Guiding microbes along their path
How physical principles of active matter reveal defined patterns

Date:
September 24, 2021
Source:
Max Planck Institute for Dynamics and Self-Organization
Summary:
The direction of movement of a microbe directly depends on the
curvature of its environment, according to new findings. The
researchers investigated the navigation of a model microbe,
a small self-propelling microalga, in confined compartments
with different shapes. They also developed theoretical models
to predict the probability flux of that microswimmer which was
confirmed by experiments. With this model available, it is now
possible to pre-define the average trajectory of such microbes
by manipulating the curvature of the compartments which directly
affects their movement.



FULL STORY ==========================================================================
The interdisciplinary field of active matter physics investigates
the principles behind the behavior and self-organization of living
organisms. The goal is to reveal general principles that allow to describe
and predict the performance of living matter and thereby support the development of novel technologies. Recently, the groups of Oliver
Ba"umchen and Marco Mazza from the MPIDS, the University of Bayreuth
and the University of Loughborough in the UK published their results
on the model describing microbial navigation. "As microbes are often
challenged with navigating through confined spaces, we were asking
ourselves if there is a pattern behind the microbial navigation in a
defined compartment," they explain the approach. To answer this question,
the researchers followed a single motile microbe and experimentally
determined the probability flux of its movements. That is to say, they subdivided an predefined compartment into sectors and determined the probability of movement direction for each sector. In this way, a map
was created according to which the navigation behavior of the microbe
can be predicted.


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The curvature determines the flux Surprisingly, the microbe was found
not to move randomly though the open space.

Instead, the average movement pattern was both highly organized and symmetrical: the map of movement patterns showed a defined distribution
of probability fluxes. "In particular, the strength of the flux was found
to depend on the curvature of the adjacent solid interface: a higher
degree of curvature resulted in a stronger flux" explain Jan Cammann
and Fabian Schwarzendahl, the lead authors of the study. For practical
reasons, all measurements were done in a quasi 2-dimensional environment, meaning that the microbe was confined from the top and bottom to better
monitor its movement and avoid defocusing. Observing its movement pattern,
the group of Marco Mazza (University of Loughborough and MPIDS) created a
model to predicts the probabilities to flow in a certain direction. This
model was then applied to compartments with more complex interface
curvatures and experimentally verified by the lab of Oliver Ba"umchen
(MPIDS and University of Bayreuth). "It turns out that the curvature
of the interface is the dominating factor which directly determines the
flux of the self-propelling microbe.," Ba"umchen summarizes.

A technological implication for the future As this discovery constitutes
a fundamental observation, the model might as well be applied to other
areas of active matter physics. "With our model, we can basically
statistically predict where the object of interest will be in the next
moment," Mazza reports. "This could not only significantly improve our understanding of the organization of life, but also help to engineer
technical devices." Understanding the principles behind the organization
of active matter therefore can have direct implications on our future technologies. Potential applications of the model could be directing the movement of photosynthetic microorganisms in such a way so their flux
can propel a generator, which would be a direct way to convert sunlight
into mechanical energy. But also, in the pharmaceutical and healthcare
sector, the findings of the scientists might be applied: "A potential application in the medical sector is the development of micro-robots
delivering drugs to their specific destination in an efficient manner," Ba"umchen concludes.

========================================================================== Story Source: Materials provided by Max_Planck_Institute_for_Dynamics_and_Self-Organization.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Jan Cammann, Fabian Jan Schwarzendahl, Tanya Ostapenko, Danylo
Lavrentovich, Oliver Ba"umchen, Marco G. Mazza. Emergent probability
fluxes in confined microbial navigation. Proceedings of the
National Academy of Sciences, 2021; 118 (39): e2024752118 DOI:
10.1073/ pnas.2024752118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210924104323.htm

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