Читать книгу Cell Biology - Stephen R. Bolsover - Страница 19

When we say prokaryote we usually mean bacterium. The prokaryotes we use to make yogurt and kimchi, those which give us diseases, and those that we use in genetic engineering (Chapter 8) are all bacteria. However, from the very origin of life on earth a second group of prokaryotes called the archaea lived alongside bacteria. Archaea are found throughout nature, for example each of our guts contains at least a trillion cells of the archaeon Methanobrevibacter smithii that help to break down complex sugars. It is now thought that the cell that incorporated bacteria to become the ancestor of the eukaryotes was an archaeon related to a present‐day group called the Asgard archaea. Asgard archaea contain several genes and proteins that are otherwise found only in eukaryotes, including the building blocks of microtubules and microfilaments (Table 1.1). When a cell similar to a present‐day Asgard archaeon engulfed an oxygen‐using bacterium it could then begin the slow process of evolving into the multitude of eukaryotes that exist today.