Dataset Information

Transposon sequencing uncovers an essential regulatory function of phosphoribulokinase for methylotrophy

ABSTRACT: Methylotrophy is the ability of organisms to grow at the expense of reduced one-carbon compounds such as methanol or methane. Here, we used transposon sequencing combining hyper-saturated transposon mutagenesis with high-throughput sequencing to define the essential methylotrophy genome of Methylobacterium extorquens PA1, a model methylotroph. To distinguish genomic regions required for growth only on methanol from general required genes, we contrasted growth on methanol with growth on succinate, a non-methylotrophic reference substrate. About 500'000 insertions were mapped for each condition, resulting in a median insertion distance of 5 base pairs. We identified 147 genes and 76 genes as specific for growth on methanol and succinate, respectively, and a set of 590 genes as required under both growth conditions. For the integration of metabolic functions, we reconstructed a genome-scale metabolic model and performed in silico essentiality analysis. In total, the approach uncovered 95 previously not described genes as crucial for methylotrophy, including genes involved in respiration, carbon metabolism, transport, and regulation. Strikingly, regardless of the absence of the Calvin cycle in the methylotroph, the screen led to the identification of the gene for phosphoribulokinase as essential during growth on methanol but not on succinate. Genetic experiments in addition to metabolomics and proteomics revealed that phosphoribulokinase serves a key regulatory function. Our data support a model according to which ribulose-1,5 bisphosphate is an essential metabolite that induces a transcriptional regulator driving one-carbon assimilation.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Methylobacterium Extorquens Pa1

SUBMITTER: Lucas Hemmerle

LAB HEAD: Julia A. Vorholt

PROVIDER: PXD006834 | Pride | 2017-07-11

REPOSITORIES: Pride

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Publications

Transposon Sequencing Uncovers an Essential Regulatory Function of Phosphoribulokinase for Methylotrophy.

Ochsner Andrea M AM Christen Matthias M Hemmerle Lucas L Peyraud Rémi R Christen Beat B Vorholt Julia A JA

Current biology : CB 20170817 17

Methylotrophy is the ability of organisms to grow at the expense of reduced one-carbon compounds, such as methanol or methane. Here, we used transposon sequencing combining hyper-saturated transposon mutagenesis with high-throughput sequencing to define the essential methylotrophy genome of Methylobacterium extorquens PA1, a model methylotroph. To distinguish genomic regions required for growth only on methanol from general required genes, we contrasted growth on methanol with growth on succinat ...[more]

PMID: 28823675

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Project description:In order to provide information about the gene expression response that occurs when cells experience a change in carbon source, succinate limited chemostat cultures of Methylobacterium extorquens AM1 were grown to and maintained at an OD of ~0.63, transferred to flasks and methanol was added. Cells were harvested for RNA extraction at time: 0 min, 10 min, 30 min, 1 hr, 2 hr, 4 hr and 6 hr post transition. At 30 min, a no methanol addition sample was extracted as a carbon starvation control. These data were used in conjunction with flux, enzymatic and metabolite measurements to assess the changes in central metabolism during this transition. Abstract from manuscript: When organisms experience environmental change, how does their metabolic network reset and adapt to the new condition? This study focused on the mechanisms of metabolic adaptation occurring during the transition from succinate to methanol growth by the methylotrophic bacterium Methylobacterium extorquens, analyzing changes in carbon flux, gene expression, metabolites and enzymatic activities over time. Initially, cells experienced metabolic imbalance with excretion of metabolites, changes in nucleotide levels and cessation of cell growth. Though assimilatory pathways were induced rapidly, a transient block in carbon flow to biomass synthesis occurred, and enzymatic assays suggested methylenetetrahydrofolate dehydrogenase as one control point. This “downstream priming” mechanism ensures that significant carbon flux through these pathways does not occur until they are fully induced, precluding the buildup of toxic intermediates. Most metabolites that are required for growth on both carbon sources did not change significantly, even though transcripts and enzymatic activities required for their production changed radically, underscoring the concept of metabolic setpoints. Gene expression in succinate limited chemostat cultures was compared to gene expression in cells transferred to flasks before and after methanol addition. As a control, a time = 0 sample (RNA prepared from cells harvested directly from the chemostat) was compared to a time = 0 sample immediately obtained after the cells were transferred to flasks, before methanol was added in order to identify changes due to flask transfer. A carbon starvation control was also done comparing expression from time = 0 (chemostat cells) to cells transferred to flasks for 30 min with no carbon source added. Two biological replicates each with two techinal replicates (dye swap) were analyzed for time = 0 (chemostat) vs 10 min, 30 min, 1 hr and 2 hr after methanol addition. One biological replicate with two technical replicates (dye swap) were analyzed for time = 0 (chemostat) vs time = 0 (flask transfer), and time = 0 (chemostat) vs time = 4 hr, 6 hr and 30 min no methanol addition.

Project description:Methyloversatilis universalis FAM5 utilizes single carbon compounds such as methanol or methylated amines as a sole source of carbon and energy. Expression profiling reveals distinct sets of genes altered during growth on methanol vs methylamine. Growth on methanol results in activation of mdh2 and a number of known accessory proteins. As expected, all genes for N-methylglutamate pathway were induced during growth on methylated amine. Among other functions, responding to a switch from methanol to methylated amines, are a heme-containing amine dehydrogenase (QHNDH), a PQQ-dependent methanol dehydrogenase homologue, a distant homologue of formaldehyde activating enzyme (fae3), molybdenum containing formate dehydrogenase, a set of transporters homologues to urea/ammonium transporters and amino-acid permeases. Genes encoding the PQQ-dependent methanol dehydrogenase and associated cytochrome, the enzymes from the assimilatory H4F-dependent pathway, and the tungsten-containing aldehyde oxidoreductase were down-regulated during growth on methylamine. Genes essential for carbon assimilation (serine cycle) and H4MTP-pathway for formaldehyde oxidation show similar level of expression on both C1-carbon sources. Phenotypic analysis of mutants lacking functional QHNDH had no growth defect on C1-compounds. M. universalis FAM5 strain with the methylene-tetrahydrofolate dehydrogenase lesion, a key enzyme of the H4-folate pathway, were not able to use any C1-compound, methanol or methylated amines. Methyloversatilis universalis FAM5 possesses three homologs of the formaldehyde activating enzymes. The relative expression of two of the formaldehyde activating enzyme (fae1) and fae2 did not change after the shift from methanol to methylamine growth. The relative expression of the third homologs, fae3, was significantly upregulated by methylamine. Single and double fae 2 and fae 3 mutants display similar to wild type growth M-BM- on methanol or methylamine. Strains lacking fae1 lost the ability to grow on both C1-compounds. However upon incubation on methylated amines the fae1-mutant produce revertants (fae1R ). The revertant strains displayed an impaired growth on methylamine but were not able to use methanol. Double mutations in fae1RM-BM- / fae3 or fae1R/fae2 and triple mutant fae1R/fae2/fae3 showed similar to fae1R phenotype. The metabolic pathways for utilization methanol and methylamine in Methyloversatilis universalis FAM5 are reconstructed. Methyloversatilis universalis FAM5 grown on methanol and methylamine with two biologial replicates for each condition. RNA-Seq was used for transcriptomics.

Project description:Methyloversatilis universalis FAM5 utilizes single carbon compounds such as methanol or methylated amines as a sole source of carbon and energy. Expression profiling reveals distinct sets of genes altered during growth on methanol vs methylamine. Growth on methanol results in activation of mdh2 and a number of known accessory proteins. As expected, all genes for N-methylglutamate pathway were induced during growth on methylated amine. Among other functions, responding to a switch from methanol to methylated amines, are a heme-containing amine dehydrogenase (QHNDH), a PQQ-dependent methanol dehydrogenase homologue, a distant homologue of formaldehyde activating enzyme (fae3), molybdenum containing formate dehydrogenase, a set of transporters homologues to urea/ammonium transporters and amino-acid permeases. Genes encoding the PQQ-dependent methanol dehydrogenase and associated cytochrome, the enzymes from the assimilatory H4F-dependent pathway, and the tungsten-containing aldehyde oxidoreductase were down-regulated during growth on methylamine. Genes essential for carbon assimilation (serine cycle) and H4MTP-pathway for formaldehyde oxidation show similar level of expression on both C1-carbon sources. Phenotypic analysis of mutants lacking functional QHNDH had no growth defect on C1-compounds. M. universalis FAM5 strain with the methylene-tetrahydrofolate dehydrogenase lesion, a key enzyme of the H4-folate pathway, were not able to use any C1-compound, methanol or methylated amines. Methyloversatilis universalis FAM5 possesses three homologs of the formaldehyde activating enzymes. The relative expression of two of the formaldehyde activating enzyme (fae1) and fae2 did not change after the shift from methanol to methylamine growth. The relative expression of the third homologs, fae3, was significantly upregulated by methylamine. Single and double fae 2 and fae 3 mutants display similar to wild type growth on methanol or methylamine. Strains lacking fae1 lost the ability to grow on both C1-compounds. However upon incubation on methylated amines the fae1-mutant produce revertants (fae1R ). The revertant strains displayed an impaired growth on methylamine but were not able to use methanol. Double mutations in fae1R / fae3 or fae1R/fae2 and triple mutant fae1R/fae2/fae3 showed similar to fae1R phenotype. The metabolic pathways for utilization methanol and methylamine in Methyloversatilis universalis FAM5 are reconstructed.

Project description:The increasing demand for non-food competitive carbon sources such as methanol for biotechnology has brought methanol-utilizing bacteria, so-called methylotrophs, to focus. The product spectrum of natural methylotrophs and their genetic accessibility is limited and as an alternative approach, the introduction of methylotrophic metabolism into a biotechnologically well-established organism, such as Escherichia coli, represents a promising concept. By performing long-term evolution over 600 days, we obtained an E. coli strain that is able to grow on methanol as its sole carbon source at rates comparable to natural methylotrophic organisms. We confirmed that the strain forms its entire biomass from methanol. Furthermore, we sequenced the genome of the evolved strain and compared it to the genome of its ancestor. Intriguingly, we found several hundreds of mutations targeting genes of various functions, such as catalysis and regulation. Like the comparison of the genome before and after evolution, the investigation of the proteome would be of high interest. Proteomics would reveal the consequences of the regulatory mutations found in the genome and provide an overall picture of the adaptations by the cell enabling it to grow on methanol. The increasing demand for non-food competitive carbon sources such as methanol for biotechnology has brought methanol-utilizing bacteria, so-called methylotrophs, to focus. The product spectrum of natural methylotrophs and their genetic accessibility is limited and as an alternative approach, the introduction of methylotrophic metabolism into a biotechnologically well-established organism, such as Escherichia coli, represents a promising concept. By performing long-term evolution over 600 days, we obtained an E. coli strain that is able to grow on methanol as its sole carbon source at rates comparable to natural methylotrophic organisms. We confirmed that the strain forms its entire biomass from methanol. Furthermore, we sequenced the genome of the evolved strain and compared it to the genome of its ancestor. Intriguingly, we found several hundreds of mutations targeting genes of various functions, such as catalysis and regulation. Like the comparison of the genome before and after evolution, the investigation of the proteome would be of high interest. Proteomics would reveal the consequences of the regulatory mutations found in the genome and provide an overall picture of the adaptations by the cell enabling it to grow on methanol.

Dataset Information

Transposon sequencing uncovers an essential regulatory function of phosphoribulokinase for methylotrophy

Publications

Transposon Sequencing Uncovers an Essential Regulatory Function of Phosphoribulokinase for Methylotrophy.

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