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K Poralla

Publications and source records attributed to K Poralla.

At least 37 records · Page 2Linked to original sources
PubMed1987

Microbial lipids betrayed by their fossils.

Novel families of microbial lipids have been betrayed by their molecular fossils. They comprise the very widespread and varied hopanoids, and 'orphan' lipids. Membrane reinforcement appears to be universally achieved by these polyterpenoids; a hypothetical phylogenetic tree comprises the above, some postulated intermediates, bacterial carotenoids, cycloartenol, and finally cholesterol.

Bacteria↗
PubMed1984

[Spoilage of fruit juice by bacilli: isolation and characterization of the spoiling microorganisms].

A Bacillus-strain was isolated from spoiled apple juice. This strain was acidophilic with a growth range between pH 2.5 and 5.5. Lipid analysis demonstrated the occurrence of omega-cyclohexane fatty acids and hopanoids. As these cell constituents have among bacilli been found only in Bacillus acidocaldarius strains, our isolated microorganism seems to be related to this species. Our organism could be a threat to fruit juices during storage at elevated temperatures (greater than or equal to 26 degrees C) because its spores were able to survive pasteurization conditions.

Bacillus↗
PubMed1983

Interaction of hopanoids with phosphatidylcholines containing oleic and omega-cyclohexyldodecanoic acid in lipid bilayer membranes.

Lipid bilayer membranes were made from hopanoid phosphatidylcholine mixtures dissolved in decane. The specific capacity of the mixed membranes was found to increase with increasing hopanoid content. This indicates an interaction between hopanoids and lipids which leads to a reduction of the chemical potential of the solvent in the membranes. The structural properties of mixtures of hopanoids and phosphatidylcholines were investigated using charged probe molecules, the negatively charged lipophilic ions dipicrylamine (DPA) and tetraphenylborate (TphiB) and the positively charged potassium complex PV-K+ (PV, cyclo (D-Val-L-Pro-L-Val-D-Pro)3). The transport properties of the lipophilic ions in the mixed membranes indicate that the electrical properties like dipolar potential and surface potentials of phosphatidylcholine membranes are not changed by the insertion of the hopanoids. The translocation rate constant K of the PV-K+ complex is drastically reduced in the hopanoid phosphatidylcholine membranes with increasing hopanoid content. This effect is discussed on the basis of an alteration of the microviscosity in the mixed membranes. There exists a close analogy between the action of cholesterol and hopanoids in bilayer membranes from phosphatidylcholines. A bilayer membrane composed of di-omega-cyclohexyldodecanoyl-phosphatidylcholine (DCPC) was found to possess a higher specific capacity as compared to other phosphatidylcholines. Also a lower translocation rate constant for PV-K+ was observed which may be caused by the relative high microviscosity of this lipid even above the phase transition temperature.

Bacillus↗
PubMed1982

The influence of hopanoids on growth of Mycoplasma mycoides.

Hopane glycolipid, isolated from Bacillus acidocaldarius, was studied in its ability to support growth from Mycoplasma mycoides var. capri as substitute for sterols. All attempts to culture Mycoplasma on hopane glycolipid failed. When added together with cholesterol, the effect of HGL was a reduction in growth rate. The hopanoid diplopterol moderately supported growth of Mycoplasma. This effect was strikingly enhanced in diplopterol adapted cultures. Application of diplopterol via dipalmitoyl-phosphatidylcholine liposomes resulted in an improved growth rate. These results suggested that diplopterol can fulfill sterol function in Mycoplasma membranes.

Adaptation, Physiological↗
PubMed1978

The influence of branched-chain and omega-alicyclic fatty acids on the transition temperature of bacillus subtilis lipids.

The influence of branched-chain and omega-alicyclic fatty acids on the transition temperature of Bacillus subtilis lipids was studied by measuring the fluorescence depolarisation of the probe 1,6-diphenyl-1,3,5-hexatriene incorporated into lipid bilayers. Only anteiso-C15 and C17 fatty acid-enriched lipids showed no transition in the observed temperature range. Compared to the transition of normal lipids iso-fatty acid-enriched lipids have a slightly higher transition temperature. The incorporation of omega-alicyclic fatty acids with increasing size of the alicycle leads to a decrease in the transition temperature. A possible role of omega-cyclohexane fatty acids in Bacillus acidocaldarius is proposed.

Bacillus subtilis↗
PubMed1976

Genetics of borrelidin resistant mutants of Saccharomyces cerivisiae and properties of their threonyl-tRNA-synthetase.

Twenty-two borrelidin resistant mutants of Saccharomyces cerivisiae were isolated, studied genetically and their threonyl-tRNA-synthetase was investigated. The borrelidin resistant mutants are classified into four groups. In the first group borrelidin resistance is coupled to the gene HOM3 coding for aspartokinase, in the second group to the gene LEU1. The borrelidin resistance in group three and four is not coupled to anyone of the genetic markers tested. Borrelidin resistance exhibited dominant behavior in all mutants except in the mutant of group 4. The properties of the ThrRS of the mutants of group one, two and four was found to be like the ones of the wild types. However the mutants of group three exhibit a structurally altered ThrRS, which is no longer inhibited by borrelidin.

Amino Acyl-tRNA Synthetases↗
PubMed1976

Some physiological functions of the L-leucine dehydrogenase in Bacillus subtilis.

Mutants of Bacillus subtilis constitutive for L-leucine dehydrogenase synthesis were selected. Using these mutants we could determine two functional roles for the L-leucine dehydrogenase. This enzyme liberates ammonium ions from branched chain amino acids when supplied as the sole nitrogen source. Another function is to synthesize from L-isoleucine, L-leucine, and L-valine the branched chain alpha-keto acids which are precursors of branched chain fatty acid biosythesis. These results together with the inducibility of the enzyme suggest that the L-leucine dehydrogenase has primarily a catabolic rather than an anabolic function in the metabolism of Bacillus subtilis.

Amino Acid Oxidoreductases↗
PubMed1976

Synthesis of omega-alicyclic fatty acids from cyclic precursors in Bacillus subtilis.

A mutant of Bacillus subtilis synthesizes a variety of omega-alicyclic fatty acids when fed with the respective alicyclic carboxylic acids. These fatty acids are: omega-cyclopropane, omega-cyclobutane, omega-cyclopentane, omega-cyclohexane, and omega-cyclohexene fatty acids. These unusual fatty acids did not lead to an inhibition of growth at 37 degrees C and pH 7. The selective advantage of these fatty acids under extrene conditions was studied in comparison with the acidophilic, thermophilic bacterium B. acidocaldarius, which normally contains a high proportion of omega-cyclohexane fatty acids.

Bacillus↗