Yeast intentionally stuffed with bacteria may teach scientists something about the origins of cells’ powerhouses.
Cellular power-generating organelles, called mitochondria, are thought to have once been bacteria captured by archaea, single-celled microbes that are one of the earliest forms of life. Now, almost all eukaryotic cells (cells with a nucleus) contain mitochondria. At first, the bacteria may have lived inside archaea as endosymbionts, independent organisms that cooperate with their hosts. Over time, mitochondria lost many of their genes and eventually became an integral part of the cell.