BN Seminar

Roman Stocker (MIT):"A behavioral perpective on bacterial individuality"
At a time when microbial ecology is largely traveling along genomic roads, we cannot forget that the functions and services of microbes depend greatly on their behaviors, encounters, and interactions with their environment. New technologies, including microfluidics, high-speed video-microscopy and image analysis, provide a powerful opportunity to spy on the lives of microbes, directly observing their behaviors at the spatiotemporal resolution most relevant to their ecology. I will illustrate this 'natural history approach to microbial ecology' by focusing on marine bacteria, unveiling striking adaptations in their motility and chemotaxis and describing how these are connected to their incredibly dynamic, gradient-rich microenvironments. Specifically, I will present (i) direct evidence for a diverse gallery of microscale microbial hotspots in the ocean; (ii) a new framework for understanding the evolution of microbial diversity in the ocean; and (iii) high-speed microscopy  experiments that unveil a new motility mode among marine bacteira, based on an original utilization of mechanical instabilities for maneuvering. Through these examples, I hope to show that direct visualization can foster a new layer of understanding in microbial ecology and can help us unlock the ocean's microscale. 

Martin Ackermann (ETH Zurich):"An evolutionary perspective on bacterial individuality" 
According to the conventional view, the properties of an organism are a product of nature and nurture - of its genes and the environment it lives in. Recent experiments with unicellular organisms have challenged this view: genetically individuals living in homogeneous laboratory environments can have markedly different properties, and express different sets of genes. We are interested in the functional consequences of this variation in bacteria: is phenotypic heterogeneity sometimes beneficial, and does it provide microbes with new functionality in their natural environment? I will first present results that suggest that, for the majority of the genes in a bacterial genome, natural selection acts to reduce phenotypic variation. Then, I will present a few exception to this rule, and discuss how phenotypic variation in clonal populations of bacteria can promote interactions between individuals, lead to the division of labor, and allow clonal groups of bacteria to cope with environmental uncertainty. The main conclusion from this work is that microbial individuality can provide groups of organisms with collective functionality.