Abstract Toxoplasma gondii is an obligate intracellular parasite. Proteins released during host cell invasion from apical secretory organelles known as rhoptries are delivered into the host cell cytosol to perform functions critical for parasite survival and virulence. How these effector proteins move across the host cell plasma membrane is unknown but may involve a previously noted temporary loss of host cell plasma membrane barrier integrity. Here, we use high-speed, multi-wavelength fluorescence imaging to spat…

Abstract The parasite Toxoplasma gondii invades its host cell only after secreting proteins such as invasion-requisite RON2 that inserts into the host cell membrane to establish the moving junction. Electrophysiological recordings at sub-200 µs resolution show a transient increase in host cell membrane conductance following parasite exposure. Transients always precede invasion, but parasites depleted of RON2 generate transients without invading. Thus RON2 is not essential for transient generation. Time-series anal…

ABSTRACT During infection, Toxoplasma gondii tachyzoites must be able to move in order to migrate through tissues, cross biological barriers, and penetrate into and egress from cells they infect. Bradyzoite-stage parasites, which establish infection in naïve hosts, also require motility to escape from cysts after they are ingested and to subsequently migrate to the gut wall, where they either invade cells of the intestinal epithelium or squeeze between these cells to infect the underlying tissue. Little is known a…

Abstract Toxoplasma gondii prevalence is due, in part, to its ability to persist in hosts while retaining the capacity to transmit and recrudesce. A process that is poorly understood. Through single-cell RNA profiling of in vivo-derived bradyzoites, we discovered that they are heterogeneous and not G1-arrested, as expected from in vitro studies. Instead, they progress through two cell cycles that branch from a single G1. While in G1b, in vivo -derived bradyzoites express cyst wall proteins predicted to replenish t…

ABSTRACT Apicomplexan parasites must discharge the contents of specialized organelles called rhoptries into host cells to initiate the process of invasion. This process requires the prior recognition and binding of the host cell by proteins released from another set of parasite organelles, the micronemes. However, the host-parasite interactions required for rhoptry discharge are largely unknown. Here we performed a host-cell directed genome-wide screen for host factors required for rhoptry discharge from Toxoplasm…