Oomycetes, also known as water moulds, are pathogenic microorganisms that resemble fungi and are responsible for a group of diseases affecting several plant species. The Oomycota were once classified as fungi, because of their filamentous growth, and because they feed on decaying matter like fungi. The cell wall of oomycetes, however, is not composed of chitin, as in the fungi, but is made up of a mix of cellulosic compounds and glycan.
To reach and infect plants, the zoospores -- i.e., self-propelled spores -- of oomycetes swim to their target using two flagella, one opposite the other. In a recent study directed by a CNRS researcher, physicists and biologists worked together to precisely measure the movement of each flagellum while a zoospore follows a linear trajectory and when it is turning. They used these data to develop a theoretical model.
The name "water mold" refers to their earlier classification as fungi and their preference for conditions of high humidity and running surface water, which is characteristic for the basal taxa of the oomycetes.
While primaiurly an infectious agent of plants, at least one species, Pythium insidiosum, is known to infect various mammals, including humans, horses, and dogs. However,given the significant impact on plants, the current research is focused in this area. The diseases they cause include seedling blights, damping-off, root rots, foliar blights and downy mildews.
The research reveals that, in order for the zoospore to turn, its anterior flagellum ceases to beat sinusoidally, as it does when moving along a straight path, and instead adopts a breaststroke. This is the first time that the movement of such organisms has been described at a microscopic scale.
Beyond the
fundamental biophysical questions the nature of their motion raises,
zoospores represent a new model of 'microswimmers' distinct from algae and
bacteria, suggesting new avenues of physics research. To reach and infect plants, the zoospores—i.e., self-propelled spores—of oomycetes swim to their target using two flagella, one opposite the other.
Through these findings we now understand how oomycete zoospores move, scientists still lack knowledge about when and why they change direction during their movement.
In the future, the researchers would like to study the interactions between the zoospores and the roots they infect, in order to identify the chemical processes that attract these pathogenic microorganisms.
See:
Quang D Tran, Eric Galiana, Philippe Thomen, Céline Cohen, François Orange, Fernando Peruani, Xavier Noblin. Coordination of two opposite flagella allows high-speed swimming and active turning of individual zoospores. eLife, 2022; 11 DOI: 10.7554/eLife.71227
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (http://www.pharmamicroresources.com/)
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