Corals Corals have been found to form characteristic associations with symbiotic nitrogen-fixing bacteria. Corals have evolved in oligotrophic waters which are typically poor in nitrogen. Corals must therefore form a mutualistic relationship with nitrogen fixing organism, in this case the subject of this study, namely
Symbiodinium. In addition to this dinoflagellate, coral also form relationships with bacteria, archae and fungi. The problem is that these dinoflagellates are also nitrogen limited and must form a symbiotic relationship with another organism; here it is suggested to be diazotrophs. In addition, cyanobacteria have been found to possess genes that enable them to undergo nitrogen fixation. that Holospora species can maintain their infectivity for a limited time and form a symbiotic relationship with Paramecium species.
Plants and rhizobial bacteria There is a mutualistic relationship between legumes and rhizobial bacteria enabling the plants to survive in an otherwise nitrogen-poor soil environment. Co-evolution is described as a situation where two organisms evolve in response to one another. In a study reported in
Functional Ecology, these scientists investigated whether such a mutualistic relationship conferred an evolutionary advantage to either plant or symbiont. They did not find that the rhizobial bacteria studied had any evolutionary advantage with their host but did find great genetic variation among the populations of rhizobial bacteria studied.
Chemosynthetic Bacteria and Mussels Symbiotic, chemosynthetic bacteria that have been discovered associated with mussels (
Bathymodiolus) located near hydrothermal vents have a gene that enables them to utilize hydrogen as a source of energy, in preference to sulphur or methane as their energy source for production of energy.
Trichonympha is an endosymbiont that lives inside termites and also acts as a host to bacterial symbionts. The bacteria inside
Trichonympha in termites produces cellulase. Cellulase enzymes are used to break down cellulose which is found in plants' cell walls. The termites, the gut protist
Trichonympha, and the cellulase-producing bacteria are all involved in a 3-way obligate symbiotic mutualism. The termites benefit from the other two species because they transform the wood into nutrients that the termites can digest. Additionally, the
Trichonympha benefit from the termites because the termites provide a place to live and access to food. The
Trichonympha also benefit from the bacteria because they help break down the cellulose in wood that the protist consumes. Finally, the bacteria benefits because it gains a place to live and the nutrients it needs to survive.
Symbiotic Bacteria in Humans Gut Bacteria The human gut contains approximately thirty-eight trillion microbes. The gut is a dynamic ecosystem as it is composed of both constant and transient components, meaning some bacteria establish themselves and remain throughout the human's lifetime and other bacteria are ingested and later leave in feces. When babies are born, they are born without any bacteria in their intestines. However, as soon as they enter the world, they begin accumulating gut bacteria through food and other means. Most bacteria in the human body are actually good for us and help with carrying out necessary life processes. Gut bacteria in humans often aid in the breakdown of foods and synthesize important vitamins that could not be processed by humans alone. Therefore, humans must be careful when taking
antibiotics when they are sick. Antibiotics do not differentiate between the good and bad bacteria in our bodies and therefore, kill both. If not treated carefully, this can lead to issues with the gastrointestinal tract because of an imbalance of bacteria in this microbiome. Therefore, some doctors recommend taking a probiotic when taking antibiotics to restore the good bacteria. == Benefits of Bacterial Symbiosis ==