Control of luciferase synthesis in a newly isolated strain of Photobacterium leiognathi

In previous studies with luminous bacteria of all different species it has been reported that the synthesis of luciferase is autoinducible: during growth at low cell densities synthesis is effectively repressed while after induction, at higher cell densities, the rate of synthesis of enzyme is up to five times the growth rate. In this paper we report on newly isolated strains of Photobacterium leiognathi which show continued luciferase synthesis irrespective of the cell density. The specific synthesis rate may nevertheless differ from the rate of growth and depends on the luciferase content of the inoculated cells. A ratio of 1 was established for cells having a maximum luciferase content varying to a ratio of about 2 for cells that contained only 1% of the maximum.Abbreviation BSA bovine serum albumin     

Expression of luminescence in Photobacterium phosphoreum: Na+ regulation of in vivo luminescence appearance

In Photobacterium phosphoreum strain 496, growth and luminescence in a complex medium are optimal with 3% NaCl. However, in the same medium with 1% NaCl growth is similar, but the development of bioluminescence does not occur. In cells grown to mid or late-log phase in 1% NaCl, light emission can be triggered by the addition of NaCl, but the time required for its appearance is quite long, at least 30–45 min. The synthesis of m-RNA and protein are required for the development of luminescence, but the long time interval suggests that some intermediate steps are required. The time required is not less in conditioned 3% NaCl medium.     

LuxA gene of light organ symbionts of the bioluminescent fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) forms a lineage closely related to that of Photobacterium leiognathi ssp. mandapamensis

A molecular phylogenetic analysis of luxA gene sequences of light organ symbionts of the fish Acropoma japonicum (Acropomatidae) and Siphamia versicolor (Apogonidae) revealed that the sequences were related to those of Photobacterium leiognathi ssp. mandapamensis, which is not known to occur as a light organ symbiont among bioluminescent P. leiognathi clades. The presence of another lux gene element, luxF, coding for nonfluorescent protein, provided additional support for the identity of the light organ symbionts of the fish. Cladogenesis of the light organ symbiont P. leiognathi may be influenced by the radiation of host fishes.     

Phylogenetic analysis of the <Emphasis Type="Italic">lux</Emphasis> operon distinguishes two evolutionarily distinct clades of <Emphasis Type="Italic">Photobacterium leiognathi</Emphasis>

The luminous marine bacterium Photobacterium mandapamensis was synonymized several years ago with Photobacterium leiognathi based on a high degree of phenotypic and genetic similarity. To test the possibility that P. leiognathi as now formulated, however, actually contains two distinct bacterial groups reflecting the earlier identification of P. mandapamensis and P. leiognathi as separate species, we compared P. leiognathi strains isolated from light-organ symbiosis with leiognathid fishes (i.e., ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1) with strains from seawater originally described as P. mandapamensis and later synonymized as P. leiognathi (i.e., ATCC 27561^T and ATCC 33981) and certain strains initially identified as P. leiognathi (i.e., PL-721, PL-741, 554). Analysis of the 16S rRNA and gyrB genes did not resolve distinct clades, affirming a close relationship among these strains. However, strains ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554 were found to bear a luxF gene in the lux operon (luxABFE), whereas ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1 lack this gene (luxABE). Phylogenetic analysis of the luxAB(F)E region confirmed this distinction. Furthermore, ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554 all produced a higher level of luminescence on high-salt medium, as previously described for PL-721, whereas ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1 all produced a higher level of luminescence on low-salt medium, a characteristic of P. leiognathi from leiognathid fish light organs. These results demonstrate that P. leiognathi contains two evolutionarily and phenotypically distinct clades, P. leiognathi subsp. leiognathi (strains ATCC 25521^T, ATCC 25587, lequu.1.1 and lleuc.1.1), and P. leiognathi subsp. mandapamensis (strains ATCC 27561^T, ATCC 33981, PL-721, PL-741 and 554).Electronic Supplementary Material Supplementary material is available for this article at .     

Iron control of the Vibrio fischeri luminescence system in Escherichia coli

Iron influences liminescence in Vibrio fischeri; cultures iron-restricted for growth rate induce luminescence at a lower optical density (OD) than faster growing, iron-replete cultures. An iron restriction effect analogous to that in V. fischeri (slower growth, induction of luminescence at a lower OD) was established using Escherichia coli tonB and tonB ⁺ strains transformed with recombinant plasmids containing the V. fischeri lux genes (luxR luxICD ABEG) and grown in the presence and absence of the iron chelator ethylenediamine-di (o-hydroxylphenyl acetic acid) (EDDHA). This permitted the mechanism of iron control of luminescence to be examined. A fur mutant and its parent strain containing the intact lux genes exhibited no difference in the OD at induction of luminescence. Therefore, an iron-binding repressor protein apparently is not involved in iron control of luminescence. Furthermore, in the tonB and in tonB ⁺ strains containing lux plasmids with Mu dI(lacZ) fusions in luxR, levels of -galactosidase activity (expression from the luxR promoter) and luciferase activity (expression from the luxICDABEG promoter) both increased by a similar amount (8–9 fold each for tonB, 2–3 fold each for tonB ⁺) in the presence of EDDHA. Similar results were obtained with the luxR gene present on a complementing plasmid. The previously identified regulatory factors that control the lux system (autoinducer-LuxR protein, cyclic AMP-cAMP receptor protein) differentially control expression from the luxR and luxICDABEG promoters, increasing expression from one while decreasing expression from the other. Consequently, these results suggest that the effect of iron on the V. fischeri luminescence system is indirect.     

Effects of sediment anoxia and light on turion germination and early growth of Potamogeton crispus

Potamogeton crispus is a cosmopolitan aquatic species and is widely used as a pioneer species for vegetation restoration of eutrophic lakes. However, many restoration projects applying P. crispus turions have not been successful. Earlier studies focused on effects of light and temperature on turion germination. The purpose of this study was to determine whether sediment anoxia and light interactively affected the turion germination and early growth of P. crispus. Anoxic conditions in the experiment were produced by adding sucrose to the sediment. The germination rate of the turions was 68–73% lower in the highly anoxic condition treatment than in the control. Medium light intensity (10% of natural light at the water surface) was more favorable for germination under slightly anoxic conditions than either low or high light intensity. The growth of newly-formed sprouts was also significantly inhibited by sediment anoxia. Photosynthesis and shoot biomass were reduced under sediment anoxia, whereas total chlorophyll content, root biomass, and soluble protein content were highest in the low anoxic condition treatment. Medium light improved net photosynthesis and biomass production of the sprouts. We conclude that turion germination and sprout growth can be significantly inhibited by sediment anoxia. Medium light intensity may alleviate this inhibition by anoxia, but light has little effect when sediment anoxia is severe. For the purposes of vegetation restoration, more attention should be paid to the role of sediment anoxia, and it is necessary to improve sediment and light conditions for turion germination and early growth of P. crispus in eutrophic lakes. These results will contribute to a more complete understanding of turion germination dynamics of P. crispus and will be useful for future restoration programs. Handling editor: S. M. Thomaz     

Effects of aldehyde and internal ions on bioluminescence expression of Photobacterium phosphoreum

In a complex medium, cells of Photobacterium phosphoreum (strain 496) grow equally well with 1% and 3% NaCl, but luminescence occurs only with 3% NaCl in the medium. However, the suppression of luminescence is not attributable to the lack of luciferase; log phase cells growing in 1% NaCl will develop luminescence following a shift to 3% NaCl, which is accompanied by an increase of intracellular potassium. Tetradecanal stimulates bioluminescence in a 1% NaCl culture, and also in the presence of nalidixic acid, an inhibitor or gyrase. It is thus suggested that the suppression of luminescence in 1% NaCl or in 3% NaCl with nalidixic acid is due to a deficiency in the synthesis of intracellular aldehyde. The increase in intracellular potassium that occurs upon shifting from 1% to 3% NaCl may also relate to aldehyde synthesis gene expression via activation of gyrase, or via an increase in negative supercoiling of the chromosome. However, since an initial decrease of light intensity is still observed during culture even with the addition of tetradecanal, an additional factor related to cell density must also be involved in bioluminescence expression.Abbreviations nal nalidixic acid - nal-r nalidixic acid resistant strain     

不同光照强度对小球藻生长的影响

【目的】优化小球藻的培养与提高资源化利用效率,得到不同光照强度对小球藻生长的影响规律。【方法】通过室内控制实验,设置0、1 000、3 000、5 500、7 000、9 000 lx共6组光照强度,在温度为20°C和曝气强度为20%的条件下,采用BG-11培养基培养小球藻(Chorella vulgaris)至稳定生长,研究不同光照强度对小球藻生长的影响,建立光照强度与最大光密度ODmax、最大比增长率μmax之间的抛物回归曲线。【结果】不同光照强度下,小球藻生长差异较大,培养初期叶绿素a浓度迅速增加直至峰值,后期迅速降低,其中5 500 lx强度下小球藻生长最好。藻类生长对溶解性总磷的消耗比溶解性总氮更大。【结论】光照强度(x)与ODmax的拟合方程为:ODmax=-1E–07x~2+0.001 6x+0.105 5(R~2=0.987 2,0≤x≤9 000 lx),光照强度(x)与μmax的拟合方程为:μmax=-2E–08x~2+0.000 3x-0.004 2(R~2=0.998 6,0≤x≤9 000 lx)。     

Phytochrome action in light-grown plants: the influence of light quality and fluence rate on extension growth in Sinapis alba L.

Using light-grown plants of Sinapis alba an analysis has been made of the effect on extension growth of adding far red light to a background photosynthetic source. It has been possible to distinguish between the increase in fluence rate and the reduction of the amount of phytochrome present as Pfr, which are both consequences of the addition of supplementary far red light, and to determine that the response of increased extension growth is due only to the latter. It is shown that the degree of fluence rate dependency varies with photoequilibrium and the significance of this interaction is discussed in terms of the mode of action of phytochrome and of its role in the natural light environment.Abbreviations PAR photosynthetically active radiation - SAN 9789 4-chloro-5-(methylamino)-2-(,,-trifluoro-m-tolyl)-3(2H) pyridazinone - Pfr far-red absorbing form of phytochrome - Pr red-absorbing form of phytochrome - LER logarithmic extension rate     

The specificity of symbiosis: Pony fish and luminescent bacteria

Luminescent bacteria isolated from light organs of seven different species (3 genera) of fishes of the family Leiognathidae were subjected to taxonomic analysis. Of the 733 isolated all but seven were identified as Photobacterium leiognathi; the others are considered to be either chance contaminants of the sampling procedure or transients within the organ. In most fish, the luminous organ appeared to contain a single predominating strain of P. leiognathi with small numbers of one to three other strains of the same species, differing by only one or two characters.     

Rapid,localized light effect on root growth in maize

A method using optical microfibers permitted localized exposure of the cap or the elongating part of growing maize (Zea mays L.) roots to white light. When the cap was illuminated, a strong and very rapid inhibition of the elongation rate of the roots was found. When the light microbeam was directed at the elongating region, the roots continued to grow at the same rate as before the illumination.     

Conditions that influence bacterial luminescence in the presence of blood serum

Conditions that influence the luminescence of natural and recombinant luminescent bacteria in the presence of blood serum were studied. In general, blood serum quenched the luminescence of the marine Photobacterium phosphoreum and the recombinant Escherichia coli strains harboring the luminescent system genes of Photobacterium leiognathi, but enhanced the luminescence of the soil bacterium Photorhabdus luminescens Zm1 and the recombinant E. coli strain harboring the lux operon of P. luminescens Zm1. The quenching effect of blood serum increased with its concentration and the time and temperature of incubation. The components of blood serum that determine the degree and specificity of its action on bacterial luminescence were identified.__________Translated from Mikrobiologiya, Vol. 74, No. 2, 2005, pp. 191–197.Original Russian Text Copyright © 2005 by Deryabin, Polyakov.     

Water stress and light intensity effects on growth and nocturnal acid accumulation in a terrestrial CAM bromeliad (Bromelia humilis Jacq.) under natural conditions

Summary Seasonal variations in CAM performance of sunexposed and partially shaded populations of Bromelia humilis were measured under natural conditions in a semi-arid region in northern Venezuela. The sun population consisted of smaller plants, with lower chlorophyll and total nitrogen contents per unit leaf area compared with plants from the partial-shade population. During the dry season CAM activity, assessed as nocturnal acid accumulation, was higher in the partial-shade population. Acid accumulation was stimulated by irrigation in both populations within 24 h after treatment. Daily changes in concentration of soluble sugars were opposite to leaf acidity indicating their role as carbon source for acid synthesis during the night. The change in nocturnal sugar concentration was always more than the amount required for acid accumulation, suggesting other carbohydrate-consuming processes such as transportation of sugars out of the leaf. CAM activity was higher during the rainy season, and differences between populations were smaller. At the end of the rainy season reduction of CAM activity caused by drought was first detected in the sun population. Measured ratios of glucan/soluble sugar show a higher proportion of readily utilizable sugars during periods of active CAM and growth. Under conditions of continuous high light intensity and air temperature leading to all year round high potential evaporation in semiarid tropical regions, fully exposed populations of B. humilis show a pronounced reduction of metabolic activity. Partial shade favours growth and CAM activity in this constitutive CAM species. It is concluded that water stress, and not light intensity, is the predominant limiting factor for growth of this species under natural conditions.     

Endogenous and exogenous auxin in the control of root growth

The endogenous indol-3yl-acetic acid (IAA) of detipped apical segments from roots of maize (cv ORLA) was greatly reduced by an exodiffusion technique which depended upon the preferential acropetal transport of the phytohormone into buffered agar. When IAA was applied to the basal cut ends of freshly prepared root segments only growth inhibitions were demonstrable but after the endogenous auxin concentration had been reduced by the exodiffusion technique it became possible to stimulate growth by IAA application. The implications of the interaction between exogenous and endogenous IAA in the control of root segment growth are discussed with special reference to the role of endogenous IAA in the regulation of root growth and geotropism.Abbreviations IAA indol-3yl-acetic acid - GC-MS gas chromatography-mass spectrometry     

The effect of light quality on the growth and development of in vitro cultured Doritaenopsis plants

The influence of light quality on growth and development of in vitro grown Doritaenopsis hort. (Orchidaceae) plants was investigated. Growth parameters like leaf and root fresh/dry mass and leaf area were highest with plants grown under red plus blue light emitting diodes (LEDs). Leaf length was greater with the plants grown under red LED. Carbohydrate (starch, sucrose, glucose and fructose) and leaf pigment (chlorophylls and carotenoids) biosynthesis of the plants was significantly increased in plants grown under red plus blue LEDs compared to red or blue LED and fluorescent light treatments. This study suggests that the production of quality Doritaenopsis plants is possible by culturing the plants in vitro under a mixture of blue plus red light sources.     

Combined effect of temperature and light intensity on growth and extracellular polymeric substance production by the cyanobacterium Arthrospira platensis

The effects of light intensity and temperature on Arthrospira platensis growth and production of extracellular polymeric substances (EPS) in batch culture were evaluated using a three-level, full-factorial design and response surface methodology. Three levels were tested for each parameter (temperature: 30, 35, 40°C; light intensity: 50, 115, 180 μmol photons m⁻² s⁻¹). Both growth and EPS production are influenced mainly by the temperature factor but the interaction term temperature*light intensity also had a significant effect. In addition, conditions optimising EPS production are different from those optimising growth. The highest growth rate (0.414 ± 0.003 day⁻¹) was found at the lowest temperature (30°C) and highest light intensity (180 μmol photons m⁻² s⁻¹) tested, no optima were detectable within the given test range. Obviously, optima for growth must be at a temperature lower than 30°C and a light intensity higher than 180 μmol photons m⁻² s⁻¹. For EPS production, light intensity had a positive linear effect (optimum obviously higher than 180 μmol photons m⁻² s⁻¹), but for the temperature parameter a maximum effect was detectable at 35°C.