Much of our understanding of bacterial behavior stems from studies in liquid culture. In nature, however, bacteria frequently live in densely packed spatially-structured communities. How does spatial structure affect bacterial cooperative behaviors? In this work, we examine rhamnolipid production—a cooperative and virulent behavior of Pseudomonas aeruginosa. Here we show that, in striking contrast to well-mixed liquid culture, rhamnolipid gene expression in spatially-structured colonies is strongly associated with colony specific growth rate, and is impacted by perturbation with diffusible quorum signals. To interpret these findings, we construct a data-driven statistical inference model which captures a length-scale of bacterial interaction that develops over time. Finally, we find that perturbation of P. aeruginosa swarms with quorum signals preserves the cooperating genotype in competition, rather than creating opportunities for cheaters. Overall, our data demonstrate that the complex response to spatial localization is key to preserving bacterial cooperative behaviors.

The endothelins and their receptors are best known for their regulation of the vascular system. Their widespread expression in epithelial cells and their overexpression in some tumors has prompted investigation into their ability to regulate cancer progression. In this study, we assessed the mRNA expression of the major endothelin B receptor gene (EDNRB) isoforms and found differences in both mRNA and protein expression in normal breast cells and breast cancer cell lines. Knocking down the EDNRB gene in breast cancer cells altered invasiveness toward endothelin 3 (ET3), and we observed EDNRB isoform-specific regulation of breast cancer cell invasion and cell signaling, as well as isoform-and subtype-specific differences in breast cancer patient survival. The results reported in this study emphasize the importance of the endothelin B receptor in breast cancer. To our knowledge, this study is the first to clarify the differential expression and roles of specific EDNRB isoforms in breast cancer.

15The ability of single-celled microbes to integrate environmental signals and control gene 16 expression enables calculated decisions on whether they should invest in a behavior in a specific 17 environment. But how can the same mechanisms of gene expression control-resulting from 18 individuals sensing, integrating and responding to diffusible queues in dynamic, densely 19 populated microbial communities-enable the evolution and stability of cooperative behaviors 20 that could easily be exploited by cheaters? Here we combine fluorescent imaging with 21 computational analyses to investigate how the micro-environment experienced by cells in 22 spatially-structured systems impacts cooperative behavior. We focus on swarming in the 23 opportunistic human pathogen Pseudomonas aeruginosa, a behavior that requires cooperative 24 secretions of rhamnolipid surfactants to facilitate collective movement over surfaces. Our 25 analysis shows that the expression of rhamnolipid synthesis varies across the colony and, counter 26 to previous knowledge, peaks at tips of swarming tendrils. To dissect the contribution of 27 competing diffusive inputs-quorum sensing signals and growth-limiting nutrients-we adapted 28 the classic Colony Forming Unit (CFU) assay to record colony growth and gene expression 29 dynamics across thousands of colonies. We found these cells capable of centimeter-scale 30 communication in a pattern of gene expression previously undetected in liquid culture systems. 31Validation experiments where we manipulated gene expression by flooding the environment 32 with quorum sensing signals could accelerate the onset of swarming, but the cooperative trait 33 remained robust to cheaters. Taken together, these results shed new light on the integration of 34 diffusible signals that stabilizes swarming motility, a cooperative microbial behavior. 35 36 quorum signals in liquid culture never showed significant alteration to rhlAB expression, the 128 same perturbation in the spatially structured system surprisingly revealed an over-expression 129 phenotype that was nonetheless cost-less in both bacterial colonies and motile swarms. Taken 130 together, these data show that there are new regimes of bacterial gene expression yet to be 131 unlocked in spatially-structured systems. Our findings reveal new scales of bacterial 132 communication and new dimension to the evolutionary robustness of bacterial cooperation. 133 Results 134 Expression of rhlAB peaks at the edge of swarming colonies 135Competition for nutrient and quorum sensing are two types of cell-cell interactions 136 mediated by diffusible processes that affect rhlAB expression. Their competing influences make 137