Biodiversity of Microbes

Biodiversity of Microbes

Bacteria are small and simple in structure when compared with eukaryotes, yet they often have characteristic shapes and sizes. Although they have a plasma membrane, which is required by all living cells, bacteria generally lack extensive, complex, internal membrane system. The prokaryotic cell wall almost always has peptidoglycon and is chemically and morphologically complex. Most bacteria can be divided into gram-negative groups based on their cell wall structure and response to the Gram stain. Components like capsules and fimbriae are located outside the cell wall. One of these is the flagellum, which many bacteria use like a propeller to swim toward attractants and away from repellents. Some bacteria from resistant endospores to survive harsh environmental conditions in a dormant state. Bacteria very in size as much as in shape. The smallest are about 0.3 µm in diameter, approximately the size of the largest viruses. Prokaryotic cells almost are bounded by a chemically complex cell wall. Inside this wall, and separated from it by a periplasmic space, lies the plasma membrane. This membrane can be invaginated to form simple internal membranous structure. Since the prokaryotic cell does not contain internal membrane-bound organelles, its interior appears morphologically simple. The genetic material is localized in a discrete region, the nucleoid, and is not separated from the surrounding cytoplasm by membranes.