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1.
A putative multidrug efflux pump, EmrD-3, belonging to the major facilitator superfamily (MFS) of transporters and sharing
homology with the Bcr/CflA subfamily, was identified in Vibrio cholerae O395. We cloned the emrD-3 gene and evaluated its role in antimicrobial efflux in a hypersensitive Escherichia coli strain. The efflux activity of this membrane protein resulted in lowering the intracellular concentration of ethidium. The
recombinant plasmid carrying emrD-3 conferred enhanced resistance to several antimicrobials. Among the antimicrobials tested, the highest relative increase in
minimum inhibitory concentration (MIC) of 102-fold was observed for linezolid (MIC = 256 μg/ml), followed by an 80.1-fold
increase for tetraphenylphosphonium chloride (TPCL) (156.2 μg/ml), 62.5-fold for rifampin (MIC = 50 μg/ml), >30-fold for erythromycin
(MIC = 50 μg/ml) and minocycline (MIC = 2 μg/ml), 20-fold for trimethoprim (MIC = 0.12 μg/ml), and 18.7-fold for chloramphenicol
(MIC = 18.7 μg/ml). Among the fluorescent DNA-binding dyes, the highest relative increase in MIC of 41.7-fold was observed
for ethidium bromide (125 μg/ml) followed by a 17.2-fold increase for rhodamine 6G (100 μg/ml). Thus, we demonstrate that
EmrD-3 is a multidrug efflux pump of V. cholerae, the homologues of which are present in several Vibrio spp., some members of Enterobacteriaceae family, and Gram-positive Bacillus spp. 相似文献
2.
Tertiary structure-related activity of tick defensin (persulcatusin) in the taiga tick, <Emphasis Type="Italic">Ixodes persulcatus</Emphasis> 总被引:1,自引:0,他引:1
Emiko Isogai Hiroshi Isogai Kazuhiko Okumura Hatsuhiro Hori Hiroki Tsuruta Yoichi Kurebayashi 《Experimental & applied acarology》2011,53(1):71-77
Defensins are small cysteine-rich cationic proteins found in both vertebrates and invertebrates constituting the front line
of host innate immunity. To examine the importance of the tertiary structure of tick defensin in its antimicrobial activity,
we synthesized two types of the peptides with tertiary structure or primary one on basis of the information of the sequence
in the defensin originated from the taiga tick, Ixodes persulcatus. Chemically synthesized peptides were used to investigate the activity spectrum against Staphylococcus aureus, Borrelia garinii and flora-associated bacteria. Both synthetic peptides showed antimicrobial activity against S. aureus in short-time killing within 1 h, but they do not show the activity against B. garinii, Stenotrophomonas maltophila and Bacillus spp., which were frequently isolated from the midgut of I. persulcatus. The teriary structure brought more potent activity to S. aureus than primary one in short-time killing. We also examined its antimicrobial activity by evaluation of growth inhibition in
the presence of the synthetic peptides. Minimum inhibitory concentration (MIC) was ranged from 1.2 to 5.0 μg/ml in tertiary
peptide and from 10 to 40 μg/ml in primary peptide, when 10 strains of S. aureus were used. From the curve of cumulative inhibition rates, MIC50 (MIC which half of the strains showed) to S. aureus is about 1.2 μg/ml in the peptide with tertiary structure and about 10 μg/ml in the linear one. Corynebacterium
renale is 10 times or more sensitive to tertiary peptide than primary one. In conclusion, the presence of 3 disulfide bridges, which
stabilize the molecule and maintain the tertiary structure, is considered to have an effect on their antimicrobial activities
against Gram-positive bacteria such as S. aureus. 相似文献
3.
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
4.
Rasanthika Nayomi Jayatissa Rohan Prasantha Perera Chamari Madhu Hettiarachchi Pathum Manjula Weerawarna 《Indian journal of microbiology》2012,52(1):83-87
The continuing increase in the incidence of multi drug resistant pathogenic bacteria and shortage of new antimicrobial agents
are the prime driver in efforts to identify the novel antimicrobial classes. In vitro antibacterial activity of 4-phenyl-1-(2-phenylallyl)
pyridinium bromide was tested against Gram positive Staphylococcus aureus, Streptococcus species, Bacillus subtilis, and Gram negative Klebsiella aerogenes and Escherichia coli using disk diffusion method. Among them S. aureus showed strong antibacterial activity (21.99 ± 0.03 mm) while E. coli showed very little activity (8.97 ± 0.06 mm) towards the compound. The MIC of 4-phenyl-1-(2-phenyl-allyl)-pyridinium bromide
for 90% S. aureus was ≤20 μg/ml and was compared with phenoxymethylpenicillin, cloxacillin, erythromycin and vancomycin. When 4-phenyl-1-(2-phenyl-allyl)pyridinium
bromide showed MIC at ≤20 μg/ml, all others showed MIC at ≤100 μg/ml. Strong antibacterial activity of 4-phenyl-1-(2-phenyl-allyl)pyridinium
bromide against S. aureus indicates that there is a possibility to use it as an effective antibacterial agent. 相似文献
5.
Linezolid is an oxazolidinone compound that has been shown to have impressive antimicrobial activity against a number of Gram-positive
bacteria. It inhibits an initiation step of protein synthesis, and its binding site has been shown to be on the 50S ribosomal
subunit. Linezolid was tested to see whether would interfere with the formation of the 50S subunit in Staphylococcus aureus cells, since a number of other 50S-specific antibiotics have this second inhibitory function. Linezolid inhibited protein
synthesis in S. aureus cells with an IC50 of 0.3 μg/ml. A concentration-dependent decline in cell number with an increase in generation time was found. Pulse-chase
labeling studies revealed a specific inhibitory effect on 50S particle formation, with no effect on 30S subunit assembly.
The compound inhibited 50S synthesis with an IC50 of 0.6 μg/ ml, indicating an equivalent effect on translation and particle assembly. A postantibiotic effect of 1 h was found
when cells were initially treated with the drug at 2 μg/ ml. 50S particle numbers recovered more rapidly than translational
capacity, consistent with the increase in viable cell numbers. The inhibitory activities of this novel antimicrobial agent
in cells are discussed.
Received: 28 June 2001 / Accepted: 27 August 2001 相似文献
6.
Pan H Feng J Cerniglia CE Chen H 《Journal of industrial microbiology & biotechnology》2011,38(10):1729-1738
Azo dyes are widely used in the plastic, paper, cosmetics, food, and pharmaceutical industries. Some metabolites of these
dyes are potentially genotoxic. The toxic effects of azo dyes and their potential reduction metabolites on Staphylococcus aureus ATCC BAA 1556 were studied. When the cultures were incubated with 6, 18, and 36 μg/ml of Orange II and Sudan III for 48 h,
76.3, 68.5, and 61.7% of Orange II and 97.8, 93.9, and 75.8% of Sudan III were reduced by the bacterium, respectively. In
the presence of 36 μg/ml Sudan III, the cell viability of the bacterium decreased to 61.9% after 48 h of incubation, whereas
the cell viability of the control culture without the dye was 71.5%. Moreover, the optical density of the bacterial cultures
at 10 h decreased from 0.74 to 0.55, indicating that Sudan III is able to inhibit growth of the bacterium. However, Orange
II had no significant effects on either cell growth or cell viability of the bacterium at the tested concentrations. 1-Amino-2-naphthol,
a metabolite common to Orange II and Sudan III, was capable of inhibiting cell growth of the bacterium at 1 μg/ml and completely
stopped bacterial cell growth at 24–48 μg/ml. On the other hand, the other metabolites of Orange II and Sudan III, namely
sulfanilic acid, p-phenylenediamine, and aniline, showed no significant effects on cell growth. p-Phenylenediamine exhibited a synergistic effect with 1-amino-2-naphthol on cell growth inhibition. All of the dye metabolites
had no significant effects on cell viability of the bacterium. 相似文献
7.
Chow-Chin Tong Yew-Keong Choong Nor-Aini-B Umar Mohamed-Mustapha Noordin Suhaila Mohamed 《World journal of microbiology & biotechnology》2009,25(4):687-695
Ganoderma lucidum powder using hot water and methanol extraction methods indicated a twofold more active cytotoxic activity with IC50 of 44 ± 3.8 μg/ml in the latter method. The representative dose-response curves of the G. lucidum crude extracts on J558 cell-lines revealed that there were great similarities between the curves which reflected rapid killing
activities. The percentage viability of the J558 cell exposed to these crude extracts was dose dependent only up to 150 μg/ml.
After which, there was no significant reduction when the dose was increased to 200 or 400 μg/ml. The morphological alterations
induced by the crude extract were examined under the phase contrast, fluorescent and electron microscopy. When J558 cells
were treated with doses higher than 50 μg/ml of the crude extract, obvious morphological changes and apoptosis occurred after
72 h. At 400 μg/ml, most of the cells showed necrosis characterized as small fragments with uniformly stained red nuclei.
The apoptotic and necrotic cells increased by 16.5 and 29.1%, respectively whereas the viable cells decreased by as much as
45.6. The mode of cell death via apoptosis was 3.6% higher than necrosis. However, these morphological changes were not observed
in the case of 3T3 cells. Results obtained from scanning electron microscopy and transmission electron microscopy further
confirmed the occurrence of various apoptotic and necrotic features. 相似文献
8.
de Niederhäusern S Bondi M Messi P Iseppi R Sabia C Manicardi G Anacarso I 《Current microbiology》2011,62(5):1363-1367
In last decade methicillin-resistant Staphylococcus aureus with high level of vancomycin-resistance (VRSA) have been reported and generally the patients with VRSA infection were also
infected with a vancomycin-resistant Enterococcus (VRE). Considering that the high level of vancomycin-resistance in VRSA isolates seems to involve the horizontal transfer
of Tn1546 transposon containing vanA gene from coinfecting VRE strains, the authors have studied the “in vitro” conjugative transfer of this resistance from VanA
enterococci to S. aureus. Out of 25 matings performed combining five vancomycin-resistant enterococci as donors (three Enterococcus faecalis and two Enterococcus faecium), and five S. aureus as recipients, all clinical isolates, two have been successful using E. faecalis as donor. The transfer of vancomycin-resistance was confirmed by vanA gene amplification in both transconjugants and the resistance was expressed at lower levels (MIC 32 μg/ml) in comparison
with the respective VRE donors (MIC > 128 μg/ml). The vancomycin-resistance of trasconjugants was maintained even after subsequent
overnight passages on MSA plates containing subinhibitory levels of vancomycin. This study shows that the vanA gene transfer can be achieved through techniques “in vitro” without the use of laboratory animals employed, in the only similar
experiment previously carried out by other authors, as substrate for the trasconjugant growth. Moreover, in that previous
experiment, contrary to this study, the vancomycin resistant S. aureus trasconjugants were selected on erythromycin agar and not by direct vancomycin agar selection. 相似文献
9.
Terrance O. Kurtz Drew J. Winston William J. Martin Lowell S. Young William L. Hewitt 《Current microbiology》1980,4(1):21-26
Moxalactam (LY127935), a novel beta-lactam antibiotic, was compared with semisynthetic penicillins, cephalosporins, and aminoglycosides
by the agar dilution method against 5,317 recent clinical isolates of facultative and anaerobic bactria. At 0.5 μg/ml, moxalactam
inhibited 90% of all Gram-negative bacilli tested except forPseudomonas aeruginosa (81% inhibited by 32 μg/ml) andAcinetobacter calcoaceticus (88% inhibited by 32 μg/ml). More than 90% ofBacteroides fragilis andStaphylococcus aureus were inhibited by 4 μg/ml and 8 μg/ml, respectively. Moxalactam was at least 16-fold more active by weight than cephalothin,
cefamandole, and cefoxitin forEscherichia coli, Klebsiella pneumoniae, andEnterobacter species, and 2- to 4-fold more active than cefoxitin forB. fragilis. Moxalactam was 4-fold less active than cefamandole and cephalothin forS. aureus and 2- to 4-fold less active than piperacillin forP. aeruginosa. Moxalactam was as active or more active than the aminoglycosides for all facultative Gram-negative bacilli except forP. aeruginosa. Moxalactam was inhibitory (minimal inhibitory concentration <16 μg/ml) for 20/27 gentamicin-resistant isolates and 8/13
amikacin-resistant organisms. Moxalactam’s in vitro activity against Gram-negative bacilli is markedly superior to presently
available cephalosporins and, except forP. aeruginosa, is comparable to the aminoglycosides. 相似文献
10.
Hélio V. Nobre-Júnior Ricardo A. Oliveira Flavio D. Maia Marcelle A. S. Nogueira Manoel Odorico de Moraes Mary Anne M. Bandeira Geanne M. Andrade Glauce S. B. Viana 《Neurochemical research》2009,34(6):1066-1075
In the present work, we showed that a chalcone-enriched fraction (CEF) isolated from the stem bark of a Brazilian medicinal
plant, Myracrodruon
urundeuva, presents neuroprotective actions on 6-hydroxydopamine (6-OHDA)-induced neuronal cell death, in rat mesencephalic cells.
In the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium] assay, which is an index of cell viability, CEF (1–100 μg/ml)
reversed in a concentration-dependent manner the 6-OHDA-induced cell death. While cells exposed to 6-OHDA (40 μM) showed an
increased concentration of thiobarbituric acid reactive substances (TBARS), the pretreatment with CEF (10–100 μg/ml) significantly
decreased the 6-OHDA-induced TBARS formation, indicative of a neuroprotection against lipoperoxidation. Furthermore, the drastic
increase of nitrite levels induced by 6-OHDA, indicative of nitric oxide formation and free radicals production, was prevented
by CEF. Double staining with acridine orange/ethidium bromide showed that cultures exposed to 6-OHDA (40 and 200 μM) presented
an increase of apoptotic and necrotic cell numbers in a concentration-dependent manner. CEF (100 μg/ml) protected cells from
apoptosis and necrosis and increased number of cells presenting a normal morphology. The immunohistochemical analysis for
tyrosine hydroxylase (TH) positive neurons indicated that 6-OHDA (40 and 200 μM) caused a concentration-dependent loss of
TH+ and TH− neurons. CEF protected both cells types from 6-OHDA-induced cell death. All together, our results demonstrated
neuroprotective effects of chalcones, which are able to reduce oxidative stress and apoptotic injury caused by 6-OHDA. Our
findings suggest that chalcones could provide benefits, along with other therapies, in neurodegenerative injuries, such as
Parkinson’s disease. 相似文献
11.
The inhibitory activities of a novel antibiotic compound have been investigated. A synthetic version of the natural product
TAN-1057A was examined for its effects on translation and ribosomal subunit formation. The antibiotic at 6 μg/ml reduced the
growth rate of wild-type Staphylococcus aureus cells by 50%. The IC50 for inhibition of protein synthesis in these cells was 4.5 μg/ml. Pulse and chase labeling kinetics showed a strong inhibitory
effect on 50S ribosomal subunit formation as well. The IC50 for this process was 9 μg/ml, indicating an equivalent inhibitory effect of the antibiotic on translation and 50S synthesis.
The post-antibiotic effect of the drug was investigated. Protein synthesis resumed rapidly after removal of the drug from
cells, but full recovery of the normal 50S subunit complement in treated cells required 1.5 h. The dual inhibitory effects
of this compound are compared with other antimicrobial agents having similar effects on cell growth.
Received: 27 December 2000 / Accepted: 22 March 2001 相似文献
12.
Ilkay Orhan Berrin Özçelik Sinem Aslan Murat Kartal Taner Karaoglu Bilge Şener Salih Terzioglu M. Iqbal Choudhary 《Phytochemistry Reviews》2007,6(1):189-196
Purpose of the present study was to evaluate antioxidant, antibacterial, antifungal, and antiviral activities of the petroleum
ether, chloroform, ethyl acetate and methanol extracts as well as the alkaloid fraction of Lycopodium clavatum L. (LC) from Lycopodiaceae growing in Turkey. Antioxidant activity of the LC extracts was evaluated by 1,1-diphenyl-2-picrylhydrazyl
(DPPH) radical-scavenging method at 0.2 mg/ml using microplate-reader assay. Antiviral assessment of LC extracts was evaluated
towards the DNA virus Herpes simplex (HSV) and the RNA virus Parainfluenza (PI-3) using Madin-Darby Bovine Kidney (MDBK) and Vero cell lines. Antibacterial and antifungal activities of the extracts
were tested against standard and isolated strains of the following bacteria; Escherichia coli, Pseudomonas aeruginosa, Proteus mirabilis, Acinobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis as well as the fungi; Candida albicans and C. parapsilosis. All of the extracts possessed noteworthy activity against ATCC strain of S. aureus (4 μg/ml), while the LC extracts showed reasonable antifungal effect. On the other hand, we found that only the chloroform
extract was active against HSV (16–8 μg/ml), while petroleum ether and alkaloid extracts inhibited potently PI-3 (16–4 μg/ml
and 32–4 μg/ml, respectively). However, all of the extracts had insignificant antiradical effect on DPPH. In addition, we
also analyzed the content of the alkaloid fraction of the plant by capillary gas chromatography-mass spectrometry (GC-MS)
and identified lycopodine as the major alkaloid. 相似文献
13.
Kittisak Chawawisit Monthon Lertcanawanichakul 《World journal of microbiology & biotechnology》2008,24(10):2199-2204
Secondary metabolites, particularly bioactive compounds, from probiotic bacteria, are good candidates for replacing antibiotics
to which bacteria have become resistant. In order to compare bioactive crude material from strain SA14 of Brevibacillus laterosporus with two antibiotics, the MICs of this bioactive crude and those of antibiotics vancomycin and oxacillin, against methicillin-resistant
Staphylococcus aureus (MRSA), were determined. The result indicated that the MIC (3.6–19.2 μg/ml) of bioactive crude was higher than vancomycin
(MIC = 1.28–2.56 μg/ml) when tested against MRSA. Interestingly, all tested strains of MRSA were susceptible to bioactive
crude and were approximately 5.2-fold more potent than oxacillin (MIC > 100 μg/ml). Its activity against MRSA gives support
for further evaluation, and the development of this substance for therapeutic use. 相似文献
14.
In order to determine the existence of synergism of the bacteriostatic action of flavonoids against G+ bacteria between a clinically interesting conventional antibiotic and a flavonoid, combinations of oxacillin (OXC) and 2,4-dihydroxychalcone
(DCH) as enhancer were assayed against methicillin-sensitive Staphylococcus aureus ATCC 29 213 and methicillin-resistant S. aureus ATCC 43 300. Using a kinetic-turbidimetric method, growth kinetics was monitored in a broth containing variable amounts of
OXC alone and combinations of variable OXC-constant DCH. The minimum inhibitory concentrations (MIC) of OXC alone and in combination
with DCH were evaluated. For the 29 213 strain, OXC MIC was 25 μg/mL, while combinations of 2–8 μg/mL OXC with 10 μg/mL of
DCH totally inhibited growth and showed synergism. The resistance of the 43 300 strain in the presence of OXC was verified;
OXC-DCH combinations decreased bacterial growth by 35 %. DCH augments the action of OXC against methicillin-susceptible S. aureus and therefore constitutes a good bacteriostatic agent for methicillin-resistant S. aureus. 相似文献
15.
Damayanti De Ananda Mukhopadhyay Ranadhir Chakraborty 《World journal of microbiology & biotechnology》2008,24(11):2727-2729
Enterobacter sp. was isolated from the diseased and dead caterpillars of the tea leaf roller (Caloptilia theivora) from the Darjeeling foothill region. When the vegetative form of the bacterium was applied via food, mortality of C. theivora showed an LC50 value at 363.1 μg/ml (bacterial wt./vol. of water) with fiducial limits 363.25 and 362.94 μg/ml respectively. The LT50 values for C. theivora were 6 days for 100 μg/ml, 5.96 days for 300 μg/ml, 5.81 days for 500 μg/ml, 4.96 days for 750 μg/ml and 4.61 days for 1,000 μg/ml
concentrations. The finding would enable one to contemplate development of a microbial pesticide using this novel Enterobacter sp. DD01 for control of the leaf rolling pest. 相似文献
16.
S. Raju Gururaj Rao S. A. Patil Chandrakanth R. Kelmani 《World journal of microbiology & biotechnology》2007,23(9):1227-1232
A methicillin-susceptible strain of Staphylococcus aureus (MSSA) showed stepwise adaptation when grown in increasing concentrations of oxacillin, eventually reaching a maximum of
35 μg/ml. The resultant oxacillin resistant mutant strain was stable and did not revert to susceptibility on frequent subculturing.
The response of the cells to different concentrations of oxacillin was examined by scanning electron microscopy, which showed
that the size of the bacterium increased with increasing concentrations of oxacillin. These changes in cell size were dependent
on the concentration of oxacillin and occurred only after addition of non-lethal concentrations. In the presence of lethal
concentrations (≥35 μg/ml) that completely inhibited cell growth, the cell sizes were smaller than those of wild-type cells
and irregular in shape. This stepwise-adapted methicillin (oxacillin) resistant S. aureus (MRSA) mutant showed a greater acid tolerance response (ATR) to lactic and citric acids than the parent susceptible strain.
These data indicates that methicillin resistance alters the morphology and ATR in stepwise-adapted MRSA mutant cells. 相似文献
17.
18.
Hafedh Hajlaoui Najla Trabelsi Emira Noumi Mejdi Snoussi Hanen Fallah Riadh Ksouri Amina Bakhrouf 《World journal of microbiology & biotechnology》2009,25(12):2227-2238
The composition of the essential oils and methanolic extracts of two cultivated mint species (M. longifolia and M. pulegium), as well as the in vitro antimicrobial and antioxidant activities of the essential oil and methanol extract of Mentha longifolia and Mentha pulegium were compared. GC-MS analysis of the essential oil identified 41 compounds constituting 96.66 and 96.13% of the total oil
from M. longifolia and M. pulegium, respectively. The later oils were rich on pulegone (47.15 and 61.11%, respectively). Moreover, 1,8 cineole (11.54%), menthone
(10.7%), α-pinene (3.57%), α-terpineol (3.17%) and d-cadinene (3.53%) were only present in M. longifolia oil, while isomenthone (17.02%), and piperitone (2.63%), were characteristic of M. pulegium oil. Shoot extract of the two species showed significantly different contents in total polyphenols (89.1 and 37.41 mg GAE/g
DW), flavonoids (63.93 and 33.83 mg CE/g DW) and tannins (1.47 and 3.07 mg CE/g DW), respectively in M. longifolia and M. pulegium. The essential oils showed strong antimicrobial activity against all 16 microorganisms tested, whereas the methanol extracts
were inactive. Moreover, the essential oils showed higher antioxidant activity than the methanolic extracts against the DPPH
and superoxide radical scavenging. In fact, antioxidant activities of the oils were the same for both M. longifolia and M. pulegium against DPPH (IC50 = 9 and 10 μg/ml, respectively) and 2-fold and 4-fold higher than shoot extracts (IC50 = 20 and 48 μg/ml, respectively). Moreover, both oils showed the same antioxidative abilities as compared to the positive
control (butylated hydroxytoluene). In the same way, the capacity to inhibit superoxide anion was very significant for the
two oils (0.1 μg/ml for M. longifolia and 0.11 μg/ml for M. pulegium). 相似文献
19.
It was found that low oxytetracycline (OTC) concentrations inhibited malic dehydrogenase (MDH) and lactic dehydrogenase (LDH)
inStaphylococcus aureus andEscherichia coli (1–5 μg/ml for MDH and 10 μg/ml for LDH). Inhibition of these enzymes occurred almost instantaneously and could be demonstrated
after 3–4 minutes. No MDH activity was found in OTC-resistant variants of these microorganisms, but LDH activity was not lowered.
The inhibitory effect of OTC is specific for bacterial MDH and LDH. The same enzymes of mammalian origin are not inhibitedin vitro even by high OTC concentrations (100 μg/ml). 相似文献
20.
Wen-Ru Li Xiao-Bao Xie Qing-Shan Shi Hai-Yan Zeng You-Sheng OU-Yang Yi-Ben Chen 《Applied microbiology and biotechnology》2010,85(4):1115-1122
The antibacterial activity and acting mechanism of silver nanoparticles (SNPs) on Escherichia coli ATCC 8739 were investigated in this study by analyzing the growth, permeability, and morphology of the bacterial cells following
treatment with SNPs. The experimental results indicated 10 μg/ml SNPs could completely inhibit the growth of 107 cfu/ml E. coli cells in liquid Mueller–Hinton medium. Meanwhile, SNPs resulted in the leakage of reducing sugars and proteins and induced
the respiratory chain dehydrogenases into inactive state, suggesting that SNPs were able to destroy the permeability of the
bacterial membranes. When the cells of E. coli were exposed to 50 μg/ml SNPs, many pits and gaps were observed in bacterial cells by transmission electron microscopy and
scanning electron microscopy, and the cell membrane was fragmentary, indicating the bacterial cells were damaged severely.
After being exposed to 10 μg/ml SNPs, the membrane vesicles were dissolved and dispersed, and their membrane components became
disorganized and scattered from their original ordered and close arrangement based on TEM observation. In conclusion, the
combined results suggested that SNPs may damage the structure of bacterial cell membrane and depress the activity of some
membranous enzymes, which cause E. coli bacteria to die eventually. 相似文献