DNA damage by a single intense shot of soft X-rays emitted by a laser-produced plasma

EnA suitable plane transmission line was developed and its behaviour analysed at 900 MHz radiofrequency fields to study the DNA mutability and repair of microorganisms. In this work, utilizing such a device, we investigated the behaviour of the DNA mutability and repair of Escherichia coli strains. The transmission line was very simple and versatile in changing its characteristic resistance and field intensity by varying its sizes. In absence of cell samples inside the transmission line, the relative modulation of the electric and/or magnetic field was ±31% with respect to the mean values, allowing the processing of more samples at different exposure fields in a single run. Slight decrease in spontaneous mutability to rifampicin-resistance of the E. Coli JC411 strain, was demonstrated in mismatch-repair proficient samples exposed to the radio-frequency fields during their growth on solid medium

Sorgenti laser per biomateriali

In questo lavoro vengono messe a confronto due diverse tecniche per migliorare le proprietà delle superfici di materiali biomedici; l‟irraggiamento laser e l‟impiantazione ionica. L‟irraggiamento laser è eseguito mediante una sorgente ad eccimeri KrF e l‟impiantazione ionica mediante l‟acceleratore Platone che utilizza la tecnica LIS (Laser Ion Source). Mi-sure di angolo di contatto e rugosità sono state eseguite sui campioni prima e dopo ogni trattamento in modo da avere informazioni sulle modifiche. L‟impiantazione ionica è stata eseguita anche su target di acciaio AISI 420, lega utilizzata per realizzare strumenti medicali. Si è visto che l‟utilizzo di fasci di ioni di Ag aumenta l‟antibattericità degli strumenti

Enhancing UHMWPE Antibacterial Properties Through Ion Implantation

We propose a new technique for the surface modification of biomedical polymers in order to strongly enhance its antimicrobial quality via ion implantation, in alternative to the well known ones that use chemical reactions or films deposition. We present the experimental results of implantation of ultra high molecular weight polyethylene (UHMWPE) samples by Ag, Cu and Ti ions. As accelerator we used “Platone”, a homemade laser ion source accelerator device. The ions were extracted from the plasma generated by a KrF excimer laser operating at 248 nm. A laser beam of 12 mJ/pulse was focused on a solid target mounted in a vacuum chamber in order to obtain plasma. The laser spot was estimated to be of 0.005 cm2. This device has an accelerating system composed by two different stages. Using pure Ag, Cu and Ti disks as laser targets and applying voltages of 40 kV to the first accelerating stage and 20 kV to the second one, we produced ion beams containing about 1011 ions/cm2 per pulse. The penetration depth of ions was estimated by the Srim code and the largest depth was achieved with Ti ions. Operating 22000 laser shots we implanted our samples with doses of about 1015 ions/cm2. Next we analyzed the effects of ion implantation on the bacterial adherence to UHMWPE samples. To test their antimicrobial quality, a Staphylococcus aureus strain isolated from a catheter-related bloodstream infection was used in these assays. The results demonstrate that the adherence of bacteria is reduced of 21%, 7% and 90% for Ag, Cu and Ti ions-implanted samples with respect to the control ones, confirming the effectiveness of our approach

Radiofrequency transmission line for bioluminescent Vibrio sp. irradiation

We present the study and the analyses of a transmission line for radiofrequency (RF) irradiation of bacteria belonging to Vibrio harveyi-related strain PS1, a bioluminescent bacterium living in symbiosis with many marine organisms. The bioluminescence represents a new biologic indicator which is useful for studying the behaviour of living samples in the presence of RF waves due to the modern communication systems. A suitable transmission line, used as an irradiating cell and tested up to the maximum frequency used by the global system for mobile communications and universal mobile telecommunications system transmissions, was characterized. In this experiment, the RF voltage applied to the transmission line was 1V. Due to short dimensions of the line and the applied high frequencies, standing waves were produced in addition to progressing waves and the electric field strength varies particularly along the longitudinal direction. The magnetic field map was not strongly linked to the electric one due to the presence of standing waves and of the outgoing irradiation. RF fields were measured by two homemade suitable probes able to diagnostic fields of high frequency. The field measurements were performed without any specimens inside the line. Being our sample made of living matter, the real field was modified and its value was estimated by a simulation code. The bioluminescence experiments were performed only at 900MHz for two different measured electric fields, 53 and 140V/m. The light emission was measured right from the beginning and after 7 and 25 h. Under RF irradiation, we found that the bioluminescence activity decreased. Compared with the control sample, the diminution was 6.8% and 44% after 7 and 25 h of irradiation, respectively, both with the low or high field. No changes of the survival factor for all the samples were observed. Besides, to understand the emission processes, we operated the deconvolution of the spectra by two Gaussian curves. The Gaussian peaks were approximately centered at 460 nm and 490 nm. The 490 nm peak was higher than the control one. Under RF, the 490 nm peak decreased compared to the 460 nm one. The decreasing was stronger for the sample in the higher field. The ratio of the emission area of the 490 nm to 460 nm was 5 for the control sample. It decreased up to 1.6 for the samples under RF. The bioluminescence improves the DNA repair by photoreactivation, and there is evidence that photolyase is preferentially activated by blue/violet light. Our finding suggests that RF exposure may stimulate DNA repair by shifting the emission spectra from blue/green (490 nm) to blue/violet (460 nm). VC 2012 American Institute of Physics

Pseudomonas aeruginosa orchestrates twitching motility by sequential control of type IV pili movements

Prokaryotes have the ability to walk on surfaces using type IV pili (TFP), a motility mechanism known as twitching1,2. Molecular motors drive TFP extension and retraction, but whether and how these movements are coordinated is unknown3. Here, we reveal how the pathogen Pseudomonas aeruginosa coordinates the motorized activity of TFP to power efficient surface motility. To do this, we dynamically visualized TFP extension, attachment and retraction events at high resolution in four dimensions using label-free interferometric scattering microscopy (iSCAT)4. By measuring TFP dynamics, we found that the retraction motor PilT was sufficient to generate tension and power motility in free solution, while its partner ATPase PilU may improve retraction only in high-friction environments. Using precise timing of successive attachment and retraction, we show that P. aeruginosa engages PilT motors very rapidly and almost only when TFP encounter the surface, suggesting contact sensing. Finally, measurements of TFP dwell times on surfaces show that tension reinforced the adhesion strength to the surface of individual pili, thereby increasing effective pulling time during retraction. The successive control of TFP extension, attachment, retraction and detachment suggests that sequential control of motility machinery is a conserved strategy for optimized locomotion across domains of life. </p

DNA studies at 900 MHz EM fields by a TEM plane transmission line

EnA suitable plane transmission line was developed and its behaviour analysed at 900 MHz radiofrequency fields to study the DNA mutability and repair of microorganisms. In this work, utilizing such a device, we investigated the behaviour of the DNA mutability and repair of Escherichia coli strains. The transmission line was very simple and versatile in changing its characteristic resistance and field intensity by varying its sizes. In absence of cell samples inside the transmission line, the relative modulation of the electric and/or magnetic field was ±31% with respect to the mean values, allowing the processing of more samples at different exposure fields in a single run. Slight decrease in spontaneous mutability to rifampicin-resistance of the E. Coli JC411 strain, was demonstrated in mismatch-repair proficient samples exposed to the radio-frequency fields during their growth on solid medium

The impact of environmental perturbation on microbial community structure and dynamics: Factors affecting growth of Clonothrix fusca in groundwater

In a previous work temporal succession of two sheathed, filamentous methanotrophic γ-Proteobacteria, Crenothrix polyspora and Clonothrix fusca, was observed by analyzing the microbial community of an artesian well. Although a correlation between physical-chemical environmental parameters and growth of these microorganisms was suggested, the link with the microbial physiology remained elusive. In this study we demonstrate that phosphatidylethanolamine and cardiolipin, generally abundant in most γ-Proteobacteria, could not be detected in C. fusca membranes by thin-layer chromatography. The absence of cardiolipin was supported by results of enzymatic assay of cardiolipin synthase activity and by Southern blot analysis that failed to detect cls homologous sequences in the genomic DNA of this microorganism. The absence of phosphatidylethanolamine and cardiolipin might account for requirement of millimolar concentrations of magnesium and calcium for growth, and for massive over-growth of this microorganism during the winter season when the water levels of magnesium and calcium increased in the artesian well. © 2007 Taylor & Francis

Antibacterial properties of composite UHMWPE/{TiO}_{2-{x}} surfaces

Due to the diffusion of severe pathogens, everyday life is exposed to the risks of contracting severe diseases. For this reason, efficient antimicrobial surfaces are of paramount importance. In this work we present the first evidences of a new technique to obtain an antibacterial ultra high molecular weight polyethylene based on a non- stoichiometric, visible light responsive, titanium oxide coating. The coating was obtained through a process in which titanium ions, resulting from laser ablation of a corresponding target, were accelerated and implanted on the samples. The samples were tested against a Staphylo- coccus aureus strain, in order to assay their antimicrobial efficacy. Results show that this treatment strongly dis- courages bacterial colonization of the treated surfaces

Improved control of rhododendron ponticum for environmental management

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