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

2004 ◽  
Vol 70 (6) ◽  
pp. 3500-3505 ◽  
Author(s):  
Hyun-Gyun Yuk ◽  
Douglas L. Marshall
Keyword(s):  
Escherichia Coli ◽  
Membrane Fluidity ◽  
Lipid Composition ◽  
Vaccenic Acid ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Membrane Lipid ◽  
Simulated Gastric Fluid ◽  
Acidic Ph ◽  
Membrane Lipid Composition

ABSTRACT 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 (C18:1ω7c) 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 108 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.

Influence of Acetic, Citric, and Lactic Acids on Escherichia coli O157:H7 Membrane Lipid Composition, Verotoxin Secretion, and Acid Resistance in Simulated Gastric Fluid†

2005 ◽  
Vol 68 (4) ◽  
pp. 673-679 ◽  
Author(s):  
HYUN-GYUN YUK ◽  
DOUGLAS L. MARSHALL
Keyword(s):  
Acetic Acid ◽  
Lactic Acid ◽  
Organic Acid ◽  
Lipid Composition ◽  
Acid Resistance ◽  
Gastric Fluid ◽  
Membrane Lipid ◽  
Simulated Gastric Fluid ◽  
Membrane Lipid Composition ◽  
D Values

The effect of organic acid (acetic, citric, and lactic acids) adaptation at equivalent initial pH values (6.4 and 5.4) on changes in membrane lipid composition, verotoxin concentration, and acid resistance in simulated gastric fluid (pH 1.5, 37°C) was determined for Escherichia coli O157:H7 ATCC 43895 (HEC) and an rpoS mutant of E. coli O157:H7 ATCC 43895 (RM, FRIK 816-3). For HEC, lactic acid–adapted (pH 5.4) cells had the greatest D-value (32.2 min) and acetic acid–adapted (pH 5.4) cells had the smallest D-value (16.6 min) in simulated gastric fluid. For RM, D-values of citric and acetic acid–adapted cells were similar to those for nonadapted cells grown at pH 7.3, but D-values increased from 13.1 to 27.9 min in lactic acid–adapted cells (from pH 7.3 to pH 5.4). For both strains, the ratio of cis-vaccenic to palmitic acids decreased for citric and lactic acid–adapted cells, but the ratio increased for acetic acid–adapted cells at pH 5.4. Organic acid–adapted cells produced less total verotoxin than did nonadapted cells at approximately 108 CFU/ml. Extracellular verotoxin concentration proportionally decreased with decreasing pH for both HEC and RM. Changes in membrane lipid composition, verotoxin concentration, and acid resistance in HEC and RM were dependent on both pH and organic acid. Deletion of the rpoS gene did not affect these changes but did decrease acid resistance in citric acid–adapted cells. Results indicate that decreased membrane fluidity may have caused increased acid resistance and decreased verotoxin secretion.

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

2003 ◽  
Vol 69 (9) ◽  
pp. 5115-5119 ◽  
Author(s):  
Hyun-Gyun Yuk ◽  
Douglas L. Marshall
Keyword(s):  
Escherichia Coli ◽  
Lipid Composition ◽  
Membrane Lipids ◽  
Vaccenic Acid ◽  
Membrane Lipid ◽  
Membrane Lipid Composition ◽  
E Coli ◽  
Heat Adaptation ◽  
Mutant Strains ◽  
Composition Changes

ABSTRACT The influence of heat adaptation (growth at 42 and 45°C) on changes in membrane lipid composition and verotoxin concentration of Escherichia coli O157:H7 (ATCC 43895), an rpoS mutant of ATCC 43895 (FRIK 816-3), a verotoxin mutant E. coli O157:H7 (B6-914), and nonpathogenic E. coli (ATCC 25922) was investigated. D values (57°C) of heat-adapted cells were up to 3.9 min longer than those of control cells for all four strains. Heat adaptation increased the amounts of palmitic acid (16:0) and cis-vaccenic acid (18:1ω7c) in membrane lipids of ATCC 43895 and the rpoS mutant, whereas there was a reduction and no change in the amount of cis-vaccenic acid in nonpathogenic and verotoxin mutant E. coli, respectively. The ratio of palmitic to cis-vaccenic acids decreased in ATCC 43895 and in the rpoS mutant, whereas the ratio increased in nonpathogenic E. coli and was not different in the verotoxin mutant with elevated growth temperature. Total verotoxin concentration decreased due to a reduction in intracellular verotoxin amount in heat-adapted ATCC 43895 and rpoS mutant strains. However, extracellular verotoxin concentration increased in heat-adapted cells. The rpoS gene did not influence membrane lipid composition changes although it did affect heat resistance. Results suggest that increased membrane fluidity may have caused increased verotoxin secretion.

Dietary Selenium or Zinc Supplementation Restores Brain Lipid Composition and Membrane Fluidity in Protein-Undernourished Rats

2016 ◽  
Vol 38 (6) ◽  
pp. 397-406
Author(s):  
Olusegun L. Adebayo ◽  
Bamidele A. Salau ◽  
Rajat Sandhir ◽  
Gbenga A. Adenuga
Keyword(s):  
Membrane Fluidity ◽  
Lipid Composition ◽  
Zinc Supplementation ◽  
Protective Role ◽  
Membrane Lipid ◽  
Limited Information ◽  
Total Lipids ◽  
Major Focus ◽  
Membrane Lipid Composition

Studies have shown that protein undernutrition (PU) modifies the membrane lipid composition in the intestine and liver, as well as in plasma and other areas. However, there is limited information on the effect of PU on synaptosomal membrane lipid composition and fluidity and the protective role of selenium (Se) and zinc (Zn), which is a major focus of the present study. For 10 weeks, rats were fed diets containing 16% casein, which constituted the adequate protein diet, or 5% casein, representing the PU diet. The animals were supplemented with Se and Zn at a concentration of 0.15 and 227 mg L-1, respectively, in drinking water for 3 weeks. The results showed a significant increase in total lipids, glycolipids, triglycerides, cholesterol, and the cholesterol/phospholipid (Chol/PL) ratio, and a significant reduction in phospholipids and membrane fluidity. Se and Zn supplementation to PU rats, however, significantly lowered total lipids, glycolipids, triglycerides, cholesterol, and the Chol/PL ratio, while phospholipids and membrane fluidity were significantly restored. It is concluded that a perturbed lipid composition induced by PU affects the membrane structure and fluidity, which in turn influences membrane functions. The study suggests that Se and Zn supplementation might be beneficial in restoring the lipid dyshomeostasis associated with PU.

Ximelagatran increases membrane fluidity and changes membrane lipid composition in primary human hepatocytes

2009 ◽  
Vol 23 (7) ◽  
pp. 1305-1310 ◽  
Author(s):  
Odile Sergent ◽  
Kim Ekroos ◽  
Luz Lefeuvre-Orfila ◽  
Mary Rissel ◽  
Gun-Britt Forsberg ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Lipid Composition ◽  
Membrane Lipid ◽  
Human Hepatocytes ◽  
Membrane Lipid Composition ◽  
Primary Human Hepatocytes

Effects of membrane lipid and fluidity modifications on HIV-1 infectibility of primate lymphocytes in vitro

1990 ◽  
Vol 10 (3) ◽  
pp. 263-270 ◽  
Author(s):  
J. Pascal Zimmer ◽  
Hans A. Lehr ◽  
Christoph Hübner ◽  
Stephan G. Lindner ◽  
Ralf Ramsperger ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Membrane Fluidity ◽  
Lipid Composition ◽  
Membrane Lipid ◽  
Serum Factors ◽  
Membrane Lipid Composition ◽  
Plasma Membrane Lipid ◽  
Hiv 1

Although most non-human primates, except the chimpanzee and the gibbon in vivo are not infectible by HIV-1, lymphocytes of several of these species can be infected by HIV-1 in vitro.In order to investigate whether the in vitro infectibility of primate lymphocytes might be attributed to plasma membrane adaptation processes or to serum factors, we compared HIV-1 infectibility of cultivated peripheral blood lymphocytes of macaques and of baboons on day one and on day ten of cultivation. These data were correlated to plasma membrane lipid composition and membrane fluidity.We found a correlation between increased HIV-1 in vitro infectibility and changes in plasma membrane lipid composition resulting in decreased membrane fluidity of cultured primate lymphocytes.

scholarly journals Structural and Functional Adaptability of Sucrose and Lactose Permeases from Escherichia coli to the Membrane Lipid Composition

Biochemistry ◽  
2020 ◽  
Vol 59 (19) ◽  
pp. 1854-1868
Author(s):  
Heidi Vitrac ◽  
Venkata K. P. S. Mallampalli ◽  
Stavros Azinas ◽  
William Dowhan
Keyword(s):  
Escherichia Coli ◽  
Lipid Composition ◽  
Membrane Lipid ◽  
Membrane Lipid Composition
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