Bacteriocins of gram-positive bacteria.

Phosphate solubilizing bacteria and their role in plant growth promotion

Organic acids, such as malate, citrate and oxalate, have been proposed to be involved in many processes operating in the rhizosphere, including nutrient acquisition and metal detoxification, alleviation of anaerobic stress in roots, mineral weathering and pathogen attraction. A full assessment of their role in these processes, however, cannot be determined unless the exact mechanisms of plant organic acid release and the fate of these compounds in the soil are more fully understood. This review therefore includes information on organic acid levels in plants (concentrations, compartmentalisation, spatial aspects, synthesis), plant efflux (passive versus active transport, theoretical versus experimental considerations), soil reactions (soil solution concentrations, sorption) and microbial considerations (mineralization). In summary, the release of organic acids from roots can operate by multiple mechanisms in response to a number of well-defined environmental stresses (e.g., Al, P and Fe stress, anoxia): These responses, however, are highly stress- and plant-species specific. In addition, this review indicates that the sorption of organic acids to the mineral phase and mineralisation by the soil's microbial biomass are critical to determining the effectiveness of organic acids in most rhizosphere processes.

Organic acids in the rhizosphere: a critical review

Bile salt biotransformations by human intestinal bacteria.

Mechanisms of membrane toxicity of hydrocarbons.

https://pure.rug.nl/ws/files/13640729/1995MicrobiolRevvdRest.pdf

The plasma membrane of Saccharomyces cerevisiae: structure, function, and biogenesis.

Anticancer Drugs, Ionophoric Peptides, and Steroids as Substrates of the Yeast Multidrug Transporter Pdr5p

Lactobacillus buchneri ST2A vigorously decarboxylates histidine to the biogenic amine histamine, which is excreted into the medium Cells grown in the presence of histidine generate both a transmembrane pH gradient, inside alkaline, and an electrical potential (delta psi), inside negative, upon addition of histidine Studies of the mechanism of histidine uptake and histamine excretion in membrane vesicles and proteoliposomes devoid of cytosolic histidine decarboxylase activity demonstrate that histidine uptake, histamine efflux, and histidine/histamine exchange are electrogenic processes Histidine/histamine exchange is much faster than the unidirectional fluxes of these substrates, is inhibited by an inside-negative delta psi and is stimulated by an inside positive delta psi These data suggest that the generation of metabolic energy from histidine decarboxylation results from an electrogenic histidine/histamine exchange and indirect proton extrusion due to the combined action of the decarboxylase and carrier-mediated exchange The abundance of amino acid decarboxylation reactions among bacteria suggests that this mechanism of metabolic energy generation and/or pH regulation is widespread

/pdf/generation-of-a-proton-motive-force-by-histidine-4j42rt1tna.pdf

Generation of a Proton Motive Force by Histidine Decarboxylation and Electrogenic Histidine/Histamine Antiport in Lactobacillus buchneri

The interaction of the peptide antibiotic nisin with liposomes has been studied. The effect of this interaction was analyzed on the membrane potential (inside negative) and the pH gradient (inside alkaline) in liposomes made from Escherichia coli phosphatidylethanolamine and egg phosphatidylcholine (9:1, wt/wt). The membrane potential and pH gradient were generated by artificial ion gradients or by the oxidation of ascorbate, N,N,N',N'-tetramethyl-p-phenylenediamine, and cytochrome c by the beef heart cytochrome c oxidase incorporated in the liposomal membranes. Nisin dissipated the membrane potential and the pH gradient in both types of liposomes and inhibited oxygen consumption by cytochrome c oxidase in proteoliposomes. The dissipation of the proton motive force in proteoliposomes was only to a minor extent due to a decrease of the oxidase activity by nisin. The results in these model systems show that a membrane potential and/or a pH gradient across the membrane enhances the activity of nisin. Nisin incorporates into the membrane and makes the membrane permeable for ions. As a result, both the membrane potential and pH gradient are dissipated. The activity of nisin was found to be influenced by the phospholipid composition of the liposomal membrane.

Mechanism of action of the peptide antibiotic nisin in liposomes and cytochrome c oxidase-containing proteoliposomes.

Lactococcin A is a bacteriocin produced by Lactococcus lactis. Its structural gene has recently been cloned and sequenced (M. J. van Belkum, B. J. Hayema, R. E. Jeeninga, J. Kok, and G. Venema, Appl. Environ. Microbiol. 57:492-498, 1991). Purified lactococcin A increased the permeability of the cytoplasmic membrane of L. lactis and dissipated the membrane potential. A significantly higher concentration of lactococcin A was needed to dissipate the membrane potential in an immune strain of L. lactis. Lactococcin A at low concentrations (0.029 microgram/mg of protein) inhibited secondary and phosphate-bond driven transport of amino acids in sensitive cells and caused efflux of preaccumulated amino acids. Accumulation of amino acids by immune cells was not affected by this concentration of lactococcin A. Lactococcin A also inhibited proton motive force-driven leucine uptake and leucine counterflow in membrane vesicles of the sensitive strain but not in membrane vesicles of the immune strain. These observations indicate that lactococcin A makes the membrane permeable for leucine in the presence or absence of a proton motive force and that the immunity factor(s) is membrane linked. Membrane vesicles of Clostridium acetobutylicum, Bacillus subtilis, and Escherichia coli were not affected by lactococcin A, nor were liposomes derived from phospholipids of L. lactis. These results indicate that lactococcin A acts on the cytoplasmic membrane and is very specific towards lactococci. The combined results obtained with cells, vesicles, and liposomes suggest that the specificity of lactococcin A may be mediated by a receptor protein associated with the cytoplasmic membrane.

/pdf/the-bacteriocin-lactococcin-a-specifically-increases-zwc8fpj09k.pdf

The bacteriocin lactococcin A specifically increases permeability of lactococcal cytoplasmic membranes in a voltage-independent, protein-mediated manner.

Wn Konings

Papers

The plasma membrane of Saccharomyces cerevisiae: structure, function, and biogenesis.

Anticancer Drugs, Ionophoric Peptides, and Steroids as Substrates of the Yeast Multidrug Transporter Pdr5p

Generation of a Proton Motive Force by Histidine Decarboxylation and Electrogenic Histidine/Histamine Antiport in Lactobacillus buchneri

Mechanism of action of the peptide antibiotic nisin in liposomes and cytochrome c oxidase-containing proteoliposomes.

The bacteriocin lactococcin A specifically increases permeability of lactococcal cytoplasmic membranes in a voltage-independent, protein-mediated manner.