Subminimal inhibitory concentrations of antibiotics have been shown to induce bacterial biofilm formation. Few studies have investigated antibiotic-induced biofilm formation in Staphylococcus aureus, an important human pathogen. Our goal was to measure S. aureus biofilm formation in the presence of low levels of β-lactam antibiotics. Fifteen phylogenetically diverse methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA) strains were employed. Methicillin, ampicillin, amoxicillin, and cloxacillin were added to cultures at concentrations ranging from 0× to 1× MIC. Biofilm formation was measured in 96-well microtiter plates using a crystal violet binding assay. Autoaggregation was measured using a visual test tube settling assay. Extracellular DNA was quantitated using agarose gel electrophoresis. All four antibiotics induced biofilm formation in some strains. The amount of biofilm induction was as high as 10-fold and was inversely proportional to the amount of biofilm produced by the strain in the absence of antibiotics. MRSA strains of lineages USA300, USA400, and USA500 exhibited the highest levels of methicillin-induced biofilm induction. Biofilm formation induced by low-level methicillin was inhibited by DNase. Low-level methicillin also induced DNase-sensitive autoaggregation and extracellular DNA release. The biofilm induction phenotype was absent in a strain deficient in autolysin (atl). Our findings demonstrate that subminimal inhibitory concentrations of β-lactam antibiotics significantly induce autolysin-dependent extracellular DNA release and biofilm formation in some strains of S. aureus.

Since their discovery, many practical applications of carbon nanotubes (CNTs) have been proposed because of their excellent properties. Many researchers have reported remarkable electrical, optical, and thermal properties of CNTs. The electrical conductivity of single-walled carbon nanotubes (SWCNTs) is very high (10 6 S m -2 ). Films made of SWCNTs also possess a low sheet resistance and exhibit an optical transmittance in the visible spectrum comparable to that of commercial indium tin oxide (ITO). [1,2] Recently, a thermal conductivity of nearly 3500 W m -1 K -1 was measured at room temperature for SWCNTs measuring 2.6 lm in length and 1.7 nm in diameter. [3] This thermal conductivity value is much higher than that of diamond. In the field of thermal engineering, research has focused on enhancing their heat-transfer properties. CNTs have been modeled as heat-sink fins in cooling channels for microelectronics, and several groups have developed various CNT mats and composites for the next generation of thermal interface materials. [4][5][6][7][8][9][10][11][12][13] Although a high thermal conductivity is a central issue in thermal engineering, few pioneering works have utilized other useful properties of CNTs, such as their high electrical conductivity and optical transparency. Therefore, we propose a unique application of SWCNT films as transparent heaters. Currently, thin ITO films has been used as transparent heaters in various applications, such as outdoor panel displays, avionic displays, liquid-crystal display (LCD) panels for use in harsh environments, periscopes, and vehicle window defrosters. However, ITO film heaters have some limitations, such as a slow thermal response and complex fabrication processes.Because CNT films have a high thermal conductivity and can be produced by using various common fabrication methods [1,2,[14][15][16] they are a promising alternative to ITO films in transparent heaters. To our knowledge, there are no reports about transparent CNT film heaters. Therefore, we fabricated the first transparent film heater using SWCNTs and investigated its heating performance. Purified SWCNTs were grown by using the arc discharge technique. We chose the vacuum filtration method to fabricate the transparent SWCNT films. In this manner we could control the transparency and obtain excellent uniformity of the networked SWCNT films.[2] First, the SWCNT samples were purified using standard processes, such as centrifugation, acid treatment, and membrane filtration. The SWCNTs were then dispersed in deionized water with a 1 wt % sodium dodecyl sulfate (SDS) solution and sonicated for several hours. The film transparency was modulated by adjusting the volume of the SWCNT solution between 0.5 and 4.0 mL. This resulted in SWCNT films with a transparency of 65-97 % and a sheet resistance of 230-3500 X m -2 . An anodic aluminium oxide (AAO) membrane with 200 nm pores (Whatman International, Anodisc 47) was used as a filter. The CNT membrane was soaked in NaOH solution for 1 h, rinsed with deionized wate...

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The neuromorphic system processes enormous information even with very low energy consumption, which practically can be achieved with photonic artificial synapse. Herein, a photonic artificial synapse is demonstrated based on an all-oxide highly transparent device. The device consists of conformally grown InO/ZnO thin films on a fluorine-doped tin oxide/glass substrate. The device showed a loop opening in current-voltage characteristics, which was attributed to charge trapping/detrapping. Ultraviolet illumination-induced versatile features such as short-term/long-term plasticity and paired-pulse facilitation were truly confirmed. Further, photonic potentiation and electrical habituation were implemented. This study paves the way to develop a device in which current can be modulated under the action of optical stimuli, serving as a fundamental step toward the realization of low-cost synaptic behavior.

Sphingosine-1-phosphate (S1P), a potent signalling lipid secreted by red blood cells and platelets, plays numerous biologically significant roles. However, the identity of its long-sought exporter is enigmatic. Here we show that the major facilitator superfamily transporter 2b (Mfsd2b), an orphan transporter, is essential for S1P export from red blood cells and platelets. Comprehensive lipidomic analysis indicates a dramatic and specific accumulation of S1P species in Mfsd2b knockout red blood cells and platelets compared with that of wild-type controls. Consistently, biochemical assays from knockout red blood cells, platelets, and cell lines overexpressing human and mouse Mfsd2b proteins demonstrate that Mfsd2b actively exports S1P. Plasma S1P level in knockout mice is significantly reduced by 42-54% of that of wild-type level, indicating that Mfsd2b pathway contributes approximately half of the plasma S1P pool. The reduction of plasma S1P in knockout mice is insufficient to cause blood vessel leakiness, but it does render the mice more sensitive to anaphylactic shock. Stress-induced erythropoiesis significantly increased plasma S1P levels and knockout mice were sensitive to these treatments. Surprisingly, knockout mice exhibited haemolysis associated with red blood cell stomatocytes, and the haemolytic phenotype was severely increased with signs of membrane fragility under stress erythropoiesis. We show that S1P secretion by Mfsd2b is critical for red blood cell morphology. Our data reveal an unexpected physiological role of red blood cells in sphingolipid metabolism in circulation. These findings open new avenues for investigating the signalling roles of S1P derived from red blood cells and platelets.