RT Journal Article SR Electronic(1) A1 Sutherland, Joan M. A1 Herdman, Michael A1 Stewart, William D. P.YR 1979 T1 Akinetes of the Cyanobacterium Nostoc PCC 7524: Macromolecular Composition, Structure and Control of Differentiation JF Microbiology, VO 115 IS 2 SP 273 OP 287 DO https://doi.org/10.1099/00221287-115-2-273 PB Microbiology Society, SN 1465-2080, AB Synchronized akinete differentiation occurred following the transition from exponential to non-exponential (linear) growth, the major trigger being energy limitation. Young akinetes first accumulated cyanophycin, then developed a multilayered extracellular envelope and a thickened wall. The dry weight, chlorophyll a, glycogen and carbon contents of mature akinetes were greater than those of vegetative cells, while their contents of DNA, RNA, protein, phycocyanin and nitrogen were similar to those of vegetative cells. Akinetes were resistant to desiccation and low temperatures, but not to temperatures above the maximum for vegetative cell growth. In N2-grown cultures heterocyst differentiation ceased at the end of exponential growth, while cell division continued, and akinetes first appeared in a regular pattern at a fixed distance (9 cells) from the nearest heterocyst. Exogenous NH4 + inhibited the differentiation of heterocysts and, in their absence, akinetes developed in irregular positions. The regular spatial pattern imposed on akinete differentiation by heterocysts was, like the heterocyst spatial pattern itself, independent of N2 fixation. Similar changes in both patterns induced by 7-azatryptophan suggested that they share a common mechanism of control., UL https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-115-2-273