page_title: Marine microbial symbiosis
section_title: Mechanisms of symbiosis
hierarchical_section_title: Marine microbial symbiosis / Mechanisms of symbiosis
caption_attribution_description: English: Main types of microbial symbioses (A) Microbial interactions range from mutually beneficial to harmful for one or more partners. Blue double headed arrows highlight that relationships can move between classifications often influenced by environmental conditions. (B) Host-microbe symbioses should be considered within the context of microbial communities where the host participates in multiple and often different symbiotic relationships. (C) Microbial communities are influenced by a variety of microbe-microbe symbioses ranging from cooperation (e.g., syntrophy or co-metabolism) to competition. Arrows depict generally beneficial (blue) and detrimental (red) outcomes for one (single arrowhead) or both (double arrowhead) members. Note as with host-microbe symbioses these relationships can be viewed as fluid and influenced by environmental conditions.
context_page_description: Microbial symbiosis in marine animals was not discovered until 1981. In the time following, symbiotic relationships between marine invertebrates and chemoautotrophic bacteria have been found in a variety of ecosystems, ranging from shallow coastal waters to deep-sea hydrothermal vents. Symbiosis is a way for marine organisms to find creative ways to survive in a very dynamic environment. They are different in relation to how dependent the organisms are on each other or how they are associated. It is also considered a selective force behind evolution in some scientific aspects. The symbiotic relationships of organisms has the ability to change behavior, morphology and metabolic pathways. With increased recognition and research, new terminology also arises, such as holobiont, which the relationship between a host and its symbionts as one grouping. Many scientists will look at the hologenome, which is the combined genetic information of the host and its symbionts. These terms are more commonly used to describe microbial symbionts.
  The type of marine animal vary greatly, for example, sponges, sea squirts, corals, worms, and algae all host a variety of unique symbionts.
context_section_description: Various mechanisms are utilized in order to facilitate symbiotic relationships and to help these associates evolve alongside one another.  By using horizontal gene transfer, certain genetic elements are able to pass from one organisms to another.  In non-mating species, this helps with genetic differentiation and adaptive evolution.  An example of this is the sponge Astroclera willeyana which has a gene that is used in expressing spherulite-forming cells which has an origin in bacteria.  Another example is the starlet sea anemone, Nematostella vectensis, which has genes from bacteria that have a role in producing UV radiation protection in the form of shikimic acid.  Another way for symbiotic relationships to co-evolve is through genome erosion.  This is a process where genes that are typically used during free-living periods aren't necessary because of the symbioses of the organisms.  Without that gene, the organism is able to decrease the energy necessary for cell maintenance and replication.
caption: Main types of microbial symbioses (A) Microbial interactions range from mutually beneficial to harmful for one or more partners. Blue double headed arrows highlight that relationships can move between classifications often influenced by environmental conditions. (B) Host-microbe symbioses should be considered within the context of microbial communities where the host participates in multiple and often different symbiotic relationships. (C) Microbial communities are influenced by a variety of microbe-microbe symbioses ranging from cooperation (e.g., syntrophy or co-metabolism) to competition. Arrows depict generally beneficial (blue) and detrimental (red) outcomes for one (single arrowhead) or both (double arrowhead) members. Note as with host-microbe symbioses these relationships can be viewed as fluid and influenced by environmental conditions.[7]
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