A Membrane-Enclosed Nucleus

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Bacteria
Bacteria are microscopic organisms whose single cells have neither a membrane-enclosed nucleus nor other membrane-enclosed organelles like mitochondria and chloroplasts. Another group of microbes, the archaea, meet these criteria but are very different from the bacteria in other ways. In fact, there is considerable evidence that you are more closely related to the archaea than they are to the bacteria! Bacteria are living things that are neither plants nor animals, but belong to a group all by themselves. They are very small--individually not more than one single cell--however there are normally millions of them together, for they can multiply really fast. A number of bacteria cause disease, these are called pathogenic bacteria. Fortunately our immune system knows how to deal with them. However not all bacteria are 'bad guys'. We need bacteria to stay alive.Bacteria are prokaryotes (single cells that do not contain a nucleus). Microbiology is the study of prokaryotes, eukaryotes and viruses. Did you know that bacteria can get sick too. Bacteriophages are able to attach themselves to certain types of bacteria and inject their genetic material in the bacterial cell. Then, using the bacterial machinery, the DNA multiplies itself. Eventually from this multiplied genetic information so many new bacteriophages are formed that the cell bursts. The offspring of the bacteriophage has destroyed its bacterial host, and in so doing millions of new bacteriophages are released. These can attach themselves to new bacteria to complete their life cycle. With our immune system we defend ourselves against a bacterial infection. Antibiotics can help us win the battle. When you report a bacterial infection to your physician, you are probably prescribed antibiotics. The term 'antibiotics' (literally 'against living things') is mainly used for substances that kill or prevent the growth of bacteria, as opposed to antiviral or antifungal substances. Antibiotics are not active...
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