Coinfection rates in φ6 bacteriophage are enhanced by virus-induced changes in host cells

Abstract

Two or more viruses infecting the same host cell can interact in ways that profoundly affect disease dynamics and control, yet the factors determining coinfection rates are incompletely understood. Previous studies have focused on the mechanisms that viruses use to suppress coinfection, but recently the phenomenon of enhanced coinfection has also been documented. In the experiments described here, we explore the hypothesis that enhanced coinfection rates in the bacteriophage ø6 are achieved by virus-induced upregulation of the ø6 receptor, which is the bacterial pilus. First, we confirmed that coinfection enhancement in ø6 is virus-mediated by showing that ø6 attaches significantly faster to infected cells than to uninfected cells. Second, we explored the hypothesis that coinfection enhancement in ø6 depends upon changes in the expression of an inducible receptor. Consistent with this hypothesis, the closely related phage, ø12, that uses constitutively expressed lipopolysaccharide as its receptor, attaches to infected and uninfected cells at the same rate. Our results, along with the previous finding that coinfection in ø6 is limited to two virions, suggest that viruses may closely regulate rates of coinfection through mechanisms for both coinfection enhancement and exclusion. © 2008 Blackwell Publishing Ltd.