scholarly journals Efficient Production of 2,5-Diketo-d-Gluconate via Heterologous Expression of 2-Ketogluconate Dehydrogenase in Gluconobacter japonicus

2015 ◽  
Vol 81 (10) ◽  
pp. 3552-3560 ◽  
Author(s):  
Naoya Kataoka ◽  
Minenosuke Matsutani ◽  
Toshiharu Yakushi ◽  
Kazunobu Matsushita
Keyword(s):  
Mutant Strain ◽  
Gluconobacter Oxydans ◽  
Efficient Production ◽  
Broad Host Range ◽  
Putative Promoter Region ◽  
Content Type ◽  
Biotransformation Process ◽  
Genes Encoding ◽  
Membrane Bound ◽  
Almost All

ABSTRACT2,5-Diketo-d-gluconate (2,5DKG) is a compound that can be the intermediate ford-tartrate and also vitamin C production. AlthoughGluconobacter oxydansNBRC3293 produces 2,5DKG fromd-glucose viad-gluconate and 2-keto-d-gluconate (2KG), with accumulation of the product in the culture medium, the efficiency of 2,5DKG production is unsatisfactory because there is a large amount of residuald-gluconate at the end of the biotransformation process. Oxidation of 2KG to 2,5DKG is catalyzed by a membrane-bound flavoprotein-cytochromeccomplex: 2-keto-gluconate dehydrogenase (2KGDH). Here, we studied thekgdSLCgenes encoding 2KGDH inG. oxydansNBRC3293 to improve 2,5DKG production byGluconobacterspp. ThekgdS,kgdL, andkgdCgenes correspond to the small, large, and cytochrome subunits of 2KGDH, respectively. ThekgdSLCgenes were cloned into a broad-host-range vector carrying a DNA fragment of the putative promoter region of the membrane-bound alcohol dehydrogenase gene ofG. oxydansfor expression inGluconobacterspp. According to our results, 2KGDH that was purified from the recombinantGluconobactercells showed characteristics nearly the same as those reported previously. We also expressed thekgdSLCgenes in a mutant strain ofGluconobacter japonicusNBRC3271 (formerlyGluconobacter dioxyacetonicusIFO3271) engineered to produce 2KG efficiently from a mixture ofd-glucose andd-gluconate. This mutant strain consumed almost all of the starting materials (d-glucose andd-gluconate) to produce 2,5DKG quantitatively as a seemingly unique metabolite. To our knowledge, this is the first report of aGluconobacterstrain that produces 2,5DKG efficiently and homogeneously.

scholarly journals Competition between Metals for Binding to Methanobactin Enables Expression of Soluble Methane Monooxygenase in the Presence of Copper

2014 ◽  
Vol 81 (3) ◽  
pp. 1024-1031 ◽  
Author(s):  
Bhagyalakshmi Kalidass ◽  
Muhammad Farhan Ul-Haque ◽  
Bipin S. Baral ◽  
Alan A. DiSpirito ◽  
Jeremy D. Semrau
Keyword(s):  
Methane Monooxygenase ◽  
High Specificity ◽  
Copper Uptake ◽  
Content Type ◽  
Soluble Methane Monooxygenase ◽  
Sds Page ◽  
Genes Encoding ◽  
Key Factor ◽  
Membrane Bound

ABSTRACTIt is well known that copper is a key factor regulating expression of the two forms of methane monooxygenase found in proteobacterial methanotrophs. Of these forms, the cytoplasmic, or soluble, methane monooxygenase (sMMO) is expressed only at low copper concentrations. The membrane-bound, or particulate, methane monooxygenase (pMMO) is constitutively expressed with respect to copper, and such expression increases with increasing copper. Recent findings have shown that copper uptake is mediated by a modified polypeptide, or chalkophore, termed methanobactin. Although methanobactin has high specificity for copper, it can bind other metals, e.g., gold. Here we show that inMethylosinus trichosporiumOB3b, sMMO is expressed and active in the presence of copper if gold is also simultaneously present. Such expression appears to be due to gold binding to methanobactin produced byM. trichosporiumOB3b, thereby limiting copper uptake. Such expression and activity, however, was significantly reduced if methanobactin preloaded with copper was also added. Further, quantitative reverse transcriptase PCR (RT-qPCR) of transcripts of genes encoding polypeptides of both forms of MMO and SDS-PAGE results indicate that both sMMO and pMMO can be expressed when copper and gold are present, as gold effectively competes with copper for binding to methanobactin. Such findings suggest that under certain geochemical conditions, both forms of MMO may be expressed and activein situ. Finally, these findings also suggest strategies whereby field sites can be manipulated to enhance sMMO expression, i.e., through the addition of a metal that can compete with copper for binding to methanobactin.

scholarly journals Faustovirus, an Asfarvirus-Related New Lineage of Giant Viruses Infecting Amoebae

2015 ◽  
Vol 89 (13) ◽  
pp. 6585-6594 ◽  
Author(s):  
Dorine Gaëlle Reteno ◽  
Samia Benamar ◽  
Jacques Bou Khalil ◽  
Julien Andreani ◽  
Nicholas Armstrong ◽  
...  
Keyword(s):  
African Swine Fever Virus ◽  
African Swine Fever ◽  
Fever Virus ◽  
Open Reading Frames ◽  
Gene Repertoire ◽  
Significant Similarity ◽  
Content Type ◽  
Genes Encoding ◽  
Giant Viruses ◽  
Almost All

ABSTRACTGiant viruses are protist-associated viruses belonging to the proposed orderMegavirales; almost all have been isolated fromAcanthamoebaspp. Their isolation in humans suggests that they are part of the human virome. Using a high-throughput strategy to isolate new giant viruses from their original protozoan hosts, we obtained eight isolates of a new giant viral lineage fromVermamoebavermiformis, the most common free-living protist found in human environments. This new lineage was proposed to be the faustovirus lineage. The prototype member, faustovirus E12, forms icosahedral virions of ≈200 nm that are devoid of fibrils and that encapsidate a 466-kbp genome encoding 451 predicted proteins. Of these, 164 are found in the virion. Phylogenetic analysis of the core viral genes showed that faustovirus is distantly related to the mammalian pathogen African swine fever virus, but it encodes ≈3 times more mosaic gene complements. About two-thirds of these genes do not show significant similarity to genes encoding any known proteins. These findings show that expanding the panel of protists to discover new giant viruses is a fruitful strategy.IMPORTANCEBy usingVermamoeba, a protist living in humans and their environment, we isolated eight strains of a new giant virus that we named faustovirus. The genomes of these strains were sequenced, and their sequences showed that faustoviruses are related to but different from the vertebrate pathogen African swine fever virus (ASFV), which belongs to the familyAsfarviridae. Moreover, the faustovirus gene repertoire is ≈3 times larger than that of ASFV and comprises approximately two-thirds ORFans (open reading frames [ORFs] with no detectable homology to other ORFs in a database).

scholarly journals Response of a Rice Paddy Soil Methanogen to Syntrophic Growth as Revealed by Transcriptional Analyses

2014 ◽  
Vol 80 (15) ◽  
pp. 4668-4676 ◽  
Author(s):  
Pengfei Liu ◽  
Yanxiang Yang ◽  
Zhe Lü ◽  
Yahai Lu
Keyword(s):  
Paddy Field ◽  
Rice Paddy ◽  
Transcription Unit ◽  
Heterodisulfide Reductase ◽  
Content Type ◽  
Acetate Assimilation ◽  
Adaptive Mechanisms ◽  
Genes Encoding ◽  
Membrane Bound ◽  
Key Steps

ABSTRACTMembers ofMethanocellalesare widespread in paddy field soils and play the key role in methane production. These methanogens feature largely in these organisms' adaptation to low H2and syntrophic growth with anaerobic fatty acid oxidizers. The adaptive mechanisms, however, remain unknown. In the present study, we determined the transcripts of 21 genes involved in the key steps of methanogenesis and acetate assimilation ofMethanocella conradiiHZ254, a strain recently isolated from paddy field soil.M. conradiiwas grown in monoculture and syntrophically withPelotomaculum thermopropionicum(a propionate syntroph) orSyntrophothermus lipocalidus(a butyrate syntroph). Comparison of the relative transcript abundances showed that three hydrogenase-encoding genes and all methanogenesis-related genes tested were upregulated in cocultures relative to monoculture. The genes encoding formylmethanofuran dehydrogenase (Fwd), heterodisulfide reductase (Hdr), and the membrane-bound energy-converting hydrogenase (Ech) were the most upregulated among the evaluated genes. The expression of the formate dehydrogenase (Fdh)-encoding gene also was significantly upregulated. In contrast, an acetate assimilation gene was downregulated in cocultures. The genes coding for Fwd, Hdr, and the D subunit of F420-nonreducing hydrogenase (Mvh) form a large predicted transcription unit; therefore, the Mvh/Hdr/Fwd complex, capable of mediating the electron bifurcation and connecting the first and last steps of methanogenesis, was predicted to be formed inM. conradii. We propose thatMethanocellamethanogens cope with low H2and syntrophic growth by (i) stabilizing the Mvh/Hdr/Fwd complex and (ii) activating formate-dependent methanogenesis.

scholarly journals Continuous Control of the Flow in Biochemical Pathways through 5′ Untranslated Region Sequence Modifications in mRNA Expressed from the Broad-Host-Range PromoterPm

2011 ◽  
Vol 77 (8) ◽  
pp. 2648-2655 ◽  
Author(s):  
Rahmi Lale ◽  
Laila Berg ◽  
Friederike Stüttgen ◽  
Roman Netzer ◽  
Marit Stafsnes ◽  
...  
Keyword(s):  
Host Range ◽  
Untranslated Region ◽  
Micrococcus Luteus ◽  
Background Level ◽  
Broad Host Range ◽  
Continuous Control ◽  
Wild Type ◽  
Content Type ◽  
Broad Host Range Plasmid ◽  
Genes Encoding

ABSTRACTThe induciblePmpromoter integrated into broad-host-range plasmid RK2 replicons can be fine-tuned continuously between the uninduced and maximally induced levels by varying the inducer concentrations. To lower the uninduced background level while still maintaining the inducibility for applications in, for example, metabolic engineering and synthetic (systems) biology, we report here the use of mutations in thePmDNA region corresponding to the 5′ untranslated region of mRNA (UTR). Five UTR variants obtained by doped oligonucleotide mutagenesis and selection, apparently reducing the efficiency of translation, were all found to display strongly reduced uninduced expression of three different reporter genes (encoding β-lactamase, luciferase, and phosphoglucomutase) inEscherichia coli. The ratio between induced and uninduced expression remained the same or higher compared to cells containing a corresponding plasmid with the wild-type UTR. Interestingly, the UTR variants also displayed similar effects on expression when substituted for the native UTR in another and constitutive promoter,P1(Pantitet), indicating a broad application potential of these UTR variants. Two of the selected variants were used to control the production of the C50carotenoid sarcinaxanthin in an engineered strain ofE. colithat produces the precursor lycopene. Sarcinaxanthin is produced in this particular strain by expressing threeMicrococcus luteusderived genes from the promoterPm. The results indicated that UTR variants can be used to eliminate sarcinaxanthin production under uninduced conditions, whereas cells containing the corresponding plasmid with a wild-type UTR produced ca. 25% of the level observed under induced conditions.

scholarly journals Species Widely Distributed in Halophilic Archaea Exhibit Opsin-Mediated Inhibition of Bacterioruberin Biosynthesis

2018 ◽  
Vol 201 (2) ◽  
Author(s):  
Ronald F. Peck ◽  
Serena M. Graham ◽  
Abby M. Gregory
Keyword(s):  
Regulatory Mechanism ◽  
Halophilic Archaea ◽  
Halobacterium Salinarum ◽  
Efficient Production ◽  
Carotenoid Pigment ◽  
Prosthetic Group ◽  
Content Type ◽  
Genes Encoding ◽  
The Common ◽  
Insight Into

ABSTRACT Halophilic Archaea are a distinctive pink color due to a carotenoid pigment called bacterioruberin. To sense or utilize light, many halophilic Archaea also produce rhodopsins, complexes of opsin proteins with a retinal prosthetic group. Both bacterioruberin and retinal are synthesized from isoprenoid precursors, with lycopene as the last shared intermediate. We previously described a regulatory mechanism by which Halobacterium salinarum bacterioopsin and Haloarcula vallismortis cruxopsin inhibit bacterioruberin synthesis catalyzed by lycopene elongase. In this work, we found that opsins in all three major Halobacteria clades inhibit bacterioruberin synthesis, suggesting that this regulatory mechanism existed in the common Halobacteria ancestor. Halophilic Archaea, which are generally heterotrophic and aerobic, likely evolved from an autotrophic, anaerobic methanogenic ancestor by acquiring many genes from Bacteria via lateral gene transfer. These bacterial “imports” include genes encoding opsins and lycopene elongases. To determine if opsins from Bacteria inhibit bacterioruberin synthesis, we tested bacterial opsins and found that an opsin from Curtobacterium, in the Actinobacteria phylum, inhibits bacterioruberin synthesis catalyzed by its own lycopene elongase, as well as that catalyzed by several archaeal enzymes. We also determined that the lycopene elongase from Halococcus salifodinae, a species from a family of Halobacteria lacking opsin homologs, retained the capacity to be inhibited by opsins. Together, our results indicate that opsin-mediated inhibition of bacterioruberin biosynthesis is a widely distributed mechanism found in both Archaea and Bacteria, possibly predating the divergence of the two domains. Further analysis may provide insight into the acquisition and evolution of the genes and their host species. IMPORTANCE All organisms use a variety of mechanisms to allocate limited resources to match their needs in their current environment. Here, we explore how halophilic microbes use a novel mechanism to allow efficient production of rhodopsin, a complex of an opsin protein and a retinal prosthetic group. We previously demonstrated that Halobacterium salinarum bacterioopsin directs available resources toward retinal by inhibiting synthesis of bacterioruberin, a molecule that shares precursors with retinal. In this work, we show that this mechanism can be carried out by proteins from halophilic Archaea that are not closely related to H. salinarum and those in at least one species of Bacteria. Therefore, opsin-mediated inhibition of bacterioruberin synthesis may be a highly conserved, ancient regulatory mechanism.

scholarly journals Utilization of d-Lactate as an Energy Source Supports the Growth of Gluconobacter oxydans

2015 ◽  
Vol 81 (12) ◽  
pp. 4098-4110 ◽  
Author(s):  
Binbin Sheng ◽  
Jing Xu ◽  
Yingxin Zhang ◽  
Tianyi Jiang ◽  
Sisi Deng ◽  
...  
Keyword(s):  
Energy Source ◽  
Carbon Source ◽  
Electron Acceptor ◽  
Gluconobacter Oxydans ◽  
The Novel ◽  
Hydroxy Acids ◽  
Lactate Oxidase ◽  
Content Type ◽  
Membrane Bound ◽  
Lactate Dehydrogenases

ABSTRACTd-Lactate was identified as one of the few available organic acids that supported the growth ofGluconobacter oxydans621H in this study. Interestingly, the strain usedd-lactate as an energy source but not as a carbon source, unlike other lactate-utilizing bacteria. The enzymatic basis for the growth ofG. oxydans621H ond-lactate was therefore investigated. Although two putative NAD-independentd-lactate dehydrogenases, GOX1253 and GOX2071, were capable of oxidizingd-lactate, GOX1253 was the only enzyme able to support thed-lactate-driven growth of the strain. GOX1253 was characterized as a membrane-bound dehydrogenase with high activity towardd-lactate, while GOX2071 was characterized as a soluble oxidase with broad substrate specificity towardd-2-hydroxy acids. The latter used molecular oxygen as a direct electron acceptor, a feature that has not been reported previously ind-lactate-oxidizing enzymes. This study not only clarifies the mechanism for the growth ofG. oxydansond-lactate, but also provides new insights for applications of the important industrial microbe and the noveld-lactate oxidase.

scholarly journals Antibodies against In Vivo-Expressed Antigens Are Sufficient To Protect against Lethal Aerosol Infection with Burkholderia mallei and Burkholderia pseudomallei

2017 ◽  
Vol 85 (8) ◽  
Author(s):  
Shawn M. Zimmerman ◽  
Jeremy S. Dyke ◽  
Tomislav P. Jelesijevic ◽  
Frank Michel ◽  
Eric R. Lafontaine ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Protective Immunity ◽  
Burkholderia Pseudomallei ◽  
Lipolytic Activity ◽  
Burkholderia Mallei ◽  
Wild Type ◽  
Content Type ◽  
Related Organism ◽  
Genes Encoding

ABSTRACT Burkholderia mallei, a facultative intracellular bacterium and tier 1 biothreat, causes the fatal zoonotic disease glanders. The organism possesses multiple genes encoding autotransporter proteins, which represent important virulence factors and targets for developing countermeasures in pathogenic Gram-negative bacteria. In the present study, we investigated one of these autotransporters, BatA, and demonstrate that it displays lipolytic activity, aids in intracellular survival, is expressed in vivo, elicits production of antibodies during infection, and contributes to pathogenicity in a mouse aerosol challenge model. A mutation in the batA gene of wild-type strain ATCC 23344 was found to be particularly attenuating, as BALB/c mice infected with the equivalent of 80 median lethal doses cleared the organism. This finding prompted us to test the hypothesis that vaccination with the batA mutant strain elicits protective immunity against subsequent infection with wild-type bacteria. We discovered that not only does vaccination provide high levels of protection against lethal aerosol challenge with B. mallei ATCC 23344, it also protects against infection with multiple isolates of the closely related organism and causative agent of melioidosis, Burkholderia pseudomallei. Passive-transfer experiments also revealed that the protective immunity afforded by vaccination with the batA mutant strain is predominantly mediated by IgG antibodies binding to antigens expressed exclusively in vivo. Collectively, our data demonstrate that BatA is a target for developing medical countermeasures and that vaccination with a mutant lacking expression of the protein provides a platform to gain insights regarding mechanisms of protective immunity against B. mallei and B. pseudomallei, including antigen discovery.

scholarly journals Escherichia coli Sequence Type 457 Is an Emerging Extended-Spectrum-β-Lactam-Resistant Lineage with Reservoirs in Wildlife and Food-Producing Animals

2020 ◽  
Vol 65 (1) ◽  
pp. e01118-20
Author(s):  
Kristina Nesporova ◽  
Ethan R. Wyrsch ◽  
Adam Valcek ◽  
Ibrahim Bitar ◽  
Khin Chaw ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Large Scale ◽  
Broad Host Range ◽  
Content Type ◽  
E Coli ◽  
South Wales ◽  
High Prevalence ◽  
Genes Encoding ◽  
Extraintestinal Disease ◽  
Sequence Types

ABSTRACTSilver gulls carry phylogenetically diverse Escherichia coli, including globally dominant extraintestinal pathogenic E. coli (ExPEC) sequence types and pandemic ExPEC-ST131 clades; however, our large-scale study (504 samples) on silver gulls nesting off the coast of New South Wales identified E. coli ST457 as the most prevalent. A phylogenetic analysis of whole-genome sequences (WGS) of 138 ST457 samples comprising 42 from gulls, 2 from humans (Australia), and 14 from poultry farmed in Paraguay were compared with 80 WGS deposited in public databases from diverse sources and countries. E. coli ST457 strains are phylogenetic group F, carry fimH145, and partition into five main clades in accordance to predominant flagella H-antigen carriage. Although we identified considerable phylogenetic diversity among the 138 ST457 strains, closely related subclades (<100 SNPs) suggested zoonotic or zooanthroponosis transmission between humans, wild birds, and food-producing animals. Australian human clinical and gull strains in two of the clades were closely related (≤80 SNPs). Regarding plasmid content, country, or country/source, specific connections were observed, including I1/ST23, I1/ST314, and I1/ST315 disseminating blaCMY-2 in Australia, I1/ST113 carrying blaCTX-M-8 and mcr-5 in Paraguayan poultry, and F2:A-:B1 plasmids of Dutch origin being detected across multiple ST457 clades. We identified a high prevalence of nearly identical I1/ST23 plasmids carrying blaCMY-2 among Australian gull and clinical human strains. In summary, ST457 is a broad host range, geographically diverse E. coli lineage that can cause human extraintestinal disease, including urinary tract infection, and displays a remarkable ability to capture mobile elements that carry and transmit genes encoding resistance to critically important antibiotics.

scholarly journals Deciphering the Regulatory Circuitry That Controls Reversible Lysine Acetylation in Salmonella enterica

mBio ◽  
2015 ◽  
Vol 6 (4) ◽  
Author(s):  
Kristy L. Hentchel ◽  
Sandy Thao ◽  
Peter J. Intile ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Mutant Strain ◽  
Salmonella Enterica ◽  
Growth Defect ◽  
Metabolic Enzyme ◽  
Transcriptional Level ◽  
Lysine Acetylation ◽  
Content Type ◽  
Expression Of Genes ◽  
Regulated Expression ◽  
Genes Encoding

ABSTRACTInSalmonella enterica, the reversible lysine acetylation (RLA) system is comprised of the protein acetyltransferase (Pat) and sirtuin deacetylase (CobB). RLA controls the activities of many proteins, including the acetyl coenzyme A (acetyl-CoA) synthetase (Acs), by modulating the degree of Acs acetylation. We report that IolR, amyo-inositol catabolism repressor, activates the expression of genes encoding components of the RLA system.In vitroevidence shows that the IolR protein directly regulatespatexpression. AniolRmutant strain displayed a growth defect in minimal medium containing 10 mM acetate, a condition under which RLA function is critical to control Acs activity. Increased levels of Pat, CobB, or Acs activity reversed the growth defect, suggesting the Pat/CobB ratio in aniolRstrain is altered and that such a change affects the level of acetylated, inactive Acs. Results of quantitative reverse transcription-PCR (qRT-PCR) analyses ofpat,cobB, andacsexpression indicated that expression of the genes alluded to in the IolR-deficient strain was reduced 5-, 3-, and 2.6-fold, respectively, relative to the levels present in the strain carrying theiolR+allele. Acs activity in cell-free extracts from aniolRmutant strain was reduced ~25% relative to that of theiolR+strain. Glucose differentially regulated expression ofpat,cobB, andacs. The catabolite repressor protein (Crp) positively regulated expression ofpatwhile having no effect oncobB.IMPORTANCEReversible lysine acylation is used by cells of all domains of life to modulate the function of proteins involved in diverse cellular processes. Work reported herein begins to outline the regulatory circuitry that integrates the expression of genes encoding enzymes that control the activity of a central metabolic enzyme in C2 metabolism. Genetic analyses revealed effects on reversible lysine acylation that greatly impacted the growth behavior of the cell. This work provides the first insights into the complexities of the system responsible for controlling reversible lysine acylation at the transcriptional level in the enteropathogenic bacteriumSalmonella enterica.

scholarly journals The IclR-Type Transcriptional Repressor LtbR Regulates the Expression of Leucine and Tryptophan Biosynthesis Genes in the Amino Acid Producer Corynebacterium glutamicum

2007 ◽  
Vol 189 (7) ◽  
pp. 2720-2733 ◽  
Author(s):  
Iris Brune ◽  
Nina Jochmann ◽  
Karina Brinkrolf ◽  
Andrea T. Hüser ◽  
Robert Gerstmeir ◽  
...  
Keyword(s):  
Corynebacterium Glutamicum ◽  
Mutant Strain ◽  
Specific Binding ◽  
Bifidobacterium Longum ◽  
Biosynthesis Pathway ◽  
Tryptophan Biosynthesis ◽  
Band Shift ◽  
Genes Encoding ◽  
Pattern Searches ◽  
Almost All

ABSTRACT The transcriptional regulator Cg1486 of Corynebacterium glutamicum ATCC 13032 is a member of the IclR protein family and belongs to the conserved set of regulatory proteins in corynebacteria. A defined deletion in the cg1486 gene, now designated ltbR (leucine and tryptophan biosynthesis regulator), led to the mutant strain C. glutamicum IB1486. According to whole-genome expression analysis by DNA microarray hybridizations, transcription of the leuB and leuCD genes encoding enzymes of the leucine biosynthesis pathway was enhanced in C. glutamicum IB1486 compared with the wild-type strain. Moreover, the genes of the trpEGDCFBA operon involved in tryptophan biosynthesis of C. glutamicum showed an enhanced expression in the cg1486 mutant strain. Bioinformatics pattern searches in the upstream regions of the differentially expressed genes revealed the common 12-bp motif CA(T/C)ATAGTG(A/G)GA that is located downstream of the −10 region of the mapped promoter sequences. DNA band shift assays with a streptavidin-tagged LtbR protein demonstrated the specific binding of the purified protein to 40-mers containing the 12-bp motif localized in front of leuB, leuC, and trpE, thereby confirming the direct regulatory role of LtbR in the expression of the leucine and tryptophan biosynthesis pathway genes of C. glutamicum. Genes homologous with ltbR were detected upstream of the leuCD genes in almost all sequenced genomes of bacteria belonging to the taxonomic class Actinobacteria. The ltbR-like genes of Corynebacterium diphtheriae, Corynebacterium jeikeium, Mycobacterium bovis, and Bifidobacterium longum were cloned and shown to complement the deregulation of leuB, leuCD, and trpE gene expression in C. glutamicum IB1486.

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