Bioluminescence has evolved independently many times; thus the responsible genes are unrelated in bacteria, unicellular algae, coelenterates, beetles, fishes, and others. Chemically, all involve exergonic reactions of molecular oxygen with different substrates (luciferins) and enzymes (luciferases), resulting in photons of visible light (approximately 50 kcal). In addition to the structure of luciferan, several factors determine the color of the emissions, such as the amino acid sequence of the luciferase (as in beetles, for example) or the presence of accessory proteins, notably GFP, discovered in coelenterates and now used as a reporter of gene expression and a cellular marker. The mechanisms used to control the intensity and kinetics of luminescence, often emitted as flashes, also vary. Bioluminescence is credited with the discovery of how some bacteria, luminous or not, sense their density and regulate specific genes by chemical communication, as in the fascinating example of symbiosis between luminous bacteria and squid.

94% 6%tinguishable from the conjugate obtained directly from naphthalene with microsomes, supernatant, and glutathione. The opening of the oxide II by glutathione also occurs nonenzymatically, but at a much slower rate.During these incubations the oxide also undergoes spontaneous isomerization to 1-naphthol. Likewise, the phenol formed from naphthalene by microsomes is also 1-naphthol.When the glutathione-conjugating system and increasing amounts of glutathione are added to liver microsomal perparations, III and IV decrease as more and more of the oxide is trapped as V. This experiment suggests that 1,2-naphthalene oxide is the obligatory intermediate in the enzymatic hydroxylation of naphthalene. That arene oxides are in general intermediates on the pathway of the hydroxylation of aromatic substrates becomes now an attractive assumption.The current view on microsomal mixed-function oxygenation favors an oxygen atom transfer reaction8 rather than endoperoxide intermediates.9,10 Complete biochemical details will be published elsewhere.

The specificity of the glycerol facilitator (glpF) of Escherichia coli was studied with an osmotic method. This transport system allowed the entry of polyols (glycerol and erythritol), pentitols, and hexitols. The analogous sugars were not transported. However, urea, glycine, and DL-glyceraldehyde could use this pathway to enter the cell. The glpF protein allowed the rapid efflux of preequilibrated xylitol. Glycerol surprisingly did not inhibit the uptake of xylitol, and xylitol only slightly reduced the uptake of glycerol. The observation and the insensitivity of the xylitol transport to low temperature suggest that the facilitator behaves as a membrane channel.

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When cells of Streptococcus lactis or Escherichia coli were suspended in-a potassium-free medium, a membrane potential (negative inside) could be artificially generated by the addition of-the potassium ionophore, valinomycin. In 'response to this inward directed protonmotive force, ATP synthesis catalyzed by the mnembrane-bound'ATPase (EC 3.6.1.3) was observed. (Fig. 1A). Thus, the electrochemical potential of protons (the protonmotive force) provides the driving force for ATP synthesis. The alternative (anaerobic) function of the ATPase is required when protons cannot be extruded by the respiratory chain. Under these conditions, the ATPase couples the hydrolysis of ATP to the electrogenic movement of protons out of the cell (Fig. 11B). The protonmotive force generated by ATP hydrolysis is then utilized by energy-dependent reactions such as the "ATP-linked" transhydrogenase, or the active transport of metabolites.Evidence in support of this anaerobic function of the ATPase has been presented by Harold and his collaborators, who have studied the anaerobe S. fecalis (faecium). They showed that glycolyzing cells establish both a pH gradient (interior alkaline) and a membrane potential (interior negative), and that DCCD inhibits the formation of each of these components of the protonmotive force (17)(18)(19) 1% (w/v)