Photobacteria

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Photobacteria
Photobacterium damselae

Photobacterium damselae

Systematics
Domain : Bacteria (bacteria)
Department : Proteobacteria (Proteobacteria)
Class : Gammaproteobacteria
Order : Vibrional
Family : Vibrionaceae
Genre : Photobacteria
Scientific name
Photobacterium
Beijerinck 1889

Photobacteria ( Photobacterium ) are a genus of gram-negative bacteria and belong to the Vibrionaceae family . Some members of this genus have the ability to produce light and are therefore bioluminescent .

Many species, including Photobacterium leiognathi and Photobacterium phosphoreum , live in symbiosis with marine life. Species such as Photobacterium profundum are adapted to optimal growth in deep, cold seas or lakes. They are psychrophilic (cold- loving) and barophilic (pressure-loving).

features

The bacteria appear as straight or curved rods with the dimensions 0.8–1.3 × 1.8–2.4 µm. The Gram stain turns out negative, so they are Gram- negative bacteria. With the exception of P. damselae subsp. piscicida they move by means of mostly 1 to 3 non-membrane-covered, polar flagella . Endospores are not formed. The bacteria are chemotrophic and capable of fermentation (fermentation). They need sodium to grow .

ecology

Photobacteria are predominantly marine life (hence the use of sodium for growth). They can be free-living or occur in colonies. These organisms do not contain any pigmentation and therefore their colonies appear white or colorless. When there is a high density of cells forming a colony, they show bioluminescence . This is based on autoinducers , which are proportional to the cell density. Therefore, free living photobacteria do not glow.

Their colonization by fish could be of a symbiotic nature, namely for the formation of luminous organs as a neutral unit on the surface or within the intestines of the fish. Their occurrence in fish is also discussed as a protection against disease.

Pathogenicity

Some of the 23 known species of Photobacterium have emerged as pathogens to marine life. Many of these diseases affect fish that are important to trade and can indirectly affect human health through consumption. Among other things, it was observed how the chitin of the deep-sea crab ( Chinoecetes tanneri ) was broken down.

The most virulent strains belong to the species Photobacterium damselae . This species is divided into two subspecies: P. d. subsp. piscicida and P. d. subsp. damsela .

Photobacterium damselae subsp. piscicida

Photobacterium damselae subsp. piscicida is the causative agent of fish pasteurellosis . Bacterial colonies grow on the infected spleen and kidney of the fish and eventually lead to death. This disease is responsible for large losses in some fish farms. Affected species include, among others, the yellowfin tuna ( Thunnus albacares ), some sea bream ( Sparus spp. ), The striped bass ( Marone saxatilis ) and sea bass ( Marone americana ). Photobacterium damselae subsp. piscicida is not pathogenic to humans.

Photobacterium damselae subsp. damselae

The subspecies P. d. subsp. damelae also attacks fish. It caused in some fish species is a sepsis such as in groupers (family Pomacentridae), eels ( Anguilla anguilla ), sandbar sharks ( Carcharhinus plumbeus ) , jackfish ( Seriiola quinqueradiata ), sea bream ( Sparus spp. ) And the turbot ( Scophtalmus spp. ). This subspecies has been shown to be pathogenic to humans when it spread from human wounds and caused sepsis in healthy humans.

Symptoms

Fishes with the subspecies P. d. subsp. damselae were infected, initially showed symptoms such as a reduced appetite accompanied by a lack of energy and festering wounds along their flanks and in the head region. Their stomachs puffed up and they began to bleed significantly, especially in their eyes, mouth, and muscles. In addition, there was bleeding in the liver and gills with a characteristic accumulation of mucus around them. The infected fish were found to swim faster a few minutes before death occurred.

Transmission / infection

Signs of the spread of this animal disease are accumulations of ulcers in the fish population, usually in combination with higher temperatures in the environment. The spread of the disease is split seasonally. This can be seen from the dependence on the water temperature and the salinity. The resistance of the bacteria increases due to physiological changes during the host's sexual maturity.

Once in contact with the outer surface of the fish, they are able to adhere to the skin and suppress the bactericidal effect of the fish's mucus layer. Hence, it is believed that the skin is the access point to the host. This bacterium can become a major threat to aquaculture , especially in crowded and cramped habitats, exposing the fish to stress . The spread of the disease can be accelerated through direct contact.

Use of bioluminescence for Photobacterium leiognathi

During studies of the effects of the luminescent bacteria Photobacterium leiognathi in the sea, it was found that the glow of photobacteria is of great importance for predators. Food particles that are colonized by Photobacterium leiognathi are discovered faster than those that are not. The Photobacterium leiognathi survives in the bowels of the animal, multiplies there and spreads with its faeces in the water. This has the advantage that Photobacterium leiognathi colonizes a safe habitat in the intestines and enables it to spread quickly.

But not only the Photobacterium leiognathi benefits from it, the predator is also favored. In the depths of the sea, where food is scarce, he finds the shining food better. However, the ingestion of food and the associated luminescence make it easier prey itself, with the advantage of finding food at all apparently outweighing this disadvantage.

Some predators have pigments in their intestines that block light emission and thus counteract the disadvantage of luminescence. The Photobacterium leiognathi is only visible again in the feces.

species

Some types:

Individual evidence

  1. ↑ a b c Dongyou Liu: Molecular Detection of Human Bacterial Pathogens. Crc Press 2011, ISBN 978-1439812389 , p. 960.
  2. ^ KH Nealson, JW Hastings: Bacterial bioluminescence: its control and ecolocigal significance. In: Microbiological Reviews , Vol. 43, 1979, pp. 496-518. PMC 281490 (free full text).
  3. ^ Brian Austin, Dawn A. Austin: Bacterial Fish Pathogens: Disease of Farmed and Wild Fish ; Springer Verlag, 4th edition ISBN 9781402060687
  4. ↑ Osorio, Toranzo, Romalde, Barja (2000): Multiplex PCR assay for ureC and 16S rRNA genes clearly discriminates between both subspecies of Photobacterium damselae. In: Diseases of Aquatic Organisms 40, pp. 177-183.
  5. ↑ B. Fouz, AE Toranzo, M. Milán, C. Amaro: Evidence that water transmits the disease caused by the fish pathogen Photobacterium damselae subsp. damselae : In: Journal of Applied Microbiology , Volume 88, Issue 3, December 25, 2001 doi : 10.1046 / j.1365-2672.2000.00992.x .
  6. ↑ M. Zarubin et al .: Bacterial bioluminescence as a lure for marine zooplankton and fish. In: Proceedings of the National Academy of Sciences. 109, 2012, p. 853, doi : 10.1073 / pnas.1116683109 .
  7. ↑ LPSN ( Memento of the original from March 3, 2012 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , List of known photobacteria, October 4, 2012. @1@ 2Template: Webachiv / IABot / www.bacterio.cict.fr

literature

  • Martin Dworkin, Stanley Falkow, Eugene Rosenberg, Karl-Heinz Schleifer, Erko Stackebrandt (Eds.) The Prokaryotes, A Handbook of the Biology of Bacteria. 7 volumes, 3rd edition, Springer-Verlag, New York et al. O., 2006, Vol. 6: Proteobacteria: Gamma Subclass. ISBN 0-387-30746-X .