The Experts below are selected from a list of 285 Experts worldwide ranked by ideXlab platform
Ambrose L Cheung - One of the best experts on this subject based on the ideXlab platform.
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role of arlrs in Autolysis in methicillin sensitive and methicillin resistant staphylococcus aureus strains
Journal of Bacteriology, 2012Co-Authors: Guido Memmi, Dhanalakshmi R Nair, Ambrose L CheungAbstract:Autolysis plays an essential role in bacterial cell division and lysis with β-lactam antibiotics. Accordingly, the expression of autolysins is tightly regulated by several endogenous regulators, including ArlRS, a two component regulatory system that has been shown to negatively regulate Autolysis in methicillin-sensitive Staphylococcus aureus (MSSA) strains. In this study, we found that inactivation of arlRS does not play a role in Autolysis of methicillin-resistant S. aureus (MRSA) strains, such as community-acquired (CA)-MRSA strains USA300 and MW2 or the hospital-acquired (HA)-MRSA strain COL. This contrasts with MSSA strains, including Newman, SH1000, RN6390, and 8325-4, where Autolysis is affected by ArlRS. We further demonstrated that the striking difference in the roles of arlRS between MSSA and MRSA strains is not due to the methicillin resistance determinant mecA. Among known autolysins and their regulators, we found that arlRS represses lytN, while no effect was seen on atl, lytM, and lytH expression in both CA- and HA-MRSA strains. Transcriptional-fusion assays showed that the agr transcripts, RNAII and RNAIII, were significantly more downregulated in the arlRS mutant of MW2 than the MSSA strain Newman. Importantly, provision of agr RNAIII in trans to the MW2 arlRS mutant via a multicopy plasmid induced Autolysis in this MRSA strain. Also, the autolytic phenotype in the arlRS mutant of MSSA strain Newman could be rescued by a mutation in either atl or lytM. Together, these data showed that ArlRS impacts Autolysis differently in MSSA and MRSA strains.
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characterization of rat an Autolysis regulator in staphylococcus aureus
Molecular Microbiology, 2003Co-Authors: Susham S Ingavale, W Van Wamel, Ambrose L CheungAbstract:In trying to identify genetic loci involved in the regulation of cap5 genes in Staphylococcus aureus, we isolated a transposon mutant that exhibited a growth defect, enhanced Autolysis and increased sensitivity to Triton X-100 and penicillin, attributable in part to increased murein hydrolase activity. Analysis of the chromosomal sequence flanking the transposon insertion site revealed that the gene disrupted in the mutant encodes an open reading frame of 147 amino acids. We named this gene rat, which stands for regulator of autolytic activity. Sequence analysis indicated that Rat is homologous to the MarR and, to a lesser extent, the SarA protein families. Mutations in rat resulted in decreased expression of known autolytic regulators lytSR, lrgAB and arlRS. Gel shift studies indicated that Rat binds to the lytRS and arlRS promoters, thus confirming Rat as a DNA-binding protein to these known repressors of autolytic activity. As anticipated, rat appears to be a negative regulator of autolysin genes including lytM and lytN. These data suggest that the rat gene product is an important regulator of autolytic activity in S. aureus.
Fereidoon Shahidi - One of the best experts on this subject based on the ideXlab platform.
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structural and biochemical changes in dermis of sea cucumber stichopus japonicus during Autolysis in response to cutting the body wall
Food Chemistry, 2018Co-Authors: Yuxin Liu, Bei Wei Zhu, Dayong Zhou, Ziqiang Liu, Liang Song, Xiuping Dong, Fereidoon ShahidiAbstract:The Autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during Autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During Autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive Autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for Autolysis of S. japonicus dermis.
Simon J. Foster - One of the best experts on this subject based on the ideXlab platform.
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Bacterial peptidoglycan (murein) hydrolases.
Fems Microbiology Reviews, 2008Co-Authors: Waldemar Vollmer, Bernard Joris, Paulette Charlier, Simon J. FosterAbstract:Most bacteria have multiple peptidoglycan hydrolases capable of cleaving covalent bonds in peptidoglycan sacculi or its fragments. An overview of the different classes of peptidoglycan hydrolases and their cleavage sites is provided. The physiological functions of these enzymes include the regulation of cell wall growth, the turnover of peptidoglycan during growth, the separation of daughter cells during cell division and Autolysis. Specialized hydrolases enlarge the pores in the peptidoglycan for the assembly of large trans-envelope complexes (pili, flagella, secretion systems), or they specifically cleave peptidoglycan during sporulation or spore germination. Moreover, peptidoglycan hydrolases are involved in lysis phenomena such as fratricide or developmental lysis occurring in bacterial populations. We will also review the current view on the regulation of autolysins and on the role of cytoplasm hydrolases in peptidoglycan recycling and induction of β-lactamase.
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the role of autolysins during vegetative growth of bacillus subtilis 168
Microbiology, 1998Co-Authors: Steve A Blackman, Thomas J Smith, Simon J. FosterAbstract:Summary: A set of isogenic mutants of Bacillus subtilis 168, insertionally inactivated in the genes encoding a number of lytic enzymes and a sigma factor (σD, which controls the expression of a number of autolysins) was constructed. Phenotypic analysis of the mutants determined the individual and combined roles of the autolysins in vegetative growth. The major vegetative autolysins of B. subtilis, LytC (50 kDa amidase) and LytD (90 kDa glucosaminidase), were shown to have roles in cell separation, cell wall turnover, antibiotic-induced lysis and motility. LytC was also shown to have a role in general cell lysis induced by sodium azide. Renaturing SDS-PAGE of cell-wall-binding protein extracts of the mutant strains revealed the presence of a novel autolysin that was previously masked by LytC. This 49 kDa enzyme was shown to be σD-controlled and was identified as a candidate cell separation and cell wall turnover enzyme. A multiple mutant strain, lacking LytC, LytD and the 49 kDa enzyme, retained at least ten bands of autolytic activity. These may correspond to individual or proteolytically processed novel autolysins, the functions of which are unknown. The multiple mutant strains facilitate the study of these, and other lytic enzymes, to determine their cellular functions.
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analysis of the autolysins of bacillus subtilis 168 during vegetative growth and differentiation by using renaturing polyacrylamide gel electrophoresis
Journal of Bacteriology, 1992Co-Authors: Simon J. FosterAbstract:The autolysins of Bacillus subtilis 168 were analyzed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis with substrate-containing gels. Four bands of vegetative autolytic activity of 90, 50, 34, and 30 kDa (bands A1 to A4) were detected in SDS and LiCl extracts and in native cell walls by using B. subtilis 168 vegetative cell walls as the substrate incorporated in the gel. The four enzyme activities showed different substrate specificities and sensitivities to various chemical treatments. The autolysin profile was not medium dependent and remained constant during vegetative growth. During sporulation, band A4 greatly increased in activity just prior to mother-cell lysis. No germination-associated changes in the profile were observed, although a soluble 41-kDa endospore-associated cortex-lytic enzyme was found. By using insertionally inactivated mutants, bands A1 and A2 were positively identified as the previously characterized 90-kDa glucosaminidase and 50-kDa amidase, respectively. The common filamentous phenotype of various regulatory mutants could not be correlated to specific changes in the autolysin profile. Images
Bei Wei Zhu - One of the best experts on this subject based on the ideXlab platform.
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structural and biochemical changes in dermis of sea cucumber stichopus japonicus during Autolysis in response to cutting the body wall
Food Chemistry, 2018Co-Authors: Yuxin Liu, Bei Wei Zhu, Dayong Zhou, Ziqiang Liu, Liang Song, Xiuping Dong, Fereidoon ShahidiAbstract:The Autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during Autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During Autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive Autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for Autolysis of S. japonicus dermis.
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Effect of matrix metalloproteinase on Autolysis of sea cucumber Stichopus japonicus
Food Science and Biotechnology, 2013Co-Authors: Li Ming Sun, Ting Ting Wang, Bei Wei Zhu, Hai Ling Niu, Rui Zhang, Hongman Hou, Gong Liang Zhang, Yoshiyuki MurataAbstract:To investigate the relationship between matrix metalloproteinase (MMPs) and Autolysis of sea cucumber Stichopus japonicus, the dermis homogenate was incubated at 25°C to induce Autolysis. EDTA Na2 and 1,10-phenanthroline were used to verify the effect of MMPs on Autolysis, which was measured by soluble protein and protein pattern. Soluble protein level increased during a 6-h Autolysis process. SDS-PAGE demonstrated obvious protein degradation with the concomitant occurrence of degradation products. The above two indicators could be inhibited significantly by EDTA Na2 and 1,10-phenanthroline, indicating that MMPs might play a significant role in Autolysis of sea cucumber.
Yuxin Liu - One of the best experts on this subject based on the ideXlab platform.
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structural and biochemical changes in dermis of sea cucumber stichopus japonicus during Autolysis in response to cutting the body wall
Food Chemistry, 2018Co-Authors: Yuxin Liu, Bei Wei Zhu, Dayong Zhou, Ziqiang Liu, Liang Song, Xiuping Dong, Fereidoon ShahidiAbstract:The Autolysis of sea cucumber body wall is caused by endogenous proteolysis of its structural elements. However, changes in collagen fibrils, collagen fibres and microfibrils, the major structural elements in sea cucumber body wall during Autolysis are less clear. Autolysis of sea cucumber (S. japonicus) was induced by cutting the body wall, and the structural and biochemical changes in its dermis were investigated using electron microscopy, differential scanning calorimetry, infrared spectroscopy, electrophoresis, and chemical analysis. During Autolysis, both collagen fibres and microfibrils gradually degraded. In contrast, damage to microfibrils was more pronounced. Upon massive Autolysis, collagen fibres disaggregated into collagen fibril bundles and individual fibrils due to the fracture of interfibrillar bridges. Meanwhile, excessive unfolding of collagen fibrils occurred. However, there was only slight damage to collagen monomers. Therefore, structural damage in collagen fibres, collagen fibrils and microfibrils rather than monomeric collagen accounts for Autolysis of S. japonicus dermis.
