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1.
Anna Vacheva Ralitsa Georgieva Svetla Danova Radka Mihova Mariana Marhova Sonia Kostadinova Krasimira Vasileva Maria Bivolarska Stoyanka R. Stoitsova 《Central European Journal of Biology》2012,7(2):219-229
E. coli biofilms cause serious problems in medical practice by contaminating surfaces and indwelling catheters. Due to the rapid
development of antibiotic resistance, alternative approaches to biofilm suppression are needed. This study addresses whether
products released by antagonistic bacteria — Lactobacillus isolates from vaginal and dairy-product samples could be useful for controlling E. coli biofilms. The effects of diluted cell-free supernatants (CFS) from late-exponential Lactobacillus cultures on the growth and biofilm production of Escherichia coli were tested. Most of the CFS applied as 10−2 had no impact on bacterial growth, biofilm development however was influenced even by 10−4 of CFS. Initial screening by crystal violet assay showed that biofilm modulation varied between different CFS and E. coli combinations from inhibition to activation; however three of the tested CFS showed consistency in biofilm suppression. This
was not due to antibacterial activity since Live/Dead fluorescence labeling showed insignificant differences in the amount
of dead cells in control and treated samples. Some E. coli strain-specific mechanisms of response to the three CFS included reduction in hydrophobicity and motility. Released exoploysaccharides
isolated from the three CFS stimulated sessile growth, but proteinase K reduced their inhibitory activities implying participation
of protein or peptide biofilm suppression factor(s). 相似文献
2.
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
3.
Christophe Sandt Truis Smith-Palmer Jonathan Comeau David Pink 《Applied microbiology and biotechnology》2009,83(6):1171-1182
The Raman spectra, water content, and biomass density of wild-type (WT) Pseudomonas aeruginosa PAO1, small colony variant (SCV) PAO1, and Pseudoalteromonas sp. NCIMB 2021 biofilms were compared in order to determine their variation with strain and species. Living, fully submerged
biofilms were analyzed in situ by confocal Raman microspectroscopy for up to 2 weeks. Water to biomass ratios (W/BRs), which
are the ratios of the O–H stretching vibration of water at 3,450 cm−1 to the C–H stretching band characteristic of biomass at 2,950 cm−1, were used to estimate the biomass density and cell density by comparison with W/BRs of protein solutions and bacterial suspensions,
respectively, on calibration curves. The hydration within SCV biofilm colonies was extremely heterogeneous whereas W/BRs were
generally constant in young WT biofilm colonies. The mean biomass in biofilm colonies of WT or colony cores of SCV was typically
equivalent to 16% to 27% protein (w/v), but was 10% or less for NCIMB 2021. The corresponding cell densities were 7.5 to >10 × 1010 cfu mL−1 for SCV, while the maximum cell density for NCIMB biofilms was 2.8 × 1010 cfu mL−1. 相似文献
4.
Pseudomonas
fluorescens-CS2 metabolized ethylbenzene as the sole source of carbon and energy. The involvement of catechol as the hydroxylated intermediate
during the biodegradation of ethylbenzene was established by TLC, HPLC and enzyme analysis. The specific activity of Catechol
2,3-dioxygenase in the cell free extracts of P.
fluorescens-CS2 was determined to be 0.428 μmoles min−1 mg−1 protein. An aqueous-organic, Two-Phase Batch Culture System (TPBCS) was developed to overcome inhibition due to higher substrate
concentrations. In TPBCS, P. fluorescens-CS2 demonstrated ethylbenzene utilization up to 50 mM without substrate inhibition on inclusion of n-decanol as the second phase. The rate of ethylbenzene metabolism in TPBCS was found enhance by fivefold in comparison with
single phase system. Alternatively the alginate, agar and polyacrylamide matrix immobilized P. fluorescens-CS2 cells efficiently degraded ethylebenzene with enhanced efficiency compared to free cell cultures in single and two-phase
systems. The cells entrapped in ployacrylamide and alginate were found to be stable and degradation efficient for a period
of 42 days where as agar-entrapped P. fluorescens was stable and efficient a period of 36 days. This demonstrates that alginate and polyacrylamide matrices are more promising
as compared to agar for cell immobilization. 相似文献
5.
L. A. Lopez-Tomas J. A. Ordoñez C. Mediavilla J. L. Rodriguez-Marin P. Sarmiento A. Zamora G. Garcia de Fernando 《Folia microbiologica》2008,53(5):423-426
No significant difference (p > 0.05) was observed in the specific aminopeptidase activity (SAA) developed by Pseudomonas fluorescens, P. putida and Flavobacterium odoratum either growing at pH 5.0–6.5 or at 7 and 12 °C. Nevertheless, a significant difference was found when comparing the SAA of
these organisms. The SAA of F. odoratum was lower than those of pseudomonads. The 4-nitroaniline test is reliable to estimate the G− load of fresh food products. 相似文献
6.
M. Prado Acosta E. Valdman S. G. F. Leite F. Battaglini S. M. Ruzal 《World journal of microbiology & biotechnology》2005,21(6-7):1157-1163
Summary Biosorption of heavy metals by gram-positive, non-pathogenic and non-toxicogenic Paenibacillus polymyxa P13 was evaluated. Copper was chosen as a model element because it is a pollutant originated from several industries. An
EPS (exopolysaccharide)-producing phenotype exhibited significant Cu(II) biosorption capacity. Under optimal assay conditions
(pH 6 and 25 °C), the adsorption isotherm for Cu(II) in aqueous solutions obeyed the Langmuir model. A high q value (biosorption capacity) was observed with whole cells (qmax=112 mgCu g−1). EPS production was associated with hyperosmotic stress by high salt (1 M NaCl), which led to a significant increase in
the biosorption capacity of whole cells (qmax=150 mgCu g−1). Biosorption capacity for Cu(II) of the purified EPS was investigated. The maximum biosorption value (q) of 1602 mg g−1 observed with purified EPS at 0.1 mg ml−1 was particularly promising for use in field applications. 相似文献
7.
Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was used to monitor Pseudomonas fluorescens biofilms in situ, non-destructively, in real time, and under fully hydrated conditions. Changes accompanying the metabolic evolution of the sessile bacterial cells from the nascent biofilm monolayer to the beginning of the multi-layered structure in the presence of nutrients were identified via the ATR-FTIR fingerprints of the young biofilm on the ATR crystal. The ATR-FTIR spectra were analysed by classical methods (time evolution of integrated intensities and profile evolution of specific bands), and also by a multivariate curve resolution, Bayesian positive source separation, to extract the pure component spectra and their change of concentration over time occurring during biofilm settlement. This work showed clearly the overproduction of glycogen by sessile P. fluorescens, which had not previously been described by other research groups. 相似文献
8.
Water-storage capacity was measured inThuja occidentalis L.,Tsuga canadensis (L.) Carr., andAcer saccharum Marsh. during the dehydration of stem segments 1.5–2.5 cm in diameter. Stem water potential was measured with a temperature-corrected
stem hygrometer and cavitations were detected acoustically. Water loss was measured by weight change. Dehydration isotherms
consistently displayed three phases. The first phase, from water potential (Ψ) 0 to about −0.2 MPa, had a high capacitance
(C>0.4kg water lost· (1 of tissue)−1· MPa−1) and we have attributed this high C to capillary water as defined by Zimmermann (1983, Xylem structure and the ascent of
sap, Springer-Verlag). The second phase from Ψ=−0.5 to about −2.0 had the lowest C values (<0.02 kg·l−1·MPa−1) and was accompanied by a few cavitation events. This phase may have been a transition zone between capillary storage and
water released by cavitation events as well as water drawn from living cells of the bark. The third phase also had a high
C (about 0.07–0.22kg·l−1·MPa−1) and was associated with many cavitation events while Ψ declined below about −2.5 MPa; we presume the high capacitance was
the consequence of water released by cavitation events. We discuss the ecological adaptive advantage of these three phases
of water-storage in trees. In moist environments, water withdrawn from capillary storage may be an important fraction of transpiration,
but may be of little adaptive advantage. For most of the growth season trees draw mainly on elastic storage, but stem elastic
storage is less than leaf elastic storage and therefore unlikely to be important. In very dry environments, water relased
by cavitation events might be important to the short-term survival of trees. 相似文献
9.
Raulio M Pore V Areva S Ritala M Leskelä M Lindén M Rosenholm JB Lounatmaa K Salkinoja-Salonen M 《Journal of industrial microbiology & biotechnology》2006,33(4):261-268
The aim of the present work was to explore possibilities of photocatalytic TiO2 coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms
on stainless steel, glass and TiO2 film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45°C under
vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1--0.3 μm in length. Adjacent cells
were connected to one another by threads of 0.5--1 μm in length. An ultrastructural analysis gave no indication for the involvement
of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO2 surfaces, submerged in water, were exposed to 20 W h m−2 of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >107 down to below 106 cells cm−2). TiO2 films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of
the TiO2 with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO2 surfaces have potential as a self-cleaning technology for warm water using industries. 相似文献
10.
11.
The ability of the benthic cyanobacterium Lyngbya wollei to fix nitrogen was studied using field samples and axenic cultures. L. wollei was collected and isolated from Lake Okeechobee, Florida, where it forms extensive mats. Rates of acetylene reduction up
to 39.1 nmol mg dry wt−1 h−1 were observed for field samples. The maximum observed rate of acetylene reduction in axenic laboratory cultures was 200 nmol
mg dry wt−1 h−1. Aerobic conditions limited nitrogen fixation activity, but dark/light cycles promoted the development of activity. Reduced
oxygen levels appeared to be required for the development of significant levels of nitrogenase activity. The level of irradiance
also had a significant impact on the level of activity. The potential significance of nitrogen fixation to Lyngbya production is discussed. 相似文献
12.
Whereas the transfer of Listeria from surfaces to foods and vice versa has been well documented, little is known about the mechanism of bacterial transfer.
The objective of this work is to gain a better understanding of the forces involved in listerial biofilms adhesion using atomic
force microscopy (AFM). L. monocytogenes Scott A was grown as biofilms on stainless steel surfaces by inoculating stainless steel coupons with Listeria and incubating the coupons for 48 h at 32 °C with a diluted 1:20 tryptic soy broth. After growth, biofilms were equilibrated
over saturated salt solutions at a constant relative humidity (%RH) before measurement of adhesion forces using AFM. The effects
of contact time, loading force, and biofilm relative humidity (%RH) suggested that neither contact time, loading force nor
biofilm %RH had a significant effect on biofilm adhesiveness at a cellular level (P > 0.05). In a second set of experiments, the influence of material type on biofilm adhesiveness was evaluated using two different
colloidal probes (SiO2 and polyethylene). Results showed that the maximum pull-off force and retraction work needed to retract the cantilever for
glass (−85.42 nN and 1.610−15 J, respectively) were significantly lower than those of polyethylene (−113.38 nN and 2.7 × 10–15 J, respectively; P < 0.001). The results of this study suggest that Listeria biofilms adhere more strongly to hydrophobic surfaces than hydrophilic surfaces when measured at a cellular level. These
results provide important insights that could lead to new ways to remediate and avoid listerial biofilm formation in the food
industry. 相似文献
13.
In this study, the effect of rhamnolipid biosurfactant produced by Pseudomonas fluorescens on bacterial strains, laboratory strains, and isolates from industrial wastewater was investigated. It was shown that biosurfactant,
depending on the concentration, has a neutral or detrimental effect on the growth and protein release of model Gram (+) strain
Bacillus subtilis 168. The growth and protein release of model Gram (−) strain Pseudomonas aeruginosa 1390 was not influenced by the presence of biosurfactant in the medium. Rhamnolipid biosurfactant at the used concentrations
supported the growth of some slow growing on hexadecane bacterial isolates, members of the microbial community. Changes in
cell surface hydrophobicity and permeability of some Gram (+) and Gram (−) isolates in the presence of rhamnolipid biosurfactant
were followed in experiments in vitro. It was found that bacterial cells treated with biosurfactant became more or less hydrophobic
than untreated cells depending on individual characteristics and abilities of the strains. For all treated strains, an increase
in the amount of released protein was observed with increasing the amount of biosurfactant, probably due to increased cell
permeability as a result of changes in the organization of cell surface structures. The results obtained could contribute
to clarify the relationships between members of the microbial community as well as suggest the efficiency of surface properties
of rhamnolipid biosurfactant from Pseudomonas fluorescens making it potentially applicable in bioremediation of hydrocarbon-polluted environments. 相似文献
14.
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
15.
J Jass J W Costerton H M Lappin-Scott 《Journal of industrial microbiology & biotechnology》1995,15(4):283-289
The combination of a modified Robbins device (MRD) attached to the effluent line of a continuous cultivation vessel was assessed by the adhesion of planktonic bacteria maintained at a controlled growth rate. This combination of a chemostat and an MRD provides a large number of sample surfaces for monitoring both the formation and control of biofilms over extended periods of time. This apparatus was used to monitor the colonization of two soil isolates,Pseudomonas fluorescens (EX101) andPseudomonas putida (EX102) onto silastic rubber surfaces. At a similar rel, both bacteria attached to the silastic, howeverP. fluorescens formed confluent, dense biofilms in less than 24 h, whereasP. putida adhered as single cells or microcolonies after the same period. The metabolic activity, measured by INT-formazan formation, was similar for both organisms with a peak at 6 h of colonization and a subsequent decrease after 24 h. Long term colonization studies ofP. fluorescens produced a population of greater than 9.5 log cfu cm–2 at 28 days demonstrating the advantages of the chemostat-MRD association. This technique proved to be successful for studying bacterial adhesion and biofilm formation in tubular devices by bacterial populations at controlled and low growth rates. 相似文献
16.
Mahmoud Abouseoud Aziza Yataghene Abdeltif Amrane Rachida Maachi 《Journal of industrial microbiology & biotechnology》2008,35(11):1303-1308
Production of biosurfactant by free and alginate-entrapped cells of Pseudomonas fluorescens Migula 1895-DSMZ was investigated using olive oil as the sole carbon and energy source. Biosurfactant synthesis was followed
by measuring surface tension and emulsifying index E24 over 5 days at ambient temperature and at neutral pH. Diffusional limitations
in alginate beads affected the kinetics of biosurfactant production when compared to that obtained with free cells culture.
Nevertheless, the emulsion stability was improved and fewer by-products interfered with the biosurfactant activity. A decrease
in pH down to 5 in the case of immobilized cells was observed during the first 3 days, after which it returned to its initial
value. The minimum values of surface tension were 30 and 35 dynes cm−1 achieved after 40 and 72 h with free and immobilized cells, respectively, while the corresponding maximum E24 values were
67 and 62%, respectively. After separation by acetone precipitation, the biosurfactant showed a rhamnolipid-type in nature,
and had a good foaming and emulsifying activities. The critical micellar concentration was found to be 290 mg l−1. The biosurfactant also showed good stability during exposure to high temperatures (up to 120 °C for 15 min), to high salinity
(10% NaCl) and to a wide range of pH (4–9). 相似文献
17.
Use of dissolved ozone for controlling planktonic and sessile bacteria in industrial cooling systems
M. R. Viera P. S. Guiamet M. F. L. de Mele H. A. Videla 《International biodeterioration & biodegradation》1999,44(4):1073
Cooling water treatment requires effective, environmentally-safe biocides compatible with system operation. The unique combination of high biocidal activity during use with no toxic discharge, could render dissolved ozone a safe biocide for cooling water treatment. Planktonic and sessile cells of Pseudomonas fluorescens (a frequent microbial contaminant of industrial systems) were used in this work to assess the biocidal effectiveness of ozone. Dissolved ozone showed to be effective at concentrations between 0.1 and 0.3 ppm, to eliminate completely the levels of planktonic cells used in this paper (107–108 cell/ml) within a range of contact times between 10 and 30 min. However, ozone at 0.15 ppm was only able to diminish sessile cell population by two or three orders of magnitude. This minor biocidal effectiveness of ozone against bacterial biofilms is discussed in this paper, taking into account recent concepts on structure and dynamics of biofilms. Different metallic substrata were assayed to verify if there was any effect of metal nature on the biocidal action. Open circuit potentials vs. time experiments and potentiodynamic polarization curves were made for assessing the effect of dissolved ozone on the corrosion behavior of the metals tested. 相似文献
18.
The bioluminescence (BLM) and colony-forming units (CFU) of Pseudomonas fluorescens HK44 were monitored during encapsulation into pre-polymerized Si(OMe)4. The non-induced BLM of free cells was increased in the presence of 0.5–2.5 % MeOH. After mixing silica sol with the cell
suspension, both BLM and CFU dropped to 1–3 and 8–18 %, respectively; both remained lowered as long as the silica biofilm
contained residual MeOH. The kinetics of MeOH being released from silica biofilms (a thickness of 2–6 mm) were first-order.
The decrease of bacterial activity due to encapsulation was proportional to the biofilm thickness. MeOH evolving during encapsulation
is probably the principal stress factor but not the only one. 相似文献
19.
Resca R. Basaglia M. Poggiolini S. Vian P. Bardin S. Walsh U. F. Enriquez Barreiros C. M. O'Gara F. Nuti M. P. Casella S. Peruch U. 《Plant and Soil》2001,232(1-2):215-226
Rhizomania is an extremely severe sugarbeet disease caused by the complex Polymyxa betae/Beet Necrotic Yellow Vein Virus (BNYVV). A relatively small number of recently introduced sugarbeet cultivars characterized by a high tolerance to rhizomania are available on the market. An integrated approach was therefore developed using Pseudomonas fluorescens biological control agents (BCAs) in order to improve yield performance of cultivars characterized by a medium tolerance to the disease. A genetically modified biological control agent, Pseudomonas fluorescens F113Rif (pCUGP), was developed for enhanced production of the antimicrobial metabolite 2,4-diacetylphloroglucinol (Phl) and lacking an antibiotic resistance marker gene, making the strain suitable for field release. The ability of synthetic Phl and P. fluorescens F113Rif (pCUGP) to antagonize the fungal vector, P. betae, was assessed in microcosm trials. Results encouraged the preparation of multiple field trials in a soil naturally infested with P. betae/BNYVV, to determine the biocontrol efficacy of P. fluorescens F113Rif (pCUGP) and to assess its impact on sugarbeet yield and quality and on the indigenous microbial population. While the colonization ability of P. fluorescens F113Rif (pCUGP) was satisfactory at sugarbeet emergence (2.5×106 CFU g–1 root), control of rhizomania was not achieved. Inoculation of sugarbeet with Pseudomonas fluorescens F113Rif (pCUGP) did not affect crop yield and quality nor affect the numbers of selected microbial populations. 相似文献
20.
Ricardo N. Pereira Federico Gómez Galindo António A. Vicente Petr Dejmek 《Food biophysics》2009,4(3):229-239
We have investigated whether transient permeabilization caused by the application of pulsed electric field would give rise
to transient changes in the potato tissue viscoelastic properties. Potato tissue was subjected to nominal field strengths
(E) ranging from 30 to 500 V/cm, with a single rectangular pulse of 10−5, 10−4, or 10−3 s. The changes on the viscoelastic properties of potato tissue during pulsed electric fields (PEF) were monitored through
small amplitude oscillatory dynamic rheological measurements. The elastic (G′) and viscous moduli (G″) were measured every 30 s after the delivery of the pulse and the loss tangent change (tan-δ) was calculated. The results were correlated with measurements of changes on electrical resistance during the delivery of
the pulse. Results show a drastic increase of tan-δ in the first 30 s after the application of the pulse, followed by a decrease 1 min after pulsation. This response is strongly
influenced by pulsing conditions and is independent of the total permeabilization achieved by the pulse. Our results, supported
by similar measurements on osmotically dehydrated control samples, clearly show that PEF causes a rapid change of the viscoelastic
properties of the tissue that could be attributed to a partial loss in turgor pressure. This would be an expected consequence
of electroporation. The recovery of tan-δ to values similar to those before pulsation strongly suggests recovery of cell membrane properties and turgor, pointing at
reversible permeabilization of the cells. A slight increase of stiffness traduced by a negative change of tan-δ after application of certain PEF conditions may also give an indication of events occurring on cell wall structure due to
stress responses. This study set the basis for further investigations on the complex cell stress physiology involving both
cell membrane functional properties and cell wall structure that would influence tissue physical properties upon PEF application. 相似文献