Genome-wide transcriptional changes induced by different carbon sources and carbon starvation in Aspergillus nidulans
Ontology highlight
ABSTRACT: Understanding the coordinated regulation of the hundreds of carbohydrate-active enzyme (CAZyme) genes occurring in the genomes of fungi has great practical importance. We recorded genome-wide transcriptional changes of Aspergillus nidulans cultivated on glucose, lactose or arabinogalactan as well as under carbon starved conditions. We determined both carbon stress specific changes (a carbon stress vs. glucose) and culture specific changes (a culture vs. all other cultures). Many CAZyme genes showed carbon stress specific and/or culture specific upregulation on arabinogalactan (138 and 62 genes, respectively). Besides galactosidase and arabinan degrading enzyme genes, enrichment of cellulolytic, pectinolytic, mannan and xylan degrading enzyme genes were observed in these gene sets. Less, 81 and 107 carbon stress specific as well as 6 and 16 culture specific upregulated genes were found on lactose and in carbon starved cultures, respectively. They were enriched only in galactosidase and xylosidase genes on lactose and rhamnogalacturonanase genes in both cultures. Some CAZyme genes (29 genes) showed culture specific upregulation on glucose and they were enriched in beta-1,4-glucanase genes. Behavioral ecological background of these characteristics was evaluated to organize comprehensively our knowledge on CAZyme production, which can lead to develop new strategies to produce enzymes for plant cell wall saccharification.
Project description:We have examined and compared the transcriptome of T. reesei growing on wheat straw and lactose as carbon sources under otherwise similar conditions. Gene expression on wheat straw exceeded that on lactose, and 1619 genes were found to be only induced on wheat straw but not on lactose. They comprised 30 % of the CAZome, but were also enriched in genes associated with phospholipid metabolism, DNA synthesis and repair and iron homeostatis. Two thirds of the CAZome was expressed both on wheat straw as well as on lactose, but 60 % of it at least >2-fold higher on the former. Major wheat straw specific genes comprised xylanases, chitinases and M-CM-^_-mannosidases. Interestingly, the latter two CAZyme families were significantly higher expressed in a strain in which xyr1 encoding the major regulator of cellulase and hemicellulase biosynthesis is non-functional, demonstrating that XYR1 is a repressor of these genes. We used two biological replicas of four T. reesei strains growing on glucose, lactose, and on wheat straw
Project description:We have examined and compared the transcriptome of T. reesei growing on wheat straw and lactose as carbon sources under otherwise similar conditions. Gene expression on wheat straw exceeded that on lactose, and 1619 genes were found to be only induced on wheat straw but not on lactose. They comprised 30 % of the CAZome, but were also enriched in genes associated with phospholipid metabolism, DNA synthesis and repair and iron homeostatis. Two thirds of the CAZome was expressed both on wheat straw as well as on lactose, but 60 % of it at least >2-fold higher on the former. Major wheat straw specific genes comprised xylanases, chitinases and ß-mannosidases. Interestingly, the latter two CAZyme families were significantly higher expressed in a strain in which xyr1 encoding the major regulator of cellulase and hemicellulase biosynthesis is non-functional, demonstrating that XYR1 is a repressor of these genes.
Project description:The present study aims to explore chemostat-based transcriptome analysis of mixed cultures by investigating interactions between the yeast S. cerevisiae and the lactic acid bacterium L. bulgaricus . S. cerevisiae and L. bulgaricus are both frequently encountered in kefir, a fermented dairy product. In the context of this study, this binary culture serves as a model for the many traditional food and beverage fermentation processes in which yeasts and lactic acid bacteria occur together. The design of the cultivation conditions was based on the observation that L. bulgaricus, but not S. cerevisiae, can use lactose as a carbon source for growth and that S. cerevisiae, but not L. bulgaricus, can grow on galactose that is released upon hydrolysis of lactose by the bacterial β-galactosidase. Mixed populations of yeasts and lactic acid bacteria occur in many dairy, food and beverage fermentations, but knowledge about their interactions is incomplete. In the present study, interactions between Saccharomyces cerevisiae and Lactobacillus delbrueckii subsp. bulgaricus, two microorganisms that co-occur in kefir fermentations, were studied during anaerobic growth on lactose. By combining physiological and transcriptome analysis of the two strains in the co-cultures, five mechanisms of interaction were identified. 1. L. bulgaricus hydrolyses lactose, which cannot be metabolized by S. cerevisiae, to galactose and glucose. Subsequently, galactose, which cannot be metabolized by L. bulgaricus, is excreted and provides a carbon source for yeast. 2. In pure cultures, L. bulgaricus only grows at increased CO2 concentrations. In anaerobic mixed cultures, the yeast provides this CO2 via alcoholic fermentation. 3. Analysis of amino acid consumption from the defined medium indicated that S. cerevisiae supplied alanine to the bacteria. 4. A mild but significant low-iron response in the yeast transcriptome, identified by DNA microarray analysis, was consistent with the chelation of iron by the lactate produced by L. bulgaricus. 5. Transcriptome analysis of L. bulgaricus in mixed cultures showed an overrepresentation of transcripts involved in lipids metabolism suggesting either a competition of the two microorganisms for fatty acids, or a response to the ethanol produced by S. cerevisiae.
Project description:The consumption of fermented food has been linked to positive health outcomes due to a variety of functional properties. Fermented dairy constitutes a major dietary source and contains lactoseas main carbohydrate and living starter cultures. To investigate whether nutritional and microbial modulation impacted intestinal microbiota composition and activity, we employed fecal microbiota fermentations and a dairy model system consisting of lactose and β-galactosidase positive and negative Streptococcus thermophilus. Based on 16S rRNA gene based microbial community analysis, we observed that lactose addition increased the abundance of Bifidobacteriaceae, and of Veillonellaceae and Enterobacteraceae in selected samples. The supplied lactose was hydrolysed within 24 h of fermentation and led to higher expression of community indigenous β-galactosidases. Targeted protein analysis confirmed that bifidobacteria contributed most β-galactosidases together with other taxa including Escherichia coli and Anaerobutyricum hallii. Lactose addition led to 1.1-1.8 fold higher levels of butyrate compared to controls likely due to (i) lactate-crossfeeding and (ii) direct lactose metabolism by butyrate producing Anaerobutyricum and Faecalibacterium spp. Representatives of both genera used lactose to produce butyrate in single cultures. When supplemented at around 5.5 log cells mL-1, S. thermophilus or its beta-galactosidase negative mutant outnumbered the indigenous Streptococcaceae population at the beginning of fermentation but had no impact on lactose utilisation and final SCFA profiles. This study brings forward new fundamental insight into interactions of major constituents of fermented dairy with the intestinal microbiota. We provide evidence that lactose addition increases fecal microbiota production of butyrate through cross-feeding and direct metabolism without contribution of starter cultures.
Project description:The present study aims to explore chemostat-based transcriptome analysis of mixed cultures by investigating interactions between the yeast S. cerevisiae and the lactic acid bacterium Lb. bulgaricus . S. cerevisiae and Lb. bulgaricus are both frequently encountered in kefir, a fermented dairy product (25). In the context of this study, this binary culture serves as a model for the many traditional food and beverage fermentation processes in which yeasts and lactic acid bacteria occur together (19,26-30). The design of the cultivation conditions was based on the observation that Lb. bulgaricus, but not S. cerevisiae, can use lactose as a carbon source for growth and that S. cerevisiae, but not Lb. bulgaricus, can grow on galactose that is released upon hydrolysis of lactose by the bacterial M-NM-2-galactosidase. Mixed populations of yeasts and lactic acid bacteria occur in many dairy, food and beverage fermentations, but knowledge about their interactions is incomplete. In the present study, interactions between Saccharomyces cerevisiae and Lactobacillus delbrueckii subsp. bulgaricus, two microorganisms that co-occur in kefir fermentations, were studied during anaerobic growth on lactose. By combining physiological and transcriptome analysis of the two strains in the co-cultures, five mechanisms of interaction were identified. 1. Lb. bulgaricus hydrolyses lactose, which cannot be metabolized by S. cerevisiae, to galactose and glucose. Subsequently, galactose, which cannot be metabolized by Lb. bulgaricus, is excreted and provides a carbon source for yeast. 2. In pure cultures, Lb. bulgaricus only grows at increased CO2 concentrations. In anaerobic mixed cultures, the yeast provides this CO2 via alcoholic fermentation. 3. Analysis of amino acid consumption from the defined medium indicated that S. cerevisiae supplied alanine to the bacteria. 4. A mild but significant low-iron response in the yeast transcriptome, identified by DNA microarray analysis, was consistent with the chelation of iron by the lactate produced by Lb. bulgaricus. 5. Transcriptome analysis of Lb. bulgaricus in mixed cultures showed an overrepresentation of transcripts involved in lipids metabolism suggesting either a competition of the two microorganisms for fatty acids, or a response to the ethanol produced by S. cerevisiae. To our knowledge, this is the first transcriptome study of a cross-kingdom binary mixed culture that analyses responses of both microorganisms. This study demonstrates that chemostat-based transcriptome analysis is a powerful tool to investigated microbial interaction in mixed populations. To investigate the impact of of co-cultivation with Lb. bulgaricus on S. cerevisiae, a DNA microarray-based transcriptome analysis of S. cerevisiae's response was performed on anaerobic, lactose-limited chemostat cultures grown in the presence and absence of L. bulgaricus.
Project description:The present study aims to explore chemostat-based transcriptome analysis of mixed cultures by investigating interactions between the yeast S. cerevisiae and the lactic acid bacterium Lb. bulgaricus . S. cerevisiae and Lb. bulgaricus are both frequently encountered in kefir, a fermented dairy product (25). In the context of this study, this binary culture serves as a model for the many traditional food and beverage fermentation processes in which yeasts and lactic acid bacteria occur together (19,26-30). The design of the cultivation conditions was based on the observation that Lb. bulgaricus, but not S. cerevisiae, can use lactose as a carbon source for growth and that S. cerevisiae, but not Lb. bulgaricus, can grow on galactose that is released upon hydrolysis of lactose by the bacterial β-galactosidase. Mixed populations of yeasts and lactic acid bacteria occur in many dairy, food and beverage fermentations, but knowledge about their interactions is incomplete. In the present study, interactions between Saccharomyces cerevisiae and Lactobacillus delbrueckii subsp. bulgaricus, two microorganisms that co-occur in kefir fermentations, were studied during anaerobic growth on lactose. By combining physiological and transcriptome analysis of the two strains in the co-cultures, five mechanisms of interaction were identified. 1. Lb. bulgaricus hydrolyses lactose, which cannot be metabolized by S. cerevisiae, to galactose and glucose. Subsequently, galactose, which cannot be metabolized by Lb. bulgaricus, is excreted and provides a carbon source for yeast. 2. In pure cultures, Lb. bulgaricus only grows at increased CO2 concentrations. In anaerobic mixed cultures, the yeast provides this CO2 via alcoholic fermentation. 3. Analysis of amino acid consumption from the defined medium indicated that S. cerevisiae supplied alanine to the bacteria. 4. A mild but significant low-iron response in the yeast transcriptome, identified by DNA microarray analysis, was consistent with the chelation of iron by the lactate produced by Lb. bulgaricus. 5. Transcriptome analysis of Lb. bulgaricus in mixed cultures showed an overrepresentation of transcripts involved in lipids metabolism suggesting either a competition of the two microorganisms for fatty acids, or a response to the ethanol produced by S. cerevisiae. To our knowledge, this is the first transcriptome study of a cross-kingdom binary mixed culture that analyses responses of both microorganisms. This study demonstrates that chemostat-based transcriptome analysis is a powerful tool to investigated microbial interaction in mixed populations.
Project description:Abstract: Transcriptome comparison of the Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose, revealed the elevated expression of various genes and operons, including the lac gene cluster that is organized into two operons i.e. lac operon-I (lacABCD) and lac operon-II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster, revealed elevated expression of lac operon-I, even in the absence of lactose. This suggests a function of LacR as a transcriptional repressor of lac operon-I that encodes enzymes involved in the Tagatose-6-P pathway in the absence of lactose or galactose. Deletion of lacR did not affect the expression of lac operon-II that encodes for a lactose-specific PTS. This finding was further confirmed by ?-galactosidase assays with PlacA-lacZ and PlacT-lacZ in the presence of either lactose or glucose as a sole carbon source in the medium. This suggests the presence of another transcriptional regulator in the regulation of lac operon-II, which could be the BglG-family transcriptional antiterminator LacT. We demonstrate the role of LacT as a transcriptional activator of lac operon-II in the presence of lactose and CcpA-independent regulation of the lac gene cluster in S. pneumoniae. This SuperSeries is composed of the SubSeries listed below. Refer to individual Series
Project description:Transcriptome comparison of the Streptococcus pneumoniae strain D39 grown in the presence of either lactose or galactose with that of the strain grown in the presence of glucose, revealed the elevated expression of various genes and operons, including the lac gene cluster that is organized into two operons i.e. lac operon-I (lacABCD) and lac operon-II (lacTFEG). Deletion of the DeoR family transcriptional regulator lacR that is present downstream of the lac gene cluster, revealed elevated expression of lac operon-I, even in the absence of lactose. This suggests a function of LacR as a transcriptional repressor of lac operon-I that encodes enzymes involved in the Tagatose-6-P pathway in the absence of lactose or galactose. Deletion of lacR did not affect the expression of lac operon-II that encodes for a lactose-specific PTS. This finding was further confirmed by ?-galactosidase assays with PlacA-lacZ and PlacT-lacZ in the presence of either lactose or glucose as a sole carbon source in the medium. This suggests the presence of another transcriptional regulator in the regulation of lac operon-II, which could be the BglG-family transcriptional antiterminator LacT. We demonstrate the role of LacT as a transcriptional activator of lac operon-II in the presence of lactose and CcpA-independent regulation of the lac gene cluster in S. pneumoniae. This SuperSeries is composed of the SubSeries listed below.
Project description:This a model from the article:
Feedback regulation in the lactose operon: a mathematical modeling study and comparison with experimental data.
Yildirim N, Mackey MC Biophys. J.
2003 12719218
,
Abstract:
A mathematical model for the regulation of induction in the lac operon in Escherichia coli is presented. This model takes into account the dynamics of the permease facilitating the internalization of external lactose; internal lactose; beta-galactosidase, which is involved in the conversion of lactose to allolactose, glucose and galactose; the allolactose interactions with the lac repressor; and mRNA. The final model consists of five nonlinear differential delay equations with delays due to the transcription and translation process. We have paid particular attention to the estimation of the parameters in the model. We have tested our model against two sets of beta-galactosidase activity versus time data, as well as a set of data on beta-galactosidase activity during periodic phosphate feeding. In all three cases we find excellent agreement between the data and the model predictions. Analytical and numerical studies also indicate that for physiologically realistic values of the external lactose and the bacterial growth rate, a regime exists where there may be bistable steady-state behavior, and that this corresponds to a cusp bifurcation in the model dynamics.
The model reproduces the time profile of beta-galactosidase activity as shown in Fig 3 of the paper. The delay functions for transcription (M) and translation (B and P) have been implemented by introducing intermediates ( I1, I2 and I3) in the reaction scheme which then give their respective products (I1-> M, I2 ->B and I3 ->P) after an appropriate length of time. The steady state values, attained upon simulation of model equations, for Allolactose (A), mRNA (M), beta-galactosidase (B), Lactose (L), and Permease (P) match with those predicted by the paper. The model was successfully tested on Jarnac, MathSBML and COPASI
This model originates from BioModels Database: A Database of Annotated Published Models (http://www.ebi.ac.uk/biomodels/). It is copyright (c) 2005-2010 The BioModels.net Team.
For more information see the terms of use
.
To cite BioModels Database, please use: Li C, Donizelli M, Rodriguez N, Dharuri H, Endler L, Chelliah V, Li L, He E, Henry A, Stefan MI, Snoep JL, Hucka M, Le Novère N, Laibe C (2010) BioModels Database: An enhanced, curated and annotated resource for published quantitative kinetic models. BMC Syst Biol., 4:92.
Project description:Aspergillus niger produces a variety of lignocellulolytic enzymes (cellulases, hemicellulases, among others) and is regarded as cell factory for the production of heterologous proteins. Therefore, there is a growing interest in the study of its genes and the understanding of the cellular mechanisms in order to expand its applications. On the other hand, we have shown that enzyme production by A. niger is higher when grown forming biofilms than when grown conventionally in submerged systems. The objective of this study was to perform a global transcriptomic analysis and an expression analysis of both lignocellulases and biofilm regulatory genes as compared to A. niger in submerged culture. DNA microarray assays were performed to investigate the global gene expression which yielded information on the expression of more than 90% of A. niger genes. To further this comparison, the two culture systems were supplemented with different carbon sources (glucose, lactose, xylose and maltose) to establish a differential gene expression under different culture conditions. Also, to validate the differential expression qPCR was performed for quantitative comparison of the transcriptional level of genes in both culture systems.