February 8 2018

11:00 158 HH

This seminar is sponsored by EEB QC Bio

Francesco Carrara
Environmental Microfluidics Group
Swiss Federal Institute of Technology

A dive into the microscale ocean: how microorganisms sense turbulence and dynamic chemical cues


Microbes have colonized every environment on Earth: lakes, oceans, soil and human bodies. While interactions and activities of microbes take place on the scale not visible to the naked eye, they play a fundamental role for a broad range of macroscale environmental processes. In the ocean, marine microbes including phytoplankton and heterotrophic bacteria are essential components of food webs and element cycles. Marine microbes live and interact in dynamic environments where turbulent fluid flow and steep nutrient gradients are two ubiquitous physicochemical features. The goal of my research is to characterize how biotic and abiotic interactions modulate behaviors, physiology, collective dynamics, and functions of microbes. In this talk, I will portray two strategies illustrating how microbes effectively navigate their aquatic habitats.

I will first describe how a population of the harmful algal-bloom-forming raphidophyte Heterosigma akashiwo actively diversifies its migratory behavior in response to turbulence. H. akashiwo exhibits negative gravitaxis – the ability to orient their swimming in the direction opposite to gravity. Upon turbulence, a rapid morphological change is triggered in half of the population, modulating the cells’ mechanical stability and underpinning the switch in the swimming direction from upward to downward. This active adaptation to turbulence highlights the advanced level of control that phytoplankton can exert on their migratory behavior.

I will then depict how marine bacteria have evolved sensing strategies to efficiently navigate dynamic chemical landscapes. Cells may increase their sensory precision in climbing gradients at the cost of producing more signaling molecules. I will show that Vibrio ordalii trade-offs the costs and benefits of intracellular noise suppression. Altogether, this work highlights the importance of integrating microfluidic, engineering, and biophysical modeling approaches into microbial ecology to mimic the complex landscapes that microbes face under field conditions, and to uncover processes that are essential for the biogeochemical cycles in the ocean.
































































































































































































































































































































































































































































































































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