Biology I

Multicellularity and collective cell behavior exemplify the emergence of complex patterns and structures across scales in living systems. When cells interact they can generate higher order patterns of gene expression or patterns of mechanical stresses and strains. There are a wide range of phenomena in which a key element to a developmental process is the appearance of a traveling wave of chemical concentration, mechanical deformation, electrical or other type of signal. Thus, studying traveling waves is relevant to our understanding of fundamental mechanisms underlying pattern formation.

The biological circadian clock aligns our bodily functions to the day-and-night cycle and is important for our health. These bodily rhythms ultimately derive from rhythmic gene expression in individual cells. Because the core clock machinery includes several transcription factors, studies of circadian gene expression have long focused on rhythmic transcriptional control. However, recent studies suggest the importance of rhythmic post-transcriptional controls as well.

Since a celebrated experiment by Monod in 1949, we know that microbes can adapt their metabolic strategies in response to their environment, thus uptaking different nutrients at different rates depending on their relative quality and availability. It is currently unclear whether this physiological plasticity of microbes contributes to maintaining the high degree of diversity found in natural microbial communities, even in the presence of very few resources.

A general framework for the generation of long wavelength patterns in multi-cellular (dis- crete) systems is proposed, which extends beyond conventional reaction-diffusion (continu- um) paradigms [2]. The standard partial differential equations of reaction-diffusion frame- work can be considered as a mean-field like ansatz which corresponds, in the biological set- ting, to sending to zero the size (or volume) of each individual cell.