If you have a deep understanding of how cells interact, then you can pilot these interactions to the benefit of the cells, the environment or even human health. Sara Mitri - SIB Group Leader at the Department of Fundamental Microbiology at the University of Lausanne - and her team carry out research on microbial ecosystems to address cell interactions and their evolution. "Microbes behave differently depending on their genotype and the wealth of nutrients at their disposal, but their behaviour also depends on their neighbours," says Sara Mitri.

So far, nothing really new, you may be thinking. But before turning to microbes, Sara spent many years studying robots and their interactions. "I discovered a book on evolutionary biology during my masters degree in Computer Science, and it fascinated me. In truth, the passage from robots to living beings seemed a logical step." During her PhD, Sara used robots as models of individual animals to study the evolution of cooperative communication. She then switched to systems biology and microbes to which she could apply her computational faculties. "What I did with robotic systems can be used to understand and predict what occurs between cells, or populations of cells" she continues.

Sara's group combines mathematical modelling, computer simulations and laboratory experiments to understand microbial behaviour - a combination of genetic heritage, interactions with neighbouring cells, nutrients, space, and time. Quorum sensing (see box) is a communication system used by microbes in response to population density. Thanks to computer simulations, for example, Sara and her team were able to show that quorum sensing is not so much a way of assessing population density than being able to sense kinship. "Biology students should be more versatile and take a greater interest in computational methods," says Sara. "Building models should be one of their focuses."

Sara Mitri studied Computer Science at the American University in Cairo, and Cognitive Science and Natural Language at the University of Edinburgh (UK). In 2009, she earned her PhD in Computer and Communication Science at the Laboratory of Intelligent Systems at the EPFL by studying the evolution of communication in robot societies. She continued her academic career at the FAS Center for Systems Biology at Harvard University and the Department of Zoology at the University of Oxford (UK). Sara came back to Switzerland in 2015 and now leads SIB's Evolutionary Microbiology Group at the Department of Fundamental Microbiology of the University of Lausanne.

What is quorum sensing?
Quorum sensing is a means of communication used by microbes to adapt their behaviour following changes that occur in their close surroundings. Each organism secretes signaling molecules into the environment; once a concentration threshold has been reached, the molecules trigger changes in gene expression. In bacteria, for instance, quorum sensing can be used to regulate biofilm formation, motility, bioluminescence or population density.

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