The Experts below are selected from a list of 291 Experts worldwide ranked by ideXlab platform
Mathias Herrmann - One of the best experts on this subject based on the ideXlab platform.
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Staphylococcus aureus ClpC is involved in protection of carbon-metabolizing enzymes from carbonylation during stationary growth Phase
International Journal of Medical Microbiology, 2011Co-Authors: Indranil Chatterjee, Etienne Maisonneuve, Benjamin Ezraty, Mathias Herrmann, Sam DukanAbstract:The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Among them, ClpC, belonging to the Hsp100/Clp ATPase family, seems to play an important role. For instance, we previously demonstrated that a functional clpC deletion resulted in enhanced survival in the late stationary Phase (Death Phase period) compared to the parental S. aureus strain. However, the mechanisms for the enhanced survival of a S. aureus clpC mutant during the Death Phase period are still elusive. In Escherichia coli, among the factors that might lead to bacterial cell Death during stationary Phase, the amount of protein aggregates and/or oxidized proteins appears to be of major importance. Thus, in the present study, we have evaluated protein aggregates and carbonylated protein (as a marker of protein oxidation) contents both in the wild type and in an S. aureus clpC mutant during the exponential growth Phase and the Death Phase. Whereas at all time points the tested clpC mutant exhibits the same amount of protein aggregates as the WT strain, the total amount of carbonylated proteins appears to be lower in the clpC mutant. Moreover, we observed that at the entrance of the Death Phase carbon-metabolizing enzymes [such as the TCA cycle enzymes Mqo2 (malate: quinone oxidoreductase) and FumC/CitG (fumarate hydratase)] albeit not the bulk proteins are carbonylated to a larger extent in the clpC mutant. Reduced activity of the TCA cycle due to specific carbonylation of these proteins will result in a decrease of endogenous oxidative stress which in turn might confer enhanced survival of the clpC mutant during the Death Phase period thus contributing to bacterial longevity and chronic infection.
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staphylococcus aureus clpc is required for stress resistance aconitase activity growth recovery and Death
Journal of Bacteriology, 2005Co-Authors: Indranil Chatterjee, Petra Becker, Matthias Grundmeier, Markus Bischoff, Greg A Somerville, Georg Peters, Bhanu Sinha, Niamh Harraghy, Richard A Proctor, Mathias HerrmannAbstract:The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Previously, it has been demonstrated that Clp homologues are important for a variety of stress conditions, and our laboratory has shown that a clpC homologue was highly expressed in the S. aureus strain DSM20231 during biofilm formation relative to expression in planktonic cells. Persistence and long-term survival are a hallmark of biofilm-associated staphylococcal infections, as cure frequently fails even in the presence of bactericidal antimicrobials. To determine the role of clpC in this context, we performed metabolic, gene expression, and long-term growth and survival analyses of DSM20231 as well as an isogenic clpC allelic-replacement mutant, a sigB mutant, and a clpC sigB double mutant. As expected, the clpC mutant showed increased sensitivity to oxidative and heat stresses. Unanticipated, however, was the reduced expression of the tricarboxylic acid (TCA) cycle gene citB (encoding aconitase), resulting in the loss of aconitase activity and preventing the catabolization of acetate during the stationary Phase. clpC inactivation abolished post-stationary-Phase recovery but also resulted in significantly enhanced stationary-Phase survival compared to that of the wild-type strain. These data demonstrate the critical role of the ClpC ATPase in regulating the TCA cycle and implicate ClpC as being important for recovery from the stationary Phase and also for entering the Death Phase. Understanding the stationary- and post-stationary-Phase recovery in S. aureus may have important clinical implications, as little is known about the mechanisms of long-term persistence of chronic S. aureus infections associated with formation of biofilms.
Jin-lan Xia - One of the best experts on this subject based on the ideXlab platform.
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Modeling the growth curve for Spirulina (Arthrospira) maxima, a versatile microalga for producing uniformly labelled compounds with stable isotopes
Journal of Applied Phycology, 2001Co-Authors: J. M. Levert, Jin-lan XiaAbstract:The paper presents a five-Phase model to describe batch culture of Spirulina maxima under limitations of light and nutrients nitrogen andsulfur. The general equation for the exponential, linear, decelerating andstationary Phases of the growth curve took into account that (i) the specificgrowth rate was proportional to the local light intensity in thephotobioreactor; (ii) light attenuation was due to cell's absorption andreflection and observed the Lambert-Beer's law with a total absorptioncoefficient (εT) that was the sum of absorption coefficient(εa) and reflection coefficient (εr); (iii) thecomposition of the alga and its absorption εa changed withtime and (iv) the specific growth rate was influenced by nutrients ofnitrogen and sulfur in the culture medium according to a Monod's law.Two successive equations describing the Death Phase were proposed basedon the hypothesis that the Death rate accelerated with the %PSC until itreached its maximum. From that point the %PSC decreased and the Deathrate reduced. Our model fitted very well the cultures grown in the photobioreactor developed in our laboratory.
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Changes in Content, Constituents and Distribution of Constitutive and Excreted Sugars of Spirulina (Arthrospira) Maxima in Nutrient-Limited Batch Cultures
Algae and their Biotechnological Potential, 2001Co-Authors: Jin-lan Xia, Zhen-yuan Nie, J. M. LevertAbstract:Changes in content, constituents and distribution of constitutive and excreted sugars of Spirulina (Arthrospira) maxima in nitrogen or sulfur-limited batch cultures were investigated in this study. The changes were influenced by both age of the culture and availability of nitrogen or sulfur in the medium. Increases in percentage of the constitutive sugars (PSC) took place at the beginning of the decelerating Phase. The increase was mainly due to the accumulation of internal soluble polysaccharides (SIPS). The maximal concentration of PSC per unit volume of reactor was obtained at the beginning of the Death Phase, at which time cells from nitrogen-limited batch cultures contained about 66% of sugars. SIPS representing 76% of PSC consisted of mainly glucose. The monosaccharide of cell wall polysaccharides (CWPS) was also glucose. Sugars from the external layers (PSEL) or from culture medium (PSCM) contained a mixture of monosaccharides. Selective fractionation of PSCM, PSEL, SIPS and CWPS was obtained by a sequential extraction procedure.
Indranil Chatterjee - One of the best experts on this subject based on the ideXlab platform.
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Staphylococcus aureus ClpC is involved in protection of carbon-metabolizing enzymes from carbonylation during stationary growth Phase
International Journal of Medical Microbiology, 2011Co-Authors: Indranil Chatterjee, Etienne Maisonneuve, Benjamin Ezraty, Mathias Herrmann, Sam DukanAbstract:The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Among them, ClpC, belonging to the Hsp100/Clp ATPase family, seems to play an important role. For instance, we previously demonstrated that a functional clpC deletion resulted in enhanced survival in the late stationary Phase (Death Phase period) compared to the parental S. aureus strain. However, the mechanisms for the enhanced survival of a S. aureus clpC mutant during the Death Phase period are still elusive. In Escherichia coli, among the factors that might lead to bacterial cell Death during stationary Phase, the amount of protein aggregates and/or oxidized proteins appears to be of major importance. Thus, in the present study, we have evaluated protein aggregates and carbonylated protein (as a marker of protein oxidation) contents both in the wild type and in an S. aureus clpC mutant during the exponential growth Phase and the Death Phase. Whereas at all time points the tested clpC mutant exhibits the same amount of protein aggregates as the WT strain, the total amount of carbonylated proteins appears to be lower in the clpC mutant. Moreover, we observed that at the entrance of the Death Phase carbon-metabolizing enzymes [such as the TCA cycle enzymes Mqo2 (malate: quinone oxidoreductase) and FumC/CitG (fumarate hydratase)] albeit not the bulk proteins are carbonylated to a larger extent in the clpC mutant. Reduced activity of the TCA cycle due to specific carbonylation of these proteins will result in a decrease of endogenous oxidative stress which in turn might confer enhanced survival of the clpC mutant during the Death Phase period thus contributing to bacterial longevity and chronic infection.
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staphylococcus aureus clpc is required for stress resistance aconitase activity growth recovery and Death
Journal of Bacteriology, 2005Co-Authors: Indranil Chatterjee, Petra Becker, Matthias Grundmeier, Markus Bischoff, Greg A Somerville, Georg Peters, Bhanu Sinha, Niamh Harraghy, Richard A Proctor, Mathias HerrmannAbstract:The ability of Staphylococcus aureus to adapt to various conditions of stress is the result of a complex regulatory response. Previously, it has been demonstrated that Clp homologues are important for a variety of stress conditions, and our laboratory has shown that a clpC homologue was highly expressed in the S. aureus strain DSM20231 during biofilm formation relative to expression in planktonic cells. Persistence and long-term survival are a hallmark of biofilm-associated staphylococcal infections, as cure frequently fails even in the presence of bactericidal antimicrobials. To determine the role of clpC in this context, we performed metabolic, gene expression, and long-term growth and survival analyses of DSM20231 as well as an isogenic clpC allelic-replacement mutant, a sigB mutant, and a clpC sigB double mutant. As expected, the clpC mutant showed increased sensitivity to oxidative and heat stresses. Unanticipated, however, was the reduced expression of the tricarboxylic acid (TCA) cycle gene citB (encoding aconitase), resulting in the loss of aconitase activity and preventing the catabolization of acetate during the stationary Phase. clpC inactivation abolished post-stationary-Phase recovery but also resulted in significantly enhanced stationary-Phase survival compared to that of the wild-type strain. These data demonstrate the critical role of the ClpC ATPase in regulating the TCA cycle and implicate ClpC as being important for recovery from the stationary Phase and also for entering the Death Phase. Understanding the stationary- and post-stationary-Phase recovery in S. aureus may have important clinical implications, as little is known about the mechanisms of long-term persistence of chronic S. aureus infections associated with formation of biofilms.
Salina Parveen - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Previous Life Cycle Phase on the Growth Kinetics, Morphology, and Antibiotic Resistance of Salmonella Typhimurium DT104 in Brain Heart Infusion and Ground Chicken Extract.
Frontiers in Microbiology, 2019Co-Authors: Jabari L. Hawkins, Joseph Uknalis, Thomas P Oscar, Jurgen G. Schwarz, Bob Vimini, Salina ParveenAbstract:Growth models are predominately used in the food industry to estimate the potential growth of selected microorganisms under environmental conditions. The growth kinetics, cellular morphology, and antibiotic resistance were studied throughout the life cycle of Salmonella Typhimurium. The effect of the previous life cycle Phase [late log Phase (LLP), early stationary Phase (ESP), late stationary Phase (LSP), and early Death Phase (EDP)] of Salmonella after reinoculation in brain heart infusion broth (BHI), ground chicken extract (GCE), and BHI at pH 5, 7, and 9 and salt concentrations 2, 3, and 4% was investigated. The growth media and previous life cycle Phase had significant effects on the lag time (λ), specific growth rate (μmax), and maximum population density (Ymax). At 2 and 4% salt concentration, the LLP had the significantly (p
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The Effect of Previous Life Cycle Phase on the Growth Kinetics, Morphology and Antibiotic Resistance of Salmonella Typhimurium DT104 in Brain Heart Infusion and Ground Chicken Extract
bioRxiv, 2018Co-Authors: Jabari L. Hawkins, Joseph Uknalis, Thomas P Oscar, Jurgen G. Schwarz, Bob Vimini, Salina ParveenAbstract:Growth models are predominately used in the food industry to estimate the potential growth of select microorganisms under environmental conditions. The growth kinetics, cellular morphology and antibiotic resistance were studied throughout the life cycle of Salmonella Typhimurium. The effect of the previous life cycle Phase (late log Phase [LLP], early stationary Phase [ESP], late stationary Phase [LSP] and early Death Phase [EDP]) of Salmonella after reinoculation in brain heart infusion broth (BHI), ground chicken extract (GCE) and BHI at pH 5, 7 and 9 and salt concentrations 2, 3 and 4% was investigated. The growth media and previous life cycle Phase had significant effects on the lag time (λ), specific growth rate (µ max ) and maximum population density (Y max ). At 2% and 4% salt concentration the LLP had the significantly (P max (1.07 and 0.69 log CFU/mL/h, respectively). As the cells transitioned from the late log Phase (LLP) to the early Death Phase (EDP), the λ significantly (P max than the LLP, ESP and LSP. As the cells transitioned from a rod shape to a coccoid shape in the EDP, the cells were more susceptible to antibiotics. The cells regained their resistance as they transitioned back to a rod shape from the EDP to the log and stationary Phase. Our results revealed that growth kinetics, cell9s length, shape and antibiotic resistance were significantly affected by the previous life cycle Phase.
J. M. Levert - One of the best experts on this subject based on the ideXlab platform.
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Modeling the growth curve for Spirulina (Arthrospira) maxima, a versatile microalga for producing uniformly labelled compounds with stable isotopes
Journal of Applied Phycology, 2001Co-Authors: J. M. Levert, Jin-lan XiaAbstract:The paper presents a five-Phase model to describe batch culture of Spirulina maxima under limitations of light and nutrients nitrogen andsulfur. The general equation for the exponential, linear, decelerating andstationary Phases of the growth curve took into account that (i) the specificgrowth rate was proportional to the local light intensity in thephotobioreactor; (ii) light attenuation was due to cell's absorption andreflection and observed the Lambert-Beer's law with a total absorptioncoefficient (εT) that was the sum of absorption coefficient(εa) and reflection coefficient (εr); (iii) thecomposition of the alga and its absorption εa changed withtime and (iv) the specific growth rate was influenced by nutrients ofnitrogen and sulfur in the culture medium according to a Monod's law.Two successive equations describing the Death Phase were proposed basedon the hypothesis that the Death rate accelerated with the %PSC until itreached its maximum. From that point the %PSC decreased and the Deathrate reduced. Our model fitted very well the cultures grown in the photobioreactor developed in our laboratory.
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Changes in Content, Constituents and Distribution of Constitutive and Excreted Sugars of Spirulina (Arthrospira) Maxima in Nutrient-Limited Batch Cultures
Algae and their Biotechnological Potential, 2001Co-Authors: Jin-lan Xia, Zhen-yuan Nie, J. M. LevertAbstract:Changes in content, constituents and distribution of constitutive and excreted sugars of Spirulina (Arthrospira) maxima in nitrogen or sulfur-limited batch cultures were investigated in this study. The changes were influenced by both age of the culture and availability of nitrogen or sulfur in the medium. Increases in percentage of the constitutive sugars (PSC) took place at the beginning of the decelerating Phase. The increase was mainly due to the accumulation of internal soluble polysaccharides (SIPS). The maximal concentration of PSC per unit volume of reactor was obtained at the beginning of the Death Phase, at which time cells from nitrogen-limited batch cultures contained about 66% of sugars. SIPS representing 76% of PSC consisted of mainly glucose. The monosaccharide of cell wall polysaccharides (CWPS) was also glucose. Sugars from the external layers (PSEL) or from culture medium (PSCM) contained a mixture of monosaccharides. Selective fractionation of PSCM, PSEL, SIPS and CWPS was obtained by a sequential extraction procedure.
