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1.
Anabaena sp., isolated from a rice paddy, was investigated for its nitrogen fixation as measured by acetylene reduction activity (ARA)
in P-limited continuous and light-limited semi-continuous cultures. Growth rate (μ) under P limitation was a function of cell
P content (q
p). Both the photosynthetic capacity (Pmax) and photosynthetic efficiency (α) increased with μ when expressed per cell, but not per unit chla. The ARA of steady-state cells under P limitation increased with μ and was linearly related to C-fixation rate. This was
apparently a consequence of the control of C-fixation by P limitation. In light-limited cells, steady state ARA, both at the
culture light intensity and in the dark, increased asymptotically with μ, but the activity in the dark was only about 51%
of that in the light. When the light level of steady-state cells grown at a high in intensity was switched to a low level,
ARA decreased exponentially with time. Dark ARA activity also showed a similar decline, but at much lower levels. Thus, ARA
depended not only on light history, but also immediate photosynthesis. Steady-state ARA at the ambient intensity or in the
dark showed a strong correlation with14C-fixation rate. ARA of light-limited cells showed the same light-saturation characteristics as their14C-fixation, with the same initial saturation intensity,I
k. The ratios of Pmax to the maximum ARA (ARAmax), and α to the slope of ARA (αara) were identical. A comparison of gross to net photosynthesis and N2 fixation suggested that there was little leakage or excretion of fixed C or N. 相似文献
2.
Removal of pathogenic factors from 2,3-butanediol-producing Klebsiella species by inactivating virulence-related wabG gene 总被引:1,自引:0,他引:1
Sung-Geun Jung Jun-Ho Jang Ah-Young Kim Min-Cheol Lim Borim Kim Jinwon Lee Young-Rok Kim 《Applied microbiology and biotechnology》2013,97(5):1997-2007
Klebsiella species are the most extensively studied among a number of 2,3-butanediol (2,3-BDO)-producing microorganisms. The ability to metabolize a wide variety of substrates together with the ease of cultivation made this microorganisms particularly promising for the application in industrial-scale production of 2,3-BDO. However, the pathogenic characteristics of encapsulated Klebsiella species are considered to be an obstacle hindering their industrial applications. Here, we removed the virulence factors from three 2,3-BDO-producing strains, Klebsiella pneumoniae KCTC 2242, Klebsiella oxytoca KCTC1686, and K. oxytoca ATCC 43863 through site-specific recombination technique. We generated deletion mutation in wabG gene encoding glucosyltransferase which plays a key role in the synthesis of outer core lipopolysaccharides (LPS) by attaching the first outer core residue d-GalAp to the O-3 position of the l,d-HeppII residue. The morphologies and adhesion properties against epithelial cells were investigated, and the results indicated that the wabG mutant strains were devoid of the outer core LPS and lost the ability to retain capsular structure. The time profile of growth and 2,3-BDO production from K. pneumoniae KCTC 2242 and K. pneumoniae KCTC 2242 ΔwabG were analyzed in batch culture with initial glucose concentration of 70 g/l. The growth was not affected by disrupting wabG gene, but the production of 2,3-BDO decreased from 31.27 to 22.44 g/l in mutant compared with that of parental strain. However, the productions of acetoin and lactate from wabG mutant strain were negligible, whereas that from parental strain reached to ~5 g/l. 相似文献
3.
Seong Rim Byeon Hyunjin Vincent Kim Mijin Jeon Young Gil Ahn Maeng Sup Kim Jae Yang Kong Hye Yun Kim Young Soo Kim Dong Jin Kim 《Bioorganic & medicinal chemistry letters》2013,23(11):3467-3469
Alzheimer’s disease drug discovery regarding exploration into the molecules and processes has focused on the intrinsic causes of the brain disorder correlated with the accumulation of amyloid-β. An anti-amyloidogenic bis-styrylbenzene derivative, KMS80013, showed excellent oral bioavailability (F = 46.2%), facilitated brain penetration (26%, iv) in mouse and target specific in vivo efficacy in acute AD mouse model attenuating the cognitive deficiency in Y-maze test. Acute toxicity (LD50 >2000 mg/kg) and hERG channel inhibition (14% at 10 μM) results indicated safety of KMS80013. 相似文献
4.
Hyun‐Joo Lee MinSeok Chang Jong‐Mook Kim HyeJin Hong KiEun Maeng Jane Koo ShinJae Chang Myung‐Sam Cho 《Biotechnology progress》2013,29(2):432-440
Host cell lines developed by genetic engineering sometimes show instabilities in maintaining their genetically acquired phenotypes. Previously, a hybrid host cell line, designated as hybrid of kidney and B cells (HKB), capable of retaining selected phenotypes originally existing in the parental cells was developed via fusion of 293 cells and HH514‐16 cells. Although HKB did indeed successfully preserve several favorable phenotypes, the expression of Epstein‐Barr virus (EBV) specific nuclear antigen 1 (EBNA1), which should be constitutively expressed for host cells to utilize oriP expression vector in transient production of therapeutic proteins, was observed to be unstable. Here, in an attempt to obtain stable expression of EBNA1, a cell type that contains an integrated EBV genome, rather than HH514‐16 cells, which harbor an episomal EBV genome, was applied for fusion with 293 cells. Fusion of 293 cells with Namalwa cells led to the creation of a new type of hybrid, F2N, which was able to stably express EBNA1 while not producing EBV particles. One of the F2N clones, F2N78, was observed to maintain EBNA1 expression for more than 1 year under serum‐free suspension culture conditions along with human specific glycosyl phenotypes observed previously in HKB. In addition, F2N78 was demonstrated to be an appropriate host cell line for both the transient and stable production of recombinant therapeutics with the features of safety expected of production cell lines for human use. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 432–440, 2013 相似文献
5.
Kim YM Park K Jung SH Choi JH Kim WC Joo GJ Rhee IK 《Journal of microbiology (Seoul, Korea)》2004,42(1):42-46
It has recently been reported that one of the most important factors of yeast resistance to the fungicide chlorothalonil is the glutathione contents and the catalytic efficiency of glutathione S-transferase (GST) (Shin et al, 2003). GST is known to catalyze the conjugation of glutathione to a wide variety of xenobiotics, resulting in detoxification. In an attempt to elucidate the relation between chlorothalonil-detoxification and GST, the GST of Escherichia coli was expressed and purified. The drug-hypersensitive E. coli KAM3 cells harboring a plasmid for the overexpression of the GST gene can grow in the presence of chlorothalonil. The purified GST showed chlorothalonil-biotransformation activity in the presence of glutathione. Thus, chlorothalonil is detoxified by the mechanism of glutathione conjugation catalyzed by GST. 相似文献
6.
Lee BH Jeong SM Ha TS Park CS Lee JH Kim JH Kim DH Han JS Kim HC Ko SR Nah SY 《Molecules and cells》2004,18(1):115-121
Treatment with ginsenosides, the major active ingredients of Panax ginseng, produces a variety of physiological effects on the central and peripheral nervous systems. Ginsenosides inhibit various types of ligand-gated ion channel but it is not clear whether they act from within or outside the cell since they are somewhat membrane-permeable. In the present study, we used the Xenopus oocyte gene expression system to determine from which side of the cell membrane the ginsenoside Rg3 (Rg3), and M4, a ginsenoside metabolite, act to regulate ligand-gated ion channel activity. Ligand-gated ion currents were measured using the two-electrode voltage clamp technique. Rg3 and M4 inhibited 5-HT3A and a3b4 nACh receptor-mediated ion currents when present outside of the cell but not when injected intracellularly. We also examined the effect of these agents on oocytes expressing the gustatory cGMP-gated ion channel, which is known to have a cGMP binding site on the intracellular side of the plasma membrane and is only activated by cytosolic cGMP. Rg3 inhibited cGMP-gated ion currents when applied extracellularly or to an outside-out patch clamp, but not when injected into the cytosol or when using an excised inside-out patch clamp. These results indicate that Rg3 and M4 regulate ligand-gated ion channel activity from the extracellular side. 相似文献
7.
8.
Use of microorganism-immobilized polyurethane foams to absorb and degrade oil on water surface 总被引:6,自引:0,他引:6
Highly oil-absorbent polyurethane foam (PUF) materials were obtained by polymerizing polyether polyol mixture and carbodiimide-modified
d-methyl diisocyanate in a weight ratio of 10:2. The foam materials were prepared to contain inorganic nutrients (slow-release
fertilizer; SRF) and oil-degrading yeast cells, Yarrowia lipolytica 180, to be applied for removal of oil films on surface waters through absorption and biodegradation after oil spills. PUFs
absorbed 7–9 times their own weight of Arabian light crude oil and the oil absorbency appeared to improve as the ratio of
surface area to foam weight increased. PUFs showed excellent floatability which was maintained for more than 6 months in sea
water, and less than 5% of the absorbed oil was released when the foams were left on water for more than 10 days. For immobilization
of yeast cells into PUFs, various immobilization techniques were tested to compare their oil degrading ability and the maintenance
thereof. All immobilized cells showed oil degrading abilities as good as those of free cells immediately after the preparation
of PUFs, however, the activity of chitin-immobilized cells remained at a high level for the longest period of preservation.
The high efficiency of oil absorption and oil degradation by PUF-immobilized yeast cells suggested that PUF-immobilized cells
have a high potential as a bioremediation technique for the treatment of oil films on surface waters.
Received: 27 September 1999 / Received revision: 6 March 2000 / Accepted: 17 March 2000 相似文献
9.
Saccharomyces cerevisiae has three distinct citrate synthases, two located in mitochondria (mature Cit1p and Cit3p) and one in peroxisomes (mature Cit2p). While the precursor of the major mitochondrial enzyme, Cit1p, has a signal for mitochondrial targeting at its N-terminus (MTS), Cit2p has one for peroxisomal targeting (PTS1) at its C-terminus. We have previously shown that the N-terminal segment of Cit2p is removed during import into peroxisomes [Lee, H.S. et al. (1994) Kor. J. Microbiol. 32, 558-564], which implied the presence of an additional N-terminal sorting signal. To analyze the function of the N-terminal region of Cit2p in protein trafficking, we constructed the N-terminal domain-swapped versions of Cit1p and Cit2p. Both fusions, Cit1::Cit2 and Cit2::Cit1, complemented the glutamate auxotrophy caused by the double-disruption of the CIT1 and CIT2 genes. In addition, part of the Cit2::Cit1 fusion protein, as well as Cit1::Cit2, was shown to be transported into both mitochondria and peroxisomes. The subcellular localization of the recombinant fusion proteins containing various N-terminal segments of Cit2p fused to a mutant version of green fluorescent protein (GFP2) was also examined. As a result, we found that the 20-amino acid N-terminal segment of Cit2p contains a cryptic cleavable targeting signal for both peroxisomes and mitochondria. In addition, we show that the peroxisomal import process mediated by the N-terminal segment of Cit2p was not affected by the disruption of either PEX5 (encoding PTS1 receptor) or PEX7 (encoding PTS2 receptor). 相似文献
10.