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1.
Martin Pipíška Miroslav Horník L’uboš Vrtoch Jozef Augustín Juraj Lesný 《Biologia》2007,62(3):276-282
Cobalt is one of the possible contaminants originating from radioactive wastes or from metal mines and refineries. This paper
describes sorption of cobalt by the foliose lichen Hypogymnia physodes from CoCl2 solutions spiked with 60Co2+ in laboratory experiments. Maximum uptake was reached within 1 hour; the biosorption after 24 hours is not pH-dependent within
the range of pH 4–7, negligible at pH 2 and is not dependent on metabolic activity. The process can be described by the Freundlich
adsorption isotherm with ln k = 2.77, 1/n = 0.22 and R
2 = 0.94. Bivalent metal ions showed a concentration-dependent competitive effect on cobalt biosorption, decreasing in the
order: Cu > Ni > Ca > Mg. Monovalent ions, such as K+ and Na+, showed only very weak competitive effect. Up to 98% of Co taken up by lichen can be removed by washing with 0.1 M NiCl2 at 20°C. This means that only a small fraction of the cobalt is localized intracellularly. These results can be used for
elucidating the behaviour of lichens as bioindicators of cobalt pollution in water systems, including the risk of cobalt leakage
from lichen probes under the influence of rain, snow and atmospheric humidity. 相似文献
2.
The phytohormone auxin regulates many aspects of plant growth and development. Auxin often acts distantly from the site of
its biosynthesis and this long-distance-transported auxin is well known to play a critical role in eliciting physiological
responses including regulating root development. Auxin can be produced in roots, yet the function of locally synthesized auxin
in root growth is unclear. The major auxin in plants, indole 3-acetic acid (IAA), is mainly synthesized through tryptophan
(Trp)-dependent pathways that require pyridoxal phosphate (an active form of vitamin B6)-dependent enzymes. We previously reported that the Arabidopsis vitamin B6 biosynthesis mutant pdx1 has stunted root growth although the underlying cause is unknown. Here we showed that the pdx1 root is deficient in auxin biosynthesis. By reciprocal grafting of pdx1 and the wild type, we demonstrated that the stunted root growth in pdx1 is caused by a locally generated signal(s) in roots. To test whether auxin might be one such signal, the auxin responsive
DR5::GUS reporter was introduced into the mutant. The DR5::GUS activity in pdx1 root tips was greatly reduced compared with that in the wild type although the auxin response was unaltered. pdx1 also suppresses the root hair growth defects in the auxin overproduction mutant yucca. These data indicate that pdx1 is impaired in Trp-dependent auxin biosynthesis, which may contribute to the short-root phenotype of pdx1. We suggest that locally synthesized auxin may play a critical role in postembryonic root growth. 相似文献
3.
Suk-Jin Ha Sang-Yong Kim Jin-Ho Seo Marimuthu Jeya Ye-Wang Zhang Thangadurai Ramu In-Won Kim Jung-Kul Lee 《Bioprocess and biosystems engineering》2009,32(5):697-700
Of various metal ions (Ca2+, Cr3+, Cu2+, Fe2+, Mg2+, Mn2+, Ni2+ and Zn2+) added to the culture medium of Agrobacterium tumefaciens at 1 mM, only Ca2+ increased Coenzyme Q10 (CoQ10) content in cells without the inhibition of cell growth. In a pH-stat fed-batch culture, supplementation with 40 mM of CaCO3 increased the specific CoQ10 content and oxidative stress by 22.4 and 48%, respectively. Also, the effect of Ca2+ on the increase of CoQ10 content was successfully verified in a pilot-scale (300 L) fermentor. In this study, the increased oxidative stress in A. tumefaciens culture by the supplementation of Ca2+ is hypothesized to stimulate the increase of specific CoQ10 content in order to protect the membrane against lipid peroxidation. Our results improve the understanding of Ca2+ effect on CoQ10 biosynthesis in A. tumefaciens and should contribute to better industrial production of CoQ10 by biological processes. 相似文献
4.
Yield of S-adenosylmethionine was improved significantly in recombinant Pichia pastoris by controlling NH4
+ concentration. The highest production rate was 0.248 g/L h when NH4
+ concentration was 450 mmol/L and no repression of cell growth was observed. Within very short induction time (47 h), 11.63 g/L
SAM was obtained in a 3.7 L bioreactor. 相似文献
5.
Xin Zhou Zhengping Zhang Xiaohe Jia Yifan Wu Lan Luo Zhimin Yin 《World journal of microbiology & biotechnology》2008,24(8):1267-1272
Bacillus subtilis glutamine synthetase (GS) was highly expressed (about 86% of total protein) as soluble protein in Escherichia coli BL21(DE3) containing pET28a-glnA, which was induced by 0.4 mM IPTG in LB medium, and maximal theanine-forming activity of
the recombinant GS induced in LB is 6.4 U/mg at a series concentration (0–100 mM) of Mn2+ at optimal pH 7.5. In order to get GS with high theanine-forming activity, safety, and low cost for food and pharmaceutics
industry, M9-A (details are described in “Materials and methods”) and 0.1% (w/v) lactose were selected as culture medium and
inducer respectively. Recombinant GS was also highly expressed (84% of total protein) and totally soluble in M9-A and the
specific activity of the recombinant GS is 6.2 U/mg which is approximate to that (6.4 U/mg) induced in LB in the presence
of 10 mM Mn2+ at optimal pH 7.5. The activity is markedly higher activated by Mn2+ than that by other nine bivalent cations. Furthermore, M9-B (5 μM Mn2+ was added into M9-A) was used to culture the recombinant strain and theanine-forming activity of the recombinant GS induced
in M9-B was improved 20% (up to 7.6 U/mg). Finally, theanine production experiment coupled with yeast fermentation system
was carried out in a 1.0 ml reaction system with 0.1 mg crude GS from M9-B or M9-A, and the yield of theanine were 15.3 and
13.1 g/L by paper chromatography and HPLC, respectively. 相似文献
6.
An effective transformation procedure for Kitasatospora setae was established based on transconjugation from Escherichia coli ET12567 (pUZ8002) using a C31-derived integration vector, pSET152, containing oriT and attP fragments. While no transconjugation was observed under the standard transconjugation conditions for Streptomyces species, sufficient transconjugation (>1×10-6) was achieved on ISP4 medium containing 30 mM MgCl2 using a 25- to 125-fold excess of E. coli donor cells. In addition, the sequence and location of the chromosomal integration site attB of K. setae was identified for the first time in genera of non-Streptomyces actinomycetes. K. setae contains a single C31 attB site. Similar to the case of Streptomyces species, the attB site of K. setae is present within an ORF encoding a pirin-homolog, but the K. setae-attB sequence deviates slightly from the consensus sequence of Streptomyces attB sequences. 相似文献
7.
The kinetics of the ubiquinol-cytochrome c reductase reaction was examined using membrane fragments and purified bc(1) complexes derived from a wild-type (WT) and a newly constructed mutant (MUT) strains of Paracoccus denitrificans. The cytochrome c(1) of the WT samples possessed an additional stretch of acidic amino acids, which was lacking in the mutant. The reaction was followed with positively charged mitochondrial and negatively charged bacterial cytochromes c, and specific activities, apparent k(cat) values, and first-order rate constant values were compared. These values were distinctly lower for the MUT fractions using mitochondrial cytochrome c but differed only slightly with the bacterial species. The MUT preparations were less sensitive to changes of ionic strength of the reaction media and showed pure first-order kinetics with both samples of cytochrome c. The reaction of the WT enzyme was first order only with bacterial cytochrome c but proceeded with a non-linear profile with mitochondrial cytochrome c. The analysis of the reaction pattern revealed a rapid onset of the reaction with a successively declining rate. Experiments performed in the absence of an electron donor indicated that electrostatic attraction could directly participate in cytochrome c reduction. 相似文献
8.
Two strains (KM3 and KM5) of halophilic methylobacteria isolated from Red Sea algae do not require vitamin B12 for growth and can use methanol, methylamine, dimethylamine, trimethylamine, dimethyl sulfide, and fructose as sources of carbon and energy. The cells of these strains are gram-negative motile monotrichous (strain KM3) or peritrichous (strain KM5) rods. The strains are strictly aerobic and require Na+ ions but not growth factors. They are oxidase-and catalase-positive and reduce nitrates to nitrites. Both strains can grow in a temperature range of 4 to 37°C (with optimal growth at 29–34°C), at pH between 5.5 and 8.5 (with optimal growth at pH 7.5–8.0), and in a range of salt concentrations between 0.5 and 15% NaCl (with optimal growth at 5–9% NaCl). The phospholipids of these strains are dominated by phosphatidylethanolamine and phosphatidylglycerol and also include phosphatidylcholine, phosphatidylserine, and cardiolipin. The dominant fatty acids are C16:1ω7c and C16:0. The major ubiquinone is Q8. The cells accumulate ectoin, glutamate, and sucrose as intracellular osmoprotectants. The strains implement the 2-keto-3-deoxy-6-phosphogluconate-dependent variant of the ribulose monophosphate pathway. The G+C content of the DNA is 44.4–44.7 mol%. Analysis of the 16S rRNA genes showed that both strains belong to Gammaproteobacteria and have a high degree of homology (99.4%) to Methylophaga marina ATCC 35842T. Based on the data of polyphasic taxonomy, isolates KM3 and KM5 are identified as new strains M. marina KM3 (VKM B-2386) and M. marina KM5 (VKM B-2387). The ability of these strains to produce auxins (indole-3-acetic acid) suggests their metabolic association with marine algae. 相似文献
9.
10.
Farrakh Mehboob Howard Junca Gosse Schraa Alfons J. M. Stams 《Applied microbiology and biotechnology》2009,83(4):739-747
Microbial (per)chlorate reduction is a unique process in which molecular oxygen is formed during the dismutation of chlorite.
The oxygen thus formed may be used to degrade hydrocarbons by means of oxygenases under seemingly anoxic conditions. Up to
now, no bacterium has been described that grows on aliphatic hydrocarbons with chlorate. Here, we report that Pseudomonas chloritidismutans AW-1T grows on n-alkanes (ranging from C7 until C12) with chlorate as electron acceptor. Strain AW-1T also grows on the intermediates of the presumed n-alkane degradation pathway. The specific growth rates on n-decane and chlorate and n-decane and oxygen were 0.5 ± 0.1 and 0.4 ± 0.02 day−1, respectively. The key enzymes chlorate reductase and chlorite dismutase were assayed and found to be present. The oxygen-dependent
alkane oxidation was demonstrated in whole-cell suspensions. The strain degrades n-alkanes with oxygen and chlorate but not with nitrate, thus suggesting that the strain employs oxygenase-dependent pathways
for the breakdown of n-alkanes. 相似文献
11.
L-Lactate cytochrome c oxidoreductase (flavocytochrome b 2, FC b 2) from the thermotolerant methylotrophic yeast Hansenula polymorpha (Pichia angusta) is, unlike the enzyme form baker’s yeast, a thermostable enzyme potentially important for bioanalytical technologies for highly selective assays of L-lactate in biological fluids and foods. This paper describes the construction of flavocytochrome b 2 producers with over-expression of the H. polymorpha CYB2 gene, encoding FC b 2. The HpCYB2 gene under the control of the strong H. polymorpha alcohol oxidase promoter in a plasmid for multicopy integration was transformed into the recipient strain H. polymorpha C-105 (grc1 catX), impaired in glucose repression and devoid of catalase activity. A method was developed for preliminary screening of the transformants with increased FC b 2 activity in permeabilized yeast cells. The optimal cultivation conditions providing for the maximal yield of the target enzyme were found. The constructed strain is a promising FC b 2 producer characterized by a sixfold increased (to 3 μmol min?1 mg?1 protein in cell-free extract) activity of the enzyme. 相似文献
12.
Low levels of fumonisins have been found frequently in corn based breakfast cereals and can occur bound to protein and other
matrix components.In vitro digestion of two samples of corn flakes was carried out under "fed conditions." Fumonisins were measured as o-phthaldialdehyde/mercaptoethanol
derivatives by LC-fluorescence. One sample of corn flakes (FN12) had high concentrations of fumonisin B1 (FB) (average 125 ng/g) and total bound FB1, (TB FB1) (average 92 ng/g) and the other (FN11) had a low level of free FB1 (average 29 ng/g) and no detectable TB FB1. After incubation of the samples with gastrointestinal tract solutions simulating saliva plus stomach and duodenal juices,
chyme was analysed for FB1, hydrolyzed FB1 (HFB1) and partially hydrolyzed fumonisin B1 (PHFB1). The bioaccessibility (percentage of FB1 released from corn flakes into chyme) was 38-78% for incurred FB1 in FN12, 8-54% for incurred plus spiked FB1 in FN12, and 19-66% for incurred plus spiked FB1 in FN11. HFB1 and PHFB1 were not detected. If free FB1 was first extracted from sample FN12, no FB1 was detected in the chyme, indicating no contribution from TB FB1. Concentrations were corrected for method recovery of FB1 or, for bound FB1, partial method recovery of HFB1
Presented at the XIIth IUPAC International Symposium on Mycotoxins and Phycotoxins, Istanbul, Turkey, 21–25 May, 2007 相似文献
13.
The toxic effect of Pb2+ has been studied in eukaryotic cells by using Tetrahymena as a target. The maximum power (P
m) and the growth rate constant (k) were determined, which showed that values of P
m and k were linked to the concentration (C) of Pb2+. The addition of Pb2+ caused a decrease of the maximum heat production and growth rate constant, indicating that Tetrahymena growth was inhibited in the presence of Pb2+, and Pb2+ took part in the metabolism of cells. From micrographs, morphological changes of Tetrahymena were observed with addition of Pb2+, indicating that the toxic effect of Pb2+ derived from destroying the membrane of surface of Tetrahymena. According to the thermogenic curves and photos of Tetrahymena under different conditions, it is clear that metabolic mechanism of Halobacterium halobium R1 growth has been changed with the addition of Pb2+. 相似文献
14.
Many bacteria adapt to microoxic conditions by synthesizing a particular cytochrome c oxidase (cbb
3) complex with a high affinity for O2, encoded by the ccoNOQP operon. A survey of genome databases indicates that ccoNOQP sequences are widespread in all sub-branches of Proteobacteria but otherwise are found only in bacteria of the CFB group (Cytophaga, Flexibacter, Bacteroides). Our analysis of available genome sequences suggests four major strategies of regulating ccoNOQP expression in response to O2. The most widespread strategy involves direct regulation by the O2-responsive protein Fnr. The second strategy involves an O2-insensitive paralogue of Fnr, FixK, whose expression is regulated by the O2-responding FixLJ two-component system. A third strategy of mixed regulation operates in bacteria carrying both fnr and fixLJ-fixK genes. Another, not yet identified, strategy is likely to operate in the -Proteobacteria Helicobacter pylori and Campylobacter jejuni which lack fnr and fixLJ-fixK genes. The FixLJ strategy appears specific for the -subclass of Proteobacteria but is not restricted to rhizobia in which it was originally discovered. 相似文献
15.
During hot and humid seasons, extensive rot of sour lime was observed to be caused by Aspergillus flavus. In view of this, investigations were undertaken to obtain data on the production of various toxins by A. flavus during post harvest pathogenesis of sour lime. Sixty percent of the pathogenic A. flavus isolates were detected to be aflatoxin B1 producers in sour lime tissue. It was also noted that thirty three percent of aflatoxigenic A. flavus isolates had the potential to coproduce cyclopiazonic acid (CPA). Such aflatoxigenic isolates produced quantitatively more CPA (ranging from 250.0 to 2501.3 g/kg) than aflatoxin B1 (ranging from 141.3 to 811.7 g/kg) in the affected sour lime. This study demonstrates for the first time that sour lime are a favourable substrate for aflatoxin B1 and cyclopiazonic acid production by A. flavus isolates. This is of great concern to the health of consumers. 相似文献
16.
We have investigated the floral ontogeny of Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis (of the eucalypt group, Myrtaceae) using scanning electron microscopy and light microscopy. Several critical characters for establishing relationships between these genera and to the eucalypts have been determined. The absence of compound petaline primordia in Arillastrum, Allosyncarpia, Stockwellia and Eucalyptopsis excludes these taxa from the eucalypt clade. Post-anthesis circumscissile abscission of the hypanthium above the ovary in Stockwellia, Eucalyptopsis and Allosyncarpia is evidence that these three taxa form a monophyletic group; undifferentiated perianth parts and elongated fusiform buds are characters that unite Stockwellia and Eucalyptopsis as sister taxa. No floral characters clearly associate Arillastrum with either the eucalypt clade or the clade of Stockwellia, Eucalyptopsis and Allosyncarpia.We gratefully acknowledge Clyde Dunlop and Bob Harwood (Northern Territory Herbarium) for collecting specimens of Allosyncarpia, and Bruce Gray (Atherton) for collecting specimens of Stockwellia. The Australian National Herbarium (CANB) kindly lent herbarium specimens of Eucalyptopsis for examination. This research was supported by a University of Melbourne Research Development Grant to Andrew Drinnan. 相似文献
17.
18.
A pea rust fungus, Uromyces viciae-fabae, has been classified into two varieties, var. viciae-fabae and var. orobi, based on differences in urediniospore wall thickness and putative host specificity in Japan. In principal component analyses, morphological features of urediniospores and teliospores of 94 rust specimens from Vicia, Lathyrus, and Pisum did not show definite host-specific morphological groups. In molecular analyses, 23 Uromyces specimens from Vicia, Lathyrus, and Pisum formed a single genetic clade based on D1/D2 and ITS regions. Four isolates of U. viciae-fabae from V. cracca and V. unijuga could infect and sporulate on P. sativum. These results suggest that U. viciae-fabae populations on different host plants are not biologically differentiated into groups that can be recognized as varieties.Contribution no. 184, Laboratory of Plant Parasitic Mycology, Institute of Agriculture and Forestry, University of Tsukuba, Japan 相似文献
19.
20.
Chunxia Wu Xiuhua Gao Xiangqiang Kong Yanxiu Zhao Hui Zhang 《Plant Molecular Biology Reporter》2009,27(1):1-12
Na+/H+ exchanger catalyzes the countertransport of Na+ and H+ across membranes. Using the rapid amplification of cDNA ends method, a Na+/H+ antiporter gene (ThNHX1) was isolated from a halophytic plant, salt cress (Thellungiella halophila). The deduced amino acid sequence contained 545 amino acid residues with a conserved amiloride-binding domain (87LFFIYLLPPI96) and shared more than 94% identity with that of AtNHX1 from Arabidopsis thaliana. The ThNHX1 mRNA level was upregulated by salt and other stresses (abscisic acid, polyethylene glycol, and high temperature). This gene
partially complemented the Na+/Li+-sensitive phenotype of a yeast mutant that was deficient in the endosomal–vacuolar Na+/H+ antiporter ScNHX1. Overexpression of ThNHX1 in Arabidopsis increased salt tolerance of transgenic plants compared with the wild-type plants. In addition, the silencing of ThNHX1 gene in T. halophila caused the transgenic plants to be more salt and osmotic sensitive than wild-type plant. Together, these results suggest
that ThNHX1 may function as a tonoplast Na+/H+ antiporter and play an important role in salt tolerance of T. halophila.
Chunxia Wu, Xiuhua Gao, and Xiangqiang Kong contributed equally to this work. 相似文献