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Identification of two mutations increasing the methanol tolerance of Corynebacterium glutamicum

ABSTRACT: Background: Methanol is present in most ecosystems and may also occur in industrial applications, e.g. as an impurity of carbon sources such as technical glycerol. Methanol often inhibits growth of bacteria, thus, methanol tolerance may limit fermentative production processes. Results: The methanol tolerance of the amino acid producing soil bacterium Corynebacterium glutamicum was improved by genetic adaption in the presence of methanol. The resulting strain Tol1 exhibited significantly increased growth rates in the presence of up to 1 M methanol. However, neither transcriptional changes nor increased enzyme activities of the linear methanol oxidation pathway were observed, which was in accordance with the finding that tolerance to the downstream metabolites formaldehyde and formate was not improved. Genome sequence analysis of strain Tol1 revealed two point mutations potentially relevant to enhanced methanol tolerance: one leading to the amino acid exchange A165T of O-acetylhomoserine sulfhydrolase MetY and the other leading to shortened CoA transferase Cat (Q342*). Introduction of either mutation into the genome of C. glutamicum wild type increased methanol tolerance and introduction of both mutations into C. glutamicum was sufficient to achieve methanol tolerance almost indistinguishable from that of strain Tol1. Conclusion: The methanol tolerance of C. glutamicum can be increased by two point mutations leading to amino acid exchange of O-acetylhomoserine sulfhydrolase MetY and shortened CoA transferase Cat. Introduction of these mutations into producer strains may be helpful when using carbon sources containing methanol as component or impurity.

ORGANISM(S): Corynebacterium glutamicum Corynebacterium glutamicum ATCC 13032

PROVIDER: GSE71590 | GEO | 2015/08/01

SECONDARY ACCESSION(S): PRJNA291592

REPOSITORIES: GEO

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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.

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.

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Identification of two mutations increasing the methanol tolerance of Corynebacterium glutamicum

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