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Unsaturated fatty acid requirement inEscherichia coli: Mechanism of palmitate-induced inhibition of growth of strain WN1 (1982)

Ingram, L. O. ; Eaton, L. C. ; Erdos, G. W. ; [et al.]

Springer

The journal of membrane biology 65 (1982), S. 31-40

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ISSN: 1432-1424

Keywords: lipids ; membranes ; Escherichia coli ; temperature adaptation ; fatty acids ; phase separations

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Summary The minimum requirement for unsaturated fatty acids was investigated inE. coli using a mutant impaired in the synthesis of vaccenic acid. Exogenously supplied palmitic acid was incorporated by this mutant which led to a reduction in the proportion of cellular unsaturated fatty acids. Growth was impaired as the level of saturated fatty acids approached 76% at 37°C and 60% at 30°C. The basis of this growth inhibition was investigated. Most transport systems and enzymes examined remained active in palmitate-grown cells although the specific activities of glutamate uptake and succinic dehydrogenase were depressed 50%. Fluorescent probes of membrane organization indicated that fluidity decreased with palmitate incorportation. Temperature scans with parinaric acid indicated that rigid lipid domains exist in palmitategrown cells at their respective growth temperature. Freeze-fracture electron microscopy confirmed the presence of phase separations (particle-free areas) in palmitate-grown cells held at their growth temperature prior to quenching. The extent of this separation into particle-free and particle-enriched domains was equivalent to that induced by a shift to 0°C in control cells. The incorporation of palmitate increased nucleotide leakage over threefold. The cytoplasmic enzyme β-galactosidase was released into the surrounding medium as the concentration of unsaturated fatty acid approached the minimum for a particular growth temperature. Lysis was observed as a decrease in turbidity when cells which had been grown with palmitate were shifted to a lower growth temperature. From these results we propose that leakage and partial lysis are the major factors contributing to the apparent decrease in growth rate caused by the excessive incorporation of palmitate. Further, we propose that membrane integrity may determine the minimum requirement for unsaturated fatty acids inE. coli rather than a specific effect on membrane transport and/or membrane-bound enzymes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01870466

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Parametric studies of ethanol production form xylose and other sugars by recombinant Escherichia coliFlorida Agricultural Experiment Station Publication Number R-01082. (1991)

Beall, David S. ; Ohta, K. ; Ingram, L. O.

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 38 (1991), S. 296-303

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ISSN: 0006-3592

Keywords: ethanol ; genetic engineering ; Escherichia coli ; lignocellulose ; xylose ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: The conversion of xylose to ethanol by recombinant Escherichia coli has been investigated in pH-controlled batch fermentations. Chemical and environmental parameters were varied to determine tolerance and to define optimal conditions. Relatively high concentrations of ethanol (56 g/L) were produced from xylose with excellent efficiencies. Volumetric productivities of up to 1.4 g ethanol/L h were obtained. Productivities, yields, and final ethanol concentrations achieved from xylose with recombinant E. coli exceeded the reported values with other organisms. In addition to xylose, all other sugar constituents of biomass (glucose, mannose, arabinose, and galactose) were efficiently converted to ethanol by recombinant E. coli. Unusually low inocula equivalent to 0.033 mg of dry cell weight/L were adequate for batch fermentations. The addition of small amounts of calcium, magnesium, and ferrous ions stimulated fermentation. The inhibitory effects of toxic compounds (salts, furfural, and acetate) which are present in hemicellulose hydrolysates were also examined.

Additional Material: 5 Ill.