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Symbiotic bacteria are able to live in or on plant or animal tissue. In digestive systems, symbiotic bacteria help break down foods that contain fiber. They also help produce vitamins. Symbiotic bacteria can live near hydrothermal vents. They usually have a mutual relationship with other bacteria. Some live in tube worms.
Humans are home to 10 13 to 10 14 bacteria, roughly equivalent to the number of human cells, [2] and while these bacteria can be pathogenic to their host most of them are mutually beneficial to both the host and bacteria. The human immune system consists of two main types of immunity: innate and adaptive.
They evolved from symbiotic bacteria and retain a remnant genome. [59] Like bacteria, plant cells have cell walls, and contain organelles such as chloroplasts in addition to the organelles in other eukaryotes. Chloroplasts produce energy from light by photosynthesis, and were also originally symbiotic bacteria. [59]
Endogenosymbiosis is an evolutionary process, proposed by the evolutionary and environmental biologist Roberto Cazzolla Gatti, in which "gene carriers" (viruses, retroviruses and bacteriophages) and symbiotic prokaryotic cells (bacteria or archaea) could share parts or all of their genomes in an endogenous symbiotic relationship with their hosts.
Graphic depicting the human skin microbiota, with relative prevalences of various classes of bacteria. The human microbiome is the aggregate of all microbiota that reside on or within human tissues and biofluids along with the corresponding anatomical sites in which they reside, [1] [2] including the gastrointestinal tract, skin, mammary glands, seminal fluid, uterus, ovarian follicles, lung ...
Primary endosymbionts of insects have among the smallest of known bacterial genomes and have lost many genes commonly found in closely related bacteria. One theory claimed that some of these genes are not needed in the environment of the host insect cell.
According to endosymbiotic theory, extreme cases of primary endosymbionts include mitochondria, plastids (including chloroplasts), and possibly other organelles of eukaryotic cells. Primary endosymbionts are usually transmitted exclusively vertically, and the relationship is always mutualistic and generally obligate for both partners.
Symbionts forming a single body live in conjunctive symbiosis, while all other arrangements are called disjunctive symbiosis. [4] When one organism lives on the surface of another, such as head lice on humans, it is called ectosymbiosis; when one partner lives inside the tissues of another, such as Symbiodinium within coral, it is termed ...