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)     

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)     

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.     

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     

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)     

Control of bacteriochlorophyll accumulation by light in an aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

The effect of light on bacteriochlorophyll (Bchl) accumulation as well as the activity of two enzymes in the initial step of the tetrapyrrole biosynthetic pathway was examined in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114. Light clearly regulated the Bchl and carotenoid accumulation, completely suppressing their levels at high light intensity. However, porphyrin and Bchl precursors were not found in either the cells or the growth medium of lighted culture. The level of Bchl showed an inverse relationship to the light energy flux. Kinetic studies showed a Hill coefficient of n = 3.3 (r = 0.973), indicating a positive cooperativity. Bchl accumulation was stopped immediately upon illumination without any lag or overshoot. Despite low Bchl content, the activities of 5-aminolevulinic acid synthetase and porphobilinogen synthase were rather stimulated, but not suppressed by light. The high activity of enzymes coincided with the results that heme contents, particularly cytochrome c and catalase activity, were increased in light-grown cells. These results suggest that light regulated Bchl accumulation, but not Bchl biosynthesis and that the effect of light is to render newly formed pigment molecules unstable.     

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.     

Photophosphorylation and oxidative phosphorylation in intact cells and chromatophores of an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114.

Light-induced ATP synthesis was studied in intact cells and chromatophores of Erythrobacter sp. strain OCh114. ATP synthesis was measured by both the pH method and the luciferin-luciferase luminescence method. The rate of ATP synthesis was moderate (a typical value of 0.65 mol of ATP per mol of bacteriochlorophyll per min), and synthesis was inhibited by antimycin A. ATP was synthesized under illumination only under aerobic conditions and not under anaerobic conditions. This characteristic was similar to that of other light-induced energy transduction processes in this bacterial species, such as oxidation of reaction center, oxidation of cytochrome c551, and translocation of H+, which were not observed under anaerobic conditions. This phenomenon was reconciled with the fact that the Erythrobacter sp. could not grow anaerobically even in the light. The characteristics of oxidative phosphorylation and ATP hydrolysis were also investigated. The respiratory ratio of chromatophores was 2.3. Typical rates of oxidative phosphorylation by NADH and by succinate were 2.9 mol of ATP per mol of bacteriochlorophyll per min (P/O = 0.22) and 1.1 mol of ATP per mol of bacteriochlorophyll per min (P/O = 0.19), respectively. A typical rate of ATP hydrolysis was 0.25 mol of ATP per mol of bacteriochlorophyll per min in chromatophores. ATPase and adenylate kinase are also involved in the metabolism of adenine nucleotides in this bacterium.     

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.     

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     

Inhibition of porphyrin biosynthesis by exogenous 5-aminolevulinic acid in an aerobic photosynthetic bacterium, Erythrobacter sp. OCh 114

Exogenously administered 5-aminolevulinic acid (ALA) inhibited the formation of bacteriochlorophyll a (Bchl a) in a dose-dependent manner in the aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh 114, under dark growth conditions. The ALA concentration required for half-inhibition after 24-h growth was estimated to be about 3.0 mM. Porphyrin and Bchl precursors were not found in either the cells or the growth medium. The same inhibition was also observed with cytochrome c formation. When ALA was incubated with intact cells, a large amount of ALA was converted to an unknown metabolite. The pH optimum of the conversion was 7.8. The metabolite did not react with Ehrlich's reagent, but did so with ninhydrin, giving a yellow color. Based on analyses by several techniques including mass spectrometry, ir spectrometry, and paper electrophoresis, it was identified as 4-hydroxy-5-aminovaleric acid (HAVA). Authentic HAVA prepared from ALA was a competitive inhibitor of the enzyme, porphobilinogen synthase of Erythrobacter. The Ki value for authentic HAVA was calculated to be 2.4 mM from a Dixon plot and the HAVA concentration required for half-inhibition was 17 mM. It is concluded that in Erythrobacter cells, exogenous ALA is converted to the metabolite, HAVA, which is responsible for the inhibition of porphobilinogen synthase as well as that of Bchl a and cytochrome formation.     

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.     

Roles of bacteriochlorophyll and carotenoid synthesis in formation of intracytoplasmic membrane systems and pigment-protein complexes in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114.

Synthesis of bacteriochlorophyll and carotenoids was inhibited in an aerobic photosynthetic bacterium, Erythrobacter sp. strain OCh114, by alpha, alpha'-dipyridyl and diphenylamine. Formation of two pigment-protein complexes, reaction center-B870 (RC-B870) and B806, and development of the intracytoplasmic membranes of the cells were studied by spectral analysis and electron microscopy. Inhibition of bacteriochlorophyll synthesis by alpha, alpha'-dipyridyl, which was accompanied by a decrease in carotenoid synthesis, suppressed formation of intracytoplasmic membranes in the cells. Growth under illumination had a similar effect on formation of pigments and membranes. On the other hand, inhibition of carotenoid synthesis by diphenylamine did not suppress either development of the membrane system or bacteriochlorophyll synthesis. Formation of RC-B870 and B806 complexes, however, was differentially affected by blockage of carotenoid synthesis. In the presence of diphenylamine, the B806 complex was formed in a much smaller amount than the RC-B870 complex. These results suggest that, in Erythrobacter sp. strain OCh114, bacteriochlorophyll plays an essential role in intracytoplasmic membrane development, and carotenoids are important for assembly of pigment-protein complexes.     

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.     

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.     

Genome Sequence of the Aerobic Bacterium Bacillus sp. Strain FJAT-13831

Bacillus sp. strain FJAT-13831 was isolated from the no. 1 pit soil of Emperor Qin''s Terracotta Warriors in Xi''an City, People''s Republic of China. The isolate showed a close relationship to the Bacillus cereus group. The draft genome sequence of Bacillus sp. FJAT-13831 was 4,425,198 bp in size and consisted of 5,567 genes (protein-coding sequences [CDS]) with an average length of 782 bp and a G+C value of 36.36%.