The human virome in health and disease

We observed a large number of phage and wondered about their growth. Phage can have two main life cycles: lytic and temperate. In the lytic cycle, phage infect a bacterial cell, replicate, and produce new particles. In the temperate cycle, phage integrate their DNA into a host cell genome and can switch to the lytic cycle under certain conditions.

We were curious about the growth of the phage we observed - whether it was lytic or lysogenic. To investigate, we isolated 24 bacterial strains from the stool of 20 infants and attempted to plate virus-like particles on each strain to look for plaques. Despite our efforts, we did not find any evidence of the infant virus-like particles growing when placed back on cells from the same infant.

This lack of growth led us to consider the possibility of lysogeny, where phage are unable to infect cells that are already lysogens producing repressors. This information suggests that lysogeny may be occurring in this case.