Transport of Nutrients and Carbon Catabolite Repression for the Selective Carbon Sources

The effect of carbon source on the levels of three (1 → 3)-β-glucanases and a (1 → 6)-β-glucanase in the culture filtrates of the filamentous fungus Acremonium persicinum was investigated. All four enzymes were produced during growth of the fungus on (1 → 3)-, (1 → 6)-, and (1 → 3)(1 → 6)-β-glucans as well as β-linked oligoglucosides. However, only one (1 → 3)-β-glucanase and the (1 → 6)-β-glucanase were detected during growth on a range of other carbon sources including glucose, carboxymethylcellulose, and the α-glucan pullulan. The presence of glucose in the medium markedly decreased the production of all four glucanases, although the concentration required to effect complete repression of enzyme levels varied for the different enzymes. Similar repressive effects were also observed with sucrose, fructose, and galactose. The most likely explanations for these observations are that the synthesis of the (1 → 6)-β-glucanase and one of the (1 → 3)-β-glucanases is controlled by carbon catabolite repression, while the remaining two (1 → 3)-β-glucanases are inducible enzymes subject to carbon catabolite repression.Key words: (1 → 3)-β-glucanase, (1 → 6)-β-glucanase, Acremonium persicinum, regulation of synthesis, fungal β-glucanases.

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Carbon Catabolite Repression Gene AoCreA Regulates Morphological Development and Ochratoxin A Biosynthesis Responding to Carbon Sources in Aspergillus ochraceus

Toxins ◽

10.3390/toxins12110697 ◽

2020 ◽

Vol 12 (11) ◽

pp. 697

Author(s):

Gang Wang ◽

Yulong Wang ◽

Bolei Yang ◽

Chenxi Zhang ◽

Haiyong Zhang ◽

...

Keyword(s):

Ochratoxin A ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Aspergillus Ochraceus ◽

Morphological Development ◽

Drastic Reduction ◽

Food And Feed ◽

Yeast Extract Sucrose ◽

Insight Into

Carbon is one of the most important nutrients for the development and secondary metabolism in fungi. CreA is the major transcriptional factor mediating carbon catabolite repression, which is employed in the utilization of carbon sources. Aspergillus ochraceus contaminates various food and feed containing different carbon sources by producing ochratoxin A (OTA). However, little is known about the function of AoCreA in regulating the morphology and OTA production of A. ochraceus. To give an insight into the mechanism of the carbon sources regulating development of A. ochraceus and OTA production, we have identified AoCreA in A. ochraceus. The homologous recombination strategy was used to generate the AoCreA deletion mutant (ΔAoCreA). We have investigated the morphology and OTA production of the wild type (WT) and ΔAoCreA of A. ochraceus with media containing different carbon sources (glucose, fructose, maltose, D-xylose, D-mannose, acetate, D-galactose, D-mannitol and lactose). ΔAoCreA showed a significant growth and conidiation defect on all media as compared with WT. Glucose and maltose were the most inducing media for OTA production by A. ochraceus, followed by sucrose and the nutrient-rich Yeast Extract Sucrose (YES) and Potato Dextrose Agar (PDA). The deletion of AoCreA led to a drastic reduction of OTA production on all kinds of media except PDA, which was supported by the expression profile of OTA biosynthetic genes. Furthermore, infection studies of ΔAoCreA on oats and pears showed the involvement of AoCreA in the pathogenicity of A. ochraceus. Thus, these results suggest that AoCreA regulates morphological development and OTA biosynthesis in response to carbon sources in A. ochraceus.

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Glucose-Mediated Repression of Plant Biomass Utilization in the White-Rot Fungus Dichomitus squalens

Applied and Environmental Microbiology ◽

10.1128/aem.01828-19 ◽

2019 ◽

Vol 85 (23) ◽

Cited By ~ 2

Author(s):

Paul Daly ◽

Mao Peng ◽

Marcos Di Falco ◽

Anna Lipzen ◽

Mei Wang ◽

...

Keyword(s):

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Plant Biomass ◽

Carbon Sources ◽

White Rot Fungi ◽

White Rot ◽

White Rot Fungus ◽

Content Type ◽

Dichomitus Squalens ◽

Genes Encoding

ABSTRACT The extent of carbon catabolite repression (CCR) at a global level is unknown in wood-rotting fungi, which are critical to the carbon cycle and are a source of biotechnological enzymes. CCR occurs in the presence of sufficient concentrations of easily metabolizable carbon sources (e.g., glucose) and involves downregulation of the expression of genes encoding enzymes involved in the breakdown of complex carbon sources. We investigated this phenomenon in the white-rot fungus Dichomitus squalens using transcriptomics and exoproteomics. In D. squalens cultures, approximately 7% of genes were repressed in the presence of glucose compared to Avicel or xylan alone. The glucose-repressed genes included the essential components for utilization of plant biomass—carbohydrate-active enzyme (CAZyme) and carbon catabolic genes. The majority of polysaccharide-degrading CAZyme genes were repressed and included activities toward all major carbohydrate polymers present in plant cell walls, while repression of ligninolytic genes also occurred. The transcriptome-level repression of the CAZyme genes observed on the Avicel cultures was strongly supported by exoproteomics. Protease-encoding genes were generally not glucose repressed, indicating their likely dominant role in scavenging for nitrogen rather than carbon. The extent of CCR is surprising, given that D. squalens rarely experiences high free sugar concentrations in its woody environment, and it indicates that biotechnological use of D. squalens for modification of plant biomass would benefit from derepressed or constitutively CAZyme-expressing strains. IMPORTANCE White-rot fungi are critical to the carbon cycle because they can mineralize all wood components using enzymes that also have biotechnological potential. The occurrence of carbon catabolite repression (CCR) in white-rot fungi is poorly understood. Previously, CCR in wood-rotting fungi has only been demonstrated for a small number of genes. We demonstrated widespread glucose-mediated CCR of plant biomass utilization in the white-rot fungus Dichomitus squalens. This indicates that the CCR mechanism has been largely retained even though wood-rotting fungi rarely experience commonly considered CCR conditions in their woody environment. The general lack of repression of genes encoding proteases along with the reduction in secreted CAZymes during CCR suggested that the retention of CCR may be connected with the need to conserve nitrogen use during growth on nitrogen-scarce wood. The widespread repression indicates that derepressed strains could be beneficial for enzyme production.

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The Absence of Pyruvate Kinase Affects Glucose-Dependent Carbon Catabolite Repression in Bacillus subtilis

Metabolites ◽

10.3390/metabo9100216 ◽

2019 ◽

Vol 9 (10) ◽

pp. 216 ◽

Cited By ~ 2

Author(s):

Sousa ◽

Westhoff ◽

Methling ◽

Lalk

Keyword(s):

Bacillus Subtilis ◽

Pyruvate Kinase ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Defined Medium ◽

Central Carbon Metabolism ◽

Alternative Pathways ◽

Distribution Point ◽

Nutritional Compounds

Pyruvate is a key intermediate of diverse metabolic pathways of central carbon metabolism. In addition to being the end product of glycolysis, pyruvate is an essential carbon distribution point to oxidative metabolism, amino acid and fatty acid syntheses, and overflow metabolite production. Hence, a tight regulation of pyruvate kinase (Pyk) activity is of great importance. This study aimed to analyze targeted metabolites from several pathways and possible changes in Bacillus subtilis lacking Pyk. Wild type and Δpyk cells were cultivated in chemically defined medium with glucose and pyruvate as carbon sources, and the extracted metabolites were analyzed by 1H-NMR, GC-MS, HPLC-MS, and LC-MS/MS. The results showed that the perturbation created in the pyruvate node drove an adaptation to new conditions by altering the nutritional compounds’ consumption. In Δpyk, pyruvate, which is subject to glucose-dependent carbon catabolite repression, did not comply with the hierarchy in carbon source utilization. Other metabolic alterations were observed such as the higher secretion of the overflow metabolites acetoin and 2,3-butanediol by Δpyk. Our results help to elucidate the regulatory transport of glucose and pyruvate in B. subtilis and possible metabolic reroute to alternative pathways in the absence of Pyk.

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Yeast Carbon Catabolite Repression

Microbiology and Molecular Biology Reviews ◽

10.1128/mmbr.62.2.334-361.1998 ◽

1998 ◽

Vol 62 (2) ◽

pp. 334-361 ◽

Cited By ~ 764

Author(s):

Juana M. Gancedo

Keyword(s):

Protein Phosphatase ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Central Element ◽

Preliminary Evidence ◽

Regulatory Proteins ◽

Regulatory Cascade ◽

Genes Encoding ◽

Single Set

SUMMARY Glucose and related sugars repress the transcription of genes encoding enzymes required for the utilization of alternative carbon sources; some of these genes are also repressed by other sugars such as galactose, and the process is known as catabolite repression. The different sugars produce signals which modify the conformation of certain proteins that, in turn, directly or through a regulatory cascade affect the expression of the genes subject to catabolite repression. These genes are not all controlled by a single set of regulatory proteins, but there are different circuits of repression for different groups of genes. However, the protein kinase Snf1/Cat1 is shared by the various circuits and is therefore a central element in the regulatory process. Snf1 is not operative in the presence of glucose, and preliminary evidence suggests that Snf1 is in a dephosphorylated state under these conditions. However, the enzymes that phosphorylate and dephosphorylate Snf1 have not been identified, and it is not known how the presence of glucose may affect their activity. What has been established is that Snf1 remains active in mutants lacking either the proteins Grr1/Cat80 or Hxk2 or the Glc7 complex, which functions as a protein phosphatase. One of the main roles of Snf1 is to relieve repression by the Mig1 complex, but it is also required for the operation of transcription factors such as Adr1 and possibly other factors that are still unidentified. Although our knowledge of catabolite repression is still very incomplete, it is possible in certain cases to propose a partial model of the way in which the different elements involved in catabolite repression may be integrated.

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Carbon Catabolite Repression in Bacillus subtilis: Quantitative Analysis of Repression Exerted by Different Carbon Sources

Journal of Bacteriology ◽

10.1128/jb.00848-08 ◽

2008 ◽

Vol 190 (21) ◽

pp. 7275-7284 ◽

Cited By ~ 68

Author(s):

Kalpana D. Singh ◽

Matthias H. Schmalisch ◽

Jörg Stülke ◽

Boris Görke

Keyword(s):

Bacillus Subtilis ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Transport Activity ◽

Phosphotransferase System ◽

Phosphorylation State ◽

Mechanism Operative

ABSTRACT In many bacteria glucose is the preferred carbon source and represses the utilization of secondary substrates. In Bacillus subtilis, this carbon catabolite repression (CCR) is achieved by the global transcription regulator CcpA, whose activity is triggered by the availability of its phosphorylated cofactors, HPr(Ser46-P) and Crh(Ser46-P). Phosphorylation of these proteins is catalyzed by the metabolite-controlled kinase HPrK/P. Recent studies have focused on glucose as a repressing substrate. Here, we show that many carbohydrates cause CCR. The substrates form a hierarchy in their ability to exert repression via the CcpA-mediated CCR pathway. Of the two cofactors, HPr is sufficient for complete CCR. In contrast, Crh cannot substitute for HPr on substrates that cause a strong repression. Determination of the phosphorylation state of HPr in vivo revealed a correlation between the strength of repression and the degree of phosphorylation of HPr at Ser46. Sugars transported by the phosphotransferase system (PTS) cause the strongest repression. However, the phosphorylation state of HPr at its His15 residue and PTS transport activity have no impact on the global CCR mechanism, which is a major difference compared to the mechanism operative in Escherichia coli. Our data suggest that the hierarchy in CCR exerted by the different substrates is exclusively determined by the activity of HPrK/P.

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Carbon Catabolite Repression in Lactobacillus pentosus: Analysis of the ccpA Region

Applied and Environmental Microbiology ◽

10.1128/aem.66.1.277-283.2000 ◽

2000 ◽

Vol 66 (1) ◽

pp. 277-283 ◽

Cited By ~ 43

Author(s):

Kerstin Mahr ◽

Wolfgang Hillen ◽

Fritz Titgemeyer

Keyword(s):

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Carbon Utilization ◽

Gene Encoding ◽

Lactobacillus Pentosus ◽

Reading Frame ◽

Ammonium Fixation ◽

Responsive Element ◽

Genetic Structures

ABSTRACT The catabolite control protein CcpA is a central regulator in low-G+C-content gram-positive bacteria. It confers carbon catabolite repression to numerous genes required for carbon utilization. It also operates as a transcriptional activator of genes involved in diverse phenomena, such as glycolysis and ammonium fixation. We have cloned theccpA region of Lactobacillus pentosus. ccpAencodes a protein of 336 amino acids exhibiting similarity to CcpA proteins of other bacteria and to proteins of the LacI/GalR family of transcriptional regulators. Upstream of ccpA was found an open reading frame with similarity to the pepQ gene, encoding a prolidase. Primer extension experiments revealed two start sites of transcription for ccpA. In wild-type cells grown on glucose, mRNA synthesis occurred only from the promoter proximal toccpA. In a ccpA mutant strain, both promoters were used, with increased transcription from the distant promoter, which overlaps a presumptive CcpA binding site called cre(for catabolite responsive element). This suggests that expression ofccpA is autoregulated. Determination of the expression levels of CcpA in cells grown on repressing and nonrepressing carbon sources revealed that the amounts of CcpA produced did not change significantly, leading to the conclusion that the arrangement of two promoters may ensure constant expression of ccpA under various environmental conditions. A comparison of the genetic structures of ccpA regions revealed that lactic acid bacteria possess the gene order pepQ-ccpA-variable while the genetic structure in bacilli and Staphylococcus xylosusis aroA-ccpA-variable-acuC.

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Carbon Catabolite Repression and Impranil Polyurethane Degradation in Pseudomonas protegens Strain Pf-5

Applied and Environmental Microbiology ◽

10.1128/aem.01448-16 ◽

2016 ◽

Vol 82 (20) ◽

pp. 6080-6090 ◽

Cited By ~ 22

Author(s):

Chia-Suei Hung ◽

Sandra Zingarelli ◽

Lloyd J. Nadeau ◽

Justin C. Biffinger ◽

Carrie A. Drake ◽

...

Keyword(s):

Carbon Source ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Regulatory Elements ◽

Dependent Manner ◽

Content Type ◽

Intergenic Sequences ◽

Degradation Activity ◽

The Impact

ABSTRACTPolyester polyurethane (PU) coatings are widely used to help protect underlying structural surfaces but are susceptible to biological degradation. PUs are susceptible to degradation byPseudomonasspecies, due in part to the degradative activity of secreted hydrolytic enzymes. Microorganisms often respond to environmental cues by secreting enzymes or secondary metabolites to benefit their survival. This study investigated the impact of exposing severalPseudomonasstrains to select carbon sources on the degradation of the colloidal polyester polyurethane Impranil DLN (Impranil). The prototypicPseudomonas protegensstrain Pf-5 exhibited Impranil-degrading activities when grown in sodium citrate but not in glucose-containing medium. Glucose also inhibited the induction of Impranil-degrading activity by citrate-fed Pf-5 in a dose-dependent manner. Biochemical and mutational analyses identified two extracellular lipases present in the Pf-5 culture supernatant (PueA and PueB) that were involved in degradation of Impranil. Deletion of thepueAgene reduced Impranil-clearing activities, whilepueBdeletion exhibited little effect. Removal of both genes was necessary to stop degradation of the polyurethane. Bioinformatic analysis showed that putative Cbr/Hfq/Crc-mediated regulatory elements were present in the intergenic sequences upstream of bothpueAandpueBgenes. Our results confirmed that both PueA and PueB extracellular enzymes act in concert to degrade Impranil. Furthermore, our data showed that carbon sources in the growth medium directly affected the levels of Impranil-degrading activity but that carbon source effects varied amongPseudomonasstrains. This study uncovered an intricate and complicated regulation ofP. protegensPU degradation activity controlled by carbon catabolite repression.IMPORTANCEPolyurethane (PU) coatings are commonly used to protect metals from corrosion. Microbiologically induced PU degradation might pose a substantial problem for the integrity of these coatings. Microorganisms from diverse genera, including pseudomonads, possess the ability to degrade PUs via various means. This work identified two extracellular lipases, PueA and PueB, secreted byP. protegensstrain Pf-5, to be responsible for the degradation of a colloidal polyester PU, Impranil. This study also revealed that the expression of the degradative activity by strain Pf-5 is controlled by glucose carbon catabolite repression. Furthermore, this study showed that the Impranil-degrading activity of many otherPseudomonasstrains could be influenced by different carbon sources. This work shed light on the carbon source regulation of PU degradation activity among pseudomonads and identified the polyurethane lipases inP. protegens.

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The PalkBFGHJKL Promoter Is under Carbon Catabolite Repression Control in Pseudomonas oleovorans but Not in Escherichia coli alk+Recombinants

Journal of Bacteriology ◽

10.1128/jb.181.5.1610-1616.1999 ◽

1999 ◽

Vol 181 (5) ◽

pp. 1610-1616 ◽

Cited By ~ 40

Author(s):

Ivo E. Staijen ◽

Rosanna Marcionelli ◽

Bernard Witholt

Keyword(s):

Escherichia Coli ◽

Catabolite Repression ◽

Carbon Catabolite Repression ◽

Carbon Sources ◽

Transcriptional Level ◽

Pseudomonas Oleovorans ◽

Hydroxylase Activity ◽

Alkane Hydroxylase ◽

Alkane Degradation ◽

E Coli

ABSTRACT The alk genes are located on the OCT plasmid ofPseudomonas oleovorans and encode an inducible pathway for the utilization of n-alkanes as carbon and energy sources. We have investigated the influence of alternative carbon sources on the induction of this pathway in P. oleovorans andEscherichia coli alk + recombinants. In doing so, we confirmed earlier reports that induction of alkane hydroxylase activity in pseudomonads is subject to carbon catabolite repression. Specifically, synthesis of the monooxygenase component AlkB is repressed at the transcriptional level. The alk genes have been cloned into plasmid pGEc47, which has a copy number of about 5 to 10 per cell in both E. coli and pseudomonads.Pseudomonas putida GPo12 is a P. oleovoransderivative cured of the OCT plasmid. Upon introduction of pGEc47 in this strain, carbon catabolite repression of alkane hydroxylase activity was reduced significantly. In cultures of recombinant E. coli HB101 and W3110 carrying pGEc47, induction of AlkB and transcription of the alkB gene were no longer subject to carbon catabolite repression. This suggests that carbon catabolite repression of alkane degradation is regulated differently inPseudomonas and in E. coli strains. These results also indicate that P alkBFGHJKL , the P alk promoter, might be useful in attaining high expression levels of heterologous genes in E. coligrown on inexpensive carbon sources which normally trigger carbon catabolite repression of native expression systems in this host.

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