearance of the culture. However, Gally is not overproduced in the stressful macrophage environment. Analysis of the Gally transcriptome and key steps of its lytic cycle suggested that Gally initiates its replication within macrophages, but its excision from the bacterial genome is repressed.
These results suggest that LF82 has evolved an efficient way to block the lytic cycle of its most active prophage in macrophages, contributing to its remarkable survival ability in this environment.
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Life Sciences [q-bio]Origin | Files produced by the author(s) |
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