Summary Although prokaryotes ordinarily undergo binary fission to produce two identical daughter cells, some are able to undergo alternative developmental pathways that produce daughter cells of distinct cell morphology and fate. One such example is a developmental program called sporulation in the bacterium Bacillus subtilis, which occurs under conditions of environmental stress. Sporulation has long been used as a model system to help elucidate basic processes of developmental biology including transcription regulation, intercellular signaling, membrane remodeling, protein localization, and cell fate determination. This review highlights some of the recent work that has been done to further understand prokaryotic cell differentiation during sporulation and its potential applications.

Pyruvate kinase isoform M2 (PKM2) plays an important role in the growth and metabolic reprogramming of cancer cells in stress conditions. Here, we report that SAICAR (succinylaminoimidazolecarboxamide ribose-5′-phosphate, an intermediate of the de novo purine nucleotide synthesis pathway) specifically stimulates PKM2. Upon glucose starvation, cellular SAICAR concentration increases in an oscillatory manner and stimulates PKM2 activity in cancer cells. Changes in SAICAR levels in cancer cells alter cellular energy level, glucose uptake, and lactate production. The SAICAR-PKM2 interaction also promotes cancer cell survival in glucose-limited conditions. SAICAR accumulation is not observed in normal adult epithelial cells or lung fibroblasts regardless of glucose conditions. This allosteric regulation may explain how cancer cells coordinate different metabolic pathways to optimize their growth in the nutrient-limited conditions commonly observed in the tumor microenvironment.