The positive role of voids in the plasma membrane in growth and energetics of Escherischia coli. (original) (raw)
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The positive role of voids in the plasma membrane in growth and energetics of Escherichia coli
Biophysical Chemistry, 2000
Bacterial respiration, endogenous as well as induced respiration by glucose, lactose and glycine betaine, was found to be sensitive to external solute concentration. Permeability of hydrogen peroxide, a non-electrolyte of molecular Ž size between water and urea, through the bacterial membranes changed directly with the rate of respiration an . activity residing in the bacterial plasma membrane in E. coli and the enhanced permeability and respiratory activity Ž were highly correlated. Hydrogen peroxide permeability and induction of voids spaces in the matrix of the bilayer into which hydrophobic fluorescent probes partition, which in turn were used to assess the modulation of these . cavities were shown to be a direct and excellent measure of leak conductance. Fluorescence intensity and anisotropy Ž . of the extrinsic fluorescent probes incorporated by growing bacteria in their presence decreased with increased respiration in bacteria, consistent with lowered molecular restriction and enhanced hydration in the membrane phase for these probes as seen in dimyristoylphosphatidylcholine bilayers due to phase transition. The physical basis of Ž . osmotic phenomena, as a relevant thermodynamic volume, could relate to water exchange or compression, depending on the osmotic domain. In the domain of compression in bacteria, i.e. well above the isotonic range, the computed activation volume was consistent with voids in the membrane. This study emphasises a major role of leak conductance in bacterial physiology and growth. ᮊ
Biophysical Journal, 1981
ABSTRACr Fluorine-19 nuclear magentic resonance spectroscopy and transport assays have been used to investigate and compare the membrane properties of unsaturated fatty acid auxotrophs of two strains of Escherichia coli, K1060B5 and ML 308-225-UFA-8. A fluorinated analog of myristic acid, 8, 8-difluoromyristic acid, can be incorporated into the membrane phospholipids by substitution for oleate in the growth medium. Growth for one generation on 8, 8-difluoromyristate results in a 20% content of fluorinated fatty acid in the membranes, changes in the protein to lipid ratio, and altered transport of methyl 1B-D-thiogalactopyranoside. The differences in membrane composition and transport behavior seen in oleate supplemented E. coli K1060B5 relative to ML 308-225-UFA-8 are enhanced by the incorporation of 8, 8-difluoromyristate. The phase transition behavior becomes distinctly different and some differences in lipid organization persist above the transition temperature. Concomitantly, the rate and extent of concentration of methyl ,B-D-thiogalactopyranoside are reduced two-fold more in E. coli K1060B5 compared to ML 308-225-UFA-8. Such behavior suggests that these fluorinated fatty acid supplemented strains of E. coli are useful to study subtle differences in protein-lipid interactions and their effects on the function of membranebound enzymes. . However, the nature of the membrane architecture surrounding the site of transport of these substances is not fully understood. Since the lactose carrier protein (or the so-called "permease") has
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1975
Escherichia coli and two partial revertants of that mutant were examined for the ability to generate a high energy membrane state with Dlactate or ATP, as measured by the quenching of the fluorescent dye quinacrine, 2. All three strains showed reductions in the aerobically-driven quenching of fluorescence compared to the wild type, but the reduction could be reversed by the addition of either N,N'-dicyclohexylcarbodiimide or the crude soluble ATPase of the wild type. 3. The mutant exhibited a decreased ability to accumulate sugars and amino acids and showed an increased permeability to protons. 4. One partial revertant showed a slight increase in active transport and a slight decrease in proton permeability. 5. The other partial revertant showed a large increase in transport ability and a large decrease in proton permeability. 6. A model is proposed in which the conformation of the Mg2+-ATPase is important in the utilization of energy derived from the electron transport chain and this function is independent of the catalytic activity of the Mg 2 ÷-ATPase.
BIO-PROTOCOL
Membrane fluidity is a key parameter of bacterial membranes that undergoes quick adaptation in response to environmental challenges and has recently emerged as an important factor in the antibacterial mechanism of membrane-targeting antibiotics. The specific level of membrane fluidity is not uniform across the bacterial cell membrane. Rather, specialized microdomains associated with different cellular functions can exhibit fluidity values that significantly deviate from the average. Assessing changes in the overall membrane fluidity and formation of membrane microdomains is therefore pivotal to understand both the functional organization of the bacterial cell membrane as well as antibiotic mechanisms. Here we describe how two fluorescent membrane dyes, laurdan and DiIC12, can be employed to assess membrane fluidity in living bacteria. We focus on Bacillus subtilis, since this organism has been relatively well-studied with respect to membrane domains. However, we also describe how these assays can be adapted for other bacteria such as Staphylococcus aureus and Streptococcus pneumoniae.
Turbidity Change During Glucose Permeation in Escherichia COLI1
Journal of Bacteriology, 1963
Rogers, Dexter (Utah State University, Logan) and Shon-Hua Yu . Turbidity change during glucose permeation in Escherichia coli . J. Bacteriol. 85: 1141–1149. 1963.—In contrast to the normal turbidity decrease, which was observed at pH 5.5, the turbidity of suspensions of Escherichia coli strain A (Weigle) increased during uptake of glucose permease substrates when uptake was studied at pH 6.5. Although the turbidity increase at pH 6.5 was the reverse of the expected change, it correlated with the uptake of substrate. During the later phase of permeation at pH 6.5, both uptake of substrate and turbidity change were reversed. We suggest that the observed turbidity response indicated the accumulation of substrate at the cell membrane when the mechanism for releasing substrate to the cytoplasm was inhibited at pH 6.5. Under this condition, uptake of substrate did not cause swelling because the substrate was osmotically inactive, since it may have been bound to the membrane. Permeability...
Effect of Energy Metabolism on Protein Motility in the Bacterial Outer Membrane
Biophysical Journal, 2009
We demonstrate the energy dependence of the motion of a porin, the l-receptor, in the outer membrane of living Escherichia coli by single molecule investigations. By poisoning the bacteria with arsenate and azide, the bacterial energy metabolism was stopped. The motility of individual l-receptors significantly and rapidly decreased upon energy depletion. We suggest two different causes for the ceased motility upon comprised energy metabolism: One possible cause is that the cell uses energy to actively wiggle its proteins, this energy being one order-of-magnitude larger than thermal energy. Another possible cause is an induced change in the connection between the l-receptor and the membrane structure, for instance by a stiffening of part of the membrane structure. Treatment of the cells with ampicillin, which directly targets the bacterial cell wall by inhibiting cross-linking of the peptidoglycan layer, had an effect similar to energy depletion and the motility of the l-receptor significantly decreased. Since the l-receptor is closely linked to the peptidoglycan layer, we propose that l-receptor motility is directly coupled to the constant and dynamic energy-consuming reconstruction of the peptidoglycan layer. The result of this motion could be to facilitate transport of maltose-dextrins through the porin.
Archives of Biochemistry and Biophysics, 2002
The thermotropic behavior of intact bacterial membranes and vesicles prepared from total and polar lipids isolated from Bacillus subtilis cultures grown at 37°C in normal (LB) and hyperosmotic (LBN) conditions was studied using 1,6-diphenyl-1,3,5-hexatriene (DPH), 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate (TMA-DPH), and 2-diethylamino-6-lauroylnaphthalene (Laurdan) as fluorescent probes. No phase transition of bulk lipids was observed in these preparations at the range of temperature studied. The anisotropy values ðr s Þ for DPH and TMA-DPH in purified membranes showed significant differences between the LB and LBN conditions, suggesting that there was an increase in membrane packing during the adaptation to osmotic stress. Furthermore, generalized polarization (GP) parameters for Laurdan indicated small but significant changes in water relaxation at the membrane hydrophobic/hydrophilic interface. Membrane preparations showed r s higher values than those of lipid vesicles and a higher temperature dependence of the Laurdan GP parameter. This fact indicates that membrane proteins increase the lipid packing and keep the membrane more sensitive to temperature changes.
Microbiological Research, 2011
Assessment of physiological states of individual bacterial cells can be useful in the monitoring of the biotechnological processes. Physiological heterogeneity of Escherichia coli population by respiration activity and membrane potential during growth and starvation in batch cultures was evaluated using 5-cyano-2,3-ditolyl tetrazolium chloride (CTC) and bis-(1,3-dibutylbarbituric acid) trimethine oxo (DiBAC 4)(3) fluorescent probes in combination with flow cytometry. The shares of CTC-reducing cells (CTC þ-cells) and cells with positively charged outside cytoplasmic membrane which were not stained by DiBAC 4 (3) (DC þ-cells), were 90% and 95% in the exponential phase of batch culture, respectively. After short-term starvation for 10 h, the shares of CTC þ-cells and DC þ-cells in the samples taken from the exponential phase dropped to 78% and 72%, respectively. After long-term starvation for 40 days, the share of CTC þ-cells dropped to 5%, whereas the share of DC þ-cells was about 50%. The conclusions from this research are as follows: (a) the physiological heterogeneity of bacterial population increased after starvation; (b) the cell respiratory activity is more sensitive to starvation than the cell membrane potential; (c) a probe for the cell membrane potential DiBAC 4 (3) is more suitable than a probe for the cell respiratory activity CTC in the detection of viable indicator bacteria in environment.