SummarySwarming in Pseudomonas aeruginosa is a coordinated movement of bacteria over semisolid surfaces (0.5%–0.7% agar). On soft agar, P. aeruginosa exhibits a dendritic swarm pattern, with multiple levels of branching. However, the swarm patterns typically vary depending upon the experimental design. In the present study, we show that the pattern characteristics of P. aeruginosa swarm are highly environment dependent. We define several quantifiable, macroscale features of the swarm to study the plasticity of the swarm, observed across different nutrient formulations. Furthermore, through a targeted screen of 113 two-component system (TCS) loci of the P. aeruginosa strain PA14, we show that forty-four TCS genes regulate swarming in PA14 in a contextual fashion. However, only four TCS genes—fleR, fleS, gacS, and PA14_59770—were found essential for swarming. Notably, many swarming-defective TCS mutants were found highly efficient in biofilm formation, indicating opposing roles for many TCS loci.

Animals possess conserved mechanisms to detect pathogens and to improve survival in their presence by altering their own behavior and physiology. Here, we utilize Caenorhabditis elegans as a model host to ask whether bacterial volatiles constitute microbe‐associated molecular patterns. Using gas chromatography–mass spectrometry, we identify six prominent volatiles released by the bacterium Pseudomonas aeruginosa. We show that a specific volatile, 1‐undecene, activates nematode odor sensory neurons inducing both flight and fight responses in worms. Using behavioral assays, we show that worms are repelled by 1‐undecene and that this aversion response is driven by the detection of this volatile through AWB odor sensory neurons. Furthermore, we find that 1‐undecene odor can induce immune effectors specific to P. aeruginosa via AWB neurons and that brief pre‐exposure of worms to the odor enhances their survival upon subsequent bacterial infection. These results show that 1‐undecene derived from P. aeruginosa serves as a pathogen‐associated molecular pattern for the induction of protective responses in C. elegans.

No abstract

No abstract

P. aeruginosa , a Gram-negative opportunistic pathogen, can adapt to diverse ecological niches and exhibits several forms of social behavior. Swarming (flagellum-driven collective motility) is a collective behavior of P. aeruginosa exclusively over semisolid surfaces.

La(Ca)CrO3 (LCC) powders have been prepared through a novel gel combustion route using metal nitrates as oxidizers and ethylene diamine tetraacetic acid (EDTA) as a fuel. The process involves the combustion of a viscous gel obtained through mixed metal nitrate-EDTA solution. The effect of amount of EDTA used in the process on the nature of combustion reaction, phase formation, and densification has been studied. It was found that use of the fuel-rich precursor facile in controlling the reaction, which in turn helps in the scale up of the batch size. The calcination of the fuel-rich gel precursor at 650 °C resulted in the well-crystalline LCC along with a small amount of calcium chromate as a secondary phase. The HRSEM studies on the powder showed agglomerated nanoparticles. The average agglomerate size was found to be 0.54 μm. The cold pressing and sintering of the calcined powder at 1250 °C resulted in the mono-phasic La0.70Ca0.30CrO3 with 94% of its theoretical density. The sintered sample exhibited conductivity of 51 S/cm at 1000 °C. The average linear thermal expansion coefficient was found to be 10.3 × 10−6 °C−1.

Mechanical strain energies in the form of movements/vibrations caused by human, machine or wind are available all around us in large quantities. A substantial amount of this renewable energy can be harvested by using piezoelectric devices. [ 1 ] Various piezoelectric energy harvesting devices (PEHDs) have been reported, mainly targeting small area applications. For example, small area PEHDs are effi cient enough to harvest substantial quantity of biological energy by human movement or by body bending. [ 2 ] According to a recent report, a mixture of BaTiO 3 nanoparticles and carbon nanotubes dispersed in a polymer matrix can generate up to 3.2 V. [ 3 ] BaTiO 3 thin fi lm based nanogenerators have been reported with an output voltage of 1.0 V and a current density of 0.19 μ A cm -2 . [ 4 ] A hybrid nanogenerator based on ZnO nanowire/poly(vinylidene fl uoride-trifl uorethylene) has been reported with output voltage, current density and power density of 0.1 V, 10 nA cm -2 and 16 μ W cm -3 , respectively. [ 5 ] Piezoelectric power generation from ZnO fi lm can be enhanced 18-fold by an addition of a p-type semiconducting polymer on top of it. [ 6 ] All these PEHDs are developed to harvest mechanical strain energy only from small areas. However, PEHDs can be used to harvest mechanical strain energy available on larger areas too. For example, PEHDs placed on a fl oor can generate energy when people walk over it. A large area sheet of PEHD in the form of a fl ag can be hung outside to harvest energy from wind. Production of large area PEHDs requires a method that can produce them in a cost effective manner with a high production speed. Roll-to-roll printing techniques, i.e., gravure, fl exography, offset and screen, can be effectively used to produce PEHDs for large area applications. These are wellestablished production techniques, available all over the world for printing applications. An advantage of fl exography printing is that it is a relatively inexpensive printing process, used mostly for package printing. For a larger area printing, which does not require a high resolution, it is a suitable production technique. In the last decade many innovative electronic components have been developed by using roll-to-roll printing methods. [7][8][9] Recently, our group has reported printed organic solar cells on a roll of paper by using gravure and fl exographic printing methods. [ 10 ] We also have reported piezoelectric loudspeakers printed by fl exography on a paper substrate. [ 11 ] Here, we report on a PEHD that is fully printed by the fl exographic printing method in ambient conditions. Although lead zirconate titanate (PZT) is one of the best piezoelectric materials, its application in energy harvesting is limited because of its mechanical rigidity. Recently, many approaches have been made to develop fl exible PZT based PEHDs, i.e., PZT ribbons and PZT fi ber composite. [ 12,13 ] As PEHDs generate alternating currents (AC), they can not be used directly to run most of the electronic devices, which require DC current...

No abstract