scholarly journals Analysis of a DtxR-Regulated Iron Transport and Siderophore Biosynthesis Gene Cluster in Corynebacterium diphtheriae

2005 ◽  
Vol 187 (2) ◽  
pp. 422-433 ◽  
Author(s):  
Carey A. Kunkle ◽  
Michael P. Schmitt
Keyword(s):  
Gene Cluster ◽  
Iron Uptake ◽  
Iron Transport ◽  
Genetic Locus ◽  
Corynebacterium Diphtheriae ◽  
Transcriptional Analysis ◽  
Biosynthesis Gene Cluster ◽  
Iron Source ◽  
Siderophore Biosynthesis ◽  
Siderophore Transport

ABSTRACT This report describes a genetic locus associated with siderophore biosynthesis and transport in Corynebacterium diphtheriae. A BLAST search of the C. diphtheriae genome identified a seven-gene cluster that included four genes, designated ciuA, ciuB, ciuC, and ciuD, whose predicted products are related to ABC-type iron transporters. Downstream from ciuD is the ciuE gene, whose predicted product is similar to the aerobactin biosynthetic enzymes IucA and IucC. The CiuE protein, which has a predicted mass of 121,582 Da and is approximately twice the size of either IucC or IucA, is homologous to each of these proteins in both its N- and C-terminal regions. C. diphtheriae ciuE deletion mutants exhibited a defect in siderophore production, iron uptake, and growth in low-iron medium. Mutations in the ciuA gene, whose predicted product is a lipoprotein component of an iron transport system, resulted in a severe defect in iron uptake and reduced ability to use the C. diphtheriae siderophore as an iron source. Site-directed mutations in irp6A, a gene previously reported to be associated with siderophore transport, had no effect on iron uptake or the utilization of the C. diphtheriae siderophore as an iron source. Transcriptional analysis demonstrated that expression of ciuA and ciuE is DtxR and iron regulated, and DNase I protection experiments confirmed the presence of DtxR binding sites upstream from each of these genes. Thus, this iron- and DtxR-regulated gene cluster is involved in the synthesis and transport of the C. diphtheriae siderophore.

scholarly journals Light-inducible carotenoid production controlled by a MarR-type regulator in Corynebacterium glutamicum

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Satoru Sumi ◽  
Yuto Suzuki ◽  
Tetsuro Matsuki ◽  
Takahiro Yamamoto ◽  
Yudai Tsuruta ◽  
...  
Keyword(s):  
Corynebacterium Glutamicum ◽  
Gene Cluster ◽  
Transcriptional Start Site ◽  
Transcriptional Regulator ◽  
Carotenoid Biosynthesis ◽  
Transcriptional Analysis ◽  
Dependent Manner ◽  
Biosynthesis Gene Cluster ◽  
Carotenoid Production

Abstract Carotenoid production in some non-phototropic bacteria occurs in a light-dependent manner to protect cells from photo-oxidants. Knowledge regarding the transcriptional regulator involved in the light-dependent production of carotenoids of non-phototrophic bacteria has been mainly confined to coenzyme B12-based photo-sensitive regulator CarH/LitR family proteins belonging to a MerR family transcriptional regulator. In this study, we found that bacteria belonging to Micrococcales and Corynebacteriales exhibit light-dependent carotenoid-like pigment production including an amino acid-producer Corynebacterium glutamicum AJ1511. CrtR is a putative MarR family transcriptional regulator located in the divergent region of a carotenoid biosynthesis gene cluster in the genome of those bacteria. A null mutant for crtR of C. glutamicum AJ1511 exhibited constitutive production of carotenoids independent of light. A complemented strain of the crtR mutant produced carotenoids in a light-dependent manner. Transcriptional analysis revealed that the expression of carotenoid biosynthesis genes is regulated in a light-dependent manner in the wild type, while the transcription was upregulated in the crtR mutant irrespective of light. In vitro experiments demonstrated that a recombinant CrtR protein binds to the specific sequences within the intergenic region of crtR and crtE, which corresponds to −58 to −7 for crtE, and +26 to −28 for crtR with respect to the transcriptional start site, and serves as a repressor for crtE transcription directed by RNA polymerase containing SigA. Taken together, the results indicate that CrtR light-dependently controls the expression of the carotenoid gene cluster in C. glutamicum and probably closely related Actinobacteria.

scholarly journals A Pseudoalteromonas clade with remarkable biosynthetic potential

2021 ◽  
Author(s):  
Rocky Chau ◽  
Leanne A. Pearson ◽  
Jesse Cain ◽  
John A. Kalaitzis ◽  
Brett A. Neilan
Keyword(s):  
Natural Products ◽  
Gene Cluster ◽  
Genome Mining ◽  
Gene Clusters ◽  
Average Density ◽  
Biologically Active ◽  
Biosynthesis Gene Cluster ◽  
Diverse Range ◽  
Siderophore Biosynthesis ◽  
Biosynthesis Gene

Pseudoalteromonas species produce a diverse range of biologically active compounds, including those biosynthesized by non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs). Here we report the biochemical and genomic analysis of Pseudoalteromonas sp. HM-SA03, isolated from the blue-ringed octopus, Hapalochalaena sp. Genome mining for secondary metabolite pathways revealed seven putative NRPS/PKS biosynthesis gene clusters, including those for the biosynthesis of alterochromides, pseudoalterobactins, alteramides and four hitherto novel compounds. Among these was a novel siderophore biosynthesis gene cluster with unprecedented architecture (NRPS-PKS-NRPS-PKS-NRPS-PKS-NRPS). Alterochromide production in HM-SA03 was also confirmed by liquid chromatography-mass spectrometry. An investigation of the biosynthetic potential of 42 publicly available Pseudoalteromonas genomes indicated that some of these gene clusters are distributed throughout the genus. Through phylogenetic analysis, a particular subset of strains formed a clade with extraordinary biosynthetic potential, with an average density of ten biosynthesis gene clusters per genome. In contrast, the majority of Pseudoalteromonas strains outside this clade contained an average of three clusters encoding complex biosynthesis. These results highlight the under-explored potential of Pseudoalteromonas as a source of new natural products. Importance This study demonstrates that the Pseudoalteromonas strain, HM-SA03, isolated from the venomous blue-ringed octopus, Hapalochalaena sp., is a biosynthetically talented organism, capable of producing alterochromides and potentially six other specialized metabolites. We have identified a pseudoalterobactin biosynthesis gene cluster and proposed a pathway for the production of the associated siderophore. A novel siderophore biosynthesis gene cluster with unprecedented architecture was also identified in the HM-SA03 genome. Finally, we have demonstrated that HM-SA03 belongs to a phylogenetic clade of strains with extraordinary biosynthetic potential. While our results do not support a role of HM-SA03 in Hapalochalaena sp. venom (tetrodotoxin) production, they emphasize the untapped potential of Pseudoalteromonas as a source of novel natural products.

scholarly journals Transcriptional Regulation of the Equol Biosynthesis Gene Cluster in Adlercreutzia equolifaciens DSM19450T

Nutrients ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 993 ◽  
Author(s):  
Flórez ◽  
Vázquez ◽  
Rodríguez ◽  
Redruello ◽  
Mayo
Keyword(s):  
Gene Cluster ◽  
Expression Patterns ◽  
Transcriptional Analysis ◽  
Whole Genome Sequence ◽  
Intestinal Bacterium ◽  
Rt Pcr ◽  
Biotechnological Production ◽  
Biosynthesis Gene Cluster ◽  
Intergenic Regions ◽  
Metabolic Transformation

Given the emerging evidence of equol’s benefit to human health, understanding its synthesis and regulation in equol-producing bacteria is of paramount importance. Adlercreutzia equolifaciens DSM19450T is a human intestinal bacterium —for which the whole genome sequence is publicly available— that produces equol from the daidzein isoflavone. In the present work, daidzein (between 50 to 200 μM) was completely metabolized by cultures of A. equolifaciens DSM19450T after 10 h of incubation. However, only about one third of the added isoflavone was transformed into dihydrodaidzein and then into equol. Transcriptional analysis of the ORFs and intergenic regions of the bacterium’s equol gene cluster was therefore undertaken using RT-PCR and RT-qPCR techniques with the aim of identifying the genetic elements of equol biosynthesis and its regulation mechanisms. Compared to controls cultured without daidzein, the expression of all 13 contiguous genes in the equol cluster was enhanced in the presence of the isoflavone. Depending on the gene and the amount of daidzein in the medium, overexpression varied from 0.5- to about 4-log10 units. Four expression patterns of transcription were identified involving genes within the cluster. The genes dzr, ddr and tdr, which code for daidzein reductase, dihydrodaidzein reductase and tetrahydrodaidzein reductase respectively, and which have been shown involved in equol biosynthesis, were among the most strongly expressed genes in the cluster. These expression patterns correlated with the location of four putative ρ-independent terminator sequences in the cluster. All the intergenic regions were amplified by RT-PCR, indicating the operon to be transcribed as a single RNA molecule. These findings provide new knowledge on the metabolic transformation of daidzein into equol by A. equolifaciens DSM19450T, which might help in efforts to increase the endogenous formation of this compound and/or its biotechnological production.

scholarly journals Transcriptional Control by A-Factor of strR, the Pathway-Specific Transcriptional Activator for Streptomycin Biosynthesis in Streptomyces griseus

2005 ◽  
Vol 187 (16) ◽  
pp. 5595-5604 ◽  
Author(s):  
Ayami Tomono ◽  
Yisan Tsai ◽  
Haruka Yamazaki ◽  
Yasuo Ohnishi ◽  
Sueharu Horinouchi
Keyword(s):  
Gene Cluster ◽  
Transcriptional Activation ◽  
Transcriptional Control ◽  
Streptomyces Griseus ◽  
Transcriptional Activator ◽  
Transcriptional Analysis ◽  
Mobility Shift ◽  
Biosynthesis Gene Cluster ◽  
Regulatory Cascade ◽  
Streptomycin Biosynthesis

ABSTRACT A-factor (2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone) triggers streptomycin production by inducing the transcription of strR, encoding the pathway-specific transcriptional activator, through signal transduction in the A-factor regulatory cascade in Streptomyces griseus. AdpA, one of the key transcriptional activators in the cascade, bound two upstream activation sites, approximately at nucleotide positions −270 and −50 with respect to the transcriptional start point of strR, as determined by gel mobility shift assays and DNase I footprinting. Transcriptional analysis of the strR promoter with mutated AdpA-binding sites showed that both sites were required for full transcriptional activation of strR by AdpA. Potassium permanganate footprinting showed that AdpA assisted RNA polymerase in forming an open complex at an appropriate position for transcriptional initiation of strR. Nine transcriptional units within the streptomycin biosynthesis gene cluster, including the strR-aphD operon, depended on StrR, indicating that StrR is the pathway-specific transcriptional activator for the whole gene cluster. Consistent with this, expression of strR under the control of a constitutively expressed promoter in an adpA null mutant caused the host to produce streptomycin.

scholarly journals Chimeric Protein IPath® with Chelating Activity Improves Atlantic Salmon’s Immunity against Infectious Diseases

Vaccines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 361
Author(s):  
Valentina Valenzuela-Muñoz ◽  
Bárbara P. Benavente ◽  
Antonio Casuso ◽  
Yeny Leal ◽  
Cristian Gallardo-Escárate
Keyword(s):  
Immune Response ◽  
Atlantic Salmon ◽  
Iron Metabolism ◽  
Iron Transport ◽  
Aeromonas Salmonicida ◽  
Transcriptional Analysis ◽  
Control Fish ◽  
Control Group ◽  
Commercial Fish ◽  
Chelating Activity

Infection processes displayed by pathogens require the acquisition of essential inorganic nutrients and trace elements from the host to survive and proliferate. Without a doubt, iron is a crucial trace metal for all living organisms and also a pivotal component in the host–parasite interactions. In particular, the host reduces the iron available to face the infectious disease, increasing iron transport proteins’ expression and activating the heme synthesis and degradation pathways. Moreover, recent findings have suggested that iron metabolism modulation in fish promotes the immune response by reducing cellular iron toxicity. We hypothesized that recombinant proteins related to iron metabolism could modulate the fish’s immune system through iron metabolism and iron-responsive genes. Here a chimeric iron transport protein (IPath®) was bioinformatically designed and then expressed in a recombinant bacterial system. The IPath® protein showed a significant chelating activity under in vitro conditions and biological activity. Taking this evidence, a vaccine candidate based on IPath® was evaluated in Atlantic salmon challenged with three different fish pathogens. Experimental trials were conducted using two fish groups: one immunized with IPath® and another injected with adjutant as the control group. After 400 accumulated thermal units (ATUs), two different infection trials were performed. In the first one, fish were infected with the bacterium Aeromonas salmonicida, and in a second trial, fish were exposed to the ectoparasite Caligus rogercresseyi and subsequently infected with the intracellular bacterium Piscirickettsia salmonis. Fish immunized with IPath® showed a significant delay in the mortality curve in response to A. salmonicida and P. salmonis infections. However, no significant differences between infected and control fish groups were observed at the end of the experiment. Notably, sea lice burden reduction was observed in vaccinated Atlantic salmon. Transcriptional analysis evidenced a high modulation of iron-homeostasis-related genes in fish vaccinated with IPath® compared to the control group during the infection. Moreover, increasing expression of Atlantic salmon IgT was associated with IPath® immunization. This study provides evidence that the IPath® protein could be used as an antigen or booster in commercial fish vaccines, improving the immune response against relevant pathogens for salmon aquaculture.

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