O2 Regulation of Bacteriochlorophyll Synthesis in the Aerobic Bacterium Erythrobacter

This study examined the effect of oxygen on the bacteriochlorophyll(Bchl) synthetic activity of the aerobic marine bacterium Erythrobacter.The activity of the orange-pigmented strain E. longus OCh 101was highest at full atmospheric oxygen tension, while that ofthe pink-pigmented strain Erythrobacter sp. OCh 114 was lowat this tension and not observed in the absence of oxygen. (Received January 26, 1987; Accepted August 13, 1987)     

Action Spectra for Inhibition by Light of Accumulation of Bacteriochlorophyll and Carotenoid during Aerobic Growth of Photosynthetic Bacteria

Action spectra for the inhibition by light of the accumulationof photosynthetic pigments during the aerobic growth of a photosyntheticbacterium, Rhodobacter sphaeroides, and an aerobic photosyntheticbacterium, Erythrobacter sp. strain OCh 114, were determinedover the range of wavelengths from 380 to 870 nm. The actionspectra for the inhibition of accumulation of bacteriochlorophyllin both R. sphaeroides and Erythrobacter sp. strain OCh 114indicated that the maximum inhibition occurred at approximately400 nm and a low level of inhibition occurred at 575 and 770nm. In R. sphaeroides, the action spectrum for the inhibitionof accumulation of carotenoid paralleled that for the inhibitionof accumulation of bacteriochlorophyll over the same range ofwavelengths. These results indicate that in both species, grownunder aerobic conditions, the same photoreceptor is involvedin the inhibition. One possible candidate for the relevant photoreceptormay be the precursor(s) to bacteriochlorophyll. It is possiblethat the photoreceptor is decomposed by light absorbed by itselfor by an unidentified photoreceptor that absorbs blue light(a photo-sensitizer). It is suggested that the accumulationof carotenoid is dependent on the stability of the bacteriochlorophyll. (Received September 16, 1988; Accepted March 2, 1989)     

Excitation and Emission Spectroscopy of Membranes and Pigment-protein Complexes of an Aerobic Photosynthetic Bacterium, Erythrobacter sp. OCh 114

Emission and excitation spectra of steady-state fluorescencefrom membranes and isolated pigment-protein complexes of anaerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114 indicated high efficiency of energy transfer from Bchl 806to Bchl 870 and from carotenoids to bacteriochlorophyll. Thus,this bacterium has a highly efficient light-harvesting systemtypical of photosynthetic bacteria. (Received August 3, 1989; Accepted January 27, 1990)     

Photochemical Activities of Bacteriochlorophyll in Aerobically Grown Cells of Aerobic Heterotrophs, Erythrobacter Species (OCh 114) and Erythrobacter longus (OCh 101)

Reversible photo-oxidation of cytochromes and reversible photobleachingof bacteriochlorophyll were observed in aerobically grown cellsof the aerobic heterotroph, the Erythrobacter species (OCh 114).Light inhibited O₂-uptake by cells of this bacterium and Erythrobacterlongus (OCh 101). A vesicular structure of intracytoplasmicmembrane systems was observed in sections of aerobically growncells of OCh 114. These bacteria may be called aerobic photosyntheticbacteria (i.e., photosynthetic bacteria which can utilize lightenergy under aerobic conditions but not under anaerobic conditions). (Received September 9, 1981; Accepted December 2, 1981)     

Bacteriochlorophyll-protein complexes of aerobic bacteria,Erythrobacter longus and Erythrobacter species OCh 114

Bacteriochlorophyll(Bchl)-protein complexes were isolated from obligate aerobic bacteria, Erythrobacter longus and Erythrobacter species OCh 114. The apparent molecular weights, absorption spectra and polypeptide compositions of the light-harvesting complexes were, in general, similar to those of the light-harvesting Bchl-protein complexes of purple photosynthetic bacteria. The reaction center complexes of these bacteria also showed similar properties to those of the purple bacteria except for slightly altered polypeptides. However, the following characteristic features of the light-harvesting systems were found in these aerobic bacteria. Major carotenoids were not bound to the Bchl-protein complex in E. longus. In Erythrobacter sp. OCh 114, a new type of Bchl-protein complex which showed a single absorption band in the near infrared region at 806 nm was obtained. The reaction center of strain OCh 114 was associated with a c-type cytochrome.Abbreviations Bchl bacteriochlorophyll a - RC reaction center - SDS sodium dodecylsulfate - PAGE polyacrylamide gel electrophoresis     

Characterization of Porphobilinogen Synthase from an Aerobic Photosynthetic Bacterium, Erythrobacter sp. Strain OCh 114

Porphobilinogen synthase (formerly 5-aminolevulinic acid dehydratase,EC 4.2.1.24 [EC] ) was purified 7,405-fold from an aerobic photosyntheticbacterium, Erythrobacter sp. strain OCh 114. The molecular weightof the enzyme was determined to be 260,000 by Sephadex G-200gel filtration. The enzyme had a single pH optimum at 8.0 andshowed no requirement for metal ion and thiol compound for itsmaximum activity. The K_m value for 5-aminolevulinic acid was0.29 mM. 4,5-Dioxovaleric acid and levulinic acid were foundto be competitive inhibitors of the enzyme, with K_i values of0.65 and 0.80 mM, respectively. The enzyme was extremely labilein acidic pH and almost completely lost its activity within1 h at pH 6.0 and 30?C. This Erythrobacter enzyme seems to besimilar to the enzyme from the anaerobic photosynthetic bacteriumRhodobacter capsulatus in its molecular and catalytic properties. (Received February 17, 1988; Accepted May 9, 1988)     

Photosynthetic electron transfer system is inoperative in anaerobic cells of Erythrobacter species strain OCh 114

Some of the photosynthetic reactions were measured under aerobic and anaerobic conditions in intact cells of an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942). In intact cells, the flash-light induced oxidation of cytochrome c-551, the continuous light-induced oxidation of reaction center bacteriochlorophyll and the continuous light-induced pH change ( ) of the suspension decreased on aerobic-anaerobic transition and almost disappeared under anaerobic conditions. These photosynthetic reactions reappeared when the suspension was aerated again. These phenomena were reconciled with the fact that Erythrobacter sp. cannot grow anaerobically even in the light. The incompetence of photoanaerobic growth of this bacterium was explained by the reduction of the primary electron acceptor (Q_I) before illumination, resulting partly from the relatively high midpoint potential of Q_I of this bacterium.Abbreviations Q_I Primary electron acceptor - E_h ambient redox potential - E_m midpoint redox potential     

Enhancement of Denitrifying Activity in Cells of Roseobacter denitrificans Grown Aerobically in the Light

The effects of light on denitrifying activity during growthwere studied in an aerobic photosynthetic bacterium, Roseobacterdenitrificans (formerly Erythrobacter sp. OCh 114). When aerobicallygrown cells were transferred to anaerobic conditions in thepresence of nitrate, this bacterium exhibited denitrifying activity,with either succinate or malate serving as an electron donorin addition to endogenous substrates. The final product of denitrificationwas identified as nitrous oxide (N₂O), a result that confirmsthe presence of nitrate and nitrite reductases, but not N₂Oreductase, in these cells. Illumination during aerobic growthcaused a marked enhancement of the denitrifying activity. Theactivity increased with increasing intensity of light up to40 mW cm^–2 and was over 20 times that in dark-grown cells.Enhancement of denitrifying activity in illuminated cells wasclosely related to increases in levels of components that areinvolved in the denitrifying pathway, namely, nitrate and nitritereductases. Development of a denitrifying system under aerobicconditions and the enhancement of denitrifying ability by lightin Roseobacter denitrificans are unique characteristics, unlikethose of other known denitrifying bacteria. (Received October 29, 1990; Accepted January 17, 1991)     

Light-Stimultated Aerobic Growth of Erythrobacter Species OCh 114

Bright light almost completely suppressed bacteriochlorophyllsynthesis in Erythrobacter species OCh 114. Consequently, theeffect of continuous illumination on growth was barely observedwhen illumination was started an inoculation and the inoculumsize was small. However, when an aerobic culture of this bacteriumgrown preliminarily in the dark was illuminated after the celldensity became high, light stimulated the growth remarkably,indicating that the utilization of light energy for growth viabacteriochlorophyll which had been formed during the growthin the dark. The maximum cell yield from a culture intenselyilluminated following preliminary growth in the dark was twofoldthat from a culture grown in the dark throughout. A continuousoxygen supply was a prerequisite for the stimulation of growthby light. Microaerobic or anaerobic incubation of a dark-grownculture in the light brought about a decrease in spheroidenonecontent and a formation of an unknown pigment. ¹ Present address: Kawaguchi Factory, Sapporo Breweries Ltd.,Namikimoto-cho, Kawaguchi, Saitama 332, Japan ² Present address: Institute of Applied Microbiology, The Universityof Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (Received October 6, 1986; Accepted January 9, 1987)     

Purification and some properties of a soluble cytochrome (cytochrome c-551) from Erythrobacter species strain OCh 114

A soluble cytochrome, cytochrome c-551 was purified from an aerobic photosynthetic bacterium Erythrobacter species strain OCh 114 (ATCC No. 33942) by ammonium sulfate fractionation, ion-exchange chromatography and gel-filtration. The cytochrome had absorption maxima at 277, 410, and 524–525 nm in the oxidized form, and at 415, 522, and 550.5 nm in the reduced form. At 77 K, the -band of the absorption spectrum of the reduced form split in two at 547 and 549 nm. The millimolar absorption coefficient at 550.5 nm was 26.8 mM^-1 cm^-1 in the reduced form. This cytochrome was an acidic protein with an isoelectric point of 4.9. Its molecular weight was determined to be 15,000 by gel-filtration on Sephadex G-100 and 14,500 by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The midpoint potential of this cytochrome was +250 mV at pH 7.0. This cytochrome did not bind CO.     

A Denitrifying Activity in an Aerobic Photosynthetic Bacterium, Erythrobacter sp. Strain OCh 114

An aerobic photosynthetic bacterium, Erythrobacter sp. strainOCh 114, was capable of growth under anaerobic conditions inthe dark with nitrate as a terminal electron acceptor. The optimalnitrate concentration was about 6 mM for anaerobic growth, althougha wide range of concentrations from 1 to 400 mM were effective.A large amount of N₂O gas was released during this anaerobicgrowth, indicating a denitrifying activity in this bacterium.Light had no stimulating or inhibiting effect on the rates ofanaerobic growth and gas release. The enzymes responsible forthe denitrifying activity, dissimilatory nitrate and nitritereductases, were present in aerobically grown cells. (Received February 19, 1988; Accepted May 16, 1988)     

Characterization of a DMSP-degrading bacterial isolate from the Sargasso Sea

A bacterium which cleaves dimethylsulfoniopropionate (DMSP) to form dimethylsulfide (DMS) was isolated from surface Sargasso Sea water by a DMSP enrichment technique. The isolate, here designated LFR, is a Gram-negative, obligately aerobic, rod-shaped, carotenoid-containing bacterium with a DNA G+C content of 70%. Sequencing and comparison of its 16S ribosomal ribonucleic acid (rRNA) with that of known eubacteria revealed highest similarity (91% unrestricted sequence similarity) to Roseobacter denitrificans (formerly Erythrobacter species strain OCh114), an aerobic, bacteriochlorophyll-containing marine representative of the -Proteobacteria. However, physiological differences between the two bacteria, and the current lack of other characterized close relatives, preclude assignment of strain LFR to the Roseobacter genus. Screening of fifteen characterized marine bacteria revealed only one, Pseudomonas doudoroffii, capable of degrading DMSP to DMS. Strain LFR is deposited with the American Type Culture Collection (ATCC 51258) and 16S rRNA sequence data are available under GenBank accession number 15345.Contribution no. 8337 of the Woods Hole Oceanographic Institution     

Phagotrophy and NH4+ regeneration in a three-member microbial food loop

In a series of batch experiments we compared the efficiencyof nitrogen regeneration of a two- and three-member microbialfood loop consisting of a mixed bacterial assemblage, a small(3–5 µm) heterotrophic flagellate (Paraphysomonassp.), and a large (7–12 µm) heterotrophic flagellate(Paraphysomonas imperforata). In the two-member system the nitrogenregeneration efficiency for NH₄⁺ (R_n) was 41% and the grossgrowth efficiency (GGE) was 57% during active grazing by thesmall flagellate on bacteria. Regeneration of NH₄⁺ continuedduring the stationary phase so that R_n was 75% after 6 daysincubation. When the larger flagellate was introduced at theend of exponential growth of the smaller grazer in the three-membersystem, initially there was rapid regrowth of bacteria, tyingup 15% of the nitrogen originally in the bacteria. The largerflagellate grazed the smaller one with a GGE of 55%. Total nitrogenregeneration efficiency through exponential growth of the largerflagellate was 73%. Because microbial food loops in naturalwaters are far more complicated and with more grazing stepsthan portrayed in this study, we would expect the bulk of nutrientswithin these systems to be recycled with little transfer tohigher trophic levels.     

Measurement of Yield Threshold and Cell Wal Extensibility of Intact Wheat Roots under Different Ionic, Osmotic and Temperature Treatments

Yield stress threshold (Y) and volumetric extensibility () arethe rheological properties that appear to control root growth.In this study they were measured in wheat roots by means ofparallel measurement of the growth rate (r) of intact wheatroots and of the turgor pressures (P) of individual cells withinthe expansion zone. Growth and turgor pressure were manipulatedby immersion in graded osmoticum (mannitol) solutions. Turgorwas measured with a pressure probe and growth rate by visualobservation. The influence of various growth conditions on Yand was investigated; (a) At 27 °C.In 0.5 mol m^–3 CaCl₂ r, P, Y and were20.7±4.6 µm min^–1, 0.77±0.05 MPa,0.07±0.03 MPa and 26±1.9 µm min^–1MPa^–1 (expressed as increase in length), respectively.Following 24 h growth in 10 mol m^–3 KC1 these parametersbecame 12.3±3.5 µm min^–1, 0.72±0.04MPa, 0.13±0.01 MPa and 21±0.7 µm min^–1MPa^–1. After 24 h osmotic adjustment in 150 mol m^–3mannitol/0.5 mol m^–3 CaCl₂ r= 19.6±4.2 µmmin^–1, P = 0.68±0.05 MPa and Y and were 0.07±0.04MPa and 30±0.2 µm min^–1 MPa^–01, respectively.After 24 h growth in 350 mol m^–3 mannitol/0.5 mol m^–3CaCl₂ r= 13.3±4.1 µm min^–1, P= 0.58±0.07MPa, Y=0.12±0.01 MPa and ø 32±0.2 tim min^–1MPa^–1. During osmotic adjustment in 200 mol m^–3mannitol/0.5 mol m^–3 CaCl₂, with or without KCl, the recoveryof growth rate corresponded to turgor pressure recovery (t1/2approximately 3 h). (b) At 15 °C. Lowered temperature dramatically influencedthe growth parameters which became r= 8.3±2.8 um min^–1,P=0.78 MPa, r=<0.2 MPa and =15±0.1 µm min^–1MPa^–1. Therefore, Y and are influenced by 10 mol m^–3 K⁺ ionsand low temperature. In each case the effective pressure forgrowth (P-Y) was large indicating that small fluctuations ofsoil water potential will not stop root elongation. Key words: Yield threshold, cell wall extensibility, wheat root growth, temperature, turgor pressur     

O2-stimulated synthesis of bacteriochlorophyll and carotenoids in marine bacteria

We examined the effects of a limitation of the O₂-supply onthe syntheses of bacteriochlorophyll a_p and carotenoids in isolatesof aerobic marine bacteria, OCh 101 and OCh 114, grown heterotrophically.Whereas they formed these pigments fairly well under high aerationin the dark, a limitation of the O₂-supply resulted in the decreasedsyntheses of bacteriochlorophyll in both strains. Synthesesof carotenoids also were depressed under low aeration but toa lesser extent (especially in OCh 101) than the depressionof bacteriochlorophyll synthesis. Aerobic incubation of a cultureof OCh 101, that previously had been grown semiaerobically,induced the supplementary synthesis of bacteriochlorophyll.This induction was inhibited almost completely by chloram-phenicol.The absorption spectra of suspensions and solvent extracts ofcells grown aerobically or semiaerobically are reported. (Received May 30, 1980; )     

O2-stimulated synthesis of bacteriochlorophyll and carotenoids in marine bacteria

We examined the effects of a limitation of the O₂-supply onthe syntheses of bacteriochlorophyll a_p and carotenoids in isolatesof aerobic marine bacteria, OCh 101 and OCh 114, grown heterotrophically.Whereas they formed these pigments fairly well under high aerationin the dark, a limitation of the O₂-supply resulted in the decreasedsyntheses of bacteriochlorophyll in both strains. Synthesesof carotenoids also were depressed under low aeration but toa lesser extent (especially in OCh 101) than the depressionof bacteriochlorophyll synthesis. Aerobic incubation of a cultureof OCh 101, that previously had been grown semiaerobically,induced the supplementary synthesis of bacteriochlorophyll.This induction was inhibited almost completely by chloram-phenicol.The absorption spectra of suspensions and solvent extracts ofcells grown aerobically or semiaerobically are reported. (Received May 30, 1980; )     

Discontinuite hydrobiologique dans le detroit du Pas-de-Calais

Hydrobiological studies in the Straits of Dover show a differencebetween the characteristics of the French coastal water andthe open sea water. A cruise between Boulogne-sur-mer and Dover(October 15, 1985) confirms the existence of a frontal area(4 miles off the French coast). This area is characterized byan increase of the salinity (1%) and decrease of the suspendedmatter content (from 27 to 20 mg l^–1), of primary production(from 15 to 3 mg C m^–3h^–1) and of chlorophyll aconcentration (from 4.5 to 1.5 mg m^–3). The presence ofdifferent zooplanktonic species in the two water masses alsocharacterizes this discontinuity. Oncaea sp., Corycaeus anglicus,Centropages typicus and Calanus helgolandicus are indicatorspecies of open sea water, while Cyciopina littoralis and ‘Saphirella’are only present in coastal water.     

Observations on pigments and morphology of Gyrodinium aureolum Hulburt, a marine dinoflagellate containing 19' -hexanoyloxyfucoxanthin as the main carotenoid

Gyrodinium aureolum, a common "red tide" dinoflagellate in Europeanwaters often associated with fish mortality, was isolated fromthe Oslofjord, Norway, and analysed for chlorophylls and carotenoids.Besides chlorophyll a and c the following carotenoids were characterizedby thin-layer chromatography, visible light spectrophotometryand mass spectrometry: ß,-carotene, ß,ß-carotene,djatoxanthin, diadinoxanthin, 19'-hexanoyloxyfucoxanthin and3 xanthophylls which could not be correlated with hitherto structurallyknown carotenoids from dinoflagellates. G. aureolum deviatesfrom most dinoflagellates by the lack of peridinin, but showsaffinity with Gyrodinium sp.-A by the possession of 19'-hexanoyloxyfucoxanthin. Preliminary light microscopical observations on the internalstructure indicate that G. aureolum is uni-nucleate with a typicaldinokaryotic nucleus containing continually condensed chromosomes.The chloroplasts seem to possess an internal pyrenoid like someother dinoflagellates with deviating carotenoid pigmentation.The similarity in carotenoid pigmentation and chloroplast structureof Emiliania huxleyi (Prymnesiophyceae) and Gyrodinium sp.-Aand G.aureolum (Dinophyceae) is pointed out. The potential chemotaxonomicvalue of the carotenoid composition in establishing identitywith morphologically similar and ichthyotoxic dinoflagellatesis briefly discussed.     

On the causes of interspecific differences in the growth-irradiance relationship for phytoplankton. II. A general review

The causes of interspecific differences in the µ-l relationshipare examined in the context of a mechanistic model which relatesµ to irradiance in terms of six factors:, k_c photosyntheticquotient (PQ), Chl a:C, respiration and excretion. The effectof cell size on the light saturated growth rate is also considered.It is shown that photosynthetic efficiency and PQ exhibit remarkablylittle interspecific variability, and average 0.024 ±0.005 µg C(µg Chl a)^–1 h^–1 (µEm^–2 s^–1)^–1 and 1.5 ± 0.2 mol 02 molC^–1 (when NO₃^– is the nitrogen source) respectively.Two useful relationships were derived: (i) between growth efficiency,_g and Chl a:C at µ. = 0; (ii) between the compensationintensity, I_c and the Chl a-specific maintenance respirationrate. Both relationships were independent of temperature anddaylength. Species best adapted to growth at low light werefound to exhibit high Chl a:C ratios and low maintenance respirationrates. As a group, diatoms were consistently the best adaptedfor growth at low irradiance. Chiorophytes, haptophytes, chrysophytesand cryptophytes were intermediate in their performance at lowirradiance. Dinoflagellates exhibited extreme diversity, withspecies spanning the spectrum from very good performance atlow irradiance to very poor. A new µ_max-cell carbon relationshipis given based on growth rates normalized to 15°C. Evidenceis presented to show that noise in this relationship can besignificantly reduced by using only carbon-specific growth ratesand using only data for species grown at the same daylength.     

Seasonal species composition of barnacle larvae (Cirripedia: Thoracica) in Rhode Island waters, 1977-1978

Cirripede larvae can occur year-round in temperate and tropicalwaters, often in significant numbers, yet the species compositionof the ‘Balanus sp.’ component is rardy studied.Weekly plankton samples were analyzed qualitatively for larvalcirripede species and stage over a year (1977–1978) attwo Rhode Island stations. Six species of larvae were foundin Lower Narragansett Bay (30° salinity). Semibalanus balanoidesand Balanus balanus have a single winter brood. S. balanoidesis the predominant winter breeder with a minor release of naupliiin early December and major release in March followed by cypridsin mid-April.B. balanus populations release all larvae in Marchwith cyprids in mid-April. Balanus crenatus is mainly a winterbreeder, but has multiple broods; it does not breed in July-Septemberwhen the water temperature is above 18°C. Balanus venustusis the predominant summer breeder, and larvae were observedfrom May through December (water >8°C). Larvae of Chthamalusfragilis and Balanus eburneus occur in low numbers from May-October.At the Pettaquamscutt River site (12 salinity), Balanus improvisuslarvae predominate and early stage nauplii (I-II) occur in samplesyear round (0–27°C). Two peaks of later stage naupliiand cyprids occur in late spring (May) and early winter (Nov.-Jan.).Continued temperatures bdow 5°C or above 20°C appearto inhibit larval development. Comparison of results with existing literature reveals severalsignificant findings. The bimodal rdease of S. balanoides larvaeis unusual and may be in response to the phytoplankton dynamicsof the year; however, the existence of distinct races of S.balanoides may also be a factor. Larvae of B. venustus predominatein the lower bay during the summer, yet this species is unreportedin past studies. B. improvisus nauplii are more cold tolerantthan previously reported. Comparison of findings with reportedbreeding patterns in Florida indicate significant differencesin temperature responses between northern and southern populations. ¹Contribution No. 188 from EPA Environmental Research Laboratory,South Ferry Rd., Narragansett, RI 02882