The rhythmic day of malaria parasites

Our rhythmic world has been a driving force for organisms to evolve a clock to
anticipate such rhythms. Similarly, our own circadian biology leads to body rhythms that
parasites experience. Malaria major symptom is fever. Malarial rhythmic fevers are a
consequence of the synchronous bursting of host’s red blood cells (RBCs) on
completion of the malaria parasite asexual cell cycle. How is this bursting synchronous
across the parasite population? Are parasites following host cues or do they also have a
clock to anticipate host daily rhythms? Through a combination of infection challenges
where we manipulate the environment or rhythms of the host by infections of circadian
mutant hosts and assess the rhythms of the parasites. We found that without any
external cue to the parasites, their transcriptome remains rhythmic with ~60% of
parasite transcripts being expressed once a day. Thus, we propose malaria parasites to
have intrinsic clocks. Parasite rhythms are aligned to the host daily rhythms but are
generated by the parasite, possibly to anticipate its circadian environment.