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Aposymbiosis occurs when symbiotic organisms live apart from one another (for example, a
Aposymbiosis occurs when symbiotic organisms live apart from one another (for example, a clownfish
Clownfish or anemonefish are fishes from the subfamily Amphiprioninae in the family Pomacentridae. Thirty species of clownfish are recognized: one in the genus '' Premnas'', while the remaining are in the genus '' Amphiprion''. In the wild, t ...
living independently of a sea anemone). Studies have shown that the lifecycles of both the host and the symbiont are affected in some way, usually negative, and that for obligate symbiosis the effects can be drastic.A. E. Douglas, Requirement of pea aphids (''Acyrthosiphon pisum'') for their symbiotic bacteria, Entomologia Experimentalis et Applicata (Historical Archive), Volume 65, Issue 2, Nov 1992, Pages 195–198 Aposymbiosis is distinct from exsymbiosis, which occurs when organisms are recently separated from a symbiotic association. Because symbionts can be vertically transmitted from parent to offspring or horizontally transmitted from the environment, the presence of an aposymbiotic state suggests that transmission of the symbiont is horizontal. A classical example of a symbiotic relationship with an aposymbiotic state is the Hawaiian bobtail squid '' Euprymna scolopes'' and the bioluminescent bacteria ''Vibrio fischeri
''Aliivibrio fischeri'' (also called ''Vibrio fischeri'') is a Gram-negative, rod-shaped bacterium found globally in marine environments. This species has bioluminescent properties, and is found predominantly in symbiosis with various marine anim ...
.'' While the nocturnal squid hunts, the bacteria emit light of similar intensity of the moon which camouflages the squid from predators. Juveniles are colonized within hours of hatching and ''Vibrio'' must outcompete other bacteria in the seawater through a system of recognition and infection.
Use in research
Aposymbiotic organisms can be used as models to observe a variety of processes. Aposymbiotic ''Euprymna'' juveniles have been studied throughout colonization in order to determine the system of recognizing ''Vibrio fischeri'' in seawater. Coral polyps without their symbiont algae are models for coral calcification and the effects of the algae on coral pH regulation. Aposymbiotic insects are used to model insect-bacteria relationships and modes of infection. These models are also used in arthropod vectors and disease transmission. ''Wolbachia
''Wolbachia'' is a genus of intracellular bacteria that infects mainly arthropod species, including a high proportion of insects, and also some nematodes. It is one of the most common parasitic microbes, and is possibly the most common reproducti ...
'' species are common insect endosymbionts and investigation into this species has yielded potential human health implications. Additionally, aposymbiotic wasps without ''Wolbachia'' are unable to reproduce. This relationship between ''Asobara tabida'' wasps and ''Wolbachia'' is an important model for insect microbiome study.
Health
Women who are aposymbiotic for certain ''Lactobacillus
''Lactobacillus'' is a genus of Gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...
'' species are more susceptible to urinary tract infections and bacterial vaginosis. Additionally, these ''Lactobacilli'' are of interest for use as a probiotic therapeutic alternative to antibiotics.
Aposymbiotic vectors, especially insects, have been used to study disease transmission. Furthermore, aposymbiotic and dysbiotic vectors are being engineered to change the rate and efficiency of disease transmission. Arthropod infection with ''Wolbachia'' can cause sterility and inhibit the transmission of vector-borne diseases.
See also
*References