Malaria plasmodium found its own biological clock

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American biologists have proved that cyclic flow
malaria due to the presence of malaria plasmodium own circadian
rhythms that can be observed even in culture in vitro and during the “asynchronous” infection
the owner. The results of the experiments are presented immediately in two articles in Science (12).

Malaria is a serious infectious disease that is caused
the simplest of the kind Plasmodium. The causative agent falls into
the victim’s blood with a bite of a certain type of mosquito, and begins to multiply inside
first liver cells, and then in red blood cells – red blood cells. Flow
malaria is characterized by intermittent fever that occurs every 24,
48 or 72 hours. The cycle of the disease corresponds to the cycle of development
plasmodia, which simultaneously destroy red blood cells and go outside.

It used to be that the parasite’s developmental cycles were regulated
host circadian rhythms, however, scientists have found that plasmodiums are mainly guided by
own biological clock, which, however, can be adjusted
under the watch of their master. Two different research groups in two ways
plasmodium monitored the expression of parasite genes and were convinced of its
cyclicity regardless of external conditions.

Scientists from the University’s Southwestern Medical Center
Texas worked on the mouse model of malaria, which is caused by the simplest Plasmodium chabaudi, and studied with a transcript of the parasite every 3 hours in
for three 24-hour cycles. They found that expression of 60 percent of genes
plasmodia is subject to regular fluctuations within the 24-hour cycle, which
preserved in mice with a down regime. In the first case, infected mice were kept
in the dark, disrupting their sleep patterns, and in the second case, randomly fed for
days, violating the diet. It turned out that neither one nor the other affects the cycle
development of plasmodium.

Plasmodium cyclicity was observed even in mutant mice with
off gene Cry,
who have had no daily regimen since birth. However, after 5-7
days of infection, the synchronism of parasite cycles in such mice disappeared. In mutant
mice with days prolonged up to 26 hours (i.e., their daily life activity was within
at 25.7 hours, while in normal mice at 23.7 hours) the life cycle
plasmodium stretched out according to the master’s. Researchers concluded
that each malarial plasmodium regulates its life cycle independently,
however, it is able to perceive signals from the host organism, which,
apparently help synchronize the parasite population.

Duke University research team studied
the behavior of four strains of the causative agent of human malaria Plasmodium falciparum in culture in
vitro. Scientists also analyzed the composition of plasmodium RNA with an interval of 3
hours for 60-70 hours. They found that at least 87 percent
Plasmodium transcripts are subject to cyclical fluctuations. It should be noted that
plasmodia do not have genes homologous to the main circadian regulators of animals,
however, even in culture, their life cycle was 48 hours with small
variations from strain to strain.

The observations of scientists are consistent with the existing theory that
that in the body, each cell has its own biological clock
(circadian rhythms), but their cycle is not necessarily exactly 24 hours. For
fine tuning of all cellular clocks requires a “master-regulator”, which in mammals
located in the hypothalamus. For the discovery of the biological clock and the mechanism of work in
2017 was awarded the Nobel Prize in Physiology or Medicine, read
more about this can be in our material “The course of the clock is only monotonous.”

Daria Spasskaya

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