Highly selective trapping of enteropathogenic E. coli on Fabry-Pérot sensor mirrors.

Untreated recycled water, such as sewage and graywater, will almost always contain a wide range of agents that are likely to present risks to human health, including chemicals and pathogenic microorganisms. The microbial hazards, such as large numbers of enteric pathogens that can cause gastroenteric illness if ingested, are the main cause of concern for human health. The presence of the enteropathogenic Escherichia coli (EPEC) serotype is of particular concern, as this group of bacteria is responsible for causing severe infant and travelers' diarrhea, gastroenteritis and hemolytic uremic syndrome. A biosensing system based on an optical Fabry-Pérot (FP) cavity, capable of directly detecting the presence of EPEC within 5 min, has been developed using a simple micro-thin double-sided adhesive tape and two semi-transparent FP mirror plates. The system utilizes a poly(methyl methacrylate) (PMMA) or glass substrates sputtered by 40-nm-thick gold thin films serving as FP mirrors. Mirrors have been activated using 0.1M mercaptopropionic acid, influencing an immobilization density of the translocated intimin receptor (TIR) of 100 ng/cm(2). The specificity of recognition was confirmed by exposing TIR functionalized surfaces to four taxonomically related and/or distantly related bacterial strains. It was found that the TIR-functionalized surfaces did not show any bacterial capture for these other bacterial strains within a 15 min incubation period.

Specific electromagnetic effects of microwave radiation on Escherichia coli.

The present study investigated the effects of microwave (MW) radiation applied under a sublethal temperature on Escherichia coli. The experiments were conducted at a frequency of 18 GHz and at a temperature below 40°C to avoid the thermal degradation of bacterial cells during exposure. The absorbed power was calculated to be 1,500 kW/m(3), and the electric field was determined to be 300 V/m. Both values were theoretically confirmed using CST Microwave Studio 3D Electromagnetic Simulation Software. As a negative control, E. coli cells were also thermally heated to temperatures up to 40°C using Peltier plate heating. Scanning electron microscopy (SEM) analysis performed immediately after MW exposure revealed that the E. coli cells exhibited a cell morphology significantly different from that of the negative controls. This MW effect, however, appeared to be temporary, as following a further 10-min elapsed period, the cell morphology appeared to revert to a state that was identical to that of the untreated controls. Confocal laser scanning microscopy (CLSM) revealed that fluorescein isothiocyanate (FITC)-conjugated dextran (150 kDa) was taken up by the MW-treated cells, suggesting that pores had formed within the cell membrane. Cell viability experiments revealed that the MW treatment was not bactericidal, since 88% of the cells were recovered after radiation. It is proposed that one of the effects of exposing E. coli cells to MW radiation under sublethal temperature conditions is that the cell surface undergoes a modification that is electrokinetic in nature, resulting in a reversible MW-induced poration of the cell membrane.

Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus attachment patterns on glass surfaces with nanoscale roughness.

Attachment tendencies of Escherichia coli K12, Pseudomonas aeruginosa ATCC 9027, and Staphylococcus aureus CIP 68.5 onto glass surfaces of different degrees of nanometer-scale roughness have been studied. Contact-angle and surface-charge measurements, atomic force microscopy (AFM), scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM) were employed to characterize substrata and bacterial surfaces. Modification of the glass surface resulted in nanometer-scale changes in the surface topography, whereas the physicochemical characteristics of the surfaces remained almost constant. AFM analysis indicated that the overall surface roughness parameters were reduced by 60-70%. SEM, CLSM, and AFM analysis clearly demonstrates that although E. coli, P. aeruginosa and S. aureus present significantly different patterns of attachment, all of the species exhibited a greater propensity for adhesion to the "nano-smooth" surface. The bacteria responded to the surface modification with a remarkable change in cellular metabolic activity, as shown by the characteristic cell morphologies, production of extracellular polymeric substances, and an increase in the number of bacterial cells undergoing attachment.

Staleya guttiformis attachment on poly(tert-butylmethacrylate) polymeric surfaces.

The attachment behaviour of Staleya guttiformis DSM 11458(T) on poly(tert-butyl methacrylate) (P(tBMA)) polymeric surfaces has been studied. The electrostatic charge of the S. guttiformis cell surface (measured as zeta potential via microelectrophoresis) was -43.18 mV. S. guttiformis cells appeared weakly hydrophilic as the water contact angle measured on lawns of bacterial cells was found to be 55+/-4.9 degrees. It was found that while attaching on P(tBMA) surfaces, S. guttiformis cells produced extracellular polymeric substances (EPS) as observed from atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis. The AFM high resolution imaging revealed the nano-topography of the 'free' (the EPS that is produced by the bacterial cells, but no longer directly attached to the cells) EPS associated on the cell surface and also found on P(tBMA) surface. The 'free' EPS exhibited granular structure with lateral dimensions of 30-50 nm and a vertical nano-roughness of 7-10nm. Another type of the EPS secreted by S. guttiformis cells appeared as a hydrogel substance, presumably polysaccharide that formed a biopolymer network that facilitated bacterial attachment.

Impact of nano-topography on bacterial attachment.

The adhesion of bacteria to surfaces is an important biological process, but one that has resisted simple categorization due to the number and complexity of parameters involved. The roughness of the substrate is known to play a significant role in the attachment process, particularly when the surface irregularities are comparable to the size of the bacteria and can provide shelter from unfavorable environmental factors. According to this scenario, roughness on a scale much smaller than the bacteria would not be expected to influence the initial attachment. To test this hypothesis, the impact of nanometer-scale roughness on bacterial attachment has been investigated using as-received and chemically etched glass surfaces. The surface modification by etching resulted in a 70% reduction in the nanoscale roughness of the glass surface with no significant alteration of its chemical composition or charge. Nevertheless, the number of bacteria adhering to the etched surface was observed to increase by a factor of three. The increase in attachment was also associated with an alteration in cellular metabolic activity as demonstrated by changes in characteristic cell morphologies and increased production of extracellular polymeric substances. The results indicate that bacteria may be more sensitive to nanoscale surface roughness than was previously believed.

Vibrio fischeri and Escherichia coli adhesion tendencies towards photolithographically modified nanosmooth poly (tert-butyl methacrylate) polymer surfaces.

This study reports the adhesion behavior of two bacterial species, Vibrio fischeri and Escherichia coli, to the photoresistant poly(tert-butyl methacrylate) (P(tBMA)) polymer surface. The data has demonstrated that ultraviolet irradiation of P(tBMA) was able to provide control over bacterial adhesion tendencies. Following photolithography, several of the surface characteristics of P(tBMA) were found to be altered. Atomic force microscopy analysis indicated that photolithographically modified P(tBMA) (henceforth termed 'modified polymer') appeared as a 'nanosmooth' surface with an average surface roughness of 1.6 nm. Although confocal laser scanning microscopy and scanning electron microscopy analysis clearly demonstrated that V. fischeri and E. coli presented largely different patterns of attachment in order to adhere to the same surfaces, both species exhibited a greater adhesion propensity towards the 'nanosmooth' surface. The adhesion of both species to the modified polymer surface appeared to be facilitated by an elevated production of extracellular polymeric substances when in contact with the substrate.

Salegentibacter flavus sp. nov.

A yellow-pigmented, non-motile, Gram-negative bacterium, designated Fg 69T, was isolated from a sediment sample collected in Chazhma Bay (Sea of Japan). The novel organism grew at 10-35 degrees C, was neutrophilic and required 3-10% NaCl for optimal growth. Strain Fg 69T was able to degrade starch and to hydrolyse gelatin and Tween 80 weakly but not casein or agar. Predominant cellular fatty acids comprised n-C15 and n-C16 branched-chain and straight-chain saturated and unsaturated fatty acids, including iso-C(15:0) (5%), anteiso-C(15:0) (11%), C(15:0) (9%), iso-C(15:1) (5%), iso-C(16:0) (8%), C(16:0) (5%) and C(16:1)omega7 (5%) and iso- and anteiso-branched 2-OH and 3-OH C(15:0) to C(17:0) fatty acids (26 % in total). The G + C content of the DNA was 40.4 mol%. 16S rRNA gene sequence data indicated that strain Fg 69T belonged to the genus Salegentibacter but was distinct from recognized Salegentibacter species (94-95 % sequence similarity). Based on these results, a novel species, Salegentibacter flavus sp. nov., is proposed. The type strain is Fg 69T (= KMM 6000T = CIP 107843T).