|Microbial Active Matter|

FOCAL POINTS

Surface-associated bacterial colonies mediate a broad range of processes in ecology, medicine, and industry. Through a series of ongoing research projects - combining experiments, theory and numerics/simulations - we are working to develop a comprehensive biomechanical picture of the cell-to-colony dynamics, taking into account the role of biophysical variations (phenotypic noise), self-regulating traits (like bacterial size) as colonies expand, and the consequences of feedback due to the emergent processes (creation of topological defects, active flows and emergent transport) on the growth and fitness of bacterial colonies.

1. Geometry and mechanics of growing bacterial colonies

Physical Review Letters 123, 178001, 2019

Physical Review X 8, 031065, 2018

2. Active biomechanics and transport in bacterial communities

Nature Physics 18, 2022

arXiv 2212.10101, 2022

Frontiers in Physics 8, 2020

Physical Review Letters 123, 178001, 2019

Physical Review X 8, 031065, 2018

3. Phenotypic noise and self-regulation of biophysical traits in expanding colonies

Nature Physics 18, 2022

arXiv 2212.10101, 2022

Frontiers in Physics 8, 2020

4. Mechanistic understanding of the cancer-microbiome

CAMEOS: Cancer Microbiome: Emergent Organisation and Stability across scales, uses a bottom up multi-scale approach that lies at an exciting interface of physics, cancer biology and machine learning (ML) tools; link to project here. Some general relevant concepts are covered in the following publications:

Advanced Materials, 2022

arXiv 2204.10059, 2022

Frontiers in Physics 8, 2020

5. Harnessing bacteria for innovative biogenic materials

μ-BITS: Microbial Biogenic Tunable Structures are sustainable and scalable, microbially-derived multi-purpose biogenic structures, produced using our in-house protocols (patent filed). μ-BITS possess tunable properties, offering critical eco-friendly micro-inclusions for a range of products including paints, cosmetics, tyres, or niche applications like dental fillers. For details contact: anupam.sengupta@uni.lu

FOCAL POINTS

Phytoplankton are photosynthetic microorganisms that form the base of most aquatic food webs, impact global biogeochemical cycles, and produce half of the world’s oxygen. Many species of phytoplankton are motile and migrate through the water column via gravitaxis, directional movement in response to gravity. They move upward toward light during the day and downward toward higher inorganic nutrient concentrations at night. Despite the minute size of individual organisms, phytoplankton’s immense numbers make these migrations some of the largest and most important on Earth. Understanding how physicochemical cues from the environment—such as light, nutrients, and turbulence—affect migration greatly impacts our ability to predict the diel vertical migration of phytoplankton.

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1. Phytoplankton strategies under ecological constraints

Phytoplankton are equipped with emergent and adaptive traits which allow them to navigate through dynamic environments. And when the conditions turn stressful, they often have the ability to elicit novel traits-on-demand.

Science Advances 8, eabn6005, 2022

Nature 543, 555 2017

2. Adaptive gravitaxis of motile phytoplankton

Motile phytoplankton adaptive their gravitactic motion by changing their shape, flagellar beating, or by reorganizing their intracellular organelles. Other biophysical mechanisms, including confounding effects of light and chemical gradients can modify the swimming ability of cells against the gravity vector.

Science Advances 8, eabn6005, 2022

PNAS 118, e2005944118, 2021

Frontiers in Physics 8, 2020

Nature 543, 555 2017

3. Environmental sensing by phytoplankton

Motile phytoplankton sense environmental fluctuations, for instance those triggered by fluid flow (or turbulence) in their environment by leverage reactive oxygen species (ROS). Furthermore, the sensing goes beyond abiotic factors, and could be relevant also for changes in biotic factors like levels of nutrients or pH.

Science Advances 8, eabn6005, 2022

PNAS 118, e2005944118, 2021

4. Perception of gravity by motile phytoplankton

Gravitactic phytoplankton have exquisite response mechanisms to changes in gravity, we tested this during a prabolic flight over the island of Corsica, France. Follow the link here. for an easy read.

The results are under revision, stay tuned for: Gravity modulations induce migratory changes and transcriptional shifts to stress protection and repair in motile phytoplankton: J. D. Wheeler, U. Pfreundt, F. Carrara, A. S*, R. Stocker*

5. Turbulence-induced behavioural & physiological adaptation in phytoplankton

Turbulence is known to be a primary determinant of plankton fitness and succession. However, open questions remain about whether phytoplankton can actively respond to turbulence and, if so, how rapidly they can adapt to it. Our research shows that phytoplankton can behaviorally respond to turbulent cues with a rapid change in shape, which over depends on their physiological state.

PNAS 118, e2005944118, 2021

Nature 543, 555 2017