Bacteria, luminescent

Physiological Role of Citric Acid. Citric acid occurs ia the terminal oxidative metabolic system of virtually all organisms. This oxidative metabohc system (Fig. 2), variously called the Krebs cycle (for its discoverer, H. A. Krebs), the tricarboxyUc acid cycle, or the citric acid cycle, is a metaboHc cycle involving the conversion of carbohydrates, fats, or proteins to carbon dioxide and water. This cycle releases energy necessary for an organism s growth, movement, luminescence, chemosynthesis, and reproduction. The cycle also provides the carbon-containing materials from which cells synthesize amino acids and fats. Many yeasts, molds, and bacteria conduct the citric acid cycle, and can be selected for thek abiUty to maximize citric acid production in the process. This is the basis for the efficient commercial fermentation processes used today to produce citric acid. 

If the luciferase sample solution contains a flavin-reductase, luciferase activity can be measured by the addition of FMN and NADH, instead of FMNH2. In this case, the turnover of luciferase takes place repeatedly using the FMNH2 that is enzymatically generated thus, the luminescence reaction continues until aldehyde or NADH is exhausted. A crude luciferase extracted from luminous bacteria usually contains a flavin-reductase. 

The autoinducer is a low molecular weight compound that is easily leached from the cells into the culture medium. By the propagation of bacterial cells, the concentration of the autoinducer in the medium increases. When the concentration reaches a certain threshold, the biosynthesis of bioluminescence system begins, and the bacteria become luminescent. The process is also called quorum sensing (Fuqua et al., 1994). 

Fig. 2.3 Luminescence spectra of the living cells of luminous bacteria. F, P. fischeri P, P. phosphoreum (Eley etal., 1970) Y, P. fischeri, strain Y-l (Ruby and Nealson, 1977). Reproduced with permission from the American Chemical Society and AAAS.

Heat stability The Oplophorus luminescence system is more thermostable than several other known bioluminescence systems the most stable system presently known is that of Periphylla (Section 4.5). The luminescence of the Oplophorus system is optimum at about 40°C in reference to light intensity (Fig. 3.3.3 Shimomura et al., 1978). The quantum yield of coelenterazine is nearly constant from 0°C to 20°C, decreasing slightly while the temperature is increased up to 50°C (Fig. 3.3.3) at temperatures above 50°C, the inactivation of luciferase becomes too rapid to obtain reliable data of quantum yield. In contrast, in the bioluminescence systems of Cypridina, Latia, Chaetopterus, luminous bacteria and aequorin, the relative quantum yields decrease steeply when the temperature is raised, and become almost zero at a temperature near 40-50°C (Shimomura et al., 1978). 

The New Zealand freshwater limpet Latia neritoides (Fig. 6.1.1) is the only known example of a freshwater luminous organism, with two possible exceptions certain species of luminous bacteria and the larvae of certain species of fireflies. The limpet inhabits shallow clear streams in the North Island of New Zealand, clinging to stones and rocks. Latia has a small oval-shaped shell (6-8 mm long), and secretes a luminous mucus that emits a greenish glow around the body only when disturbed the limpet does not show a spontaneous luminescence. The luminescence of Latia was first reported by Suter (1890) and further details including a positive luciferin-luciferase reaction were described by Bowden (1950). Both the luciferin and the luciferase have... 

Low luciferin content. Luminous fungus in various growth stages contains relatively small amounts of luciferin that can sustain the luminescence for a period of only 3-100 s, in resemblance to the situation found in luminous bacteria. In luminous bacteria,... 

Ferri, S. R., and Meighen, E. A. (1991). A Lux-specific myristoyl transferase in luminescent bacteria related to eukaryotic serine esterases. J. Biol. Chem. 266 12852-12857. 

Hirose, E., Aoki, M., and Chiba, K. (1996). Fine structures of tunic cells and distribution of bacteria in the tunic of the luminescent ascidian Clavelina miniate. Zool. Sci. 13 519-523. 

Johnston, T. C., et al. (1990). The nucleotide sequence of the luxA and luxB genes of Xenorhabdus luminescence HM and a comparison of the amino acid sequences of luciferases from four species of bioluminescent bacteria. Biochem. Biophys. Res. Commun. 170 407- 115. 

Bioluminescence can be used for spedfic detection of separated bioactive compounds on layers (BioTLC) [46]. After development and drying the mobile phase by evaporation, the layer is coated with microorganisms by immersion of the plate. Single bioactive substances in multicomponent samples are located as zones of differing luminescence. The choice of the luminescent cells determines the specificity of detection. A specific example is the use of the marine bacterium Vibrio fischeri with the BioTLC format. The bioluminescence of the bacteria cells on the layer is reduced by toxic substances, which are detected as dark zones on a fluorescent background. BioTLC kits are available from ChromaDex, Inc. (Santa Ana, CA). 

Pivato A, Gaspari L (2006) Acute toxicity test of leachates from traditional and sustainable landfills using luminescent bacteria. Waste Manag 26(10) 1148-1155... 

The bacterial bioluminescent reaction is also catalyzed by a luciferase (EC 1.14.14.3) isolated from marine bacteria. The four most studied types are Vibrio harveyi, Vibrio fischeri, Photobacterium phosphoreum and Photobacterium leiognathi18, 19. In these different luminescent bacteria the... 

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