Biochemistry and physiology of bioluminescent bacteria

Light organ symbioses in fishes

Most bioluminescent fishes are self-luminescent, but a substantial minority of bioluminescent teleosts produce light that is due to symbiotic luminous bacteria housed in elaborate light organs. The majority of symbiotically bioluminescent fishes (ten families in five orders) harbors common free-living species of marine luminous bacteria: Photobacterium phosphoreum, P. leiognathi, and P. fischeri (= Vibrio fischeri). Others, associated with the beryciform family Anomalopidae and nine families in the lophiiform suborder Ceratioidei, have apparently obligate symbionts that have recently been identified by small subunit (16S) rRNA analysis as new groups within the genus Vibrio. This article summarizes what is currently known about relationships between light organ symbionts and their hosts, including characteristics of light organ environments, physiology of light organ symbionts, and the evolution of light organ symbionts and their associations.

Chemiluminescence in the crude extracts of soybean seedlings. Postulated mechanism on the formation of hydroperoxide intermediates

It has been reported that weak chemiluminescence (CL) from crude extracts of soybean seedlings is remarkably enhanced with the addition of various aldehydes (Biochim. Biophys. Acta 1058, 209-216). The reactivity of certain emitter(s) with oxygen species was examined in the autoclaved extracts of seedlings. When samples were reduced by the addition of hydrosulfite, two different types of reactivities in CL were defined. One type showed an initial rapid increase and a subsequent fast decay in CL upon mixing with oxygen. This rapid increase in CL intensity was independent of the presence of aldehydes, and was significantly suppressed by SOD. However, the subsequent slow decay phase in CL was dependent on the presence of aldehydes. In the sample reduced more moderately by borohydride, the same slow decay of CL appeared upon mixing with acetaldehyde and oxygen. This second type of CL was not inhibited by active oxygen scavengers. Hydrogen peroxide added to unreduced (oxidized) samples also elicited CL. Three types of primary emitters may be oxidized to form transient hydroperoxide, and excited for light emission by slightly different ways: two of them are excited by abstraction of one atomic oxygen from the hydroperoxy intermediate with aldehyde or hydrogen peroxide, leading to formation of an excited hydroxide intermediate. The third is excited directly on the binding of superoxide anion to the reduced primary emitter.

Determination of flavin contents in neutrophils by a sensitive chemiluminescence assay: evidence for no translocation of flavoproteins from the cytosol to the membrane upon cell stimulation

A sensitive and specific chemiluminescence (CL) method with bacterial luciferase was adapted for accurate measurement of the flavins FAD and FMN in the membrane and cytosolic fractions of neutrophils prepared from pig and human blood. The FAD and FMN contents (FAD/FMN = 100:2) in the membranes were essentially the same in resting (R) and myristate-stimulated (S) cells, although O2(-)-generation was markedly enhanced exclusively in S membranes. The O2(-)-forming activity of S samples remained unchanged or even increased after washing the membranes with buffer, although one-third of the FAD was lost during washing (a decrease from 140 to 95 pmol/10(8) cell-equivalent (CE) during washing). The cytosol is known to contain at least three components that are essential for O2- production (p47-phox, p67-phox, and a G-protein), and that are translocated to membranes upon activation, but its flavin content was one tenth of that of the membranes. The cytosol was treated with fatty acids in the absence of membranes to induce substantial precipitation of p47-phox, p67-phox and a protein of 32 kDa. No difference relative to a solvent-control was noted in the low flavin content of the precipitate indicating that these cytosolic components are not flavoproteins. These results do not support the possibility of translocation of a cytosolic flavoprotein to the membrane upon activation of the respiratory burst.

Specific and Quantitative Assessment of Naphthalene and Salicylate Bioavailability by Using a Bioluminescent Catabolic Reporter Bacterium

A bioassay was developed and standardized for the rapid, specific, and quantitative assessment of naphthalene and salicylate bioavailability by use of bioluminescence monitoring of catabolic gene expression. The bioluminescent reporter strain Pseudomonas fluorescens HK44, which carries a transcriptional nahG-luxCDABE fusion for naphthalene and salicylate catabolism, was used. The physiological state of the reporter cultures as well as the intrinsic regulatory properties of the naphthalene degradation operon must be taken into account to obtain a high specificity at low target substrate concentrations. Experiments have shown that the use of exponentially growing reporter cultures has advantages over the use of carbon-starved, resting cultures. In aqueous solutions for both substrates, naphthalene and salicylate, linear relationships between initial substrate concentration and bioluminescence response were found over concentration ranges of 1 to 2 orders of magnitude. Naphthalene could be detected at a concentration of 45 ppb. Studies conducted under defined conditions with extracts and slurries of experimentally contaminated sterile soils and identical uncontaminated soil controls demonstrated that this method can be used for specific and quantitative estimations of target pollutant presence and bioavailability in soil extracts and for specific and qualitative estimations of napthalene in soil slurries.

Stabilization of luciferase intermediates by fatty amines, amides, and nitriles

Long-chain aliphatic amides, mono- and diamines, mono- and dialcohols, and nitriles were found to inhibit the bacterial luciferase reaction by binding with an enzyme intermediate (II, the luciferase-bound 4 alpha-flavin hydroperoxide). Inhibition was determined by measuring the decay rates of the inhibitor-intermediate II complex at different inhibitor concentrations. The data fit a model which was used to estimate the KI. At high concentrations, a plot of the decay rate (k) vs 1/[I] produced a straight line; extrapolation of this to 1/[I] = 0 yields an estimate of the decay rate at infinite inhibitor concentration which we defined as the inhibitor-enzyme-substrate stabilization constant, kESI.

A blue fluorescent protein from a yellow-emitting luminous bacterium

Vibrio fischeri strain Y1 emits yellow light in vivo due to the participation of a yellow fluorescent protein (YFP) in the luciferase reaction. In this study it was found that the organism also produces a protein (referred to as Y1-BFP) emitting strong blue fluorescence. Its molecular weight, about 25 kDa, is the same as or very close to that of YFP. The fluorescence excitation and emission maxima of the purified Y1-BFP are at 416 and 461 nm, respectively, and the fluorescence lifetime is 12.5 ns at 2 degrees C. The molar extinction coefficient of Y1-BFP at 416 nm was estimated to be approx. 9500. With the homologous luciferase, Y1-BFP decreases the intensity and rate of decay in the in vitro reaction but has no effect on its emission spectrum (in contrast to YFP, which has a striking effect on the spectrum). With luciferase isolated from Vibrio harveyi, however, Y1-BFP causes a small blue-shift (approximately 10 nm) in the emission of the enzyme catalyzed reaction, whereas YFP has no effect on the emission spectrum.

The lux genes of the luminous bacterial symbiont, Photobacterium leiognathi, of the ponyfish. Nucleotide sequence, difference in gene organization, and high expression in mutant Escherichia coli

The lux genes required for light expression in the luminescent bacterium Photobacterium leiognathi (ATCC 25521) have been cloned and expressed in Escherichia coli and their organization and nucleotide sequence determined. Transformation of a recombinant 9.5-kbp chromosomal DNA fragment of P. leiognathi into an E. coli mutant (43R) gave luminescent colonies that were as bright as those of the parental strain. Moreover, expression of the lux genes in the mutant E. coli was strong enough so that not only were high levels of luciferase detected in crude extracts, but the fatty-acid reductase activity responsible for synthesis of the aldehyde substrate for the luminescent reaction could readily be measured. Determination of the 7.3-kbp nucleotide sequence of P. leiognathi DNA, including the genes for luciferase (luxAB) and fatty-acid reductase (luxCDE) as well as a new lux gene (luxG) found recently in luminescent Vibrio species, showed that the order of the lux genes was luxCDABEG. Moreover, luxF, a gene homologous to luxB and located between luxB and luxE in Photobacterium but not Vibrio strains, was absent. In spite of this different lux gene organization, an intergenic stem-loop structure between luxB and luxE was discovered to be highly conserved in other Photobacterium species after luxF.

Green flavoprotein from P. leiognathi: purification, characterization and identification as the product of the lux G(N) gene

A green flavoprotein (GFP) was isolated and purified to homogeneity from Photobacterium leiognathi, strain 208. GFP is a homodimer of molecular weight 54,000 and contains two molecules of an unusual flavin per molecule of protein. Various biochemical characteristics including isoelectric point, trypsin and chymotrypsin degradation, SDS and temperature influence on subunit dissociation and the dissociation of the flavin chromophore, were investigated. The sequence of 23 N-terminal amino acids was determined and found to be concurrent with the N-terminal amino acid sequence encoded by the lux G(N) gene of P. leiognathi. This fact suggests that GFP is a structural component of the Photobacterium luminescence system.

Evidence of luminous bacterial symbionts in the light organs of myctophid and stomiiform fishes

The myctophids and stomiiforms represent two common groups of luminous fishes, but the source of luminescence in these animals has remained undetermined. In this study, labeled luciferase gene fragments from luminous marine bacteria were used to probe DNA isolated from specific fish tissues. A positive signal was obtained from skin DNA in all luminous fishes examined, whereas muscle DNA gave a weaker signal and brain DNA was negative. This observation is consistent with luminous bacteria acting as the light source in myctophids and stomiiforms and argues against the genes necessary for luminescence residing on the fish chromosomes. To confirm the location of this signal, a bacterial probe was hybridized in situ to sections of a stomiiform. A strong signal was generated directly over specific regions of the fish light organs, whereas no signal was found over other internal or epidermal tissues of the fish. Taken together, these data provide the first indication that luminous bacterial symbionts exist in myctophids and stomiiforms and that these symbionts account for luminescence in these fishes.

Structure and properties of luciferase from Photobacterium phosphoreum

The nucleotide sequences of the luxA and luxB genes coding for the alpha and beta subunits, respectively, of luciferase from Photobacterium phosphoreum have been determined. The predicted amino acid sequences of the alpha and beta subunits were shown to be significantly different from other bacterial luciferases with 62 to 88% identity with the alpha subunits and 47 to 71% identity with the beta subunits of other species. Expression of the different luciferases appear to correlate with the number of modulator codons. Kinetic properties of P. phosphoreum luciferase were shown to reflect the bacterium's natural cold temperature habitat.

Molecular biology of bacterial bioluminescence

The cloning and expression of the lux genes from different luminescent bacteria including marine and terrestrial species have led to significant advances in our knowledge of the molecular biology of bacterial bioluminescence. All lux operons have a common gene organization of luxCDAB(F)E, with luxAB coding for luciferase and luxCDE coding for the fatty acid reductase complex responsible for synthesizing fatty aldehydes for the luminescence reaction, whereas significant differences exist in their sequences and properties as well as in the presence of other lux genes (I, R, F, G, and H). Recognition of the regulatory genes as well as diffusible metabolites that control the growth-dependent induction of luminescence (autoinducers) in some species has advanced our understanding of this unique regulatory mechanism in which the autoinducers appear to serve as sensors of the chemical or nutritional environment. The lux genes have now been transferred into a variety of different organisms to generate new luminescent species. Naturally dark bacteria containing the luxCDABE and luxAB genes, respectively, are luminescent or emit light on addition of aldehyde. Fusion of the luxAB genes has also allowed the expression of luciferase under a single promoter in eukaryotic systems. The ability to express the lux genes in a variety of prokaryotic and eukaryotic organisms and the ease and sensitivity of the luminescence assay demonstrate the considerable potential of the widespread application of the lux genes as reporters of gene expression and metabolic function.

Cloning and nucleotide sequences of lux genes and characterization of luciferase of Xenorhabdus luminescens from a human wound

Xenorhabdus luminescens HW is the only known luminous bacterium isolated from a human (wound) source. A recombinant plasmid was constructed that contained the X. luminescens HW luxA and luxB genes, encoding the luciferase alpha and beta subunits, respectively, as well as luxC, luxD, and a portion of luxE. The nucleotide sequences of these lux genes, organized in the order luxCDABE, were determined, and overexpression of the cloned luciferase genes was achieved in Escherichia coli host cells. The cloned luciferase was indistinguishable from the wild-type enzyme in its in vitro bioluminescence kinetic properties. Contrary to an earlier report, our findings indicate that neither the specific activity nor the size of the alpha (362 amino acid residues, Mr 41,389) and beta (324 amino acid residues, Mr 37,112) subunits of the X. luminescens HW luciferase was unusual among known luminous bacterial systems. Significant sequence homologies of the alpha and beta subunits of the X. luminescens HW luciferase with those of other luminous bacteria were observed. However, the X. luminescens HW luciferase was unusual in the high stability of the 4a-hydroperoxyflavin intermediate and its sensitivity to aldehyde substrate inhibition.

A cyanide-aldehyde complex inhibits bacterial luciferase

Cyanide at high (millimolar) concentrations inhibited in the in vitro Vibrio harveyi luciferase reaction. Cyanide reacted with free aldehyde to form an inhibitor. Inhibitor formation was accelerated by alkaline conditions and bovine serum albumin.

Bioluminescence decay kinetics in the reaction of bacterial luciferase with different aldehydes

At 22 degrees C the bioluminescence decay kinetics in the in vitro reaction catalysed by Vibrio harveyi luciferase in the presence of different aldehydes--nonanal, decanal, tridecanal and tetradecanal did not follow the simple exponential pattern and could be fitted to a two-exponential process. One more principal distinction from the first-order kinetics is the dependence of the parameters on aldehyde concentration. The complex bioluminescence decay kinetics are interpreted in terms of a scheme, where bacterial luciferase is able to perform multiple turnovers using different flavin species to produce light. The initial phase of the bioluminescent reaction appears to proceed mainly with fully reduced flavin as the substrate while the final one results from the involvement of flavin semiquinone in the catalytic cycle.

Inhibition of bioluminescence in Photobacterium phosphoreum by sulfamethizole and its stimulation by thymine

In bioluminescent bacteria very few agents have been reported that can selectively inhibit the luminescence. In sensitivity tests with Photobacterium phosphoreum, using 55 different antibiotics, it was found that sulfamethizole, an inhibitor of dihydropteroate synthetase and the formation of folic acid, inhibited bioluminescence more than growth. Likewise, in mutants requiring thymine for growth, the luminescence per cell was much less in a medium low in thymine. In neither case could the decreased specific luminescence be attributed to a decrease in the cellular level of luciferase or aldehyde factor; the involvement of additional but unidentified factors in the regulation of in vivo bioluminescence is postulated.

Cloning and nucleotide sequence of luxR, a regulatory gene controlling bioluminescence in Vibrio harveyi

Mutagenesis with transposon mini-Mulac was used previously to identify a regulatory locus necessary for expression of bioluminescence genes, lux, in Vibrio harveyi (M. Martin, R. Showalter, and M. Silverman, J. Bacteriol. 171:2406-2414, 1989). Mutants with transposon insertions in this regulatory locus were used to construct a hybridization probe which was used in this study to detect recombinants in a cosmid library containing the homologous DNA. Recombinant cosmids with this DNA stimulated expression of the genes encoding enzymes for luminescence, i.e., the luxCDABE operon, which were positioned in trans on a compatible replicon in Escherichia coli. Transposon mutagenesis and analysis of the DNA sequence of the cloned DNA indicated that regulatory function resided in a single gene of about 0.6-kilobases named luxR. Expression of bioluminescence in V. harveyi and in the fish light-organ symbiont Vibrio fischeri is controlled by density-sensing mechanisms involving the accumulation of small signal molecules called autoinducers, but similarity of the two luminescence systems at the molecular level was not apparent in this study. The amino acid sequence of the LuxR product of V. harveyi, which indicates a structural relationship to some DNA-binding proteins, is not similar to the sequence of the protein that regulates expression of luminescence in V. fischeri. In addition, reconstitution of autoinducer-controlled luminescence in recombinant E. coli, already achieved with lux genes cloned from V. fischeri, was not accomplished with the isolation of luxR from V. harveyi, suggesting a requirement for an additional regulatory component.

A time-dependent bacterial bioluminescence emission spectrum in an in vitro single turnover system: energy transfer alone cannot account for the yellow emission of Vibrio fischeri Y-1

Yellow fluorescent protein (YFP), which has a bound FMN, was isolated from the marine bacterium Vibrio fischeri strain Y-1b. Its presence in a luciferase [alkanal monooxygenase (FMN-linked); alkanal, reduced-FMN:oxygen oxidoreductase (1-hydroxylating, luminescing), EC 1.14.14.3] reaction mixture causes a striking color change, and an increase in bioluminescence intensity, as well as a faster rate of intensity decay, so that the quantum yield is not changed. The emission spectrum shows two distinct color bands, one at 490 nm attributed to the unaltered emission of the luciferase system, the other peaking in the yellow around 540 nm due to YFP emission. The kinetics of the two color bands differ, so the spectrum changes with time. The yellow emission reaches its initial maximum intensity later than the blue, and then both blue and yellow emissions decay exponentially with nearly the same pseudo-first-order rate constants, linearly dependent on [YFP] (from 0.01 sec-1 with no YFP to a maximum of approximately 0.1 sec-1 at 4 degrees C) but exhibiting a saturation behavior. The data can be interpreted by assuming the interaction of YFP with the peroxyhemiacetal intermediate in the luciferase reaction to form an unstable new complex whose breakdown gives the yellow emitter in its excited state. This simple model fits well the data at [YFP] less than 15 microM. The results indicate that a single primary excited state cannot be responsible for the blue and the yellow emissions.

A sensitive and specific assay for superoxide anion released by neutrophils or macrophages based on bioluminescence of polynoidin

Using the luminescent protein polynoidin, present in the bioluminescent system isolated from the marine annelid Harmothoe lunulata, we have developed a new method to measure, specifically, superoxide anion (O2-) released by macrophages or neutrophils. A small quantity of an aqueous crude extract of polynoidin is used to detect O2- released by stimulated cells. Light emission is linearly dependent on the number of cells over a wide range (10(3) to 10(7) cells), and the assay is thus more sensitive than either luminol or ferricytochrome c reduction. Luminescence is enhanced 20% by mannitol, 80% by catalase, and is totally quenched by superoxide dismutase. For the same number of cells, neutrophils showed a threefold higher release of O2- and a twofold faster first-order light decay than stimulated macrophages, in accordance with data obtained by other methods.

Isolation of bioluminescent functions from Photobacterium leiognathi: analysis of luxA, luxB, luxG and neighboring genes

Genes encoding luminescence of Photobacterium leiognathi have been cloned in Escherichia coli. The luminescent clones were readily apparent. Among them, a clone containing a recombinant plasmid with a 13.5-kb insertion was identified. This DNA fragment contained all of the luminescence-encoding genes. The luciferase-encoding genes (lux) in this DNA fragment were localized. We have sequenced a part of the cloned lux region and identified the luxA, luxB and luxG genes encoding the alpha and beta subunits of luciferase and a gamma protein with an Mr of 26,180, respectively. The analysis of deduced amino acid sequences and comparison with known luciferase sequences from Vibrio harveyi, indicate the common origin of these proteins.

Bioluminescence of the insect pathogen Xenorhabdus luminescens

Luminescence of batch cultures of Xenorhabdus luminescens was maximal when cultures approached stationary phase; the onset of in vivo luminescence coincided with a burst of synthesis of bacterial luciferase, the enzyme responsible for luminescence. Expression of luciferase was aldehyde limited at all stages of growth, although more so during the preinduction phase. Luciferase was purified from cultures of X. luminescens Hm to a specific activity of 4.6 x 10(13) guanta/s per mg of protein and found to be similar to other bacterial luciferases. The Xenorhabdus luciferase consisted of two subunits with approximate molecular masses of 39 and 42 kilodaltons. A third protein with a molecular mass of 24 kilodaltons copurified with luciferase, and in its presence, either NADH or NADPH was effective in stimulating luminescence, indicating that this protein is an NAD(P)H oxidoreductase. Luciferases from two other luminous bacteria, Vibrio harveyii (B392) and Vibrio cholerae (L85), were partially purified, and their subunits were separated in 5 M urea and tested for complementation with the subunits prepared from X. luminescens Hb. Positive complementation was seen with luciferase subunits among all three species. The slow decay kinetics of the Xenorhabdus luciferase were attributed to the alpha subunit.

Bioluminescence emission of bacterial luciferase with 1-deaza-FMN. Evidence for the noninvolvement of N(1)-protonated flavin species as emitters

The reaction of reduced 1-d-FMN with oxygen and decanal results in bioluminescence with kinetic and spectral properties similar to those of the reaction with FMNH2, even though the spectral (absorbance, fluorescence) and chemical properties of the oxidized forms differ greatly. This emission, which is about 10-15% as efficient as with FMNH2, is postulated to involve the intermediacy of the corresponding 4a-hydroperoxide, the fluorescence of which occurred transiently. The N(1) protonated species had been proposed as the emitter in the reaction with FMNH2, but the 1-deaza analog cannot be protonated at the corresponding position, thus excluding this possibility.

Elongation of exogenous fatty acids by the bioluminescent bacterium Vibrio harveyi

Bioluminescent bacteria require myristic acid (C14:0) to produce the myristaldehyde substrate of the light-emitting luciferase reaction. Since both endogenous and exogenous C14:0 can be used for this purpose, the metabolism of exogenous fatty acids by luminescent bacteria has been investigated. Both Vibrio harveyi and Vibrio fischeri incorporated label from [1-14C]myristic acid (C14:0) into phospholipid acyl chains as well as into CO2. In contrast, Photobacterium phosphoreum did not exhibit phospholipid acylation or beta-oxidation using exogenous fatty acids. Unlike Escherichia coli, the two Vibrio species can directly elongate fatty acids such as octanoic (C8:0), lauric (C12:0), and myristic acid, as demonstrated by radio-gas liquid chromatography. The induction of bioluminescence in late exponential growth had little effect on the ability of V. harveyi to elongate fatty acids, but it did increase the amount of C14:0 relative to C16:0 labeled from [14C]C8:0. This was not observed in a dark mutant of V. harveyi that is incapable of supplying endogenous C14:0 for luminescence. Cerulenin preferentially decreased the labeling of C16:0 and of unsaturated fatty acids from all 14C-labeled fatty acid precursors as well as from [14C]acetate, suggesting that common mechanisms may be involved in elongation of fatty acids from endogenous and exogenous sources. Fatty acylation of the luminescence-related synthetase and reductase enzymes responsible for aldehyde synthesis exhibited a chain-length preference for C14:0, which also was indicated by reverse-phase thin-layer chromatography of the acyl groups attached to these enzymes. The ability of V. harveyi to activate and elongate exogenous fatty acids may be related to an adaptive requirement to metabolize intracellular C14:0 generated by the luciferase reaction during luminescence development.

The transcription of bacterial luminescence is regulated by sigma 32

Luminescence in the marine bacterium, Vibrio fischeri, is regulated by a small molecule, the autoinducer. The transcription of the V. fischeri lux genes also requires a regulatory protein, (luxR), cAMP and CRP. We show that, apart from these components, the transcription of the PR lux operon is also controlled by the activity of sigma 32 (htpR protein). In luminescent Escherichia coli (E. coli/pChv1), as well as in different marine luminous bacteria and their naturally occurring dark (K) variants, the luminescence system can be induced by starvation under microaerophilic conditions. Heat shock also induces luminescence in htpR+ but not in htpR- strains of E. coli/pChv1. An htpR- mutant of E. coli containing pChv1 is very dim and its luminescence is not induced by starvation or heat shock. The addition of a plasmid bearing the gene for htpR+ into such cells restores their response to starvation and heat shock. Cells of wild type E. coli/pChv1 that have been starved or heat shocked respond to lower concentrations of V. fischeri inducer than untreated cells. These cultures also produce more extracellular inducer than untreated cells. Starvation, heat shock and the presence of sigma 32 do not induce luminescence in luxl deleted E. coli/pChv1 cells. SOS-inducing agents advance the onset of luminescence in both htpR+ and htpR- strains but not in luxl deleted E. coli/pChvi cells. DNA sequencing of the luxR-luxl region reveals the presence of a promoter region of the kind typical for sigma 32 at the beginning of the luxl gene. In addition we find a LexA protein-DNA binding site in the non-consensus sequence for the -35 region of the PR operon. It is proposed that the regulatory protein-inducer complex displaces the LexA protein and allows the transcription of the right operon. SOS-inducing agents result in proteolysis of LexA protein and advance the onset of luminescence. sigma 32 enhances the transcription from the PR operon and thus initiates a positive control circuit. It seems that sigma 32 is the major controlling element in determining the onset of luminescence both in vivo and in vitro.

Purification of the yellow fluorescent protein from Vibrio fischeri and identity of the flavin chromophore

A low molecular weight protein (approximately 25,000 D) exhibiting a yellow fluorescence emission peaking at approximately 540 nm was isolated from Vibrio fischeri (strain Y-1) and purified to apparent homogeneity. FMN is the chromophore, but it exhibits marked red shifts in both the absorption (lambda max = 380, 460 nm) and the fluorescence emission. When added to purified luciferase from the same strain, which itself catalyzes an emission of blue-green light (lambda max approximately 495 nm), this protein induces a bright yellow luminescence (lambda max approximately 540 nm); this corresponds to the emission of the Y-1 strain in vivo. This yellow bioluminescence emission is thus ascribed to the interaction of these two proteins, and to the excitation of the singlet FMN bound to this fluorescent protein.

Mobilization of cloned luciferase genes into Vibrio harveyi luminescence mutants

A recombinant plasmid which carried a 5 kb fragment of Vibrio harveyi DNA containing the luxA and luxB genes was mobilized from Escherichia coli into luminescence-deficient mutants of V. harveyi. The cloned genes complemented a temperature sensitive luciferase mutation, but failed to complement lesions in two different aldehyde deficient mutants. Expression of the cloned genes was not subject to autoinduction in either E. coli or in V. harveyi.