- Volume 131, Issue 1, 1985
Volume 131, Issue 1, 1985
- Physiology And Growth
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Does an Increase in Membrane Unsaturated Fatty Acids Account for Tween 80 Stimulation of Glucosyltransferase Secretion by Streptococcus salivarius?
More LessWhen Streptococcus salivarius was grown in batch culture in the presence of various Tween detergents, the fatty acid moiety of the detergent was incorporated into the lipids of its membrane. Tween 80 (containing primarily oleic acid) markedly stimulated the production of extracellular glucosyltransferase and also increased the degree of unsaturation of the membrane lipid fatty acids. The possibility that an increase in membrane unsaturated fatty acids promoted extracellular glucosyltransferase production was examined by growing cells at different temperatures in the presence or absence of Tween 80. The membrane lipids of cells grown at 30°C, 37°C and 40°C without Tween 80 exhibited unsaturated/saturated fatty acid ratios of 2·06, 1·01 and 0·87 respectively. A significant increase in the production of extracellular glucosyltransferase was observed at 30°C compared to cells grown at 40°C. However, cells produced much more exoenzyme at all temperatures when grown with Tween 80. The results indicated that an increase in the unsaturated fatty acid content of the membrane lipids was not by itself sufficient to account for the stimulation of extracellular glucosyltransferase production by Tween 80, but that the surfactant also had to be present.
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The Effect of Sorbic Acid and Esters of p-Hydroxybenzoic Acid on the Protonmotive Force in Escherichia coli Membrane Vesicles
More LessThe effect of three food preservatives, sorbic acid and methyl and butyl esters of p-hydroxybenzoic acid, on the protonmotive force in Escherichia coli membrane vesicles was investigated. Radioactive chemical probes were used to determine the two components of the protonmotive force: ΔpH (pH difference) and Δψ (membrane potential). Both types of compound selectively eliminated ΔpH across the membrane, while leaving Δψ much less disturbed indicating that transport inhibition by neutralization of the protonmotive force cannot be the only mechanism of action for the food preservatives tested.
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Energy Coupling to K+ Uptake Via the Trk System in Escherichia coli: the Role of ATP
More LessThe dual energy requirement (protonmotive force and ATP) of the Escherichia coli Trk potassium transport system has been investigated. Using inhibitors and unc mutants we show that Trk is not an ATPase but may be regulated by ATP. Possible mechanisms of energy coupling to Trk are discussed.
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Isolation and Partial Characterization of Structural Components of the Walls of Alkalophilic Bacillus Strain C-125
More LessAfter trichloroacetic acid extraction of the walls of alkalophilic Bacillus sp. strain C-125 grown at an alkaline or a neutral pH, two acidic structural polymer fractions were isolated by ionexchange chromatography and gel chromatography. One was a teichuronic acid fraction containing N-acetyl-d-fucosamine, glucuronic acid and galacturonic acid in a molar ratio of 1: 1: 1. This teichuronic acid amounted to 390 μg per mg peptidoglycan in the walls of the bacterium grown at an alkaline pH or 80 μg per mg at a neutral pH. The molecular weight of the teichuronic acid from the cells grown at an alkaline pH was 70000 compared to a molecular weight of 48000 at a neutral pH as estimated by gel chromatography. The other fraction contained glucuronic acid and l-glutamic acid in a molar ratio of 1: 5. This fraction was either a copolymer of both the acids or a mixture of polyglucuronate and polyglutamate. This fraction amounted to 560 μg per mg peptidoglycan in the walls of the bacterium grown at an alkaline pH or 240 μg per mg at a neutral pH. The molecular weight of the fraction from both the wall preparations was about 19000.
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The Effect of Copper Ions on Membrane Content and Methane Monooxygenase Activity in Methanol-grown Cells of Methylococcus capsulatus (Bath)
More LessMethylococcus capsulatus (Bath) was grown in continuous culture with methanol (1·0%, v/v) as sole carbon and energy source. Cells grown on methanol exhibited differences in methane monooxygenase (MMO) activity which were dependent on the concentration of copper sulphate present in the growth medium; an increase in the concentration of copper in the growth medium enhanced both in vivo and in vitro MMO activity. The MMO activity in methanol-grown Methylococcus capsulatus (Bath) was always associated with the particulate fraction of cell-free extracts; at no time was soluble MMO activity detected. In vitro MMO activity was also stimulated by the addition of copper compounds to the assay system and the stimulation was shown to be pH-dependent. The concentration of copper sulphate in the growth medium also determined the intracytoplasmic membrane content of the cells, as judged by electron microscopy of thin-sections, which could be correlated with particulate MMO activity, although it is not possible at this time to say whether the increase in MMO activity seen is due to the increased membrane content or due to the copper ions per se.
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- Systematics
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Nucleic Acid Studies on Halophilic Archaebacteria
More LessDNA–16SrRNA hybridization studies of archaebacterial halophiles revealed nine major groups. High (>45%) DNA–DNA homologies were found only within DNA–rRNA groups. The DNA–DNA homology between the type strains of Halobacterium halobium, Hb. salinarium and Hb. cutirubrum was > 70%. The implications for the taxonomy of the extreme halophiles are discussed.
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Fatty Acid Composition of Oral Isolates of Selenomonas
More LessFatty acids of 16 strains of Selenomonas isolated from the human oral cavity were examined by gas-liquid chromatography. The strains showed similar patterns, characterized by the presence of straight-chain fatty acids in the range C11 to C18. Fatty acids of odd-numbered carbon atoms dominated and the major acids were n-pentadecanoate and 3-hydroxytridecanoate. The general fatty acid pattern of Selenomonas differed distinctly from those of other previously analysed anaerobic or microaerophilic Gram-negative bacilli.
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The Growth-inhibitory Effects of Some Dyes on Different Mycoplasma and Acholeplasma spp.
More LessA microtitre-plate method for evaluating the inhibitory effect of dyes on the growth of mycoplasmas in fluid medium is described. Different species were shown to differ in their sensitivity to dyes. Statistical analysis (a) compared the general sensitivity and resistance of different mycoplasma species to the dyes and (b) showed that the dyes fell into two main groups in their effects on the mycoplasma species.
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