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     

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; )     

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 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)     

Growth Characteristics and Substrate Specificity of Aerobic Photosynthetic Bacterium, Erythrobacter Sp. (OCh 114)

Optimal growth conditions and substrate specificity of the aerobicphotosynthetic bacterium, Erythrobacter sp. (OCh 114), wereinvestigated. Erythrobacter utilized 19 out of 26 substratestested, including several sugars and amino acids. Glycerol andlactate were the most effective as electron donors or carbonsources. Maximum growth was obtained at a salinity of about25, pH 8–9 and temperature 28°C in a glycerol-enrichedmedium. A suitable growth medium for Erythrobacter sp. (OCh114) is proposed. (Received October 18, 1985; Accepted January 10, 1986)     

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)     

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)     

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)     

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)     

Trimethylamine N-oxide respiration by aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

Erythrobacter sp. OCh 114, an aerobic photosynthetic bacterium, had trimethylamine N-oxide (TMAO) reductase activity, which increased when the culture medium contained TMAO. The reductase was located in the periplasm. The bacteria grew anaerobically in the presence of TMAO. These results suggested that Erythrobacter OCh 114 has the ability to reduce TMAO through the respiratory chain. The TMAO respiration system of this organism was different from those of facultative purple photosynthetic bacteria in two respects: (a) TMAO reductase did not have activity to reduce dimethyl sulfoxide and (b) soluble c-type cytochrome, cytochrome c551, and cytochrome b-c1 complex appeared to be involved. The photochemical activity, which is usually inoperative in the anaerobic cell suspension, was restored by TMAO, suggesting that the photosynthesis and the TMAO respiration share a common electron transfer chain.     

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     

Light-induced changes of carotenoid pigments in anaerobic cells of the aerobic photosynthetic bacterium,Roseobacter denitrificans (Erythrobacter species OCh 114): reduction of spheroidenone to 3,4-dihydrospheroidenone

Roseobacter denitrificans, previously named Erythrobacter species OCh 114, synthesized spheroidenone as a major carotenoid under aerobic dark conditions. When the dark-grown cells were subjected to illumination under anacrobic conditions, many unknown yellow pigments appeared and a considerable amount of spheroidenone disappeared. Absorption maxima of these pigments were blue-shifted from those of spheroidenone. The most abundant of the pigments was isolated, and its chemical structure was determined as 3,4-dihydrospheroidenone on spectroscopic and chemical evidence. Presumably, over-reduction of the photosynthetic apparatus interfered with normal photosynthetic electron transfer and resulted in photoreduction of C=C double bond at the 3,4-position of spheroidenone.     

A novel phosphatase specific for pyridoxal 5'-phosphate in an aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

Abstract An acid phosphatase highly spcific for pyridoxal 5'-phosphate (PLP) was found and partially purified from the aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114. The enzyme showed a pH optimum at 5.5; its activity was stimulated by magnesium ions. This enzyme also hydrolyzed p -nitrophenyl phosphate (NPP) and flavin mononucleotide (FMN). The enzyme level varied depending on growth conditions. Supplementing the growth medium with glycerol, glucose, xylose or mannitol increased the level of phosphatase activity. An inverse relationship between free phosphate content in the cells and enzyme level was observed.     

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)     

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.     

Complete amino acid sequence of cytochrome c551 from Erythrobacter species strain OCh 114

The complete amino acid sequence of cytochrome c551 isolated from an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114, was determined. The cytochrome molecule was composed of a total of 119 amino acid residues and its molecular weight including heme was calculated to be 13,235. The sequence was (Sequence: see text). Its molecular weight indicates that this cytochrome is of the L-type. Sequence alignment with other bacterial cytochromes c shows that this cytochrome is similar to cytochromes c of Rhodobacter capsulatus, Rhodobacter sphaeroides, and Paracoccus denitrificans, which were grouped into the alpha-3 subcluster from the 16S rRNA sequence analysis.     

Two types of cytochrome cd1 in the aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

Components I and II of cytochrome cd1 which had different spectral features were purified from the aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114. Component I showed an absorption maxima at 700 and 406 nm in the oxidized form, and at 621, 552.5, 548 and 416 nm in the reduced form. Component II showed an absorption maxima at 635 and 410 nm in the oxidized form and at 628, 552.5, 548 and 417 nm in the reduced form. The relative molecular mass, Mr, of both cytochromes was determined to be 135,000 with two identical subunits. Components I and II showed pI values of 7.6 and 6.8, respectively. The redox potential of hemes ranged from +234 mV to +242 mV, except for the heme d1 of component I (Em7 = +134 mV). Components I and II showed both cytochrome c oxidase and nitrite reductase activities. Cytochrome c oxidase activity was strongly inhibited by a low concentration of nitrite and cyanide. Erythrobacter cytochromes c-551 and c-552 were utilized as electron donors for the cytochrome c oxidase reaction. The high affinity of cytochrome c-552 to component II (Km = 1.27 microM) suggested a physiological significance for this cytochrome. Erythrobacter cytochromes cd1 are unique in their presence in cells grown under aerobic conditions as compared to other bacterial cytochromes cd1 which are formed only under denitrifying conditions.     

Phage Resistance of a Marine Bacterium, Roseobacter denitrificans OCh114, as Revealed by Comparative Proteomics

Roseobacter is a dominant lineage in the marine environment. This group of bacteria is diverse in terms of both their phylogenetic composition and their physiological potential. Roseobacter denitrificans OCh114 is one of the most studied bacteria of the Roseobacter lineage. Recently, a lytic phage (RDJLΦ1) that infects this bacterium was isolated and a mutant strain (M1) of OCh114 that is resistant to RDJLΦ1 was also obtained. Here, we investigate the mechanisms supporting phage resistance of M1. Our results excluded the possibilities of several phage resistance mechanisms, including abortive infection, lysogeny, and the clustered regularly interspaced short palindromic repeats (CRISPRs) related mechanism. Adsorption kinetics assays revealed that adsorption inhibition might be a potential cause for the phage resistance of M1. Comparative proteomic analysis of M1 and OCh114 revealed significant changes in the membrane protein compliment of these bacteria. Five membrane proteins with important biological functions were significantly down-regulated in the phage-resistant M1. Meanwhile, several outer membrane porins with different modifications and an OmpA family domain protein were markedly up-regulated. We hypothesize that the down-regulated membrane proteins in M1 may serve as the potential phage receptors, whose absence prevented the adsorption of phage RDJLΦ1 to host cells and subsequent infection.     

Reaction center complex from an aerobic photosynthetic bacterium,Erythrobacter species OCh 114

A photosynthetic reaction center complex has been purified from an aerobic photosynthetic bacterium, Erythrobacter species OCh 114. The reaction center was solubilized with 0.45% lauryldimethylamine N-oxide and purified by DEAE-Sephacel column chromatography. Absorption spectra of both reduced and oxidized forms of the reaction center were very similar to those of the reaction center from Rhodopseudomonas sphaeroides R-26 except for the contributions due to cytochrome and carotenoid. 1 mol reaction center contained 4 mol bacteriochlorophyll a, 2 mol bacteriopheophytin a, 4 mol cytochrome c-554, 2 mol ubiquinone-10, and carotenoid. The reaction center consisted of four different polypeptides of 26, 30, 32 and 42 kDa. The last one retained heme c. Absorbance at 450 nm oscillated with the period of two on consecutive flashes. The light-minus-dark difference spectrum had two peaks at 450 nm and 420 nm, indicating that odd flashes generated a stable ubisemiquinone anion and even flashes generated quinol. o-Phenanthroline accelerated the re-reduction of flash-oxidized reaction centers, indicating that o-phenanthroline inhibited the electron transfer between Q_A and Q_B. The cytochrome (cytochrome c-554) in the reaction center was oxidized on flash activation. The midpoint potential of the primary electron acceptor (Q_A) was determined by measuring the extent of oxidation of cytochrome c-554 at various ambient potentials. The mid-point potential of Q_A was −44 mV, irrespective of pH between 5.5 and 5.9.