Studies of replicative and chronological lifespan in Saccharomyces cerevisiae have advanced understanding of longevity in all eukaryotes. Chronological lifespan in this species is defined as the agedependent viability of nondividing cells. To date this parameter has only been estimated under calorie restriction, mimicked by starvation. Because postmitotic cells in higher eukaryotes often do not starve, we developed a model yeast system to study cells as they age in the absence of calorie restriction. Yeast cells were encapsulated in a matrix consisting of calcium alginate to form ∼3 mm beads that were packed into bioreactors and fed ad libitum. Under these conditions cells ceased to divide, became heat shock and zymolyase resistant, yet retained high fermentative capacity. Over the course of 17 d, immobilized yeast cells maintained >95% viability, whereas the viability of starving, freely suspended (planktonic) cells decreased to <10%. Immobilized cells exhibited a stable pattern of gene expression that differed markedly from growing or starving planktonic cells, highly expressing genes in glycolysis, cell wall remodeling, and stress resistance, but decreasing transcription of genes in the tricarboxylic acid cycle, and genes that regulate the cell cycle, including master cyclins CDC28 and CLN1. Stress resistance transcription factor MSN4 and its upstream effector RIM15 are conspicuously up-regulated in the immobilized state, and an immobilized rim15 knockout strain fails to exhibit the long-lived, growth-arrested phenotype, suggesting that altered regulation of the Rim15-mediated nutrient-sensing pathway plays an important role in extending yeast chronological lifespan under calorie-unrestricted conditions. cell longevity | Ca-alginate encapsulation U nicellular microbes senesce and die (for reviews, see refs.

No abstract

No abstract

Racism remains a root cause of underrepresentation of Black, Indigenous, and Latinx scholars across STEM. It also contributes to a lack of diversity in science communication, the types of science stories that are told, and the communities science communicators seek to engage. Racism is omnipresent in STEM, from education to research to science communication (SciComm), because STEM institutions operate within a culture systematically privileging Whiteness, i.e., a White supremacy culture (WSC), that dictates the norms and practices that most in these fields heedlessly accept and replicate. In this Perspective, we acknowledge the ways in which SciComm and SciComm training perpetuate WSC and examine how SciComm trainers can use their power to dismantle it. SciComm trainers pioneer new methods of sharing ideas and influence the culture of STEM, so are uniquely situated to bring about systemic change to address these problems in SciComm, STEM, and society, starting with four core themes for action: (1) Authentic Interrogation, Acknowledgment, and Accountability; (2) Representation; (3) Culturally Responsive Practice; and (4) Inclusion. We also describe our current work, which builds upon the Key Traits of Inclusive SciComm identified by leaders in the field, to co-create a framework to guide authentic, culturally competent, and inclusive SciComm. The draft framework integrates the Key Traits across spheres of influence (e.g., self, interpersonal, community, institution, society: politics and culture), with the ultimate goal of using SciComm to supplant WSC across these spheres of influence, with new co-created norms centering minoritized scholars, science communicators, and audiences in STEM.

For the past 200 years, humans have benefited from the abundant, inexpensive, and easily obtained energy of fossil fuels. Energy surpluses such as this are unusual in human history. In systems with little surplus energy, population growth is low and complexity emerges slowly due to the energetic costs it carries. On the rare occasions when energy is readily available, societies respond by growing rapidly. They must become more complex in response to the social, economic, and resource challenges of dense population. More complex societies are more expensive, requiring greater energy per capita. The process of increasing complexity necessitates greater energy production, creating a positive feedback cycle. Past societies have collapsed under such pressures. Population and complexity grew rapidly when the Industrial Revolution replaced economies based on annual solar radiation with economies fueled by fossil energy. The Green Revolution of the 20th century is credited with preventing mass starvation, but it has made food production and sustaining population ever‐more dependent on high‐energy (low‐entropy) inputs. Some believe innovation will overcome the limitations of resources and permit unchecked growth. However, increases in complexity, innovation, and fossil energy are all subject to diminishing returns, and cannot continue to support population at current levels.