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10 results on '"Chu, Ya-Yun"'

2. A Photorhabdus Natural Product Inhibits Insect Juvenile Hormone Epoxide Hydrolase

Author

Nollmann, Friederike I, Heinrich, Antje K, Brachmann, Alexander O, Morisseau, Christophe, Mukherjee, Krishnendu, Casanova-Torres, Ángel M, Strobl, Frederic, Kleinhans, David, Kinski, Sebastian, Schultz, Katharina, Beeton, Michael L, Kaiser, Marcel, Chu, Ya-Yun, Ke, Long Phan, Thanwisai, Aunchalee, Bozhüyük, Kenan AJ, Chantratita, Narisara, Götz, Friedrich, Waterfield, Nick R, Vilcinskas, Andreas, Stelzer, Ernst HK, Goodrich-Blair, Heidi, Hammock, Bruce D, and Bode, Helge B

Subjects
Biological Sciences, Medicinal and Biomolecular Chemistry, Chemical Sciences, Infection, Animals, Biological Products, Enzyme Inhibitors, Epoxide Hydrolases, Insecta, Photorhabdus, Structure-Activity Relationship, Urea, biosynthesis, entomopathogenic bacteria, juvenile hormone epoxide hydrolase inhibitor, natural products, Biochemistry and Cell Biology, Organic Chemistry, Biochemistry and cell biology, Medicinal and biomolecular chemistry
Abstract

Simple urea compounds ("phurealipids") have been identified from the entomopathogenic bacterium Photorhabdus luminescens, and their biosynthesis was elucidated. Very similar analogues of these compounds have been previously developed as inhibitors of juvenile hormone epoxide hydrolase (JHEH), a key enzyme in insect development and growth. Phurealipids also inhibit JHEH, and therefore phurealipids might contribute to bacterial virulence.

Published
2015

4. A New Class of Molecules from Staphylococcus Species Affects Quorum Sensing and Growth of Gram-Negative Bacteria

Author

Chu, Ya-Yun and Götz, Friedrich

Subjects
Staphylococcus
Abstract

This thesis addressed bacterial communication between Gram positive and Gram negative bacteria. The knowledge that many pathogens rely on cell-to-cell communication mechanisms known as quorum sensing, opens a new disease control strategy: quorum quenching. While studying the interaction of staphylococci with Gram-negative bacteria, we came across another communication system in a Staphylococcus intermedius group (SIG) species which can act as a zoonotic pathogen. This is one of the rare examples where Gram-positive bacteria excrete two compounds in comparatively high amounts that suppress the quorum sensing signaling and inhibit the growth of a broad spectrum of Gram-negative beta- and gamma-proteobacteria. The excreted compounds, named yayurea A and B, were isolated from S. delphini and structurally characterized. In vitro studies with the Nacyl homoserine lactone (AHL) responding receptor LuxN of V. harveyi indicated that both compounds stimulated the LuxN-mediated phosphorylation of LuxU and caused the opposite effects with AHL. Furthermore, growth of yayurea A and B producing S. delphini is not suppressed by respiratory toxins when co-cultured with P. aeruginosa. Taken together, yayureas are presumably involved in self-protection and ensuring competitiveness in natural environments shared with Gram-negatives. In the second part of thesis, the role of protein A in Staphylococcus aureus adhesion to ethylene glycol coated surfaces was investigated. It was found that the coating materials, HS(CH2)11EG3OMe (EG3OMe) and poly-ethylene-glycol (PEG) prevented bacterial adhesion of S. aureus cells. However, pretreatment of EG3OMe and PEG coatings with r-globulins or serum strongly promoted adherence of S. aureus cell. Furthermore, the spa-deletion mutant S. aureus, lacking the IgG binding protein A, showed reduced adherence and pretreatment of S. aureus with serum significantly decreased adherence. These results suggested that r-globulins play a crucial role in promoting S. aureus cells adhesion by its IgG binding proteins. Particularly γglobulins bound to the coated surfaces thus mediating adherence of S. aureus via its protein A. Intercepting this adherence should prove to be useful in preventing biofilm formation.

Published
2014

5. A Photorhabdus natural product inhibits insect juvenile hormone epoxide hydrolase.

Author

Nollmann, Friederike, Nollmann, Friederike, Heinrich, Antje, Brachmann, Alexander, Morisseau, Christophe, Mukherjee, Krishnendu, Casanova-Torres, Ángel, Strobl, Frederic, Kleinhans, David, Kinski, Sebastian, Schultz, Katharina, Beeton, Michael, Kaiser, Marcel, Chu, Ya-Yun, Phan Ke, Long, Thanwisai, Aunchalee, Bozhüyük, Kenan, Chantratita, Narisara, Götz, Friedrich, Waterfield, Nick, Vilcinskas, Andreas, Stelzer, Ernst, Goodrich-Blair, Heidi, Hammock, Bruce, Bode, Helge, Nollmann, Friederike, Nollmann, Friederike, Heinrich, Antje, Brachmann, Alexander, Morisseau, Christophe, Mukherjee, Krishnendu, Casanova-Torres, Ángel, Strobl, Frederic, Kleinhans, David, Kinski, Sebastian, Schultz, Katharina, Beeton, Michael, Kaiser, Marcel, Chu, Ya-Yun, Phan Ke, Long, Thanwisai, Aunchalee, Bozhüyük, Kenan, Chantratita, Narisara, Götz, Friedrich, Waterfield, Nick, Vilcinskas, Andreas, Stelzer, Ernst, Goodrich-Blair, Heidi, Hammock, Bruce, and Bode, Helge

Abstract

Simple urea compounds (phurealipids) have been identified from the entomopathogenic bacterium Photorhabdus luminescens, and their biosynthesis was elucidated. Very similar analogues of these compounds have been previously developed as inhibitors of juvenile hormone epoxide hydrolase (JHEH), a key enzyme in insect development and growth. Phurealipids also inhibit JHEH, and therefore phurealipids might contribute to bacterial virulence.

Published
2015

10. A New Class of Quorum Quenching Molecules from Staphylococcus Species Affects Communication and Growth of Gram-Negative Bacteria.

Author

Chu, Ya-Yun, Nega, Mulugeta, Wölfle, Martina, Plener, Laure, Grond, Stephanie, Jung, Kirsten, and Götz, Friedrich

Subjects
*STAPHYLOCOCCUS, *QUORUM sensing, *PREVENTIVE medicine, *GRAM-positive bacteria, *PATHOGENIC microorganisms, *PHOSPHORYLATION
Abstract

The knowledge that many pathogens rely on cell-to-cell communication mechanisms known as quorum sensing, opens a new disease control strategy: quorum quenching. Here we report on one of the rare examples where Gram-positive bacteria, the ‘Staphylococcus intermedius group’ of zoonotic pathogens, excrete two compounds in millimolar concentrations that suppress the quorum sensing signaling and inhibit the growth of a broad spectrum of Gram-negative beta- and gamma-proteobacteria. These compounds were isolated from Staphylococcus delphini. They represent a new class of quorum quenchers with the chemical formula N-[2-(1H-indol-3-yl)ethyl]-urea and N-(2-phenethyl)-urea, which we named yayurea A and B, respectively. In vitro studies with the N-acyl homoserine lactone (AHL) responding receptor LuxN of V. harveyi indicated that both compounds caused opposite effects on phosphorylation to those caused by AHL. This explains the quorum quenching activity. Staphylococcal strains producing yayurea A and B clearly benefit from an increased competitiveness in a mixed community. [ABSTRACT FROM AUTHOR]

Published
2013
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