Biologists separate the bacteria into two groups that differ in the composition of their cell walls and cell membranes and in the structure of some of their proteins. Because the differences between these two group are so great, it is likely that they diverged early in the history of life. One group is the eubacteria, or "true bacteria" the most common bacteria today. Most living bacteria, including those that cause disease and decay, are eubacteria. Eukaryotic cells contain mitochondria and chloroplast, which are probably descendants of ancient eubacteria.
Divergent Event
The ancestors of modern bacteria were single-celled microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, all organisms were microscopic, and bacteria and archaea were the dominant forms of life. Eukaryotes resulted from ancient bacteria entering into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea. This involved the engulfment by proto-eukaryotic cells of alpha-proteobacterial symbionts to form either mitochondria or hydrogenosomes, which are still found in all known Eukarya (sometimes in highlyreduced form, e.g. in ancient "amitochondrial" protozoa).
Body Plan is unicellular.
Metabolism
Heterotrophs: This bacteria lives about anywhere, including in your body the form of a parasite. Saprobes feed off of non-living organisms and recycles the nutrients back in to the environment where it can be used to create new life.
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| Bacillus |
Autotrophs: This bacteria obtains energy through photosynthesis. Most are blue-green color and are often called blue-green bacteria. They get this color from chlorophyll, which is also found in plants. They typically live in chains in ponds, lakes, and moist regions.
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| Chloroflexi |
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| Thiobacillus ferrooxidans |
Nervous: no specific system.
Circulatory: no specific system.
Respiratory
Respiration of eubacteria may be either aerobic, which is the metabolic process that uses oxygen to break down food and release energy, or anaerobic, a way for an organism to produce usable energy without the involvement of oxygen. Anaerobes undergo a form of respiration called fermentation.
Reproduction
Bacteria can reproduce at tremendous speeds. Some bacteria can reproduce as often as once every 20 minutes! However, bacteria have to have certain conditions in which to reproduce. These conditions are not often met, and tat is one thing that keeps bacteria from growing out of control.
Bacteria reproduce using two basic methods: asexual and sexual reproduction.
- Asexual reproduction involves only one individual or parent. The offspring generated by sexual reproduction are exact duplicates of the parent. Binary fission is the process by which a bacteria splits into two cells. Each cell gets an exact copy of the parent cell's genetic material.
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| Binary Fission |
- Sexual reproduction involves the joining of two parent cells and the exchanging of genetic materials. In sexual reproduction, the offspring will have a mixture of the parent cells' traits. Conjugation is the proces by which bacteria join and exchange genetic materials. Once genetic materials are exchanged, each bacteria cell will go through binary fission to produce an offspring with a new genetic makeup.
Examples
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| Clostridium perfringens |
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Bacillus antracis |
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Esherischia coli |
