A comparison of characteristic temperatures for transport in two unsaturated fatty acid auxotrophs of escherichia coli

Abstract

'The rate of sugar transport as a function of temperature has been compared in t w o unsaturated fatty acid auxotrophs. O n e of these, the parent strain 30E, can 0-oxidize the unsaturated fatty acid supplements, whereas the p-oxidation defective progeny strain 30Epox-cannot. In a previous study, Arrhenius plots for transport of 0-glucosides and 8-galactosides by strain 30Eoox-~ revealed striking departures from linearity at both a lower and an upper characteristic temperatures. By electron spin resonance (esr) these temperatures were shown t o correlate with the temperatures where the membrane lipids undergo a transition from a totally solid state to a solidliquid equilibrium and from a solid-liquid equilibrium t o a totally liquid state, respectively ( 1 ) . In the present study with strain 30E we have made the following observations:I . Arrhenius plots for transport rate are usually more complex, often revealing three characteristic temperatures. T w o of these correlate with the upper and lower characteristic temperatures observed in strain 30Epox -. The third characteristic temperature falls between the previously described upper and lower ones.2. In cells supplemented during growth with elaidate, the third characteristic temperature was identical within experimental limits for both 0-glucoside and p-galactoside transport. indicating that it is likely t o arise from some interaction in the bulk lipid phase. This conclusion is supported by the fact that the boundary of a change in physical state is also observed at this temperature by electron spin resonance.3. In cells supplemented during growth with oleate, two o r three characteristic temperatures were observed depending upon the transport system studied. Although glucoside and galactoside transport had the same lower characteristic temperature, these systems had n o common upper characteristic temperature.acid, three characteristic temperatures were observed for P-glucoside transport in 120th strains 30E and 30Epox-.4. In cells supplemented during growth with the lipid density label, bromostearic

Physical properties of the lipid phase of membranes from cultured animal cells

“…Membranes were isolated as described by Schimmel et al (12) with the following modifications: (1) Before homogenization, the cell suspension was incubated in Earle's salt solution for 10 min. This facilitated lysis during homogenization.…”

“…These mark the beginning and end of melting of lipids in the membrane bilayer. Correlations between these physical characteristic temperatures and characteristic temperatures for membrane processes have been demonstrated in E. coli (1)(2)(3)(4)(5)(6)(7)(8) and Mycoplasma (9). However, n o detailed correlative study of this sort has been made with animal cell membranes; therefore, much of what is known about lipid phase behavior in animal cells is by inference.…”

“…These mark the beginning and end of melting of lipids in the membrane bilayer. Correlations between these physical characteristic temperatures and characteristic temperatures for membrane processes have been demonstrated in E. coli (1)(2)(3)(4)(5)(6)(7)(8) Recent studies by Wisnieski et al (10) were undertaken to determine the physical state of the plasma membrane of LM cells, a cultured line of mouse fibroblasts. Electron spin resonance (ESR) studies revealed that extracted lipids from these membranes behaved like ideal binary lipid systems in that they displayed only two characteristic temperatures, a t, and a t h , Intact membranes, however, displayed four or more characteristic temperatures by ESR and by biochemical assays of amino acid transport and membrane ATPase.…”

Fusion of dipalmitoylphosphatidylcholine vesicle membranes induced by concanavalin A.

“…In studies of sugar transport across membranes of fatty acid auxotrophic Escherichia coli mutants, optima of the transport rate have been observed at the onset temperatures of lateral phospholipid phase separations (30,31). Similarly, enhanced cation permeabilities have been observed at the transition temperature in pure DPPC (32,33) and in DPPC systems that contain valinomycin (33).…”

Attractant-Directed Motility in Escherichia coli : Requirement for a Fluid Lipid Phase

“…The rate at which cells entered the capillary containing attractant decreased precipitously for elaidate-grown cells over the 32 to 28 C temperature interval, whereas chemotaxis by cells grown with an oleate supplement varied by only 3-fold over the 25 to 35 C decade. Independent physical studies with strain 30E and related strains of E. coli that are auxotrophic for unsaturated fatty acids reveal a characteristic temperature of approximately 30 C, below which all the membrane lipids in elaidate-grown cells are in a frozen, immobile state (5)(6)(7). Cells grown with an oleate supplement, on the other hand, reveal this same phase boundary temperature at approximately 14 C. Comparison of these physiological and physical data indicate that motility in response to the attractant, a-methylaspartate, requires a fluid lipid phase.…”