FlcA regulation of metabolism and stress response in 'Azospirillum brasilense' Sp7

In 'Azospirillum brasilense', a possible transcriptional regulator, FlcA, controls the differentiation of cells from vegetative to cyst forms. In this study, a suicide plasmid pSUP-flcAΔ was constructed, and by homologous recombination between the plasmid and the genomic DNA of 'Azospirillum brasilense' Sp7, the open reading frame of flcA was deleted in the genome of wild-type Sp7. In contrast to wild-type 'A. brasilense' Sp7, this flcA in-frame knock-out strain, named Sp7-flcAΔ, did not aggregate and remained in vegetative form under flocculation conditions. These FlcA deficient bacteria binded weakly Congo-red, lacked an extra-cellular polysaccharides coat on their cell surface and lacked poly-β-hydroxybutyrate granules within the cells under flocculation conditions. Compared to the wild-type Sp7, Sp7-flcAΔ weakly attached to wheat roots, and showed a significant reduction of survival rates under stress conditions, like UV radiation, heat and osmotic stress

Cellular Responses during Morphological Transformation in 'Azospirillum brasilense' and Its flcA Knockout Mutant

FlcA is a response regulator controlling flocculation and the morphological transformation of 'Azospirillum' cells from vegetative to cyst-like forms. To understand the cellular responses of 'Azospirillum' to conditions that cause morphological transformation, proteins differentially expressed under flocculation conditions in 'A. brasilense' Sp7 and its flcA knockout mutant were investigated. Comparison of 2-DE protein profiles of wild-type (Sp7) and a flcA deletion mutant (Sp7-flcAΔ) revealed a total of 33 differentially expressed 2-DE gel spots, with 22 of these spots confidently separated to allow protein identification. Analysis of these spots by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and MASCOT database searching identified 48 proteins (≥10% emPAI in each spot). The functional characteristics of these proteins included carbon metabolism (beta-ketothiolase and citrate synthase), nitrogen metabolism (Glutamine synthetase and nitric oxide synthase), stress tolerance (superoxide dismutase, Alkyl hydroperoxidase and ATP-dependent Clp protease proteolytic subunit) and morphological transformation (transducer coupling protein). The observed differences between Sp7 wild-type and flcA⁻ strains enhance our understanding of the morphological transformation process and help to explain previous phenotypical observations. This work is a step forward in connecting the Azospirillum phenome and genome

Dopant-Free Hole-Transporting Material Based on Poly(2,7-(9,9-bis(N,N-di-p-methoxylphenylamine)-4-phenyl))-fluorene for High-Performance Air-Processed Inverted Perovskite Solar Cells

It is a great challenge to develop low-cost and dopant-free polymer hole-transporting materials (HTM) for PSCs, especially for efficient air-processed inverted (p-i-n) planar PSCs. A new homopolymer HTM, poly(2,7-(9,9-bis(N,N-di-p-methoxylphenyl amine)-4-phenyl))-fluorene (denoted as PFTPA), with appropriate photo-electrochemical, opto-electronic and thermal stability, was designed and synthesized in two steps to meet this challenge. By employing PFTPA as dopant-free hole-transport layer in air-processed inverted PSCs, a champion power conversion efficiency (PCE) of up to 16.82% (0.1 cm2) was achieved, much superior to that of commercial HTM PEDOT:PSS (13.8%) under the same conditions. Such a superiority is attributed to the well-aligned energy levels, improved morphology, and efficient hole-transporting, as well as hole-extraction characteristics at the perovskite/HTM interface. In particular, these PFTPA-based PSCs fabricated in the air atmosphere maintain a long-term stability of 91% under ambient air conditions for 1000 h. Finally, PFTPA as the dopant-free HTM was also fabricated the slot-die coated perovskite device through the same fabrication condition, and a maximum PCE of 13.84% was obtained. Our study demonstrated that the low-cost and facile homopolymer PFTPA as the dopant-free HTM are potential candidates for large-scale production perovskite solar cell

Cellular responses during morphological transformation in Azospirillum brasilense and its flcA knockout mutant

FlcA is a response regulator controlling flocculation and the morphological transformation of Azospirillum cells from vegetative to cyst-like forms. To understand the cellular responses of Azospirillum to conditions that cause morphological transformation, proteins differentially expressed under flocculation conditions in A. brasilense Sp7 and its flcA knockout mutant were investigated. Comparison of 2-DE protein profiles of wild-type (Sp7) and a flcA deletion mutant (Sp7-flcAΔ) revealed a total of 33 differentially expressed 2-DE gel spots, with 22 of these spots confidently separated to allow protein identification. Analysis of these spots by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and MASCOT database searching identified 48 proteins (≥10% emPAI in each spot). The functional characteristics of these proteins included carbon metabolism (beta-ketothiolase and citrate synthase), nitrogen metabolism (Glutamine synthetase and nitric oxide synthase), stress tolerance (superoxide dismutase, Alkyl hydroperoxidase and ATP-dependent Clp protease proteolytic subunit) and morphological transformation (transducer coupling protein). The observed differences between Sp7 wild-type and flcA− strains enhance our understanding of the morphological transformation process and help to explain previous phenotypical observations. This work is a step forward in connecting the Azospirillum phenome and genome

High Power Diode Laser Array Development using Completely Indium Free Packaging Technology with Narrow Spectrum

The high power diode lasers have been widely used in many fields. In this work, a sophisticated high power and high performance horizontal array of diode laser stacks have been developed and fabricated with high duty cycle using hard solder bonding technology. CTE-matched submount and Gold Tin (AuSn) hard solder are used for bonding the diode laser bar to achieve the performances of anti-thermal fatigue, higher reliability and longer lifetime. This array consists of 30 bars with the expected optical output peak power of 6000W. By means of numerical simulation and analytical results, the diode laser bars are aligned on suitable positions along the water cooled cooler in order to achieve the uniform wavelength with narrow spectrum and accurate central wavelength. The performance of the horizontal array, such as outputpower, spectrum, thermal resistance, life time, etc., is characterized and analyzed

qRT-PCR primer sets used in this study.

<p>qRT-PCR primer sets used in this study.</p

Plant-root binding abilities of <i>A. brasilense</i> strain.

<p>Colonization of wheat root by Sp7 (1 and 4), Sp7-flcAΔ (2 and 5) and Sp72001 (3 and 6). <i>A</i>. <i>brasilense</i> strains harbor the reporter plasmid pLA-lacZ, containing a constitutively expressed <i>lacZ</i> gene and were stained with X-gal. Sp7 (1, 4) has strong binding ability to wheat roots and can be found all over the root surface; Sp7-flcAΔ (2, 5) and Sp72001 (3, 6) lost the ability to bind to wheat roots and could only be found in lateral root emergence areas. Scale bars indicate 50 µm (group A) and 5 µm (group B) (Magnification ×100 in group A and ×1000 in group B).</p