Topoisomerases are required for alleviating supercoiling of DNA during transcription and replication. Recent evidence suggests that supercoiling of bacterial DNA can affect bacterial pathogenicity. ...To understand the potential regulatory role of a topoisomerase I (TopA) in
we investigated a previously isolated
mutation using genetic approaches. We here report the effects of the altered topoisomerase in
on type III secretion system, antibiotic susceptibility, biofilm initiation, and pyocyanin production. We found that
was essential in
, but a transposon mutant lacking the 13 amino acid residues at the C-terminal of the TopA and a mutant, named
-RM, in which
was split into three fragments were viable. The reduced T3SS expression in
-RM seemed to be directly related to TopA functionality, but not to DNA supercoiling. The drastically increased pyocyanin production in the mutant was a result of up-regulation of the pyocyanin related genes, and the regulation was mediated through the transcriptional regulator PrtN, which is known to regulate bacteriocin. The well-established regulatory pathway, quorum sensing, was unexpectedly not involved in the increased pyocyanin synthesis. Our results demonstrated the unique roles of TopA in T3SS activity, antibiotic susceptibility, initial biofilm formation, and secondary metabolite production, and revealed previously unknown regulatory pathways.
Annamocarya sinensis, a plant species with extremely small populations endemic to Xichou county of Yunnan province, has been classified as a national second-class protected wild plant. In this study, ...we assembled its complete chloroplast genome. The total genome size of A. sinensis was 158,484 bp in length, containing a large single-copy region of 89,871 bp, a small single-copy region of 20,558 bp, and a pair of inverted repeat regions of 24,029 bp. The all GC content of A. sinensis chloroplast genome was 36.2%. It encodes a total of 114 unique genes, including 79 protein-coding genes, 31 tRNA genes, and four rRNA genes. Eleven genes contain a single intron, and three genes have two introns. Phylogenetic analysis results strongly supported that Annamocarya sinensis was closely related to Carya kweichowensis.
Agroforestry is important for forest management and rehabilitation in the southeast Asia-Pacific Region (APR), where economic issues, intensive land use, deforestation, and forest degradation are ...common. Species selection is a key process in establishing agroforestry systems. In this study, we reviewed the agroforestry literature across eight economies within the southeast APR, documented the species used, and compared the existing systems to better understand the challenges and opportunities for the region’s agroforestry expansion. We conducted rule and Maptree analyses using 108 species, belonging to 95 genera and 49 families of plants, to unravel the various agroforestry practices in this region. We identified the most common plant families used in agroforestry combinations within each economy. We then divided the economies into three groups based on the most commonly used genera: (1) Thailand, Vietnam, Papua New Guinea and Fiji (Hevea, Oryza, Eucalyptus, Acacia, and Zea); (2) Nepal and Yunnan China (Zea, Leucaena, Morus, and Hevea); and (3) Indonesia and the Philippines (Oryza, Hevea, Zea, and Brassica). Although this study focused on high-level taxonomic classification (family and genus), we believe that this work will fill the current knowledge gaps, offering guidance to economies in the southeast APR regarding species selection and the adoption of sustainable agroforestry practices.
We propose multi-parameter regularization methods for high-resolution image reconstruction which is described by an ill-posed problem. The regularization operator for the ill-posed problem is ...decomposed in a multiscale manner by using bi-orthogonal wavelets or tight frames. In the multiscale framework, for different scales of the operator we introduce different regularization parameters. These methods are analyzed under certain reasonable hypotheses. Numerical examples are presented to demonstrate the efficiency and accuracy of these methods.
Thrombin activates protease-activated receptor-1 (PAR-1) by cleavage of the amino terminus to unmask a tethered ligand. Although peptide analogs can activate PAR-1, we show that the functional ...responses mediated via PAR-1 differ between the agonists. Thrombin caused endothelial monolayer permeability and mobilized intracellular calcium with EC50 values of 0.1 and 1.7 nm, respectively. The opposite order of activation was observed for agonist peptide (SFLLRN-CONH2 or TFLLRNKPDK) activation. The addition of inactivated thrombin did not affect agonist peptide signaling, suggesting that the differences in activation mechanisms are intramolecular in origin. Although activation of PAR-1 or PAR-2 by agonist peptides induced calcium mobilization, only PAR-1 activation affected barrier function. Induced barrier permeability is likely to be Gα12/13-mediated as chelation of Gαq-mediated intracellular calcium with BAPTA-AM, pertussis toxin inhibition of Gαi/o, or GM6001 inhibition of matrix metalloproteinase had no effect, whereas Y-27632 inhibition of the Gα12/13-mediated Rho kinase abrogated the response. Similarly, calcium mobilization is Gαq-mediated and independent of Gαi/o and Gα12/13 because pertussis toxin Y-27632 and had no effect, whereas U-73122 inhibition of phospholipase C-β blocked the response. It is therefore likely that changes in permeability reflect Gα12/13 activation, and changes in calcium reflect Gαq activation, implying that the pharmacological differences between agonists are likely caused by the ability of the receptor to activate Gα12/13 or Gαq. This functional selectivity was characterized quantitatively by a mathematical model describing each step leading to Rho activation and/or calcium mobilization. This model provides an estimate that peptide activation alters receptor/G protein binding to favor Gαq activation over Gα12/13 by ∼800-fold.
High-resolution image reconstruction refers to the reconstruction of high-resolution images from multiple low-resolution, shifted, degraded samples of a true image. In this paper, we analyze this ...problem from the wavelet point of view. By expressing the true image as a function in ${\cal L}({\Bbb R}^2)$, we derive iterative algorithms which recover the function completely in the ${\cal L}$ sense from the given low-resolution functions. These algorithms decompose the function obtained from the previous iteration into different frequency components in the wavelet transform domain and add them into the new iterate to improve the approximation. We apply wavelet (packet) thresholding methods to denoise the function obtained in the previous step before adding it into the new iterate. Our numerical results show that the reconstructed images from our wavelet algorithms are better than that from the Tikhonov least-squares approach. Extension to super-resolution image reconstruction, where some of the low-resolution images are missing, is also considered.
We present a variational approach to obtain high-resolution images from multiframe low-resolution video stills. The objective functional for the variational approach consists of a data fidelity term ...and a regularizer. The fidelity term is formed by adaptively mimicking l 1 and l 2 norms. The regularization uses the l 1 norm of the framelet coefficients of a high-resolution image with a geometric tight framelet system constructed in this paper. The tight framelet system has abilities to detect multi-orientation and multi-order variations of an image. A two-phase iterative method for super-resolution reconstruction is proposed to construct a high-resolution image. The first phase is to get an approximation of the solution (i.e., the ideal image) using the steepest descent method. The second phase is to enhance the sparsity of the approximate solution by using the soft thresholding operator with variable thresholding parameters. Numerical results based on both synthetic data and real videos show that our algorithm is efficient in terms of removing visual artifacts and preserving edges in restored images.
Pseudomonas aeruginosa is a human pathogen with increased intrinsic resistance to a large number of antibiotics used in clinical therapy. Therefore, understanding the mechanisms of resistance and ...developing therapy alternatives for P. aeruginosa are of profound importance. Previous work from our laboratory demonstrated that several mutants have isolated with altered expression of the phzA1B1C1D1E1F1G1 (phzA1) operon in the presence of sub-inhibitory concentrations (SICs) of tetracycline (TET). The present study investigates the roles of the PA0011 gene in mediating phzA1 expression at SIC of TET. The PA0011 gene encodes 2-OH-lauroytransferase by controlling the synthesis of the cell envelope and the outer membrane. We found that the PA0011 mutant strain was susceptible to several different antibiotics and environmental stresses. Complementation in the PA0011 mutant restored these phenotypes to wild-type levels. In addition, expression of the PA0011 gene, as monitored through a luciferase reporter, is increased at SICs of antibiotics. Indeed, the expression of the PA0011 gene increased about threefold in pqsR and pqsH mutants compared with the wild-type PAO1. However, the PA0011 gene negatively regulates the quorum sensing (QS) system. Taken together, these data suggest that PA0011 is involved in susceptibility to antimicrobial agents in P. aeruginosa, and that its susceptibility effect maybe partly dependent on increased QS expression.
The respiratory chain is very important for bacterial survival and pathogenicity, yet the roles of the respiratory chain in P. aeruginosa remain to be fully elucidated. Here, we not only proved ...experimentally that the operon PA4427-PA4431 of Pseudomonas aeruginosa PAO1 encodes respiratory chain complex III (cytobc1), but also found that it played important roles in virulence and pathogenicity. PA4429–31 deletion reduced the production of the virulence factors, including pyocyanin, rhamnolipids, elastase, and extracellular polysaccharides, and it resulted in a remarkable decrease in pathogenicity, as demonstrated in the cabbage and Drosophila melanogaster infection models. Furthermore, RNA-seq analysis showed that PA4429–31 deletion affected the expression levels of the genes related to quorum-sensing systems and the transport of iron ions, and the iron content was also reduced in the mutant strain. Taken together, we comprehensively illustrated the function of the operon PA4427–31 and its application potential as a treatment target in P. aeruginosa infection.
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