BACTERIA

Bacteria The two most basic types of cells are eukaryotic and

prokaryotic. Animal cells fall under the eukaryotic classification while bacteria, which will be the topic discussed, fall into the prokaryotic classification. Bacteria have a wide variety of characteristics, which includes, cell structure, oxygen usage, and source of energy. A cell is the fundamental structural unit of all living things. All cells have a surrounding membrane and an internal, water-rich substance called the cytoplasm. A more or less typical bacterium is comparatively much simpler than a typical eukaryotic cell. Within the eukaryotic cell is genetic material, deoxyribonucleic acid (DNA), and organelles. DNA, combined with protein, is organized inside the nucleus into structural units called chromosomes. Cells are made mostly of organic compounds such as proteins, nucleic acids, lipids, and carbohydrates. Water makes up 60 to 65 percent of the cell. Bacteria lack the membrane-bound nuclei of eukaryotes; their DNA forms a tangle known as a nucleoid, but there is no membrane around the nucleoid, and the DNA is not bound to proteins as it is in eukaryotes. Whereas eukaryote DNA is organized into linear pieces, the chromosomes, bacterial DNA forms loops. Bacteria contain plasmids, or small loops of DNA, that can be transmitted from one cell to another, either in the course of multiplication or by viruses. This ability to trade genes with all comers makes bacteria amazingly adaptible; beneficial genes, like those for antibiotic resistance, may be spread very rapidly through bacterial populations. It also makes bacteria favorites of molecular biologists and genetic engineers; new genes can be inserted into bacteria with ease. Bacteria do not contain membrane-bound organelles such as mitochondria or chloroplasts, as eukaryotes do. However, photosynthetic bacteria, such as cyanobacteria, may be filled with tightly packed folds of their outer membrane.