Prevention of Pseudomonas aeruginosa adhesion by electric currents

The process of controlling bacterial adhesion using an electric current deserves attention because of its ease of automation and environmentally friendly nature. This study investigated the role of electric currents (negative, positive, alternating) for preventing adhesion of Pseudomonas aeruginosa and achieving bacterial inactivation. Indium tin oxide (ITO) film was used as a working electrode to observe adhesion and inactivation under electric polarization. Electric current types were classified into negative, positive, and alternating current. The working electrode acted as a cathode or anode by applying a negative or positive current, and an alternating current indicates that the negative current was combined sequentially with the positive current. The numbers of adhered cells were compared under a flow condition, and the in situ behavior of the bacterial cells and the extent of their inactivation were also investigated using time-lapse recording and live/dead staining, respectively. The application of a negative current prevented bacterial adhesion significantly (～81% at 15.0 μA cm^?2). The positive current did not significantly inhibit adhesion (<20% at 15.0 μA cm^?2), compared to the nonpolarized case. The alternating current had a similar effect as the negative current on preventing bacterial adhesion, but it also exhibited bactericidal effects, making it the most suitable method for bacterial adhesion control.     

Inhibition of adhesion to buccal epithelial cells of Pseudomonas aeruginosa by dextran

Adhesion of Pseudomonas aeruginosa strains to buccal epithelial cells appears to be a necessary precondition for colonization and infection of respiratory tract. There are many strategies to prevent host organisms for Pseudomonas aeruginosa. The purpose of these studies was to evaluate the potential for preventing adhesion of Pseudomonas aeruginosa to epithelial cells with dextran. Dextran (5,000 MW) inhibited adhesion of Pseudomonas aeruginosa to buccal cells, at 20 mM was most inhibitory. The inhibitory effect appeared to be nonspecific because other neutral polysaccharides (glycogen and mannan) were also inhibitory. Dextran is an inexpansive and nontoxic agent and may be useful to prevent colonization and infection of respiratory tract with Pseudomonas aeruginosa.     

Effect of nutrient limitation on adhesion characteristics of Pseudomonas aeruginosa

Pseudomonas aeruginosa causes a variety of diseases in humans including lung and ocular infections. Infections of the cornea are usually associated with wearing contact lenses and can result in loss of vision. This study aimed to determine the effect of carbon or nitrogen limitation on the adhesion to contact lenses of a strain of Ps. aeruginosa isolated from contact lens-related corneal inflammation. Cells were grown in a continuous culture apparatus in varying levels of glucose or ammonia to effect nutrient limitation. Adhesion to contact lenses was measured as total counts and viable counts. The cell surface hydrophobicity and charge were measured using adhesion to surface-modified Sepharose. Changes in lipopolysaccharide were determined using 1D SDS-PAGE and changes in cell-surface proteins were measured using 2D gel electrophoresis. The more the cultures were nitrogen limited, the greater the increase in adhesion to unworn hydrogel contact lenses 0.3 x 10(3) - 2.2 x 10(3) cells/mm2 on Etafilon A lenses. Cells that were carbon limited showed a greater increase in adhesion to contact lenses when the lenses had been coated in artificial tears. It appeared that lipopolysaccharide may have been involved in the constitutive adhesion to unworn lenses that occurred during C-limitation, whereas changes in the outer membrane proteins contributed to the increased adhesion under nitrogen limitation, or the change in adhesion that occurred to carbon-limited cells using contact lenses coated in artificial tears. Nine cell-surface proteins appeared during nitrogen limitation with kDa/pI of 75/4.8, 4.9, 5.0; 62/5.6; 89/6.5; 38/6.4; 28/1.5; 18/6.4; 12/4.5. Any or all of these may have been involved in the increased adhesion and further experiments are underway to examine this possibility.     

大蒜素对铜绿假单胞菌生物膜早期黏附及胞外多糖的影响

目的研究大蒜素对铜绿假单胞菌PA01菌株生物膜（biofilm,BF）早期黏附及胞外多糖复合物（Extracellular Polymeric Substances,EPS）的影响。方法利用荧光多功能酶标仪检测各组不同时间点96孔板中pGF-Puv转化PA01菌株的荧光强度,计算黏附率以表示干预对不同时间点细菌黏附的影响,利用荧光显微镜下定性观察细菌的黏附量;应用异硫氰酸标记的刀豆蛋白A（FITC conjugated concanavalin A,FITC-conA）特异性结合细菌EPS,荧光显微镜下定性观察各组EPS的变化;利用硫酸-苯酚法定量各组细菌EPS的产量。结果6h组,大蒜素高浓度干预后细菌的黏附率由0．70±0．03下降至0．50±0．01,t=15．014,P〈0．05,大蒜素低浓度干预后黏附率也有下降,但不及高浓度组明显;除了9h组其他时间组趋势与6h组大致相似,可能与大蒜素含量下降有关。荧光显微镜观察可见生理盐水对照组细菌菌落分布,干预组黏附的细菌稀疏散在分布,以高浓度为甚。FITC-conA可使胞外多糖显色,在荧光显微镜下观察可见大蒜素干预后EPS减少,稀薄;EPS定量实验,EPS总量大蒜素高浓度干预组（181．19±1．59）μg较生理盐水对照组（602．66±21．94）μg有明显降低,t=60．589,P〈0．05。结论大蒜素可显著减少PA01菌株黏附及产EPS的能力。     

Shear stress increases the residence time of adhesion of Pseudomonas aeruginosa

Although ubiquitous, the processes by which bacteria colonize surfaces remain poorly understood. Here we report results for the influence of the wall shear stress on the early-stage adhesion of Pseudomonas aeruginosa PA14 on glass and polydimethylsiloxane surfaces. We use image analysis to measure the residence time of each adhering bacterium under flow. Our main finding is that, on either surface, the characteristic residence time of bacteria increases approximately linearly as the shear stress increases (∼0–3.5 Pa). To investigate this phenomenon, we used mutant strains defective in surface organelles (type I pili, type IV pili, or the flagellum) or extracellular matrix production. Our results show that, although these bacterial surface features influence the frequency of adhesion events and the early-stage detachment probability, none of them is responsible for the trend in the shear-enhanced adhesion time. These observations bring what we believe are new insights into the mechanism of bacterial attachment in shear flows, and suggest a role for other intrinsic features of the cell surface, or a dynamic cell response to shear stress.     

Development of a high throughput Pseudomonas aeruginosa epithelial cell adhesion assay

Pseudomonas aeruginosa colonizes the lungs of cystic fibrosis and mechanically ventilated patients by binding to specific carbohydrate residues on the surface of lung epithelial cells. Studies have shown that blocking this interaction may have therapeutic effects in vivo. To test compounds that may have an effect on the binding of P. aeruginosa to epithelial cells, we have developed a pseudomonal adhesion assay that is compatible with high throughput technology. This assay utilizes a 96-well culture plate assay and P. aeruginosa strains that have been modified to bioluminesce. This method has proven to be a rapid, sensitive and reproducible system for screening agents that inhibit bacterial adhesion.     

Slime Production by Pseudomonas aeruginosa

Adequate experimental conditions for slime production by Pseudomonas aeruginosa were investigated using a cellophane plate method. Definite slime production was observed on heart infusion agar, brain heart infusion agar, yeast extract agar and synthetic agar, but not on nutrient agar. The addition of phosphate to the nutrient agar above 0.05% caused visible slime formation. Incubation at 37 C resulted in a higher yield of slime than at 25 C. Longer incubation seemed more favorable for slime production, while the pH reaction of the test media did not effect the slime yield. All the test cultures of P. aeruginosa produced large amounts of slime by this procedure. Cultures of Pseudomonas fluorescens, other Pseudomonas spp. and certain vibrios also produced slime under these experimental conditions.     

Slime Production by Pseudomonas aeruginosa

Chemical properties and compositions of slimes produced by two Pseudomonas aeruginosa strains of different colonial types were investigated. The main component of the slime from strain IFO 3445 was found to be DNA, contaminated with small amounts of protein. On the other hand, the slime from a mucoid-type strain No. 24 was an alginate-like substance consisting of mannuronic and glucuronic acids, and contained traces of protein and nucleic acid. Slimes from twenty clinical isolates of P. aeruginosa were investigated for their chemical compositions. Slimes from eighteen strains consisted of DNA, while, two strains of a mucoid-type produced slimes composed of polyuronic acid.     

Heterotrophic nitrification by Pseudomonas aeruginosa

Summary Several soil bacteria and fungi produce nitrite when provided with acetaldoxime. Nitrite formation by one isolate, identified as a strain of Pseudomonas aeruginosa, is not directly linked to growth but rather proceeds mainly after the active growth period. The added oxime-nitrogen is converted completely to nitrite, and nitrate is not formed. Extracts of the bacterium generate nitrite, but not nitrate, more rapidly from nitroethane than from the added oxime. The enzyme system catalyzing the formation of nitrite in oxime solutions is soluble and inducible, whereas the enzyme catalyzing the release of equimolar quantities of nitrite and acetaldehyde from nitroethane is constitutive. The slow rate of nitrite production when the enzyme preparation is provided with acetaldoxime is not markedly increased by added cofactors. The soluble enzymes also generate nitrite when incubated with several aliphatic and alicyclic oximes and nitro compounds. Nitroethane is not formed from acetaldoxime. The possible mechanism of this nitrification reaction catalyzed by a heterotrophic microorganism is discussed.     

Pentachlorophenol degradation by Pseudomonas aeruginosa

Five Pseudomonas species were tested for ability to degrade pentachlorophenol (PCP). Pseudomonas aeruginosa completely degraded PCP up to 800 mg/l in 6 days with glucose as co-substrate. With 1000 mg PCP/l, 53% was degraded. NH₄ ⁺ salts were better at enhancing degradation than organic nitrogen sources and shake-cultures promoted PCP degradation compared with surface cultures. Degradation was maximal at pH 7.6 to 8.0 and at 30 to 37°C. Only PCP induced enzymes that degraded PCP and chloramphenicol inhibited this process. The PCP was degraded to CO₂, with release of Cl^-.The authors are with the Bacteriology Laboratory, Central Leather Research Institute, Madras-600 020, India.     

Chemotaxis by Pseudomonas aeruginosa.

Chemotaxis by Pseudomonas aeruginosa RM46 has been studied, and conditions required for chemotaxis have been defined, by using the Adler capillary assay technique. Several amino acids, organic acids, and glucose were shown to be attractants of varying effectiveness for this organism. Ethylenediaminetetraacetic acid was absolutely required for chemotaxis, and magnesium was also necessary for a maximum response. Serine taxis was greatest when the chemotaxis medium contained 1.5 X 10(-5) M ethylenediaminetetraacetic acid and 0.005 M magnesium chloride. It was not necessary to include methionine in the chemotaxis medium. The strength of the chemotactic responses to glucose and to citrate was dependent on prior growth of the bacteria on glucose and citrate, respectively. Accumulation in response to serine was inhibited by the addition of succinate, citrate, malate, glucose, pyruvate, or methionine to the chemotaxis medium. Inhibition by succinate was not dependent on the concentration of attractant in the capillary. However, the degree to which glucose and citrate inhibited serine taxis was dependent on the carbon source utilized for growth. Further investigation of this inhibition may provide information about the mechanisms of chemotaxis in P. aeruginosa.     

Slime Production by Pseudomonas aeruginosa

Using Pseudomonas aeruginosa culture IFO 3445, the nutritional requirements and cultural conditions suitable for slime production were investigated. A synthetic medium was established from the experimental results, which was composed of sodium glutamate, glucose, phosphate and magnesium salt. When a cellophane plate method was used, incubation at 37 C for 3 days attained the highest relative viscosity. In the presence of an oxidizable carbohydrate the relative viscosity of the culture fluid was reduced with the acidic reaction, and recovered if the reaction was adjusted to pH 7–8.     

Slime Production by Pseudomonas aeruginosa

Two samples of slime obtained from Pseudomonas aeruginosa strains, IFO 3445 and No. 24, the latter which produced mucoid colonies on brain heart infusion agar as well as on the synthetic agar medium, were investigated for their physicochemical properties, primarily for their viscosities. Results obtained indicated that the principal component of the slime from strain IFO 3445 might be a deoxyribonucleic acid-like substance, while the slime from the mucoid strain No. 24 might be an alginic acid-like substance.     

Cyanide production by Pseudomonas fluorescens and Pseudomonas aeruginosa

Of 200 water isolates screened, five strains of Pseudomonas fluorescens and one strain of Pseudomonas aeruginosa were cyanogenic. Maximum cyanogenesis by two strains of P. fluorescens in a defined growth medium occurred at 25 to 30 degrees C over a pH range of 6.6 to 8.9. Cyanide production per cell was optimum at 300 mM phosphate. A linear relationship was observed between cyanogenesis and the log of iron concentration over a range of 3 to 300 microM. The maximum rate of cyanide production occurred during the transition from exponential to stationary growth phase. Radioactive tracer experiments with [1-14C]glycine and [2-14C]glycine demonstrated that the cyanide carbon originates from the number 2 carbon of glycine for both P. fluorescens and P. aeruginosa. Cyanide production was not observed in raw industrial wastewater or in sterile wastewater inoculated with pure cultures of cyanogenic Pseudomonas strains. Cyanide was produced when wastewater was amended by the addition of components of the defined growth medium.     

Transport of Glycerol by Pseudomonas aeruginosa

In Pseudomonas aeruginosa, the transport of glycerol was shown to be genetically controlled and to be dependent on induction by glycerol. Accumulation of (14)C-glycerol was almost completely absent in uninduced cells and in a transport-negative mutant. Kinetic studies with induced cells suggested that glycerol may be transported by two systems with different affinities for glycerol. Osmotically shocked cells did not transport glycerol, and the supernatant fluid from shocked cells contained glycerol-binding activity demonstrable by equilibrium dialysis. The binding protein was not glycerol kinase. Binding activity was absent in shock fluids from the transport-negative mutant and from uninduced cells. The glycerol-binding protein was partially purified by precipitation with ammonium sulfate. Mild heat treatment completely eliminated the binding activity of shock fluid and of the partially purified protein. Sodium azide and N-ethylmaleimide inhibited both transport by whole cells and binding of glycerol by shock fluid. It is concluded that transport of glycerol by P. aeruginosa involves a binding protein responsible for recognition of glycerol and may occur by facilitated diffusion or active transport. A requirement for energy has not been demonstrated.     

Production of rhamnolipids by Pseudomonas aeruginosa

Pseudomonas aeruginosa produces glycolipidic surface-active molecules (rhamnolipids) which have potential biotechnological applications. Rhamnolipids are produced by P. aeruginosa in a concerted manner with different virulence-associated traits. Here, we review the rhamnolipids biosynthetic pathway, showing that it has metabolic links with numerous bacterial products such as alginate, lipopolysaccharide, polyhydroxyalkanoates, and 4-hydroxy-2-alkylquinolines (HAQs). We also discuss the factors controlling the production of rhamnolipids and the proposed roles this biosurfactant plays in P. aeruginosa lifestyle.