Heat Adaptation Alters
            <i>Escherichia coli</i>
            O157:H7 Membrane Lipid Composition and Verotoxin Production

Yuk, Hyun‐Gyun; Marshall, Douglas L.

doi:10.1128/aem.69.9.5115-5119.2003

Cited by 80 publications

(48 citation statements)

References 28 publications

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“…Being strain specific, lipid profiles of E. coli membranes nevertheless overlap (22,44,45). Ions corresponding to the m/z of several of these fatty acids were seen in the mass spectra of P450 lipid extracts (Figs.…”

Section: Discussionmentioning

confidence: 99%

Phospholipids modify substrate binding and enzyme activity of human cytochrome P450 27A1

Murtazina

Andersson

Hahn

et al. 2004

Journal of Lipid Research

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Cytochrome P450 27A1 (P450 27A1) is an important metabolic enzyme involved in bile acid biosynthesis and the activation of vitamin D 3 in mammals. Recombinant P450 27A1 heterologously expressed in Escherichia coli was found to be copurified with phospholipids (PLs). The PL content varied in different preparations and was dependent on the purification protocol. A link between the increased amounts of PLs and deterioration of the enzyme substrate binding properties was also observed. Tandem negative ionization mass spectrometry identified phosphatidylglycerol (PG) as the major PL copurified with P450 27A1. Subsequent reconstitution of P450 into exogenous PG vesicles assessed the effect of this contamination on substrate binding and enzyme activity. Two other PLs, phosphatidylethanolamine (PE) and phosphatidylserine (PS), were also tested. PG and PE increased the K d for 5 ␤ -cholestane-3 ␣ ,7 ␣ ,12 ␣ -triol and cholesterol binding, whereas PS had no effect on either substrate binding. PG and PE did not significantly alter 5 ␤ -cholestane-3 ␣ ,7 ␣ ,12 ␣ -triol hydroxylase activity and even stimulated cholesterol hydroxylase activity. PS inhibited 5 ␤ -cholestane-3 ␣ ,7 ␣ ,12 ␣ -triol hydrolyase activity and had no effect on cholesterol hydroxylase activity. Our study shows the potential for PLs to regulate the activity of P450 27A1 in vivo and alter the amount of cholesterol degraded through the "classical" and "alternative" bile acid biosynthetic pathways.

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Section: Discussionmentioning

confidence: 99%

Phospholipids modify substrate binding and enzyme activity of human cytochrome P450 27A1

Murtazina

Andersson

Hahn

et al. 2004

Journal of Lipid Research

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“…An example of such an alteration is the homeoviscous adaptation that occurs with heat stress (47). Also, increasing evidence suggests that structural modification of the OM can change membrane functions by regulating the expression, transportation, or secretion of the membrane-associated proteins (3,62). Pathogens that thrive in diverse habitats likely adapt their membrane structure to optimize survival under various in vivo and ex vivo conditions.…”

mentioning

confidence: 99%

Involvement of theEscherichia coliO157:H7(pO157)ecfOperon and Lipid A Myristoyl Transferase Activity in Bacterial Survival in the Bovine Gastrointestinal Tract and Bacterial Persistence in Farm Water Troughs

et al. 2005

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Escherichia coli O157:H7 is an important food-borne pathogen that causes hemorrhagic colitis and the hemolytic-uremic syndrome in humans. Recently, we reported that the pO157 ecf (E. coli attaching and effacing gene-positive conserved fragments) operon is thermoregulated by an intrinsically curved DNA and contains the genes for bacterial surface-associated proteins, including a second copy of lipid A myristoyl transferase, whose chromosomal copy is the lpxM gene product. E. coli O157:H7 survives and persists well in diverse environments from the human and bovine gastrointestinal tracts (GIT) to nutrient-dilute farm water troughs. Transcriptional regulation of the ecf operon by intrinsic DNA curvature and the genetic redundancy of lpxM that is associated with lipid A modification led us to hypothesize that the pO157 ecf operon and lpxM are associated with bacterial survival and persistence in various in vivo and ex vivo environments by optimizing bacterial membrane structure and/or integrity. To test this hypothesis, three isogenic ecf operon and/or lpxM deletion mutants of E. coli O157:H7 ATCC 43894 were constructed and analyzed in vitro and in vivo. The results showed that a double mutant carrying deletions in the ecf and lpxM genes had an altered lipid A structure and membrane fatty acid composition, did not survive passage through the bovine GIT, did not persist well in farm water troughs, had increased susceptibility to a broad spectrum of antibiotics and detergents, and had impaired motility. Electron microscopic analyses showed gross changes in bacterial membrane structure.The outer membrane (OM) of gram-negative bacteria provides an effective physical barrier to various environments (39). An important component for this function is the lipopolysaccharide (LPS), which is a highly ordered and rigid quasicrystalline structure occupying the outer leaflet of the bacterial OM (29). The inner leaflet of the OM is composed of glycerophospholipids. It is well known that under stress conditions, bacteria can alter their membrane lipid composition (52). An example of such an alteration is the homeoviscous adaptation that occurs with heat stress (47). Also, increasing evidence suggests that structural modification of the OM can change membrane functions by regulating the expression, transportation, or secretion of the membrane-associated proteins (3, 62). Pathogens that thrive in diverse habitats likely adapt their membrane structure to optimize survival under various in vivo and ex vivo conditions. Escherichia coli O157:H7 is the most common serotype of Shiga toxin-producing E. coli (STEC) associated with hemorrhagic colitis and the hemolytic-uremic syndrome in the United States and other countries around the world (36). Healthy cattle are the principal reservoir of this microorganism, and a bacterial colonization site has been recently identified at the most distal part of the bovine gastrointestinal tract (GIT), the recto-anal junction (RAJ) mucosa (21, 37). Major virulence factors identified in animal models incl...

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“…Generally, environmental stresses induce the alteration of membrane lipid composition as cells attempt to cope with these stresses. For example, growth temperature affects membrane fluidity by regulating the ratio of saturated to unsaturated fatty acids (35,36,37).…”

mentioning

confidence: 99%

Adaptation of Escherichia coli O157:H7 to pH Alters Membrane Lipid Composition, Verotoxin Secretion, and Resistance to Simulated Gastric Fluid Acid

Yuk

Marshall

2004

Appl Environ Microbiol

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140

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The influence of adaptation to pH (from pH 5.0 to 9.0) on membrane lipid composition, verotoxin concentration, and resistance to acidic conditions in simulated gastric fluid (SGF) (pH 1.5, 37°C) was determined for Escherichia coli O157:H7 (HEC, ATCC 43895), an rpoS-deficient mutant of ATCC 43895 (HEC-RM, FRIK 816-3), and nonpathogenic E. coli (NPEC, ATCC 25922). Regardless of the strain, D values (in SGF) of acid-adapted cells were higher than those of non-acid-adapted cells, with HEC adapted at pH 5.0 having the greatest D value, i.e., 25.6 min. Acid adaptation increased the amounts of palmitic acid (C16:0) and decreased cis-vaccenic acid (C18:17c) in the membrane lipids of all strains. The ratio of cis-vaccenic acid to palmitic acid increased at acidic pH, causing a decrease in membrane fluidity. HEC adapted to pH 8.3 and HEC-RM adapted to pH 7.3 exhibited the greatest verotoxin concentrations (2,470 and 1,460 ng/ml, respectively) at approximately 10 8 CFU/ml. In addition, the ratio of extracellular to intracellular verotoxin concentration decreased at acidic pH, possibly due to the decrease of membrane fluidity. These results suggest that while the rpoS gene does not influence acid resistance in acid-adapted cells it does confer decreased membrane fluidity, which may increase acid resistance and decrease verotoxin secretion.

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Heat Adaptation Alters Escherichia coli O157:H7 Membrane Lipid Composition and Verotoxin Production

Cited by 80 publications

References 28 publications

Phospholipids modify substrate binding and enzyme activity of human cytochrome P450 27A1

Phospholipids modify substrate binding and enzyme activity of human cytochrome P450 27A1

Involvement of theEscherichia coliO157:H7(pO157)ecfOperon and Lipid A Myristoyl Transferase Activity in Bacterial Survival in the Bovine Gastrointestinal Tract and Bacterial Persistence in Farm Water Troughs

Adaptation of Escherichia coli O157:H7 to pH Alters Membrane Lipid Composition, Verotoxin Secretion, and Resistance to Simulated Gastric Fluid Acid

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