共查询到20条相似文献,搜索用时 15 毫秒
1.
Olesja Bondarenko Pattanathu K. S. M. Rahman Thahira J. Rahman Anne Kahru Angela Ivask 《Microbial ecology》2010,59(3):588-600
In this study, the mixture of mono- and di-rhamnolipids produced by Pseudomonas aeruginosa DS10-129 was characterized for its toxicity and modulatory effects on Cd availability to different bacteria. Gram-negative
naturally bioluminescent Vibrio fischeri and recombinant bioluminescent Pseudomonas fluorescens, P. aeruginosa, Escherichia coli, and Gram-positive Bacillus subtilis were used as model organisms. Rhamnolipids reduced the bioluminescence of these bacteria in less than a second of exposure
even in relatively low concentrations (30-min EC50 45–167 mg l−1). Toxicity of Cd to Gram-negative bacteria (30-min EC50 values 0.16 mg l−1 for E. coli, 0.96 mg l−1 for P. fluorescens, and 4.4 mg l−1 for V. fischeri) was remarkably (up to 10-fold) reduced in the presence of 50 mg l−1 rhamnolipids. Interestingly, the toxicity of Cd to Gram-positive B. subtilis (30-min EC50 value 0.49 mg l−1) was not affected by rhamnolipids. Rhamnolipids had an effect on desorption of Cd from soil: 40 mg l−1 rhamnolipids increased the water-extracted fraction of Cd twice compared with untreated control. However, this additionally
desorbed fraction of Cd remained bound with rhamnolipids and was not available to bacteria. Hence, in carefully chosen concentrations
(still effectively complexing heavy metals but not yet toxic to soil bacteria), rhamnolipids could be applied in remediation
of polluted areas. 相似文献
2.
Kiyoon Kang Munyoung Park Sangkyu Park Young Soon Kim Sungbeom Lee Seong-Gene Lee Kyoungwhan Back 《Biotechnology letters》2009,31(9):1469-1475
Plant-specific bioactive compounds including feruloyltyramine (FT), 4-coumaroyltyramine (CT), and caffeoyltyramine (CaT) were
simultaneously produced in Escherichia coli by heterologous expression of two biosynthetic genes encoding 4-coumarate:coenzyme A ligase and tyramine N-hydroxycinnamoyltransferase (THT) cloned from Arabidopsis thaliana and pepper, respectively. Simultaneous supplementation of substrates to the recombinant E. coli resulted in the secretion of multiple tyramine derivatives into the medium at high yield: CT (189 mg l−1), FT (135 mg l−1), CaT (40 mg l−1). In addition, the recombinant E. coli also produced, albeit at low concentration, a range of dopamine derivatives such as feruloyldopamine due to THT’s ability
to accept dopamine as a substrate. 相似文献
3.
Willis RE White CR Merritt DJ 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2011,181(4):477-486
Trap-building, sit-and-wait predators such as spiders, flies and antlions tend to have low standard metabolic rates (SMRs)
but potentially high metabolic costs of trap construction. Members of the genus Arachnocampa (glowworms) use an unusual predatory strategy: larvae bioluminesce to lure positively phototropic insects into their adhesive
webs. We investigated the metabolic costs associated with bioluminescence and web maintenance in larval Arachnocampa flava. The mean rate of CO2 production ([(V)\dot] \dot{V}CO2) during continuous bioluminescence was 4.38 μl h−1 ± 0.78 (SEM). The mean [(V)\dot] \dot{V}CO2 of inactive, non-bioluminescing larvae was 3.49 ± 0.35 μl h−1. The mean [(V)\dot] \dot{V}CO2 during web maintenance when not bioluminescencing was 8.95 ± 1.78 μl h−1, a value significantly lower than that measured during trap construction by other predatory arthropods. These results indicate
that bioluminescence itself is not energetically expensive, in accordance with our prediction that a high cost of bioluminescence
would render the Arachnocampa sit-and-lure predatory strategy inefficient. In laboratory experiments, both elevated feeding rates and daily web removal
caused an increase in bioluminescent output. Thus, larvae increase their investment in light output when food is plentiful
or when stressed through having to rebuild their webs. As light production is efficient and the cost of web maintenance is
relatively low, the energetic returns associated with continuing to glow may outweigh the costs of continuing to attract prey. 相似文献
4.
5.
Wang Y Manow R Finan C Wang J Garza E Zhou S 《Journal of industrial microbiology & biotechnology》2011,38(9):1371-1377
Due to its excellent capability to ferment five-carbon sugars, Escherichia coli has been considered one of the platform organisms to be engineered for production of cellulosic ethanol. Nevertheless, genetically
engineered ethanologenic E. coli lacks the essential trait of alcohol tolerance. Development of ethanol tolerance is required for cost-effective ethanol fermentation.
In this study, we improved alcohol tolerance of a nontransgenic E. coli KC01 (ldhA pflB ackA frdBC pdhR::pflBp6-aceEF-lpd) through adaptive evolution. During ~350 generations of adaptive evolution, a gradually increased concentration of ethanol
was used as a selection pressure to enrich ethanol-tolerant mutants. The evolved mutant, E. coli SZ470, was able to grow anaerobically at 40 g l−1 ethanol, a twofold improvement over parent KC01. When compared with KC01 for small-scale (500 ml) xylose (50 g l−1) fermentation, SZ470 achieved 67% higher cell mass, 48% faster volumetric ethanol productivity, and 50% shorter time to complete
fermentation with ethanol titer of 23.5 g l−1 and yield of 94%. These results demonstrate that an industry-oriented nontransgenic E. coli strain could be developed through incremental improvements of desired traits by a combination of molecular biology and traditional
microbiology techniques. 相似文献
6.
The behavior ofEscherichia coli immersed in aqueous systems amended with humic acids, under PAR, UV-A, UV-B, and simulated solar radiation was examined.
Culturability, ability to elongate, functioning of the electron transport systems, and glucose uptake were assessed. Humic
substances in the range from 1 to 50 mg L−1 protected cells from photoinactivation. Decrease in culturability and cellular activities was significantly (p<0.05) less in the presence of humic material. However, humic acid were not used as nutrients. Neither irradiated nor nonirradiated
humic solutions (50 mg L−1) supported the growth of 105 cells ml−1. However, humic acids dissolved in 0.9% NaCl efficiently absorbed light over wavelengths from 270 to 500 nm. Also, a photoprotective
effect against simulated sunlight was observed when humic acid were not in contact with but rather enveloped the cellular
suspensions in double-wall microcosms. The protection afforded by humic acids against luminous radiation likely derives from
their ability to absorb these radiations and hence reduces the amount of energy reaching the cells. 相似文献
7.
Pietro Carlozzi Cristina Pintucci Raffaella Piccardi Arianna Buccioni Sara Minieri Maurizio Lambardi 《Biotechnology letters》2010,32(4):477-481
Rhodopseudomonas palustris was grown under continuous irradiances of 36, 56, 75, 151, 320, 500, and 803 W m−2, for a co-production of both bio-H2 and biodiesel (lipids) using fed-batch conditions. The highest overall bio-H2 produced [4.2 l(H2) lculture
−1] was achieved at 320 W m−2, while the highest dry biomass (3.18 g l−1) was attained at 500 W m−2. Dry biomass contained between 22 and 39% lipid. The total energy conversion efficiency was at its highest (6.9%) at 36 W m−2. 相似文献
8.
Lipopolysaccharide of Escherichia coli, polyamines, and acetic acid stimulate cell proliferation in intestinal epithelial cells 总被引:1,自引:0,他引:1
Jaime Olaya Vadim Neopikhanov Andrés Uribe 《In vitro cellular & developmental biology. Animal》1999,35(1):43-48
Summary Our aim was to examine whether lipopolysaccharide of Escherichia coli, polyamines of dietetic and/or bacterial origin, and products of the bacterial metabolism influence cell proliferation in
epithelial cells from the colon and small intestine. Lipopolysaccharide of Escherichia coli 0111:B4 was incubated with cultures from human colonic mucosa. The mitoses were arrested with Vincristine and the total number
of metaphases per crypt was counted. In addition, lipopolysaccharide was incubated with a human colonic epithelial cell line
from adenocarcinoma (LS-123 cells) and with a nontransformed small intestinal cell line from germ-free rats (IEC-6 cells)
for 24 h. In the last 4 h, the cells were labeled with tritiated thymidine. The cells were incubated with putrescine, cadaverine,
and spermidine at 10−11–10−3
M and with acetic acid (10−5–10−1
M), acetaldehyde (10−10–10−4
M) and ammonium chloride (1–20 mM). Lipopolysaccharide of Escherichia coli increased the number of arrested metaphases in human colonic crypts and DNA synthesis in L-123 and IEC-6 cells (P<0.001). All polyamines increased DNA synthesis in the colonic and small intestinal cell lines, the effects being more marked
for putrescine (P<0.001). The higher concentrations of acetic acid increased DNA synthesis in both epithelial cell lines (P<0.001). Acetaldehyde slightly decreased DNA synthesis in LS-123 cells at cytotoxic concentrations. Ammonium chloride did
not significantly affect DNA synthesis. The final concentration of nonionized ammonia was less than 3%. It is concluded that
lipopolysaccharides of Escherichia coli and intraluminal factors derived from microorganisms increase cell proliferation in human colonic crypts and intestinal epithelial
cell lines. 相似文献
9.
Ping Su Anders Henriksson Christina Nilsson Hazel Mitchell 《World journal of microbiology & biotechnology》2008,24(9):1837-1842
The aim of this study was to assess the effect of a commercial green tea extract (TEAVIGO™) on the microbial growth of three
probiotic strains (Lactobacillus and Bifidobacterium), as well as three pathogenic bacteria. MIC and co-culture studies were performed. The MICs of the green tea extract against
Staphylococcus aureus and Streptococcus pyogenes (100 μg ml−1) were considerably lower than those against the probiotic strains tested (>800 μg ml−1) and Escherichia coli (800 μg ml−1). In co-culture studies, a synergistic effect of the probiotic strains and the green tea extract was observed against both
Staph. aureus and Strep. pyogenes. Green tea extract in combination with probiotics significantly reduced the viable count of both pathogens at 4 h and by
24 h had completely abolished the recovery of viable Staph. aureus and Strep. pyogenes. These reductions were more significant than the reductions induced by probiotics or green tea extracts used separately.
These results demonstrate the potential for combined therapy using the green tea extract plus probiotics on microbial infections
caused by Staph. aureus and Strep. pyogenes. As probiotics and the green tea extract are derived from natural products, treatment with these agents may represent important
adjuncts to, or alternatives to, conventional antibiotic therapy. 相似文献
10.
Eliana Alves Liliana Costa Carla MB Carvalho Jo?o PC Tomé Maria A Faustino Maria GPMS Neves Augusto C Tomé José AS Cavaleiro ?ngela Cunha Adelaide Almeida 《BMC microbiology》2009,9(1):70
Background
In recent times photodynamic antimicrobial therapy has been used to efficiently destroy Gram (+) and Gram (-) bacteria using cationic porphyrins as photosensitizers. There is an increasing interest in this approach, namely in the search of photosensitizers with adequate structural features for an efficient photoinactivation process. In this study we propose to compare the efficiency of seven cationic porphyrins differing in meso-substituent groups, charge number and charge distribution, on the photodynamic inactivation of a Gram (+) bacterium (Enterococcus faecalis) and of a Gram (-) bacterium (Escherichia coli). The present study complements our previous work on the search for photosensitizers that might be considered good candidates for the photoinactivation of a large spectrum of environmental microorganisms. 相似文献11.
Dan Wang Qiang Li Yu Mao Jianmin Xing Zhiguo Su 《Applied microbiology and biotechnology》2010,87(6):2025-2035
Escherichia coli strains with foreign genes under the isopropyl-β-d-thiogalactopyranoside-inducible promoters such as lac, tac, and trc were engineered and considered as the promising succinic acid-producing bacteria in many reports. The promoters mentioned
above could also be induced by lactose, which had not been attempted for succinic acid production before. Here, the efficient
utilization of lactose as inducer was demonstrated in cultures of the ptsG, ldhA, and pflB mutant strain DC1515 with ppc overexpression. A fermentative process for succinic acid production at high level by this strain was developed. In flask
anaerobic culture, 14.86 g l−1 succinic acid was produced from 15 g l−1 glucose with a yield of 1.51 mol mol−1 glucose. In two-stage culture carried out in a 3-l bioreactor, the overall yield and concentration of succinic acid reached
to 1.67 mol mol−1 glucose and 99.7 g l−1, respectively, with a productivity of 1.7 g l−1 h−1 in the anaerobic stage. The efficient utilization of lactose as inducer made recombinant E. coli a more capable strain for succinic acid production at large scale. 相似文献
12.
Abrevaya XC Sacco N Mauas PJ Cortón E 《Extremophiles : life under extreme conditions》2011,15(6):633-642
In this work, two archaea microorganisms (Haloferax volcanii and Natrialba magadii) used as biocatalyst at a microbial fuel cell (MFC) anode were evaluated. Both archaea are able to grow at high salt concentrations.
By increasing the media conductivity, the internal resistance was diminished, improving the MFC’s performance. Without any
added redox mediator, maximum power (P
max) and current at P
max were 11.87/4.57/0.12 μW cm−2 and 49.67/22.03/0.59 μA cm−2 for H. volcanii, N. magadii and E. coli, respectively. When neutral red was used as the redox mediator, P
max was 50.98 and 5.39 μW cm−2 for H. volcanii and N. magadii, respectively. In this paper, an archaea MFC is described and compared with other MFC systems; the high salt concentration
assayed here, comparable with that used in Pt-catalyzed alkaline hydrogen fuel cells, will open new options when MFC scaling
up is the objective necessary for practical applications. 相似文献
13.
14.
The tolerances of 20 Beauveria bassiana isolates derived from host insects worldwide to UV-B irradiation were assessed quantitatively in multi-dose bioassays. Conidial
suspensions of the isolates smeared on glass slides were exposed to the gradient UV-B doses of 0.1–1.6 J cm−2 (D), which generated from 0.75 to 10.17 min irradiation of weighted 312-nm wavelength at 2.0–2.61 mW cm−2. Irradiated conidia were then incubated for 24 h at 25°C under saturated humidity. The ratio of germination at each dose
over that in the blank control was defined as survival index (I
s). For all isolates, the I
s − D observations fit well with the survival model I
s = 1/[1 + exp(a + bD)] (0.94 ≤ r
2 ≤ 0.99) generated widely spanned lethal doses of 0.154–0.928, 0.240–1.139, and 0.383–1.493 J cm−2 for their losses of 50%, 75%, and 95% viabilities, respectively. These were far below the solar UV-B dose of 2.439 J cm−2 measured in a sunny day during the summer. The large variation of UV-B tolerance among the isolates indicates a necessity
to select UV-tolerant candidates for formulations applied to insect control during summer. The highly efficient bioassay method
was developed to measure accurately the UV-B tolerances of fungal biocontrol agents as lethal doses. 相似文献
15.
Jung-Soo Kim Manish Kumar Tiwari Hee-Jung Moon Marimuthu Jeya Thangadurai Ramu Deok-Kun Oh In-Won Kim Jung-Kul Lee 《Applied microbiology and biotechnology》2009,83(2):273-283
Nitrile groups are catabolized to the corresponding acid and ammonia through one-step reaction involving a nitrilase. Here,
we report the use of bioinformatic and biochemical tools to identify and characterize the nitrilase (NitPf5) from Pseudomonas fluorescens Pf-5. The nitPf5 gene was identified via sequence analysis of the whole genome of P. fluorescens Pf-5 and subsequently cloned and overexpressed in Escherichia coli. DNA sequence analysis revealed an open-reading frame of 921 bp, capable of encoding a polypeptide of 307 amino acids residues
with a calculated isoelectric point of pH 5.4. The enzyme had an optimal pH and temperature of 7.0°C and 45°C, respectively,
with a specific activity of 1.7 and 1.9 μmol min−1 mg protein−1 for succinonitrile and fumaronitrile, respectively. The molecular weight of the nitrilase as determined by sodium dodecyl
sulfate-polyacrylamide gel electrophoresis and gel filtration chromatography was 33,000 and 138,000 Da, respectively, suggesting
that the enzyme is homotetrameric. Among various nitriles, dinitriles were the preferred substrate of NitPf5 with a K
m = 17.9 mM and k
cat/K
m = 0.5 mM−1 s−1 for succinonitrile. Homology modeling and docking studies of dinitrile and mononitrile substrate into the active site of
NitPf5 shed light on the substrate specificity of NitPf5. Although nitrilases have been characterized from several other sources,
P. fluorescens Pf-5 nitrilase NitPf5 is distinguished from other nitrilases by its high specific activity toward dinitriles, which make
P. fluorescens NitPf5 useful for industrial applications, including enzymatic synthesis of various cyanocarboxylic acids. 相似文献
16.
Improved biodesulfurization of hydrodesulfurized diesel oil using Rhodococcus
erythropolis and Gordonia sp. 总被引:1,自引:0,他引:1
Substituted benzothiophenes (BTs) and dibenzothiophenes (DBTs) remain in diesel oil following conventional desulfurization
by hydrodesulfurization. A mixture of washed cells (13.6 g dry cell wt l−1) of Rhodococcus erythropolis DS-3 and Gordonia sp. C-6 were employed to desulfurize hydrodesulfurized diesel oil; its sulfur content was reduced from 1.26 g l−1 to 180 mg l−1, approx 86% (w/w) of the total sulfur was removed from diesel oil after three cycles of biodesulfurization. The average desulfurization
rate was 0.22 mg sulfur (g dry cell wt)−1 h−1. A bacterial mixture is therefore efficient for the practical biodesulfurization of diesel oil. 相似文献
17.
G. E. Zdorovennova 《Aquatic Ecology》2009,43(3):629-639
The thermal structures in the vicinity of the ice–water and water–sediment boundaries of a shallow lake, L. Vendyurskoe (Northwestern
Russia) during four winter seasons are described. The heat flux at the water-ice boundary was 0.1–0.2 W m−2 during winter. The maximal heat flux at the water–sediment boundary was 4.5 W m−2 at the beginning and 0.5 W m−2 at the end of winter. The daily average value of the solar radiation penetrating into the water was 0.5 W m−2 during main part of winter and 2–50 W m−2 during April. During winter, temperature showed an oscillation in the vicinity of the sediment-water interface. Most periods
corresponding to the main oscillation frequencies in the near-bottom water layer (0–0.4 m) and upper layer sediment (0–0.35 m),
identified by FFT analysis, fall within the scale of synoptic variations (3–10 days), and in a number of cases were equal
to 1 day. The theoretical periods of the first baroclinic seiche mode of Lake Vendyurskoe are 4.5–8.5 days that compares well
with identified temperature oscillation periods. The comparison between the rate of heat content change in a water column
and the difference of vertical heat fluxes from sediment to water and from water to ice show that the horizontal heat transport
takes place in the lake during winter as a result of heat advection along the bottom. 相似文献
18.
Microbial reduction of toxic Cr6+ to the less toxic Cr3+ is potentially a useful bioremediation process. Among the matrices tested for whole cell immobilization of an efficient chromate-reducing
Streptomyces griseus strain, PVA-alginate was the most effective and was used for reduction of Cr(VI) in a bioreactor. Cr6+ reduction efficiency decreased as Cr6+ was increased from 2 to 12 mg l−1 but increased with an increase in biomass concentration. However, increasing the flow rate from 2 to 8 ml h−1 did not significantly affect Cr6+ reduction. The reduction was faster in simulated effluent than in synthetic medium and complete removal of 8 mg Cr6+ l−1 from effluent and synthetic medium occurred in 2 and 12 h, respectively. Our results indicate that immobilized S. griseus cells could be applied for the large-scale bioremediation of chromate-containing effluents and wastewaters. 相似文献
19.
Sergey A. Piontkovski Alexandr V. Melnik Irina M. Serikova Ivan A. Minsky Vladimir F. Zhuk 《Luminescence》2023,38(4):505-512
Mesoscale eddies of the ocean (with a characteristic diameter of about 100 km and a life time-span of about several weeks) are habitats of plankton organisms, many of which are bioluminescent. The spatial heterogeneity of bioluminescence of the upper mixed layer associated with the impact of mesoscale eddies is poorly studied. The 45-year historical data set was retrieved, in order to select the bathy-photometric surveys carried out in the form of station grids and transects across eddies. Data from 71 expeditions deployed in 1966–2022 to the Atlantic Ocean, Indian Ocean and Mediterranean Sea basin were analyzed, in order for the spatial heterogeneity of bioluminescent fields to be elucidated across eddy fields. The stimulated bioluminescence intensity was characterized by the bioluminescent potential, which represented the maximal amount of radiant energy emitted in a given volume of water by bioluminescent organisms. The normalized bioluminescent potential over oceanographic station grids exhibited correlation with the eddy kinetic energy and zooplankton biomass (r = 0.8, at P = 0.001 and r = 0.7, at P = 0.05, respectively), in a broad range of energy and bioluminescence units (0.02–0.2 m2 s−2; 0.4–92.0 × 10−8 W cm−2 L−1, respectively). Overall, estimates of bioluminescent potential variability on the mesoscale contribute to the assessment of the multiple-scale variation of the bioluminescent field of the World Ocean. 相似文献
20.
Prabhu P Tiwari MK Jeya M Gunasekaran P Kim IW Lee JK 《Applied microbiology and biotechnology》2008,81(2):283-290
Based on analysis of the genome sequence of Bacillus licheniformis ATCC 14580, an isomerase-encoding gene (araA) was proposed as an l-arabinose isomerase (L-AI). The identified araA gene was cloned from B. licheniformis and overexpressed in Escherichia coli. DNA sequence analysis revealed an open reading frame of 1,422 bp, capable of encoding a polypeptide of 474 amino acid residues
with a calculated isoelectric point of pH 4.8 and a molecular mass of 53,500 Da. The gene was overexpressed in E. coli, and the protein was purified as an active soluble form using Ni–NTA chromatography. The molecular mass of the purified enzyme
was estimated to be ~53 kDa by sodium dodecyl sulfate–polyacrylamide gel electrophoresis and 113 kDa by gel filtration chromatography,
suggesting that the enzyme is a homodimer. The enzyme required a divalent metal ion, either Mn2+or Co2+, for enzymatic activity. The enzyme had an optimal pH and temperature of 7.5 and 50°C, respectively, with a k
cat of 12,455 min−1 and a k
cat/K
m of 34 min−1 mM−1 for l-arabinose, respectively. Although L-AIs have been characterized from several other sources, B. licheniformis L-AI is distinguished from other L-AIs by its wide pH range, high substrate specificity, and catalytic efficiency for l-arabinose, making B. licheniformis L-AI the ideal choice for industrial applications, including enzymatic synthesis of l-ribulose. This work describes one of the most catalytically efficient L-AIs characterized thus far. 相似文献