Жарқыраған бактерия: Aliivibrio fischeri және теңіз жануарларымен симбиозы

Species of bacterium

Aliivibrio fischeri (formerly 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 animals, such as the Hawaiian bobtail squid. It is heterotrophic, oxidase positive, and motile by means of a single polar flagella. Free living A. fischeri cells survive on decaying organic matter. The bacterium is a key research organism for examination of microbial bioluminescence, quorum sensing, and bacterial animal symbiosis. It is named after Bernhard Fischer, a German microbiologist. Ribosomal RNA comparison led to the reclassification of this species from genus Vibrio to the newly created Aliivibrio in 2007. The change is valid publication, and according to LPSN the correct name. However, the name change is not generally accepted by most researchers, who still publish Vibrio fischeri (see Google Scholar for 2018–2019).

The genome for A. fischeri was completely sequenced in 2004 and consists of two chromosomes, one smaller and one larger. Chromosome 1 has 2.9 million base pairs (Mbp) and chromosome 2 has 1.3 Mbp, bringing the total genome to 4.2 Mbp. This relationship has been best characterized in the Hawaiian bobtail squid (Euprymna scolopes), where A. fischeri is the only species of bacteria inhabiting the squid's light organ.

A. fischeri colonization of the light organ of the Hawaiian bobtail squid is currently studied as a simple model for mutualistic symbiosis, as it contains only two species and A. fischeri can be cultured in a lab and genetically modified. This mutualistic symbiosis functions primarily due to A. fischeri bioluminescence. A. fischeri colonizes the light organ of the Hawaiian bobtail squid and luminesces at night, providing the squid with counter illumination camouflage, which prevents the squid from casting a shadow on the ocean floor. A. fischeri colonization occurs in juvenile squids and induces morphological changes in the squids light organ. Interestingly, certain morphological changes made by A. fischeri do not occur when the microbe cannot luminesce, indicating that bioluminescence (described below) is truly essential for symbiosis. In the process of colonization, ciliated cells within the animals' photophores (light producing organs) selectively draw in the symbiotic bacteria. These cells promote the growth of the symbionts and actively reject any competitors. The bacteria cause these cells to die off once the light organ is sufficiently colonized. The light organs of certain squid contain reflective plates that intensify and direct the light produced, due to proteins known as reflectins. They regulate the light for counter illumination camouflage, requiring the intensity to match that of the sea surface above. Sepiolid squid expel 90% of the symbiotic bacteria in their light organ each morning in a process known as "venting". Venting is thought to provide the source from which newly hatched squid are colonized by A. fischeri.

Natural bacterial transformation is an adaptation for transferring DNA from one individual cell to another. Natural transformation, including the uptake and incorporation of exogenous DNA into the recipient genome, has been demonstrated in A. fischeri. This process requires induction by chitohexaose and is likely regulated by genes tfoX and tfoY. Natural transformation of A. fischeri facilitates rapid transfer of mutant genes across strains and provides a useful tool for experimental genetic manipulation in this species.

In 2014, Hawaiian State Senator Glenn Wakai submitted SB3124 proposing Aliivibrio fischeri as the state microbe of Hawaii. The bill was in competition with a bill to make Flavobacterium akiainvivens the state microbe, but neither passed. In 2017, legislation similar to the original 2013 F. akiainvivens bill was submitted in the Hawaii House of Representatives by Isaac Choy and in the Hawaii Senate by Brian Taniguchi.