Project description:The acetic acid bacterium Gluconobacter oxydans 621H is characterized by its exceptional ability to incompletely oxidize a great variety of carbohydrates in the periplasm. The metabolism of this ?-proteobacterium has been characterized to some extent, yet little is known about its transcriptomes and related data. In this study, we applied two different RNAseq approaches. Primary transcriptomes enriched for 5'-ends of transcripts were sequenced to detect transcription start sites, which allow subsequent analysis of promoter motifs, ribosome binding sites, and 5´-UTRs. Whole transcriptomes were sequenced to identify expressed genes and operon structures.Sequencing of primary transcriptomes of G. oxydans revealed 2449 TSSs, which were classified according to their genomic context followed by identification of promoter and ribosome binding site motifs, analysis of 5´-UTRs including validation of predicted cis-regulatory elements and correction of start codons. 1144 (41%) of all genes were found to be expressed monocistronically, whereas 1634 genes were organized in 571 operons. Together, TSSs and whole transcriptome data were also used to identify novel intergenic (18), intragenic (328), and antisense transcripts (313).This study provides deep insights into the transcriptional landscapes of G. oxydans. The comprehensive transcriptome data, which we made publicly available, facilitate further analysis of promoters and other regulatory elements. This will support future approaches for rational strain development and targeted gene expression in G. oxydans. The corrections of start codons further improve the high quality genome reference and support future proteome analysis.
Project description:Gluconobacter oxydans is characterized by its ability to incompletely oxidize carbohydrates and alcohols. The high yields of its oxidation products and complete secretion into the medium make it important for industrial use. We report the finished genome sequence of Gluconobacter oxydans H24, an industrial strain with high l-sorbose productivity.
Project description:Gene expression in the obligatory aerobic acetic acid bacterium Gluconobacter oxydans was shown to respond to oxygen limitation, but the regulators involved are unknown. In this study, we analyzed the function of a transcriptional regulator named GoxR, which belongs to the FNR family. Here, we aplied RNAseq to identify target genes of GoxR by comparing genes expression of a delta-goxR and its parental strain after 20 min of oxygen limitation.
Project description:BACKGROUND:Gluconobacter oxydans is a strictly aerobic Gram-negative acetic acid bacterium used industrially for oxidative biotransformations due to its exceptional type of catabolism. It incompletely oxidizes a wide variety of carbohydrates regio- and stereoselectively in the periplasm using membrane-bound dehydrogenases with accumulation of the products in the medium. As a consequence, only a small fraction of the carbon and energy source enters the cell, resulting in a low biomass yield. Additionally, central carbon metabolism is characterized by the absence of a functional glycolysis and absence of a functional tricarboxylic acid (TCA) cycle. Due to these features, G. oxydans is a highly interesting model organism. Here we analyzed global mRNA decay in G. oxydans to describe its characteristic features and to identify short-lived mRNAs representing potential bottlenecks in the metabolism for further growth improvement by metabolic engineering. RESULTS:Using DNA microarrays we estimated the mRNA half-lives in G. oxydans. Overall, the mRNA half-lives ranged mainly from 3 min to 25 min with a global mean of 5.7 min. The transcripts encoding GroES and GroEL required for proper protein folding ranked at the top among transcripts exhibiting both long half-lives and high abundance. The F-type H+-ATP synthase transcripts involved in energy metabolism ranked among the transcripts with the shortest mRNA half-lives. RNAseq analysis revealed low expression levels for genes of the incomplete TCA cycle and also the mRNA half-lives of several of those were short and below the global mean. The mRNA decay analysis also revealed an apparent instability of full-length 23S rRNA. Further analysis of the ribosome-associated rRNA revealed a 23S rRNA fragmentation pattern exhibiting new cleavage regions in 23S rRNAs which were previously not known. CONCLUSIONS:The very short mRNA half-lives of the H+-ATP synthase, which is likely responsible for the ATP-proton motive force interconversion in G. oxydans under many or most conditions, is notably in contrast to mRNA decay data from other bacteria. Together with the short mRNA half-lives and low expression of some other central metabolic genes it could limit intended improvements of G. oxydans' biomass yield by metabolic engineering. Also, further studies are needed to unravel the multistep process of the 23S rRNA fragmentation in G. oxydans.
Project description:Gluconobacter oxydans is an important Gram-negative industrial microorganism that produces vitamin C and other products due to its efficient membrane-bound dehydrogenase system. Its incomplete oxidation system has many crucial industrial applications. However, it also leads to slow growth and low biomass, requiring further metabolic modification for balancing the cell growth and incomplete oxidation process. As a non-model strain, G. oxydans lacks efficient genome editing tools and cannot perform rapid multi-gene editing and complex metabolic network regulation. In the last 15 years, our laboratory attempted to deploy multiple CRISPR/Cas systems in different G. oxydans strains and found none of them as functional. In this study, Cpf1-based or dCpf1-based CRISPRi was constructed to explore the targeted binding ability of Cpf1, while Cpf1-FokI was deployed to study its nuclease activity. A study on Cpf1 found that the CRISPR/Cpf1 system could locate the target genes in G. oxydans but lacked the nuclease cleavage activity. Therefore, the CRISPR/Cpf1-FokI system based on FokI nuclease was constructed. Single-gene knockout with efficiency up to 100% and double-gene iterative editing were achieved in G. oxydans. Using this system, AcrVA6, the anti-CRISPR protein of G. oxydans was discovered for the first time, and efficient genome editing was realized.
Project description:In Gluconobacter oxydans, pyrroloquinoline quinone (PQQ) serves as the cofactor for various membrane-bound dehydrogenases that oxidize sugars and alcohols in the periplasm. Proteins for the biosynthesis of PQQ are encoded by the pqqABCDE gene cluster. Our reverse transcription-PCR and promoter analysis data indicated that the pqqA promoter represents the only promoter within the pqqABCDE cluster of G. oxydans 621H. PQQ overproduction in G. oxydans was achieved by transformation with the plasmid-carried pqqA gene or the complete pqqABCDE cluster. A G. oxydans mutant unable to produce PQQ was obtained by site-directed disruption of the pqqA gene. In contrast to the wild-type strain, the pqqA mutant did not grow with d-mannitol, d-glucose, or glycerol as the sole energy source, showing that in G. oxydans 621H, PQQ is essential for growth with these substrates. Growth of the pqqA mutant, however, was found with d-gluconate as the energy source. The growth behavior of the pqqA mutant correlated with the presence or absence of the respective PQQ-dependent membrane-bound dehydrogenase activities, demonstrating the vital role of these enzymes in G. oxydans metabolism. A different PQQ-deficient mutant was generated by Tn5 transposon mutagenesis. This mutant showed a defect in a gene with high homology to the Escherichia coli tldD gene, which encodes a peptidase. Our results indicate that the tldD gene in G. oxydans 621H is involved in PQQ biosynthesis, possibly with a similar function to that of the pqqF genes found in other PQQ-synthesizing bacteria.
Project description:Background2,3-Butanediol is a platform and fuel biochemical that can be efficiently produced from biomass. However, a value-added process for this chemical has not yet been developed. To expand the utilization of 2,3-butanediol produced from biomass, an improved derivative process of 2,3-butanediol is desirable.ResultsIn this study, a Gluconobacter oxydans strain DSM 2003 was found to have the ability to transform 2,3-butanediol into acetoin, a high value feedstock that can be widely used in dairy and cosmetic products, and chemical synthesis. All three stereoisomers, meso-2,3-butanediol, (2R,3R)-2,3-butanediol, and (2S,3S)-2,3-butanediol, could be transformed into acetoin by the strain. After optimization of the bioconversion conditions, the optimum growth temperature for acetoin production by strain DSM 2003 was found to be 30°C and the medium pH was 6.0. With an initial 2,3-butanediol concentration of 40 g/L, acetoin at a high concentration of 89.2 g/L was obtained from 2,3-butanediol by fed-batch bioconversion with a high productivity (1.24 g/L?·?h) and high yield (0.912 mol/mol).ConclusionsG. oxydans DSM 2003 is the first strain that can be used in the direct production of acetoin from 2,3-butanediol. The product concentration and yield of the novel process are both new records for acetoin production. The results demonstrate that the method developed in this study could provide a promising process for efficient acetoin production and industrially produced 2,3-butanediol utilization.