Biofilms are the predominant bacterial lifestyle and can protect microorganisms from environmental stresses. Multi-species biofilms can affect the survival of enteric pathogens that contaminate food ...products, and thus investigating the underlying mechanisms of multi-species biofilms is essential for food safety and human health. In this study, we investigated the ability of the natural isolate
PS-216 to restrain
biofilm formation and adhesion to abiotic surfaces as well as to disrupt pre-established
biofilms. Using confocal laser scanning microscopy and colony counts, we demonstrate that the presence of
PS-216 prevents
biofilm formation, decreases growth of the pathogen by 4.2 log
and disperses 26 h old pre-established
biofilms. Furthermore, the co-inoculation of
and
interferes with the adhesion of
to abiotic surfaces reducing it by 2.4 log
We also show that contact-independent mechanisms contribute to the inhibitory effect of
PS-216 on
biofilm. Using
mutants in genes coding for non-ribosomal peptides and polyketides revealed that bacillaene significantly contributes to the inhibitory effect of
PS-216. In summary, we show a strong potential for the use of
PS-216 against
biofilm formation and adhesion to abiotic surfaces. Our research could bring forward novel applications of
in animal production and thus contribute to food safety.
is an intestinal commensal in animals (including broiler chickens), but also the most frequent cause of bacterial food-borne infection in humans. This pathogen forms biofilms which mend survival of
in food processing and thus threaten human health. Probiotic bacteria represent a potential alternative in the prevention and control of food-borne infections. The beneficial bacterium,
has an excellent probiotic potential to reduce
in the animal gastrointestinal tract. However, data on the effect of
on
biofilms are scarce. Our study shows that the
natural isolate PS-216 prevents adhesion to the abiotic surfaces and the development of submerged
biofilm during co-culture and destroys the pre-established
biofilm. These insights are important for development of novel applications of
that will reduce the use of antibiotics in human and animal health and increase productivity in animal breeding.
In this paper we report on the timing resolution obtained in a beam test with pions of 180 GeV/c momentum at CERN for the first production of 45 μm thick Ultra-Fast Silicon Detectors (UFSD). UFSD are ...based on the Low- Gain Avalanche Detector (LGAD) design, employing n-on-p silicon sensors with internal charge multiplication due to the presence of a thin, low-resistivity diffusion layer below the junction. The UFSD used in this test had a pad area of 1.7 mm2. The gain was measured to vary between 5 and 70 depending on the sensor bias voltage. The experimental setup included three UFSD and a fast trigger consisting of a quartz bar readout by a SiPM. The timing resolution was determined by doing Gaussian fits to the time-of-flight of the particles between one or more UFSD and the trigger counter. For a single UFSD the resolution was measured to be 34 ps for a bias voltage of 200 V, and 27 ps for a bias voltage of 230 V. For the combination of 3 UFSD the timing resolution was 20 ps for a bias voltage of 200 V, and 16 ps for a bias voltage of 230 V.
The foodborne pathogen Campylobacter jejuni is typically found in an agricultural environment; in animals, such as birds, as an intestinal commensal; and also in food products, especially fresh ...poultry meat. Campylobacter interactions within mixed species biofilms are poorly understood, especially at the microscale. We have recently shown that the beneficial bacterium Bacillus subtilis reduces C. jejuni survival and biofilm formation in coculture by secreting the antibiotic bacillaene. We extend these studies here by providing evidence that besides bacillaene, the antagonistic effect of B. subtilis involves a nonribosomal peptide bacilysin and that the fully functional antagonism depends on the quorum-sensing transcriptional regulator ComA. Using confocal laser scanning microscopy, we also show that secreted antibiotics influence the distribution of C. jejuni and B. subtilis cells in the submerged biofilm and decrease the thickness of the pathogen’s biofilm. Furthermore, we demonstrate that genes encoding structural or regulatory proteins of the efflux apparatus system (cmeF and cmeR), respectively, contribute to the survival of C. jejuni during interaction with B. subtilis PS-216. In conclusion, this study demonstrates a strong potential of B. subtilis PS-216 to reduce C. jejuni biofilm growth, which supports the application of the PS-216 strain to pathogen biofilm control. IMPORTANCE Campylobacter jejuni is a prevalent cause of foodborne infections worldwide, while Bacillus subtilis as a potential probiotic represents an alternative strategy to control this alimentary infection. However, only limited literature exists on the specific mechanisms that shape interactions between B. subtilis and C. jejuni in biofilms. This study shows that in the two species biofilms, B. subtilis produces two antibiotics, bacillaene and bacilysin, that inhibit C. jejuni growth. In addition, we provide the first evidence that specific pathogen efflux pumps contribute to the defense against B. subtilis attack. Specifically, the CmeDEF pump acts during the defense against bacilysin, while CmeR-dependent overexpression of CmeABC nullifies the bacillaene attack. The role of specific B. subtilis antibiotics and these polyspecific pumps, known for providing resistance against medically relevant antibiotics, has not been studied during bacterial competition in biofilms before. Hence, this work broadens our understanding of mechanisms that shape antagonisms and defense during probiotic-pathogen interactions.
This paper introduces a new concept of silicon radiation detector with intrinsic multiplication of the charge, called Low Gain Avalanche Detector (LGAD). These new devices are based on the standard ...Avalanche Photo Diodes (APD) normally used for optical and X-ray detection applications. The main differences to standard APD detectors are the low gain requested to detect high energy charged particles, and the possibility to have fine segmentation pitches: this allows fabrication of microstrip or pixel devices which do not suffer from the limitations normally found 1 in avalanche detectors. In addition, a moderate multiplication value will allow the fabrication of thinner devices with the same output signal of standard thick substrates.
The investigation of these detectors provides important indications on the ability of such modified electrode geometry to control and optimize the charge multiplication effect, in order to fully recover the collection efficiency of heavily irradiated silicon detectors, at reasonable bias voltage, compatible with the voltage feed limitation of the CERN High Luminosity Large Hadron Collider (HL-LHC) experiments 2. For instance, the inner most pixel detector layers of the ATLAS tracker will be exposed to fluences up to 2×10161MeVneq/cm2, while for the inner strip detector region fluences of 1×1015neq/cm2 are expected.
The gain implemented in the non-irradiated devices must retain some effect also after irradiation, with a higher multiplication factor with respect to standard structures, in order to be used in harsh environments such those expected at collider experiments.
Summary
Bacillus subtilis is a widespread and diverse bacterium t exhibits a remarkable intraspecific diversity of the ComQXPA quorum‐sensing (QS) system. This manifests in the existence of distinct ...communication groups (pherotypes) that can efficiently communicate within a group, but not between groups. Similar QS diversity was also found in other bacterial species, and its ecological and evolutionary meaning is still being explored. Here we further address the ComQXPA QS diversity among isolates from the tomato rhizoplane, a natural habitat of B. subtilis, where these bacteria likely exist in their vegetative form. Because this QS system regulates production of anti‐pathogenic and biofilm‐inducing substances such as surfactins, knowledge on cell–cell communication of this bacterium within rhizoplane is also important from the biocontrol perspective. We confirm the presence of pherotype diversity within B. subtilis strains isolated from a rhizoplane of a single plant. We also show that B. subtilis rhizoplane isolates show a remarkable diversity of surfactin production and potential plant growth promoting traits. Finally, we discover that effects of surfactin deletion on biofilm formation can be strain specific and unexpected in the light of current knowledge on its role it this process.
This study reveals that Bacillus subtilis strains representing at least three distinct quorum sensing groups can coexists within a rhizoplane of a single plant and that they can show remarkable diversity of social traits involved in plant growth promotion (e.g. surfactin secretion, which is directly regulated by ComQXPA). This opens up many new ecological and evolutionary questions about the origin of such phenotypic diversity within the species, its evolutionary role, and its influence on stable coexistence and biocontrol performance of rhizoplane communities.
Ljubljana marsh in Slovenia is a 16 000 ha area of partly drained fen, intended to be flooded to restore its ecological functions. The resultant water-logging may create anoxic conditions, eventually ...stimulating production and emission of methane, the most important greenhouse gas next to carbon dioxide. We examined the upper layer (~30 cm) of Ljubljana marsh soil for microbial processes that would predominate in water-saturated conditions, focusing on the potential for iron reduction, carbon mineralization (CO2 and CH4 production), and methane emission. Methane emission from water-saturated microcosms was near minimum detectable levels even after extended periods of flooding (>5 months). Methane production in anoxic soil slurries started only after a lag period of 84 d at 15°C and a minimum of 7 d at 37°C, the optimum temperature for methanogenesis. This lag was inversely related to iron reduction, which suggested that iron reduction out-competed methanogenesis for electron donors, such as H2 and acetate. Methane production was observed only in samples incubated at 14–38°C. At the beginning of methanogenesis, acetoclastic methanogenesis dominated. In accordance with the preferred substrate, most (91%) mcrA (encoding the methyl coenzyme-M reductase, a key gene in methanogenesis) clone sequences could be affiliated to the acetoclastic genus Methanosarcina. No methanogens were detected in the original soil. However, a diverse community of iron-reducing Geobacteraceae was found. Our results suggest that methane emission can remain transient and low if water-table fluctuations allow re-oxidation of ferrous iron, sustaining iron reduction as the most important process in terminal carbon mineralization.
An analytical technique that can be effectively used for the calculation of the end-winding leakage inductance of a turbogenerator has been presented. It is based on a three-dimensional geometric ...model of the end-winding region in which each coil is modeled as a set of serially connected straight filaments. The calculation of the mutual inductance of the end coils is based on the multiple solutions of the Neumann integral. The method also accounts for the influence of stator core iron on the end-winding leakage inductance by using the method of images. The results of the calculations have been compared with the measured values of the leakage inductance for 247-MVA turbogenerator manufactured by KONCAR Generators and Motors Inc., Zagreb, Croatia. The principle of the end-winding leakage inductance calculation described herein can be effectively used for other types of machines and windings as well.
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