Symbiotic luminous bacteria

The source of light emission. Each individual animal in a colony of Pyrosoma has two groups of luminous cells at the entrance to the branchial sac (Herring, 1978a). The luminous cells contain tubular inclusions whose identity has been a matter of dispute for nearly a century. Buchner (1914) originally suggested that the inclusions were symbiotic luminous bacteria. However, efforts to cultivate luminous bacteria from the luminous cells of Pyrosoma consistently failed. In... 

EXPULSION OF SYMBIOTIC LUMINOUS BACTERIA FROM PONY FISH, LEIOGNATHUS NUCHALIS... 

Expulsion of Symbiotic Luminous Bacteria from Pony Fish... 

Nonetheless, the consistent and periodic SW light emission in repeated trials can be best explained by the expulsion of the symbiotic luminous bacteria. ... 

Wada M, Azuma N, Mizuno N, Kurokura H. Transfer of symbiotic luminous bacteria from parental Leiognathus nuchalis to their offspring. Mar Biol 1999 135 683-87. 

Hastings JW, Nealson KH. The symbiotic luminous bacteria. In Starr MP, Stolp H, Triiper HG, Balows A, Schlegel HG. eds. The Prokaryotes A Handbook on Habitats, Isolation, and Identification of Bacteria. Berlin Springer-Verlag, 1981 1322-45. 

For bioluminescent symbiotic fish and squid, expulsion of luminous bacteria into surrounding SW is a fundamental process that ensures horizontal transfer of the bacterial partner to future host generations. Considering the sophisticated coordination of various shutter mechanisms surrounding the internal LO of leiognathids, we believe the expulsion event to be a finely controlled discharge of symbiotic bacteria, rather than an uncontrolled phenomenon. 

Quorum sensing may be useful for symbiotic associations, and especially for bioluminescent fish and ceph-alopods. The Hawaiian squid Euprymna sco/opcs hosts the luminous bacteria Vibrio fisheri in its light organs, and uses quorum sensing to bioluminescence at high cell densities with 3-oxo-C6-HSL as autoinducer (Ruby and Lee, 1998). 

In contrast to the bacterial-squid story, little is known about the horizontal transfer of luminous symbionts in bacteria-fish symbioses. Recently, however, we successfully raised Leiognathus nuchalis, pony fish juveniles, and infected them with symbiotic Photobacterium leiognathi. Juvenile L nuchalis raised separately from adults are apo-symbiotic and therefore not luminous. When the juveniles were kept with adults, a significant number became infected and luminescent. These results strongly support, the horizontal transfer of expelled P. leiognathi. 

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