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1.
In this study, the glucose 6-phosphate dehydrogenase gene (XOO2314) was inactivated in order to modulate the intracellular
glucose 6-phosphate, and its effects on xanthan production in a wild-type strain of Xanthomonas oryzae were evaluated. The intracellular glucose 6-phosphate was increased from 17.6 to 99.4 μmol g−1 (dry cell weight) in the gene-disrupted mutant strain. The concomitant increase in the glucose 6-phosphate was accompanied
by an increase in xanthan production of up to 2.23 g l−1 (culture medium). However, in defined medium supplemented with 0.4% glucose, the growth rate of the mutant strain was reduced
to 52.9% of the wild-type level. Subsequently, when a family B ATP-dependent phosphofructokinase from Escherichia coli was overexpressed in the mutant strain, the growth rate was increased to 142.9%, whereas the yields of xanthan per mole of
glucose remained approximately the same. 相似文献
2.
Genome sequence analysis of Xanthomonas
oryzae pv. oryzae has revealed a cluster of 12 ORFs that are closely related to the gum gene cluster of Xanthomonas campestris pv. campestris. The gum gene cluster of X. oryzae encodes proteins involved in xanthan production; however, there is little experimental evidence supporting this. In this
study, biochemical analyses of xanthan produced by a defined set of X. oryzae
gum mutant strains allowed us to preliminarily assign functions to most of the gum gene products: biosynthesis of the pentasaccharide repeating unit for GumD, GumM, GumH, GumK, and GumI, xanthan polymerization
and transport for GumB, GumC, GumE, and GumJ, and modification of the pentasaccharide repeating unit for GumF, GumG, and GumL.
In addition, we found that the exopolysaccharides are essential but not specific for the virulence of X. oryzae.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Sang-Yoon Kim and Jeong-Gu Kim contributed equally to this work. 相似文献
3.
Peng Wang Juan Li Li Wang Ming-li Tang Zeng-liang Yu Zhi-ming Zheng 《Journal of industrial microbiology & biotechnology》2009,36(11):1363-1368
Low-energy ion beam irradiation (10–200 keV) has been proved to have a wide range of biological effects in recent years. When
Rhizopus oryzae PW352 was irradiated with a 15-keV low-energy ion beam an l(+)-lactic acid high-yield mutant, RQ4015, was obtained. When 150 g/l glucose was used as the sole carbon source, l(+)-lactic acid of RQ4015 reached 121 g/l after 36 h shake-flask cultivation. However, the highest lactic acid concentration
74 g/l was obtained when 100 g/l xylose was present in the medium as the sole carbon source. When mixed xylose (25 g/l) and
glucose (75 g/l) were present in a bubble column, l(+)-lactic acid production of RQ4015 reached 83 g. A high mutation rate and a wide mutation spectrum of low-energy ion implantation
were observed in the experiment, suggesting that ion implantation can be a highly efficient mutagenic means for microorganism
breeding in many commercial applications. 相似文献
4.
Md. Aminul Hoque Atefeh Taherian Fard Mosfequr Rahman Omar Alattas Kohei Akazawa Amir Feisal Merican 《Biologia》2011,66(6):954-966
We conducted an integrated study of cell growth parameters, product formation, and the dynamics of intracellular metabolite
concentrations using Escherichia coli with genes knocked out in the glycolytic and oxidative pentose phosphate pathway (PPP) for glucose catabolism. We investigated
the same characteristics in the wild-type strain, using acetate or pyruvate as the sole carbon source. Dramatic effects on
growth parameters and extracellular and intracellular metabolite concentrations were observed after blocking either glycolytic
breakdown of glucose by inactivation of phosphoglucose isomerase (disruption of pgi gene) or pentose phosphate breakdown of glucose by inactivation of glucose-6-phosphate dehydrogenase (disruption of zwf gene). Reducing power (NADPH) was mainly produced through PPP when the pgi gene was knocked out, while NADPH was produced through the tricarboxylic acid (TCA) cycle by isocitrate dehydrogenase or
NADP-linked malic enzyme when the zwf gene was knocked out. As expected, when the pgi gene was knocked out, intracellular concentrations of PPP metabolites were
high and glycolytic and concentrations of TCA cycle pathway metabolites were low. In the zwf gene knockout, concentrations of PPP metabolites were low and concentrations of intracellular glycolytic and TCA cycle metabolites
were high. 相似文献
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7.
G. Lorda J. D. Breccia V. Barbeito F. Pagliero S. Boeris C. Castaño A. Pordomingo F. Altolaguirre M. D. Pastor 《World journal of microbiology & biotechnology》2007,23(1):1-5
The addition of xanthan to high water retention capacity peat (HWRC) inoculants did not show differences on the survival of
Bradyrhizobium japonicum E109. In low water retention capacity peats (LWRC) however, xanthan increased the survival of B.japonicum significantly. Xanthan showed the best effect at 0.1 g/l for B. japonicum, in contrast to Sinorhizobium fredii USDA205 where the concentrations evaluated (0–1.0 g/l) did not affected significantly its survival. Nevertheless, when the
symbiotic performance on soybean was evaluated, the presence of 0.1 g xanthan/l increased the nodule number for both strains. 相似文献
8.
Zeinab Salehi Farzaneh Vahabzadeh Morteza Sohrabi Shohreh Fatemi Hussein Tawfiq Znad 《Biodegradation》2010,21(4):645-657
The effect of p-nitrophenol (PNP) concentration with or without glucose and yeast extract on the growth and biodegradative capacity of Ralstonia eutropha was examined. The chemical constituents of the culture medium were modeled using a response surface methodology. The experiments
were performed according to the central composite design arrangement considering PNP, glucose and yeast extract as the selected
variables whose influences on the degradation was evaluated (shaking in reciprocal mode, temperature of 30°C, pH 7 and test
time of about 9 h). Quadratic polynomial regression equations were used to quantitatively explain variations between and within
the models (responses: the biodegradation capacity and the biomass formation). The coefficient of determination was high (R
adjusted2 = 0.9783), indicating the constructed polynomial model for PNP biodegradative capacity explains the variation between the
regressors fairly well. A PNP removal efficiency of 74.5% occurred within 9 h (15 mg/L as the initial concentration of PNP
with use of yeast extract at 0.5 g/L). 相似文献
9.
10.
Xuefeng Wu Shaotong Jiang Mo Liu Lijun Pan Zhi Zheng Shuizhong Luo 《Journal of industrial microbiology & biotechnology》2011,38(4):565-571
Semicontinuous fermentation using pellets of Rhizopus oryzae has been recognized as a promising technology for l-lactic acid production. In this work, semicontinuous fermentation of R. oryzae AS 3.819 for l-lactic acid production has been developed with high l-lactic acid yield and volumetric productivity. The effects of factors such as inoculations, CaCO3 addition time, and temperature on l-lactic acid yield and R. oryzae morphology were researched in detail. The results showed that optimal fermentation conditions for the first cycle were: inoculation
with 4% spore suspension, CaCO3 added to the culture medium at the beginning of culture, and culture temperature of 32–34°C. In orthogonal experiments, high
l-lactic acid yield was achieved when the feeding medium was (g/l): glucose, 100; (NH4)2SO4, 2; KH2PO4, 0.1; ZnSO4·7H2O, 0.33; MgSO4·7H2O, 0.15; CaCO3, 50. Twenty cycles of semicontinuous fermentation were carried out in flask culture. l-lactic acid yield was 78.75% for the first cycle and 80–90% for the repeated cycles; the activities of lactate dehydrogenases
(LDH) were 7.2–9.2 U/mg; fermentation was completed in 24 h for each repeated cycle. In a 7-l magnetically stirred fermentor,
semicontinuous fermentation lasted for 25 cycles using pellets of R. oryzae AS 3.819 under the optimal conditions determined from flask cultures. The final l-lactic acid concentration (LLAC) reached 103.7 g/l, and the volumetric productivity was 2.16 g/(l·h) for the first cycle;
in the following 19 repeated cycles, the final LLAC reached 81–95 g/l, and the volumetric productivities were 3.40–3.85 g/(l·h). 相似文献
11.
Xanthomonas oryzae pv. oryzae causes bacterial leaf blight, one of the most widespread and destructive bacterial diseases in rice. In order to understand
the gene of zinc uptake regulator (zur) involved in virulence of the pathogen in rice, we generated a mutant OSZRM by homologous suicide plasmid integration. The
mutant failed to grow in NYGB medium supplemented with Zn2+ or Fe3+ at a concentration of 500 μM or 6 mM, whereas the wild-type strain grew well at the same conditions. The zur mutant was hypersensitive to hydrogen peroxide and exhibited reduction catalase activity and the production of extracellular
polysaccharide (EPS). Interestingly, the mutant showed a reduction in virulence on rice but still kept triggering hypersensitive
response (HR) in tobacco. When the mutant was complemented with the zur gene, the response was recovered to wild-type. These results suggested that zur gene is a functional member of the Zur regulator family that controls zinc and iron homeostasis, oxidative stress, and EPS
production, which is necessary for virulence in X. oryzae pv. oryzae.
Wanfeng Yang and Yan Liu contributed equally to this work 相似文献
12.
Mauricio Soto-Suárez Diana Bernal Carolina González Boris Szurek Romain Guyot Joe Tohme Valérie Verdier 《BMC microbiology》2010,10(1):170
Background
Bacterial leaf blight causes significant yield losses in rice crops throughout Asia and Africa. Although both the Asian and African strains of the pathogen, Xanthomonas oryzae pv. oryzae (Xoo), induce similar symptoms, they are nevertheless genetically different, with the African strains being more closely related to the Asian X. oryzae pv. oryzicola (Xoc). 相似文献13.
Katherine Muñoz Mario Vega Gisela Rios Rolf Geisen Gisela H. Degen 《Mycotoxin Research》2011,27(4):239-247
Ochratoxin A (OTA) is one of the most widespread mycotoxins, and is produced by several Aspergillus or Penicillium species. Human exposure to OTA is mainly by intake of contaminated food, with cereal products, followed by coffee and red
wine as the main sources of OTA. In this study, the OTA production of four ochratoxigenic fungi (two Aspergillus and two Penicillium species) was investigated in four different media, i.e. wheat and coffee model media as food-based media and two standard laboratory media (malt extract glucose agar, MEA and yeast
extract sucrose agar, YES). Colony growth was documented and OTA concentrations in cultures were determined at day 2, 4 and
8 of incubation at 25°C by high-performance thin-layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC).
OTA production clearly depended upon time of incubation, fungal species, and medium composition. On coffee based medium, moderate
OTA levels were produced by A. ochraceus BFE635 (9.8 μg/g) and by A. niger BFE632 (10.6 μg/g) on day 8 of incubation. In wheat-based medium, these strains produced much more OTA than in coffee. The
highest OTA concentration (83.8 μg/g on day 8) was formed by A. ochraceus BFE635 followed by the other Aspergillus niger BFE632 (49 μg/g). Lower OTA levels were produced by P. verrucosum BFE550 and P. nordicum BFE487, in both wheat and in YES medium, whilst OTA was hardly detectable in coffee and in MEA in case of P. nordicum. Colony growth of the tested strains on different media was not indicative of OTA production. Guttation droplets developed
on wheat-based medium with the Aspergillus strains within a week, and this phenomenon coincided with the high OTA amounts formed by these species. Results from this
study add to our knowledge on the behaviour of ochratoxigenic fungal species when cultured on food based media. 相似文献
14.
Alka Singh Niraj K. Nirala Sandip Das Alka Narula M. V. Rajam P. S. Srivastava 《Acta Physiologiae Plantarum》2011,33(6):2453-2459
Scopolamine is widely used for its anticholinergic properties. Because of higher physiological activity and less side effects
the world demand of scopolamine is estimated to be ten times greater than other anticholinergic agents, hyoscyamine and atropine.
Since natural production is limited, alternatives are required to boost the production. We report the introduction of mouse
odc gene of polyamine biosynthesis pathway which is also the primary pathway of tropane alkaloids in Datura innoxia. Polyamines, mainly putrescine, serve as the common metabolite for tropane alkaloids and nicotine. We have overexpressed
odc gene to modulate the metabolic flux downstream and eventually achieved higher accumulation of scopolamine in transgenic plants.
Among six independent transformed lines one line (O10) produced scopolamine (0.258 μg/g dry weight) almost six times higher
than that produced by control plants (0.042 μg/g DW). To our knowledge, this is the first report of odc overexpression in D. innoxia leading to higher scopolamine yield. 相似文献
15.
Rosa Garcia Sanchez Bärbel Hahn-Hägerdal Marie F Gorwa-Grauslund 《Microbial cell factories》2010,9(1):40
Background
In Saccharomyces cerevisiae galactose is initially metabolized through the Leloir pathway after which glucose 6-phosphate enters glycolysis. Galactose is controlled both by glucose repression and by galactose induction. The gene PGM2 encodes the last enzyme of the Leloir pathway, phosphoglucomutase 2 (Pgm2p), which catalyses the reversible conversion of glucose 1-phosphate to glucose 6-phosphate. Overexpression of PGM2 has previously been shown to enhance aerobic growth of S. cerevisiae in galactose medium. 相似文献16.
The effect of gene knockout on metabolism in the pflA–, pflB–, pflC–, and pflD– mutants of Escherichia coli was investigated. Batch cultivations of the pfl
– mutants and their parent strain were conducted using glucose as a carbon source. It was found that pflA– and pflB– mutants, but not pflC– and pflD– mutants, produced large amounts of d-lactate from glucose under the microaerobic condition, and the maximum yield was 73%. In order to investigate the metabolic regulation mechanism, we measured enzyme activities for the following eight enzymes: glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), pyruvate kinase, lactate dehydrogenase (LDH), phosphoenolpyruvate carboxylase, acetate kinase, and alcohol dehydrogenase. Intracellular metabolite concentrations of glucose 6-phosphate, fructose 1,6-bisphosphate, phosphoenolpyruvate, pyruvate, acetyl coenzyme A as well as ATP, ADP, AMP, NADH, and NAD+ were also measured. It was shown that the GAPDH and LDH activities were considerably higher in pflA– and pflB– mutants, which implies coupling between NADH production and consumption between the two corresponding reactions. The urgent energy requirement was shown by the lower ATP/AMP level due to both oxygen limitation and pfl gene knockout, which promoted significant stepping-up of glycolysis when using glucose as a carbon source. It was shown that the demand for energy is more important than intracellular redox balance, thus excess NADH produced through GAPDH resulted in a significantly higher intracellular NADH/NAD+ ratio in pfl
– mutants. Consequently, the homolactate production was achieved to meet the requirements of the redox balance and the energy production through glycolysis. The effect of using different carbon sources such as gluconate, pyruvate, fructose, and glycerol was investigated. 相似文献
17.
Xanthomonas oryzae pv. oryzae, the bacterial blight pathogen of rice, is known to produce phytotoxic polysaccharides. The extracellular polysaccharide (EPS)
was isolated from virulent (BXO1) and virulence-deficient gum G mutant (BXO1002) strains of X. oryzae pv. oryzae and characterized using fourier transform infrared (FT-IR) and nuclear magnetic resonance (NMR). Data from the FT-IR suggested
that the aldehyde (R-CHO) group and C=O of acid anhydride are present in BXO1 but absent in BXO1002. The 1H-NMR spectra showed the presence of an acetyl amine of hexose or pentose, free amines of glucose, an β-anomeric carbon of
hexose and pentose, hydrogen next to hydroxyl group, an acetyl amine of hexose and pentose in the polysaccharides of both
BXO1 and BXO1002, and the absence of α-anomeric carbon of hexose or pentose and the glucuronic acid in the polysaccharides
produced by BXO1002. The test for glucuronic acid also confirmed the absence of glucuronic acid in the polysaccharides of
BXO1002 and the presence glucuronic acid (32 μg/mg) in the polysaccharides produced by BXO1.
Received: 14 May 2002 / Accepted: 21 June 2002 相似文献
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19.
Moslem Papizadeh Mohammad Roayaei Ardakani Gholamhossein Ebrahimipour Hossein Motamedi 《World journal of microbiology & biotechnology》2010,26(7):1195-1200
Oil-polluted soils were sampled from National Iranian South Oil Company (NISOC) for isolation and screening of C–S and not
C–C targeted Dibenzothiophene (DBT) degrading microorganisms. Microbacterium sp. NISOC-06, a C–S targeted DBT degrading bacterium, was selected and its desulfurization ability was studied in aqueous phase and water-gasoline
biphasic systems. The 16srRNA gene was amplified using universal eubacteria-specific primers, PCR product was sequenced and
the sequence of nearly 1,500 bp 16srDNA was studied. Based on Gas Chromatography results Microbacterium sp. NISOC-06 utilized 94.8% of 1 mM DBT during the 2 weeks of incubation. UV Spectrophotometry and biomass production measurements showed
that the Microbacterium sp. NISOC-06 was not able to utilize DBT as a carbon source. There was no accumulation of phenolic compounds as Gibb’s assay showed. Biomass
production in a biphasic system for which DBT-enriched gasoline was used as the sulfur source indicated the capability of
Microbacterium sp. NISOC-06 to desulfurize gasoline. 相似文献
20.
Phytochrome-like proteins have been recently identified in prokaryotes but their features and functions are not clear. We
cloned a gene encoding the phytochrome-like protein (XoBphP) in a pathogenic bacteria, Xanthomonas oryzae pv. oryzae (Xoo) and investigated characteristics of the protein using a recombinant XoBphP. The N-terminal region of XoBphP containing the
PAS/GAF/PHY domains is highly similar to most bacteriophytochromes, but Cys4, corresponding to Cys24 of DrBphP, isn’t involved
in chromophore attachment. Recombinant XoBphP could bind a bilin molecule and a differential spectrum from Pr/Pfr shows that
XoBphP has similar characteristics of known bacteriophytochromes with shifted absorption maxima of 683 and 757 nm for the
Pr and Pfr forms. Unlike other bacteriophytochromes, XoBphP has no histidine kinase domain at C-terminus. The domain was predicted
from amino-acid 279 to 342 with less significance than the required threshold. This result suggests that XoBphP probably has
different signal transduction mechanisms for its intracellular function. 相似文献