首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 78 毫秒
1.
The oleaginous bacterium, Rhodococcus jostii RHA1 has attracted considerable attention due to its capability to accumulate significant levels of triacylglycerol as renewable hydrocarbon. To enable the strain to utilize arabinose derived from lignocellulosic biomass, the metabolic pathway of L-arabinose utilization was introduced into R. jostii RHA1 by heterogenous expression of the operon, araBAD from Escherichia coli. The results showed that recombinant bearing araBAD could grow on L-arabinose as the sole carbon source, and additional expression of araFGH encoding the arabinose transporter from E. coli could improve the cell biomass yield from high contents of arabinose. We further increased the content of lipid produced from arabinose in the recombinants from 47.9 to 56.8 % of the cell dry weight (CDW) by overexpression of a gene, atf1 encoding a diglyceride acyltransferase from R. opacus PD630. This work demonstrated the feasibility of producing lipid from arabinose by genetic modification of the rhodococci strain.  相似文献   

2.
3.

Objectives

To deregulate the purine operon of the purine biosynthetic pathway and optimize energy generation of the respiratory chain to improve the yield of guanosine in Bacillus amyloliquefaciens XH7.

Results

The 5′-untranslated region of the purine operon, which contains the guanine-sensing riboswitch, was disrupted. The native promoter Pw in B. amyloliquefaciens XH7 was replaced by different strong promoters. Among the promoter replacement mutants, XH7purE::P41 gave the highest guanosine yield (16.3 g/l), with an increase of 23% compared with B. amyloliquefaciens XH7. The relative expression levels of the purine operon genes (purE, purF, and purD) in the XH7purE::P41 mutant were upregulated. The concentration of inosine monophosphate (IMP), the primary intermediate in the purine pathway, was also significantly increased in the XH7purE::P41 mutant. Combined modification of the low-coupling branched respiratory chains (cytochrome bd oxidase) improved guanosine production synergistically. The final guanosine yield in the XH7purE::P41△cyd mutant increased by 41% to 19 g/l compared with B. amyloliquefaciens XH7.

Conclusion

The combined modification strategy used in this study is a novel approach to improve the production of guanosine in industrial bacterial strains.
  相似文献   

4.
Many bacteria belonging to the order Rhizobiales have fixNOQP genes which encode cytochrome oxidase with high affinity to oxygen required for oxidative phosphorylation in microaerophilic conditions. There is one copy of the identified fixNOQP operon in ancestral forms of rhizobia (Bradyrhizobium), as well as in their putative evolutionary predecessors (bacteria related to Rhodopseudomonas). At the same time, forms deeply specialized in symbiosis (Rhizobium leguminosarum, Sinorhizobium meliloti) have multiple (2–3) copies, some of them have a high similarity (>90%) to fixNOQP genes of Bradyrhizobium and Rhodopseudomonas, and others have only 30–50% similarity. Two divergent copies fixNOQP are detected in Tardiphaga, which is a representative of the Bradyrhizobiaceae family, lacking the ability to fix N2 (lack of nif genes encoding the synthesis of nitrogenase) and to induce the formation of nodules on legumes roots (lack of nod genes encoding the synthesis of signal Nod factors activating symbiosis development). The presence of Tardiphaga in nodule bacterial communities from a range of legumes, including Vavilovia formosa (relic representative of the tribe Fabeae, for which R. leguminosarum bv. viciae is the main microsymbiont), suggests that the ancestral gene duplication and subsequent divergence of fixNOQP operon in bacteria related to Tardiphaga opened the possibility of wide dissemination of functionally different copies of this cluster among symbiotically active forms of Rhizobiales. It is possible that the acquisition of fixNOQP genes determines adaptation of bacteria to microaerophilic niches not only in plants nodules but also in their environment (the rhizosphere, rhizoplane, internal portions of soil aggregates).  相似文献   

5.
Gemmata obscuriglobus is a Gram-negative bacterium with several intriguing biological features. Here, we present a complete, de novo whole genome assembly for G. obscuriglobus which consists of a single, circular 9 Mb chromosome, with no plasmids detected. The genome was annotated using the NCBI Prokaryotic Genome Annotation pipeline to generate common gene annotations. Analysis of the rRNA genes revealed three interesting features for a bacterium. First, linked G. obscuriglobus rrn operons have a unique gene order, 23S–5S–16S, compared to typical prokaryotic rrn operons (16S–23S–5S). Second, G. obscuriglobus rrn operons can either be linked or unlinked (a 16S gene is in a separate genomic location from a 23S and 5S gene pair). Third, all of the 23S genes (5 in total) have unique polymorphisms. Genome analysis of a different Gemmata species (SH-PL17), revealed a similar 23S–5S–16S gene order in all of its linked rrn operons and the presence of an unlinked operon. Together, our findings show that unique and rare features in Gemmata rrn operons among prokaryotes provide a means to better define the evolutionary relatedness of Gemmata species and the divergence time for different Gemmata species. Additionally, these rrn operon differences provide important insights into the rrn operon architecture of common ancestors of the planctomycetes.  相似文献   

6.
Heterologous expression is an efficient strategy for target protein production. Dlt operon plays the important role in the d-alanylation of lipoteichoic acid, which might affect the net negative charge of cell wall for protein secretion. In this study, dlt operon was deleted to improve the target protein production, and nattokinase, α-amylase and β-mannanase with different isoelectric points (PIs) were served as the target proteins. Firstly, our results implied that deletions of dltA, dltB, dltC and dltD improved the net negative charge of cell wall for extracellular protein secretion respectively, and among which, the dltB deficient strain DW2ΔdltB showed the best performance, its nattokinase (PI: 8.60) activity was increased by 27.50% compared with that of DW2/pP43SacCNK. Then, the dltABCD mutant strain was constructed, and the net negative charge and nattokinase activity were increased by 55.57% and 37.13% respectively, due to the deficiency of dltABCD. Moreover, it was confirmed that the activities of α-amylase (PI: 6.26) and β-mannanase (PI: 5.75) were enhanced by 44.53% and 53.06% in the dltABCD deficient strains, respectively. Collectively, this study provided a strategy that deletion of dlt operon improves the protein secretion in B. licheniformis, and which strategy was more conducive to the target protein with lower PI.  相似文献   

7.
8.
λ DNA stimulates a low level of protein synthesis in extracts of E. coli supplemented with RNA polymerase. The synthesis is efficiently and specifically repressed by addition of purified λ repressor. About 90% of the protein product is from the rightwards, or tof, promoter (P R ) and 10% from the leftwards, or N, promoter (P L ). The main polypeptide product is a low molecular species from the tof operon.  相似文献   

9.
The detection of the gene ara C protein using a DNA-dependent in vitro protein synthesizing system represents the first isolation of an operon specific positive regulator with an in vivo role that has been genetically defined.  相似文献   

10.
The conserved two-domain ribosomal protein (r-protein) L1 is a structural part of the L1 stalk of the large ribosomal subunit and regulates the translation of the operon that comprises its own gene. The regulatory properties of the bacterial r-protein L1 have only been studied in detail for Escherichia coli; however, there were no such studies for other bacteria, in particular, Thermus thermophilus and Thermotoga maritima, which are more evolutionarily ancient. It is known that domain I of the r-protein L1 might have regulatory properties of the whole protein. The aim of this study was to identify regulatory sites on the mRNA of T. thermophilus and T. maritima that interact with r-proteins L1, as well as with their domains I from the same organisms. An analysis of the mRNA of the L11 operon T. thermophilus showed the presence of one potential binding site of the L1 r-protein, two such regions were found also in the mRNA sequence of the L11 operon of T. maritima. The dissociation constants for the L1 proteins from T. thermophilus and T. maritima and their domains I with mRNA fragments from the same organisms that contain the supposed L1-binding sites were determined by surface plasmon resonance. It has been shown that the ribosomal proteins L1 as their domains I bind specific fragments of mRNA from the same organisms that may suggest regulatory activity of the L1 protein in the T. thermophilus and T. maritima and conservatism of the principles of L1-RNA interactions.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号