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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.
Etchegaray A de Castro Bueno C de Melo IS Tsai SM Fiore MF Silva-Stenico ME de Moraes LA Teschke O 《Archives of microbiology》2008,190(6):611-622
Lipopeptides produced by Bacillus subtilis are known for their high antifungal activity. The aim of this paper is to show that at high concentration they can damage
the surface ultra-structure of bacterial cells. A lipopeptide extract containing iturin and surfactin (5 mg mL−1) was prepared after isolation from B. subtilis (strain OG) by solid phase extraction. Analysis by atomic force microscope (AFM) showed that upon evaporation, lipopeptides
form large aggregates (0.1–0.2 μm2) on the substrates silicon and mica. When the same solution is incubated with fungi and bacteria and the system is allowed
to evaporate, dramatic changes are observed on the cells. AFM micrographs show disintegration of the hyphae of Phomopsis phaseoli and the cell walls of Xanthomonas campestris and X. axonopodis. Collapses to fungal and bacterial cells may be a result of formation of pores triggered by micelles and lamellar structures,
which are formed above the critical micelar concentration of lipopeptides. As observed for P.
phaseoli, the process involves binding, solubilization, and formation of novel structures in which cell wall components are solubilized
within lipopeptide vesicles. This is the first report presenting evidences that vesicles of uncharged and negatively charged
lipopeptides can alter the morphology of gram-negative bacteria. 相似文献
3.
Chavan SP Lokhande VH Nitnaware KM Nikam TD 《Applied microbiology and biotechnology》2011,89(6):1701-1707
The present study examined the effects of plant growth hormones, incubation period, biotic (Trametes versicolor, Mucor sp., Penicillium notatum, Rhizopus stolonifer, and Fusarium oxysporum) and abiotic (NaCl, MgSO4, FeSO4, ZnSO4, and FeCl3) elicitors on cell growth and α-tocopherol and pigment (red and yellow) productions in Carthamus tinctorius cell cultures. The cell growth and α-tocopherol and pigment contents improved significantly on Murashige and Skoog (MS) liquid
medium containing 50.0 μM α-naphthalene acetic acid (NAA) and 2.5 μM 6-Benzyladenine (BA) at 28 days of incubation period.
Incorporation of T. versicolor (50 mg l−1) significantly enhanced the production of α-tocopherol (12.7-fold) and red pigment (4.24-fold). Similarly, supplementation
of 30 mg l−1
T. versicolor (7.54-fold) and 70 mg l−1
Mucor sp. (7.40-fold) significantly increased the production of yellow pigment. Among abiotic elicitors, NaCl (50–70 mg l−1) and MgSO4 (10–30 mg l−1) significantly improved production of α-tocopherol (1.24-fold) and red pigment (20-fold), whereas yellow pigment content
increased considerably by all the abiotic elicitor treatments. Taken together, the present study reports improved productions
of α-tocopherol and the pigment as a stress response of safflower cell cultures exposed to these elicitors. 相似文献
4.
Ki-Hyun Park O-Mi Lee Ho-Il Jung Jin-Ha Jeong Young-Dong Jeon Dae-Youn Hwang Chung-Yeol Lee Hong-Joo Son 《Applied microbiology and biotechnology》2010,86(3):947-955
We isolated and characterized novel insoluble phosphate (P)-solubilizing bacteria tolerant to environmental factors like high
salt, low and high pHs, and low temperature. A bacterium M6 was isolated from a ginseng rhizospheric soil and confirmed to
belong to Burkholderia vietnamiensis by BIOLOG system and 16S rRNA gene analysis. The optimal cultural conditions for the solubilization of P were 2.5% (w/v) glucose, 0.015% (w/v) urea, and 0.4% (w/v) MgCl2·6H2O along with initial pH 7.0 at 35°C. High-performance liquid chromatography analysis showed that B. vietnamiensis M6 produced gluconic and 2-ketogluconic acids. During the culture, the pH was reduced with increase in gluconic acid concentration
and was inversely correlated with P solubilization. Insoluble P solubilization in the optimal medium was about 902 mg l−1, which was approximately 1.6-fold higher than the yield in NBRIP medium (580 mg l−1). B. vietnamiensis M6 showed resistance against different environmental stresses like 10–45°C, 1–5% (w/v) salt, and 2–11 pH range. The maximal concentration of soluble P produced by B. vietnamiensis M6 from Ca3(PO4)2, CaHPO4, and hydroxyapatite was 1,039, 2,132, and 1,754 mg l−1, respectively. However, the strain M6 produced soluble P with 20 mg l−1 from FePO4 after 2 days and 100 mg l−1 from AlPO4 after 6 days, respectively. Our results indicate that B. vietnamiensis M6 could be a potential candidate for the development of biofertilizer applicable to environmentally stressed soil. 相似文献
5.
In order to enhance the removal efficiency of chemical oxygen demand (COD) in the high-salinity landfill leachate, the dominant
strains were isolated from high-salinity landfill leachate. The dominant strains and bacteria consortium were screened for
COD treatment potential using an aerobic COD concentration decrease test. Ten strains, TJ01–TJ10, were isolated, of which
six strains TJ02, TJ03, TJ05, TJ06, TJ07, and TJ09 were found to have higher COD removal when the single bacteria were added,
all more than 20%. The most effective combination was TJ06 + TJ09; the COD removal efficiency reached 45.57%. 16S rDNA gene
sequence analysis revealed that TJ06 and TJ09 belonged to the genus Bacillus. The effects of the dominant bacteria consortium on the high-salinity landfill leachate varied with pH value and the volume
fraction of leachate. The COD removal efficiencies maintained higher when the pH value was 6–8 and the volume fractions of
leachate were less than 80%. The result also suggested that there is little effect on the growth of TJ06 and TJ09 when the
range of Cl− concentration is 0–30,000 mg/L. 相似文献
6.
Gupta RS 《Photosynthesis research》2003,76(1-3):173-183
To understand the evolution of photosynthetic bacteria it is necessary to understand how the main groups within Bacteria have evolved from a common ancestor, a critical issue that has not been resolved in the past. Recent analysis of shared conserved
inserts or deletions (indels) in protein sequences has provided a powerful means to resolve this long-standing problem in
microbiology. Based on a set of 25 indels in highly conserved and widely distributed proteins, all main groups within bacteria
can now be defined in clear molecular terms and their relative branching orders logically deduced. For the 82 presently completed
bacterial genomes, the presence or absence of these signatures in various proteins was found to be almost exactly as predicted
by the indel model, with only 11 exceptions observed in 1842 observations. The branching order of different bacterial groups
as deduced using this approach is as follows: low G+C Gram-positive (Heliobacterium chlorum) ↔ high G+C Gram-positive ↔ Clostridium–Fusobacterium–Thermotoga ↔ Deinococcus–Thermus ↔ green nonsulfur bacteria (Chloroflexus aurantiacus) ↔ Cyanobacteria ↔ Spirochetes ↔ Chlamydia–Cytophaga–Flavobacteria–green sulfur bacteria (Chlorobium tepidum) ↔ Aquifex ↔ Proteobacteria (δ and ∈) ↔ Proteobacteria (α) ↔ Proteobacteria (β) and ↔ Proteobacteria (γ). The Heliobacterium species, which contain an Fe–S type of reaction center (RC 1) and represent the sole photosynthetic phylum from the Gram-positive
or monoderm bacteria (i.e., bounded by only a single membrane), is indicated to be the most ancestral of the photosynthetic
lineages. Among the Gram-negative or diderm bacteria (containing both inner and outer cell membranes) the green nonsulfur
bacteria, which contain a pheophytin-quinone type of reaction center (RC 2), are indicated to have evolved first. The later
emerging photosynthetic groups which contain either one or both of these reaction centers could have acquired such genes from
the earlier branching lineages by either direct descent or by means of lateral gene transfer.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
7.
Lactoferricin B (LfcinB), a 25 residue peptide derived from the N-terminal of bovine lactoferrin (bLF), causes depolarization
of the cytoplasmic membrane in susceptible bacteria. Its mechanism of action, however, still needs to be elucidated. In the
present study, synthetic LfcinB (without a disulfide bridge) and LfcinB (C–C; with a disulfide bridge) as well as three derivatives
with 15-, 11- and 9-residue peptides were prepared to investigate their antimicrobial nature and mechanisms. The antimicrobial
properties were measured via minimum inhibitory concentration (MIC) determinations, killing kinetics assays and synergy testing,
and hemolytic activities were assessed by hemoglobin release. Finally, the morphology of peptide-treated bacteria was determined
by atomic force microscopy (AFM). We found that there was no difference in MICs between LfcinB and LfcinB (C–C). Among the
derivatives, only LfcinB15 maintained nearly the same level as LfcinB, in the MIC range of 16–128 μg/ml, and the MICs of LfcinB11
(64–256 μg/ml) were 4 times more than LfcinB, while LfcinB9 exhibited the lowest antimicrobial activity. When treated at MIC
for 1 h, many blebs were formed and holes of various sizes appeared on the cell surface, but the cell still maintained its
integrity. This suggested that LfcinB had a major permeability effect on the cytoplasmic membrane of both Gram-positive and
Gram-negative bacteria, which also indicated it may be a possible intracellular target. Among the tested antibiotics, aureomycin
increased the bactericidal activity of LfcinB against E. coli, S. aureus and P. aeruginosa, but neomycin did not have such an effect. We also found that the combination of cecropin A and LfcinB had synergistic effects
against E. coli. 相似文献
8.
Thailand border market is where the local Thais, Cambodians, Laotians, and Burmeses exchange their goods and culture at the
border checkpoints. It is considered to be the source of aerial disease transmission especially for foreigners because it
is always very crowded with people from all walks of life. Unhealthy air quality makes this area high risk of spread of airborne
diseases. This study assessed airborne concentrations of bacteria and fungi in a border market to improve exposure estimates
and develop efficient control strategies to reduce health risk. The density and distribution of airborne bacteria and fungi
were investigated in the Chong Chom border market in Surin Province, Thailand. Eighteen air sampling sites were taken from
outdoors and various work environments including indoor footpaths, wooden handicraft shops, electronic shops, the secondhand
clothing shops, and fruit market areas. Exposed Petri plate method and liquid impinger sampler were used for sampling at the
breathing zone, 1.5 m above the floor level, during weekend and holiday. Meteorological factors such as relative humidity,
temperature, and light intensity were collected by portable data logger. The relative humidity was 67–73%, and temperature
29–33°C, and light varied between 18 and 270 Lux m−2. Gram-positive and Gram-negative bacteria were found at a mean value of 104 CFU m−3, and airborne fungi of 103 CFU m−3 were recorded. The highest concentration of culturable airborne microorganisms was found along the indoor footpath (9.62 × 104 CFU m−3 and 750.00 CFU/plate/h for impingement and sedimentation methods, respectively), the fruit market area (7.86 × 104 CFU m−3 and 592.42 CFU/plate/h for impingement and sedimentation methods, respectively), and the secondhand clothing shop (4.59 × 103 CFU m−3 and 335.42 CFU/plate/h for impingement and sedimentation methods, respectively) for Gram-positive bacteria, Gram-negative
bacteria, and fungi, respectively. The lowest concentration of Gram-positive bacteria, Gram-negative bacteria, and fungi was
found only at the outdoor area at 1.53 × 104 CFU m−3, 0.93 × 104 CFU m−3 and 0.80 × 103 CFU m−3 by means of impingement method and 136.67 CFU/plate/h, 69.25 CFU/plate/h, and 62.00 CFU/plate/h by means of sedimentation
methods for Gram-positive bacteria, Gram-negative bacteria, and fungi, respectively. The most frequently present airborne
bacteria were identified as Bacillus, Corynebacteria, Diplococcus, Micrococcus, Acinetobacter, Alcaligenes, Enterobacter, and spore former rods. Acremonium, Aspergillus, Cladosporium, Penicillium, and Sporotrichum were the most frequently found aerosol fungi genera. The distribution of airborne microorganisms correlated with relative
humidity and light factors based on principal component analysis. In conclusion, the border market is a potential source of
aerial disease transmission and a various hazards of bioaerosols for workers, consumers, sellers, and tourists. The bioaerosol
concentration exceeded the standard of occupational exposure limit. Many major indicators of allergenic and toxigenic airborne
bacteria and fungi, Acinetobacter, Enterobacter, Pseudomonas, Cladosporium, Alternaria, Aspergillus, and Penicillium, were found in the various market environments. 相似文献
9.
Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater 总被引:4,自引:0,他引:4
It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio
in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification
efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH4+–N g total suspended solids (TSS)−1 day−1, COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification
occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria
(AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia
load. At the ammonia load of 0.3 ± 0.002 mg NH4+–N g TSS−1 day−1, a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass. 相似文献
10.
Ángeles Verástegui Julia Verde Santos García Norma Heredia Azucena Oranday Catalina Rivas 《World journal of microbiology & biotechnology》2008,24(7):1249-1252
The in vitro antimicrobial activity against pathogenic bacteria, yeast, and molds were examined in extracts of the Agave species A. lecheguilla, A. picta, A. scabra and A. lophanta using an agar diffusion technique. The extracts of A. picta produced zones of inhibition of 9–13 mm for E. coli, L. monocytogenes, S. aureus, and V. cholerae, while B. cereus and Y. enterocolitica were not inhibited. The other Agave species did not show any detectable inhibitory activity against the bacteria tested; however, all four Agave sp. were inhibitory against all yeast and molds analyzed as evident by 9–20 mm zones of inhibition. The minimum microbicidal
concentration (MMC) of the active extract ranged from 1.8 to 7.0 mg/ml for the sensitive bacteria, and 2.0–3.0 mg/ml for yeast.
In the case of molds, the minimum inhibitory concentration (MIC) of the active extracts ranged from 3.0 to 6.0 mg/ml. Together,
these data suggest that the Agave sp. analyzed are potential antimicrobial candidates with a broad range of activity. 相似文献
11.
LT Ngan JK Moon JH Kim T Shibamoto YJ Ahn 《World journal of microbiology & biotechnology》2012,28(4):1575-1583
The growth-inhibiting activities of Paeonia lactiflora (Paeoniaceae) root steam distillate constituents and structurally related compounds against nine harmful intestinal bacteria
and eight lactic acid-producing bacteria were compared with those of two antibiotics, amoxicillin and tetracycline. Thymol,
α-terpinolene, (−)-perilla alcohol and (1R)-(−)-myrtenol exhibited high to extremely high levels of growth inhibition of all the harmful bacteria, whereas thymol and
α-terpinolene (except for Lactobacillus casei ATCC 393) inhibited the growth of all the beneficial bacteria (MIC, both 0.08–0.62 mg mL−1). Tetracycline and amoxicillin exhibited extremely high level of growth inhibition of all the test bacteria (MIC, <0.00002–0.001 mg mL−1). 1,8-Cineole, geraniol, (−)-borneol, (1S,2S,5S)-(−)-myrtanol, nerol, (S)-(−)-β-citronellol and (±)-lavandulol also exhibited inhibitory activity but with differing specificity and levels of activity.
Structure–activity relationship indicates that structural characteristics, such as geometric isomerism, degrees of saturation,
types of functional groups and types of carbon skeleton, appear to play a role in determining the growth-inhibiting activity
of monoterpenoids. Global efforts to reduce the level of antibiotics justify further studies on naturally occurring P. lactiflora root-derived materials as potential preventive agents against various diseases caused by harmful intestinal bacteria such
as clostridia. 相似文献
12.
David J. Smith Dale W. Griffin Richard D. McPeters Peter D. Ward Andrew C. Schuerger 《Aerobiologia》2011,27(4):319-332
Spores of Bacillus subtilis were exposed to a series of stratosphere simulations. In total, five distinct treatments measured the effect of reduced pressure,
low temperature, high desiccation, and intense ultraviolet (UV) irradiation on stratosphere-isolated and ground-isolated B. subtilis strains. Environmental conditions were based on springtime data from a mid-latitude region of the lower stratosphere (20 km).
Experimentally, each treatment consisted of the following independent or combined conditions: −70°C, 56 mb, 10–12% relative
humidity and 0.00421, 5.11, and 54.64 W/m2 of UVC (200–280 nm), UVB (280–315 nm), UVA (315–400 nm), respectively. Bacteria were deposited on metal coupon surfaces in
monolayers of ~1 × 106 spores and prepared with palagonite (particle size < 20 μm). After 6 h of exposure to the stratosphere environment, 99.9%
of B. subtilis spores were killed due to UV irradiation. In contrast, temperature, desiccation, and pressure simulations without UV had
no effect on spore viability up through 96 h. There were no differences in survival between the stratosphere-isolated versus
ground-isolated B. subtilis strains. Inactivation of most bacteria in our simulation indicates that the stratosphere can be a critical barrier to long-distance
microbial dispersal and that survival in the upper atmosphere may be constrained by UV irradiation. 相似文献
13.
T. M. Fahima Azira A. A. Nursolehah Y. Norhayati M. I. A. Majid A. A. Amirul 《World journal of microbiology & biotechnology》2011,27(10):2287-2295
A locally isolated Gram-negative bacterium, Cupriavidus sp. USMAA2-4 was found capable of producing terpolymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] using γ-butyrolactone or 1,4-butanediol with either valeric acid or 1-pentanol as the carbon source. The present of
3HB, 3HV and 4HB monomers were confirmed by gas chromatography (GC) and nuclear magnetic resonance (NMR) analysis. PHA concentration
of 1.9 g/l was the highest value obtained using the combination of 1,4-butanediol and 1-pentanol through one-step cultivation
process. PHA concentration obtained through two-step cultivation process was higher for all the combinations and the highest
value achieved was 2.5 g/l using γ-butyrolactone and 1-pentanol as carbon source. Various molar fractions of 4HB and 3HV ranging
from 6 to 14 mol% and 39 to 87 mol%, respectively were produced through two-step cultivation process by manipulating the concentration
of γ-butyrolactone. As the culture aeration was reduced, the molar fraction of 3HV and 4HB increased from 40 to 67 mol% and
10 to 24 mol%, respectively while the dry cell weight and PHA content decreased. The terpolymer produced was characterized
using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The number-average molecular weight
(M
n) and the melting temperature (T
m)) of the terpolymer were in the range of 177–484 kDa and 160–164°C, respectively. 相似文献
14.
Dejan Marcic Irena Ogurlic Slavka Mutavdzic Pantelija Peric 《Experimental & applied acarology》2010,50(3):255-267
Laboratory bioassays were conducted to evaluate the effects of spiromesifen on gross fecundity, gross fertility, net fertility
and population growth of two-spotted spider mite (Tetranychus urticae Koch) after treatments with four acaricide concentrations: 180 mg/l, i.e. maximum recommended concentration for use in glasshouses
against spider mites, 18, 1.8, and 0.18 mg/l, i.e. concentration discriminative for eggs and immatures in preliminary studies
which produced 100% mortality of these stages. Quiescent female deutonymphs were treated in the first assay, and young pre-ovipositing
females in the second and third, in which exposure lasted 6 h and 20 h, respectively. In the first assay, the 180, 18, and
1.8 mg/l concentrations significantly reduced gross fecundity (61–85%), gross fertility (64–87%) and net fertility (85–94%)
of the surviving females. In the second one, only the highest concentration achieved a significant statistical reduction in
gross fecundity (52%), gross fertility (67%) and net fertility (84%). In the third assay, fecundity and fertility reduction
under the two highest concentrations was 98–99% and 93–98%, whereas it was 50–74% under the 1.8 mg/l concentration, and statistically
different from control values. In all three trials, treatments with 180, 18, and 1.8 mg/l concentrations significantly reduced
the instantaneous rate of increase. In the third assay, treatments with the two highest concentrations caused population decline.
Sublethal activity of the 0.18 mg/l concentration was not found in any assay to be statistically significant. Sublethal effects
of spiromesifen and its impact on T. urticae management are discussed. 相似文献
15.
P. J. Strong 《World journal of microbiology & biotechnology》2010,26(1):133-144
Amarula Cream is an alcoholic beverage derived from the distillation of fermented marula fruit and to date there is no scientific
data as to the characteristics of the distillery wastewater generated from its production. The wastewater was found to have
a chemical oxygen demand (COD) of 27 g/l, a pH of 3.8, a high concentration of phenolic compounds (866 mg/l) and a high suspended
solids content (10.5 g/l), all of which could adversely affect biological treatment. Full-strength wastewater was treated
using shake-flask monocultures of four white rot fungi (Trametes pubescens MB 89, Ceriporiopsis subvermispora, Pycnoporus cinnabarinus or Phanerochaete chrysosporium) at pH 5.0 with no additional carbon or nitrogen supplements. Trametes pubescens performed the best with regards to degrading phenolic compounds, COD and colour, while P. cinnabarinus improved the pH to the greatest extent. Laccase synthesis was only detected in the T. pubescens and C. subvermispora cultures. Six wastewater concentrations (100, 80, 60, 40, 20 and 10%) were assessed at pH 4.5 to establish an optimum concentration
for remediation and laccase production by T. pubescens. Similar COD removal efficiencies (71–77%) and phenolic removal efficiencies (87–92%) were achieved at all concentrations.
The phenolic removal efficiencies improved by approximately 5% compared to the screening experiment at pH 5.0, indicating
that the laccase was more efficient at pH 4.5. The pH became more basic as a result of treatment and the colour decreased
for samples below 60% wastewater concentration. The maximum laccase activity (1063 ± 26 units/l) was obtained in the 80% wastewater
concentration. This study has resulted in the first characterization of Amarula distillery wastewater and showed that it has
a high phenolic compound concentration, COD and suspended solids content. It was possible to biologically treat the wastewater
at full strength using a number of white-rot fungi just by raising the pH. 相似文献
16.
Gang-Guk Choi Byung-Hyuk Kim Chi-Yong Ahn Hee-Mock Oh 《Journal of applied phycology》2011,23(6):1031-1037
The influence of nitrogen (N) deficiency on the cell growth and intracellular lipid production of the alga Botryococcus braunii UTEX 572 was investigated. Biomass concentration and lipid content of B. braunii cultivated in modified Chu-13 medium containing 0.04, 0.37, and 3.66 mM nitrate were 0.23–0.38 g L−1 and 36–63% of dry cell weight, respectively. The specific growth rate of B. braunii reached a constant of 0.185 day−1 during cultivation with an initial nitrate feed of 3.66 mM. The maximum lipid content of B. braunii was 63% with 0.04 mM nitrate. However, the maximum lipid productivity of 0.019 g L−1 day−1 was achieved with 0.37 mM nitrate. The level of oleic acid, an important component of biodiesel, was higher at 86% of the
total fatty acids under N-limited conditions (0.04 mM nitrate) compared to 69% under N-sufficient conditions (3.66 mM nitrate).
Furthermore, expression of the stearoyl-ACP desaturase gene (sad) encoding a stearoyl-ACP desaturase involved in the synthesis of oleic acid was 2.6-fold higher under N-limited conditions
than under N-sufficient conditions. 相似文献
17.
Escherichia coli K-12(λ) was sensitive toward low-intensity (non-thermal, flux capacity 0.06 mW cm−2) electromagnetic irradiation (EMI) of extremely high frequency—70.6 and 73 GHz. 1 h exposure to EMI markedly depressed growth
and cell viability of bacteria. Membrane-associated processes—total H+ efflux and H2 evaluation by whole cells during glucose fermentation were shown to be lowered as well. At the same time, the F0F1-ATPase activity of membrane vesicles was little depressed with 70.6 GHz irradiation only. This finding was in conformity
with non-changed N,N′-dicyclohexylcarbodiimide-sensitive H+ efflux. Furthermore, for understanding the different frequencies action mechanisms, the effects of antibiotics (chloramphenicol,
ceftriaxone, kanamycin, and tetracycline) on irradiated cells growth and survival were determined. EMI with the frequencies
of 70.6 and 73 GHz as with 51.8 and 53.0 GHz enhanced the sensitivity of bacteria toward antibiotics, but comparison revealed
that each frequency had a different portion. Probably, EMI of specific frequency triggered changes in biological processes
and afterward in growth and viability of bacteria, creating conditions when the action of antibiotics became facilitated. 相似文献
18.
The antibacterial effects of tea polyphenols (TPP) extracted from Korean green tea (Camellia sinensis) against clinical isolates of methicillin-resistant Staphylococcus aureus (MRSA) were evaluated. Characterization of the minimal inhibitory concentration (MIC) of oxacillin for 30 S. aureus strains isolated from patients treated with oxacillin identified 13 strains with an oxacillin MIC ≥ 4 μg/mL as methicillin-resistant
Staphylococcus aureus (MRSA) (range: 8 to 512 μg/mL), while 17 strains were methicillin-susceptible Staphylococcus aureus (MSSA) (range: 0.25–0.5 μg/mL). The MICs of TPP ranged from 50 to 180 μg/mL for both the MSSA and the MRSA strains. The MICs
of oxacillin for each of the 13 MRSA strains were reduced between 8- and 128-fold when these strains were coincubated with
sub-MIC (≤0.5× MIC) levels of TPP, demonstrating that the combination of TPP plus oxacillin was synergistic for all of the
clinical MRSA isolates. Two-dimensional polyacrylamide gel electrophoresis identified 14 extracellular proteins of MRSA-13
down-regulated and 3 proteins up-regulated by exposure to TPP. These studies demonstrate that TPP can differentially stimulate
the expression of various proteins in these bacteria and synergize the bactericidal activity of oxacillin for MRSA. 相似文献
19.
Magdalena Wegiera Urszula Kosikowska Anna Malm Helena D. Smolarz 《Central European Journal of Biology》2011,6(6):1036-1043
This study was designed primarily to investigate the antibacterial and antifungal activity of the extracts from fruits of
six Rumex L. species: R. acetosa L., R. acetosella L., R. confertus Willd., R. crispus L., R. hydrolapathum Huds. and R. obtusifolius L. The 7 Grampositive and 7 Gram-negative bacteria strains and 5 fungal ones were tested by agar and broth dilution method.
Determination of minimal inhibitory concentration (MIC) revealed that the extracts from R. confertus, R. crispus, R. hydrolapathum and R. obtusifolius exerted differential inhibitory effect on the growth of Gram-positive bacteria — staphylococci (MIC=62.5–125 μg/mL) and Gramnegative
bacteria — Escherichia coli ATCC 3521, Proteus mirabilis, Pseudomonas aeruginosa (MIC=125→500 μg/mL); MIC values determined by agar dilution method were somewhat higher. The same extracts inhibited also
the growth of fungi — Candida spp. or Trichophyton mentagrophytes ATCC 9533 (MIC=250–500 μg/mL), as found by agar dilution method. The total content of polyphenols (11.66–78.36 mg/g), anthracene
derivatives (0.26–12.93 mg/g) and tannins (4.00–11.16%) was also determined. 相似文献
20.
To clarify the relationship between denitrification activity and dry–wet levels in the littoral wetland sediments of Lake
Biwa, Japan, denitrification rates and their regulating parameters (degree of dryness, redox potential, nitrate concentration)
were measured on different moisture sediments. Redox potential in sediments was higher in the exposed region in contact with
atmosphere than the flooded region covered with water. The nitrate concentration in interstitial waters was undetectable in
the flooded region. On the other hand, concentration in the exposed region increased with increase in the degree of sediment
dryness. The denitrification rate ranged from <0.001 to 0.88 μg N cm−3 h−1 in the exposed region and increased with the increase in the degree of dryness. In the flooded region, on the other hand,
no detectable rate (<0.001 μg N cm−3 h−1) was observed. This indicates that the rates in the exposed region were mainly influenced by nitrate concentration in the
interstitial waters accumulated by desiccation of sediments, whereas rates in the flooded region were strongly limited by
no accumulation of nitrate in the anaerobic conditions. The potential denitrification rate, under the application condition
of nitrate, ranged from 0.13 to 0.26 μg N cm−3 h−1 in the flooded region and from 0.77 to 1.5 μg N cm−3 h−1 in the exposed region. The potential rates in the flooded region had a tendency to be lower than those in the exposed region,
implying that the number of denitrifying bacteria in the flooded region was low due to inactivation of aerobic respiration
and denitrification in the denitrifying bacteria community. Kinetic parameters, maximum rate (V
max) and half-saturation constant (K
s) for denitrification were calculated on the experimental procedures of the wetting–drying cycles of sediments. Both parameters
decreased by the wetting treatment and increased by the drying treatment. The fluctuation of V
max values with wetting–drying cycles indicated that the number of denitrifying bacteria was influenced by aerobic respiration
and denitrification in the denitrifying bacteria community similar to the potential rates, and denitrifying enzyme was induced
by the nitrate supplied by nitrification accelerated through the drying process. On the other hand, the fluctuation of K
s values implied that members of denitrifying bacteria were shifted to members of high nitrate affinity by wetting treatment
and of low nitrate affinity by drying treatment. 相似文献