| effect of periplasmic nitrate reductase on diauxic lag of paracoccus pantotrophus. | paracoccus pantotrophus expresses two nitrate reductases-membrane bound nitrate reductase (nar) and periplasmic nitrate reductase (nap). in growth experiments with two denitrifying species (paracoccus pantotrophus and alcaligenes eutrophus) that have both nap and nar and two species (pseudomonas denitrificans and pseudomonas fluorescens) with nar only, it was found that diauxic lag is shorter for bacteria that express nap. in p. pantotrophus, napedabc encodes the periplasmic nitrate reductase. t ... | 2009 | 19399903 |
| the cobt gene of salmonella typhimurium encodes the namn: 5,6-dimethylbenzimidazole phosphoribosyltransferase responsible for the synthesis of n1-(5-phospho-alpha-d-ribosyl)-5,6-dimethylbenzimidazole, an intermediate in the synthesis of the nucleotide loop of cobalamin. | we present in vitro evidence which demonstrates that cobt is the nicotinate nucleotide:5,6-dimethylbenzimidazole (dmb) phosphoribosyltransferase (ec 2.4.2.21) that catalyzes the synthesis of n1-(5-phospho-alpha-d-ribosyl)-5,6-dimethylbenzimidazole, a biosynthetic intermediate of the pathway that assembles the nucleotide loop of cobalamin in salmonella typhimurium. mutants previously isolated as dmb auxotrophs are shown by physical and genetic mapping studies and complementation studies to carry ... | 1994 | 8206834 |
| betaine-homocysteine transmethylase in pseudomonas denitrificans, a vitamin b 12 overproducer. | a pantothenate-methionine auxotroph (j741) of pseudomonas denitrificans was isolated whose growth requirement for methionine could not be satisfied by known precursors of the amino acid, including homocysteine. however, some "methyl rich" compounds such as betaine and dimethylacetothetin (dmt) could satisfy the requirement. s-methyl-methionine and s-adenosylmethionine were ineffective. extracts were found to contain an enzyme, betaine-homocysteine transmethylase (bhtase), that uses betaine or dm ... | 1973 | 4688138 |
| dependence of betaine stimulation of vitamin b(12) overproduction on protein synthesis. | the betaine-stimulated differential synthesis of vitamin b(12), i.e., the increase in b(12) per increase in dry cell weight, by pseudomonas denitrificans was inhibited by rifampin and chloramphenicol but not by benzylpenicillin and carbenicillin at concentrations of antibiotic that inhibit growth. the level of the first enzyme of corrin (and porphyrin) biosynthesis, delta-aminolevulinic acid synthetase, was decreased to a much greater degree by rifampin and chloramphenicol than by the penicillin ... | 1984 | 16346536 |
| inducible gene expression system by 3-hydroxypropionic acid. | 3-hydroxypropionic acid (3-hp) is an important platform chemical that boasts a variety of industrial applications. gene expression systems inducible by 3-hp, if available, are of great utility for optimization of the pathways of 3-hp production and excretion. | 2015 | 26500695 |
| effect of chloramphenicol on denitrification in flexibacter canadensis and "pseudomonas denitrificans". | it was recently reported that chloramphenicol inhibits existing denitrification enzyme activity in sediments and carbon-starved cultures of "pseudomonas denitrificans." therefore, we studied the effect of chloramphenicol on denitrification by flexibacter canadensis and "p. denitrificans." production of n(inf2)o from nitrate by f. canadensis cells decreased as the concentration of chloramphenicol was increased, and 10.0 mm chloramphenicol completely inhibited n(inf2)o production. "p. denitrifican ... | 1995 | 16534926 |
| real-time quantitative lamp (loop-mediated isothermal amplification of dna) as a simple method for monitoring ammonia-oxidizing bacteria. | loop-mediated isothermal amplification (lamp) of dna is a novel technique for the amplification of dna under isothermal conditions. for the first time, we applied this method to develop a simple and quantitative monitoring method for environmental microorganisms targeting amoa gene in ammonia-oxidizing bacteria. quantitative analysis was performed first by measuring fluorescence derived from an intercalation dye using a real-time thermal cycler, and then by measuring the turbidity of the reactio ... | 2006 | 16790287 |
| studies on cyclopropane fatty acid synthesis. correlation between the state of reduction of respiratory components and the accumulation of methylene hexadecanoic acid by pseudomonas denitrificans. | a delay in the onset of accumulation of methylene hexadecanoic acid could be engendered in pseudomonas denitrificans growing under limited oxygen conditions when the concentration of citrate but not the concentration of succinate in the medium was increased from 0.1 to 0.5%. ascorbate, which specifically reduced a cytochrome component possessing a maximum absorbance at 551 nm, partially inhibited the accumulation of methylene hexadecanoic acid under conditions which otherwise led to maximal prod ... | 1981 | 7284425 |
| mechanism of the ring contraction process in vitamin b12 biosynthesis by the anaerobe propionibacterium shermanii under aerobic conditions. | the mechanism of the ring contraction process during vitamin b(12) biosynthesis by the anaerobe propionibacterium shermanii was investigated under both aerobic and anaerobic conditions by means of feeding experiments with delta-amino[1-(13)c]levulinic acid (a biosynthetic intermediate of tetrapyrrole) and delta-amino[1-(13)c,1,1,4-(18)o(3)]levulinic acid in combination with (13)c-nmr spectroscopy. we showed that the characteristic mechanism of the ring contraction process (the generation of prec ... | 2007 | 17561959 |
| an effective and simplified ph-stat control strategy for the industrial fermentation of vitamin b(12) by pseudomonas denitrificans. | in order to improve the productivity of vitamin b(12) by pseudomonas denitrificans carried out in a 120-m(3) fermenter, the effect of ph on vitamin b(12) biosynthesis was investigated. results obtained from shake flask experiments showed that the feeding of carbon source (beet molasses or glucose) and methyl-group donor (betaine or choline chloride) significantly influenced the ph and the biosynthesis of vitamin b(12). in contrast to beet molasses or choline chloride, using glucose as a feed med ... | 2008 | 18320234 |
| improved large-scale production of vitamin b12 by pseudomonas denitrificans with betaine feeding. | the strategy of betaine control for vitamin b12 large-scale fermentation by pseudomonas denitrificans was investigated in this paper. the results obtained in shake-flask experiments demonstrated that betaine could greatly stimulate vitamin b12 biosynthesis but had an inhibition to cell growth. based on the influence of betaine on the fermentation of p. denitrificans, betaine feeding was a beneficial strategy to solve the inconsistency between cell growth and vitamin b12 production. as a result, ... | 2008 | 18440227 |
| fundamental denitrification kinetic studies with pseudomonas denitrificans. | fundamental kinetic studies on the reduction of nitrate, nitrite, and their mixtures were performed with a strain of pseudomonas denitrificans (atcc 13867). methanol served as the carbon source and was supplied in excess (2:1 mole ratio relative to nitrate and/or nitrite). nitrate and nitrite served as terminal electron acceptors as well as sources of nitrogen for biomass synthesis. the results were explained under the assumption that respiration is a growth-associated process. it was found that ... | 1995 | 18623364 |
| structure of nitrogen-converting communities induced by hydraulic retention time and cod/n ratio in constantly aerated granular sludge reactors treating digester supernatant. | this study investigated how hydraulic retention time (hrt) and cod/n ratio affect nitrogen-converting consortia in constantly aerated granules treating high-ammonium digester supernatant. three hrts (10, 13, 19 h) were tested at cod/n ratios of 4.5 and 2.3. denaturing gradient gel electrophoresis and relative real-time pcr were used to characterize the microbial communities. when changes in hrt and cod/n increased nitrogen loading, the ratio of the relative abundance of aerobic to anaerobic ammo ... | 2014 | 24384323 |
| [biosynthesis, fermentation and application of vitamin b12--a review]. | vitamin b12 is an important nutrient widely used in feed, food and medicine field. china is the primary producing area and the vb12 production is 27 t in 2007, 77% of total production in the world. vb12 is the most complex small molecule difficult to chemosynthesize. it ismanufactured by bacteria and archaea via two alternative routes, aerobic or anaerobic pathway. the main strains used in industry fermentation are propionibacterium freudenrechii and pseudomonas denitrificans. the basic characte ... | 2008 | 18807971 |
| demonstration that cobg, the monooxygenase associated with the ring contraction process of the aerobic cobalamin (vitamin b12) biosynthetic pathway, contains an fe-s center and a mononuclear non-heme iron center. | the ring contraction process that occurs during cobalamin (vitamin b(12)) biosynthesis is mediated via the action of two enzymes, cobg and cobj. the first of these generates a tertiary alcohol at the c-20 position of precorrin-3a by functioning as a monooxygenase, a reaction that also forms a gamma lactone with the acetic acid side chain on ring a. the product, precorrin-3b, is then acted upon by cobj, which methylates at the c-17 position and promotes ring contraction of the macrocycle by catal ... | 2009 | 19068481 |
| biocontrol: bacillus penetrans and related parasites of nematodes. | bacillus penetrans mankau, 1975, previously described as duboscqia penetrans thorne 1940, is a candidate agent for biocontrol of nematodes. this review considers the life stages of this bacterium: vegetative growth phase, colony fragmentation, sporogenesis, soil phase, spore attachment, and penetration into larvae of root-knot nematodes. the morphology of the microthallus colonies and the unusual external features of the spore are discussed. taxonomic affinities with the actinomycetes, particula ... | 1980 | 19300701 |
| biosynthesis of the corrin macrocycle of coenzyme b12 in pseudomonas denitrificans. | studies with cell-free protein preparations from a series of recombinant strains of pseudomonas denitrificans demonstrated that precorrin-3 is converted into a further trimethylated intermediate, named precorrin-3b, along the pathway to coenzyme b12. it was then shown that the part of the pathway from precorrin-3 (called precorrin-3a hereafter) to precorrin-6x involves three intermediates, precorrin-3b, precorrin-4, and precorrin-5. precorrin-3b was isolated in its native (reduced) as well as it ... | 1993 | 8226690 |
| simultaneous nitrification and denitrification using immobilized microorganisms. | nitrogen removal from wastewaters is a multiple step process in which nitrification is often a problem due to the slow growth rates of the nitrifying bacteria. by immobilization of these bacteria, nitrification can be efficiently accomplished in compact reactors. in this paper, the possibilities of integrated nitrification and denitrification within a single reactor system are evaluated. two main systems are studied: a) nitrosamines europaea and pseudomonas denitrificans co-immobilized in a a ge ... | 1993 | 8399972 |
| biosynthesis of vitamin b12: the preparative multi-enzyme synthesis of precorrin-3a and 20-methylsirohydrochlorin (a 2,7,20-trimethylisobacteriochlorin). | the bacillus subtilis genes hemb, hemc and hemd, encoding respectively the enzymes porphobilinogen synthase, hydroxymethylbilane synthase and uroporphyrinogen iii synthase, have been expressed in escherichia coli using a single plasmid construct. an enzyme preparation from this source converts 5-aminolaevulinic acid (ala) preparatively and in high yield into uroporphyrinogen iii. the pseudomonas denitrificans genes coba and cobi, encoding respectively the enzymes s-adenosyl-l-methionine:uroporph ... | 1996 | 8546704 |
| salmonella typhimurium cobalamin (vitamin b12) biosynthetic genes: functional studies in s. typhimurium and escherichia coli. | in order to study the salmonella typhimurium cobalamin biosynthetic pathway, the s. typhimurium cob operon was isolated and cloned into escherichia coli. this approach has given the new host of the cob operon the ability to make cobalamins de novo, an ability that had probably been lost by this organism. in total, 20 genes of the s. typhimurium cob operon have been transferred into e. coli, and the resulting recombinant strains have been shown to produce up to 100 times more corrin than the pare ... | 1996 | 8550510 |
| a role for salmonella typhimurium cbik in cobalamin (vitamin b12) and siroheme biosynthesis. | the role of cbik, a gene found encoded within the salmonella typhimurium cob operon, has been investigated by studying its in vivo function in escherichia coli. first, it was found that cbik is not required for cobalamin biosynthesis in the presence of a genomic cysg gene (encoding siroheme synthase) background. second, in the absence of a genomic cysg gene, cobalamin biosynthesis in e. coli was found to be dependent upon the presence of coba(p. denitrificans) (encoding the uroporphyrinogen iii ... | 1997 | 9150215 |
| biosynthesis of vitamin b12: the multi-enzyme synthesis of precorrin-4 and factor iv. | in order to study the biosynthesis of vitamin b12, it is necessary to produce various intermediates along the biosynthetic pathway by enzymic methods. recently, information on the organisation of the biosynthetic pathway has permitted the selection of the set of enzymes needed to biosynthesise any specific identified intermediate. the aim of the present work was to use recombinant enzymes in reconstituted multi-enzyme systems to biosynthesise particular intermediates. | 1997 | 9224567 |
| biosynthesis of porphyrins and related macrocycles, part 43. isolation and characterization of intermediates of coenzyme b12 biosynthesis, a cobyrinic acid triamide, the a,c-diamide and their co-(5'-deoxy-5'-adenosyl) derivatives, from propionibacterium shermanii. | vitamin b12 is synthesized by many different organisms, for example pseudomonas denitrificans (aerobic) and propionibacterium shermanii ('microaerophilic', or essentially anaerobic). the biosynthetic pathways in these two organisms show strong similarities but also some differences. there have been conflicting reports on where differences between these two organisms lie in the stages beyond the formation of the corrin macrocycle. characterization of intermediates in the pathway will help resolve ... | 1995 | 9383456 |
| definition of the redox states of cobalt-precorrinoids: investigation of the substrate and redox specificity of cbil from salmonella typhimurium. | the enzyme cbil from the facultative anaerobe salmonella typhimurium exhibits a high degree of homology to cobi from the aerobe pseudomonas denitrificans (29% identity; 51% conservation obtained by a blastp search of the ncbi database). as cobi catalyzes the third methylation in the aerobic pathway to vitamin b12 it is proposed that cbil catalyzes the analogous step in the anaerobic pathway. potential metallo and metal-free substrates were characterized and their redox states defined by a combin ... | 1998 | 9778368 |
| effect of hemin and oxygen tension on growth and nitrate reduction by bacteria. | jacobs, n. j. (american meat institute foundation, chicago, ill.), r. e. heady, j. m. jacobs, k. chan, and r. h. deibel. effect of hemin and oxygen tension on growth and nitrate reduction by bacteria. j. bacteriol. 87:1406-1411. 1964.-the effect of hemin supplementation of growth media on the ability of several bacteria to reduce nitrate was studied. added hemin had no detectable effect on the ability of these organisms to reduce nitrate when grown in stationary cultures exposed to air. however, ... | 1964 | 14188721 |
| structure/function studies on a s-adenosyl-l-methionine-dependent uroporphyrinogen iii c methyltransferase (sumt), a key regulatory enzyme of tetrapyrrole biosynthesis. | the crystallographic structure of the pseudomonas denitrificans s-adenosyl-l-methionine-dependent uroporphyrinogen iii methyltransferase (sumt), which is encoded by the coba gene, has been solved by molecular replacement to 2.7a resolution. sumt is a branchpoint enzyme that plays a key role in the biosynthesis of modified tetrapyrroles by controlling flux to compounds such as vitamin b(12) and sirohaem, and catalysing the transformation of uroporphyrinogen iii into precorrin-2. the overall topol ... | 2004 | 15522295 |
| a simple model for diauxic growth of denitrifying bacteria. | a simple model has been formulated to simulate diauxic growth of denitrifying bacteria. it is capable of fitting the experimental results of batch growth experiments with pseudomonas denitrificans under various conditions. it successfully predicts the observed lags when a pure culture of this bacterium switches from oxygen to nitrate as terminal electron acceptor. the model includes the effect of carbon substrate limitation and length of aerobic phase and does not run into problems when switchin ... | 2005 | 15899290 |
| improved vitamin b(12) production by step-wise reduction of oxygen uptake rate under dissolved oxygen limiting level during fermentation process. | effects of different oxygen transfer rates (otr) on the cell growth and vitamin b(12) biosynthesis of pseudomonas denitrificans were first investigated under dissolved oxygen limiting conditions. the results demonstrated that high otr accelerated cell growth and initial vitamin b(12) biosynthesis rate, while lower otr was critical for higher productivity in the late fermentation process. the oxygen uptake rates (our) corresponded well with otr. based on the metabolic intermediate analysis, a ste ... | 2010 | 20022743 |
| influence of alternating oxic/anoxic conditions on growth of denitrifying bacteria. | denitrifying bacteria that are switched from oxic to anoxic conditions can experience diauxic lag, which is the time required for re-synthesis of nitrate reductase and other denitrifying enzymes. pseudomonas denitrificans were exposed to alternating oxic/anoxic phases in a continuous flow reactor with either 4-h or 8-h anoxic phase lengths, in comparison to a measured diauxic lag of 9.5h following steady-state oxic conditions. the p. denitrificans were unable to sustain anoxic growth at either o ... | 2010 | 20045547 |
| development of amplified fragment length polymorphism-derived functional strain-specific markers to assess the persistence of 10 bacterial strains in soil microcosms. | to augment the information on commercial microbial products, we investigated the persistence patterns of high-priority bacterial strains from the canadian domestic substance list (dsl). specific dna markers for each of the 10 dsl bacterial strains were developed using the amplified fragment length polymorphism (aflp) technique, and the fates of dsl strains introduced in soil were assessed by real-time quantitative pcr (qpcr). the results indicated that all dna markers had high specificity at the ... | 2010 | 20817796 |
| identification and phylogenetic characterization of cobalamin biosynthetic genes of ensifer adhaerens. | ensifer adhaerens csba was screened as a cobalamin producer. the draft genome sequence revealed that the strain possesses 22 cobalamin biosynthetic genes (cob genes). the cob gene arrangement on the genome of e. adhaerens csba was similar to that of other ensifer species, and most similar to that of pseudomonas denitrificans sc510. the cobn sequence phylogeny was generally congruent with that of the 16s rrna gene, and it is suggeted that e. adhaerens csba might have inherited the cob genes from ... | 2012 | 23257908 |
| coenzyme b12 can be produced by engineered escherichia coli under both anaerobic and aerobic conditions. | coenzyme b12 (vitamin b12 ) is one of the most complex biomolecules and an essential cofactor required for the catalytic activity of many enzymes. pseudomonas denitrificans synthesizes coenzyme b12 in an oxygen-dependent manner using a pathway encoded by more than 25 genes that are located in six different operons. escherichia coli, a robust and suitable host for metabolic engineering was used to produce coenzyme b12 . these genes were cloned into three compatible plasmids and expressed heterolo ... | 2014 | 25146562 |
| cloning, expression and characterization of 3-hydroxyisobutyrate dehydrogenase from pseudomonas denitrificans atcc 13867. | the gene encoding an nad(+)-dependent, 3-hydroxyisobutyrate dehydrogenase (3hibdh-iv) from pseudomonas denitrificans atcc 13867 was cloned and expressed in escherichia coli bl 21 (de3) and characterized to understand its physiological relevance in the degradation of 3-hydroxypropionic acid (3-hp). the deduced amino acid sequence showed high similarity to other 3-hydroxyisobutyrate dehydrogenase isozymes (3hibdhs) of p. denitrificans atcc 13867. a comparison of 3hibdh-iv with its relevant enzymes ... | 2013 | 23658760 |
| production of 3-hydroxypropionic acid from glycerol by recombinant pseudomonas denitrificans. | 3-hydroxypropionic acid (3-hp) can be produced from glycerol through two sequential enzymatic reactions that are catalyzed by a coenzyme b12 -dependent glycerol dehydratase and an nad(p)(+) -dependent aldehyde dehydrogenase (aldh), respectively. pseudomonas denitrificans synthesizes coenzyme b12 under aerobic conditions, where nad(p)(+) is regenerated efficiently. hence, it is considered an ideal host for the production of 3-hp from glycerol under aerobic conditions. in this study, recombinant s ... | 2013 | 23775313 |
| industrial vitamin b12 production by pseudomonas denitrificans using maltose syrup and corn steep liquor as the cost-effective fermentation substrates. | the aerobic pseudomonas denitrificans is widely used for industrial and commercial vitamin b12 fermentation, due to its higher productivity compared to the anaerobic vitamin b12-producing microorganisms. this paper aimed to develop a cost-effective fermentation medium for industrial vitamin b12 production by p. denitrificans in 120,000-l fermenter. it was found that maltose syrup (a low-cost syrup from corn starch by means of enzymatic or acid hydrolysis) and corn steep liquor (csl, a by-product ... | 2015 | 25561346 |
| development of a deletion mutant of pseudomonas denitrificans that does not degrade 3-hydroxypropionic acid. | pseudomonas denitrificans is a gram-negative bacterium that can produce vitamin b12 under aerobic conditions. recently, recombinant strains of p. denitrificans overexpressing a vitamin b12-dependent glycerol dehydratase (dhab) were developed to produce 3-hydroxypropionic acid (3-hp) from glycerol. the recombinant p. denitrificans could produce 3-hp successfully under aerobic conditions without an exogenous supply of vitamin b12, but the 3-hp produced disappeared during extended cultivation due t ... | 2014 | 24519457 |
| comparative genome analysis of pseudomonas knackmussii b13, the first bacterium known to degrade chloroaromatic compounds. | pseudomonas knackmussii b13 was the first strain to be isolated in 1974 that could degrade chlorinated aromatic hydrocarbons. this discovery was the prologue for subsequent characterization of numerous bacterial metabolic pathways, for genetic and biochemical studies, and which spurred ideas for pollutant bioremediation. in this study, we determined the complete genome sequence of b13 using next generation sequencing technologies and optical mapping. genome annotation indicated that b13 has a va ... | 2015 | 24803113 |
| the online morphology control and dynamic studies on improving vitamin b12 production by pseudomonas denitrificans with online capacitance and specific oxygen consumption rate. | the relationship between the morphological character of pseudomonas denitrificans and vitamin b12 synthesis based on real-time capacitance measurement and online specific oxygen consumption rate (q o2) control was established for enhancing vitamin b12 production. results demonstrated that the threshold q o2 value lower than 2.0 mmol/gdcw/l would greatly stimulate the state transfer from the cell number growth phase to the cell elongation phase and promote rapid vitamin b12 biosynthesis, while th ... | 2016 | 27022751 |
| characterisation of a 3-hydroxypropionic acid-inducible system from pseudomonas putida for orthogonal gene expression control in escherichia coli and cupriavidus necator. | 3-hydroxypropionic acid (3-hp) is an important platform chemical used as a precursor for production of added-value compounds such as acrylic acid. metabolically engineered yeast, escherichia coli, cyanobacteria and other microorganisms have been developed for the biosynthesis of 3-hp. attempts to overproduce this compound in recombinant pseudomonas denitrificans revealed that 3-hp is consumed by this microorganism using the catabolic enzymes encoded by genes hpdh, hbdh and mmsa. 3-hp-inducible s ... | 2017 | 28496205 |
| interactive performances of betaine on the metabolic processes of pseudomonas denitrificans. | the performances of betaine on the metabolic processes of vitamin b12-producing pseudomonas denitrificans were investigated in this paper. the results showed that betaine was an indispensable methyl-group donor for vitamin b12 biosynthesis, but large amounts of the extracellular glycine accompanied by betaine metabolism would impose a severe restriction on the cell growth of p. denitrificans. by further using a comparative metabolomics approach coupled with intracellular free amino acids analysi ... | 2015 | 25502424 |
| improved vitamin b12 fermentation process by adding rotenone to regulate the metabolism of pseudomonas denitrificans. | our previous research had revealed that the dissolved oxygen limitation was more favorable for vitamin b12 fermentation, due to its inducement to the increased glycolytic flux in pseudomonas denitrificans. in this paper, a novel strategy was implemented to further investigate the metabolic characteristics of p. denitrificans under different oxygen supply levels, by exogenously adding rotenone (a respiratory chain inhibitor interfering with the oxygen consumption) to the fermentation broths. comp ... | 2014 | 24687557 |
| complete genome sequence of pseudomonas denitrificans atcc 13867. | pseudomonas denitrificans atcc 13867, a gram-negative facultative anaerobic bacterium, is known to produce vitamin b12 under aerobic conditions. this paper reports the annotated whole-genome sequence of the circular chromosome of this organism. | 2013 | 23723394 |