valinomycin and arsenic-acid

A new procedure for transformation of Amycolatopsis (Nocardia) mediterranei LBG A3136 was developed. The method makes use of polyethylene glycol and alkaline cations and enables direct transformation of the A. mediterranei mycelium with high efficiency: more than 10(6) transformants per microgram of DNA were obtained. Transformation of A. mediterranei is stimulated by the ionophore antibiotic valinomycin and abolished by arsenate and p-chloromercuribenzenesulfonate. pMEA123, a vector based on the indigenous plasmid pMEA100 and containing the erythromycin resistance gene, was constructed.

Topics: 4-Chloromercuribenzenesulfonate; Arsenates; Blotting, Southern; Cations; Drug Resistance, Microbial; Electrophoresis, Agar Gel; Erythromycin; Kinetics; Nocardia; Plasmids; Polyethylene Glycols; Transformation, Bacterial; Valinomycin

The respiration rate of Pi-deprived cells of Micrococcus lysodeikticus is markedly increased by Pi, and returns to the original level following Pi consumption. The stimulation of the respiration was found to be specific for Pi and arsenate. Although succinate and valinomycin enhanced the respiration of both Pi-grown and Pi-deprived cells, only the latter could be further stimulated by Pi. The effect of Pi on the respiration rate was found to be concentration dependent. The control of respiration by Pi is due to its rapid uptake and its subsequent polymerization to polyphosphate via ATP. Both of these processes are coupled to proton influx into the cell, and thus stimulate the proton efflux and the respiration rate.

Topics: Adenosine Triphosphate; Arsenates; Micrococcus; Oxygen Consumption; Phosphates; Polyphosphates; Protons; Succinates; Succinic Acid; Valinomycin

It is possible to select transmembrane potential (delta psi)-altered mutants in Streptococcus pneumoniae on the basis of their resistance to the antifolate methotrexate. Comparison of such a mutant strain ( amiA9 ) with its parent was used to evaluate the role of delta psi in the uptake of certain amino acids. The delta psi-dependent uptake of isoleucine, leucine, valine, and asparagine showed a reduced maximum velocity of uptake, and decrease in the transport constant of the energy-dependent, delta psi-independent uptake of lysine, methionine, and glutamine was observed. No reduction of the intracellular pool of ATP or of lactate excretion could be detected in the mutant strain. Moreover, studies on membrane preparations suggest that the phenotype expressed by the amiA mutation is not a consequence of alteration of its ATPase activity or susceptibility to N,N'-dicyclohexylcarbodiimide. Therefore, it is unlikely that the amiA mutation affects the H+ F1F0 ATPase which is involved in the establishment of the proton motive force in anaerobic bacteria. We propose that another function contributes to delta psi in S. pneumoniae. The amiA gene may be the structural gene of that function.

Topics: Adenosine Triphosphatases; Amino Acids; Arsenates; Biological Transport; Cell Membrane; Dicyclohexylcarbodiimide; Drug Resistance, Microbial; Isoleucine; Kinetics; Membrane Potentials; Methotrexate; Mutation; Streptococcus pneumoniae; Valinomycin

Mutant strains of Escherichia coli male cells defective in Ca2+,Mg2+-dependent ATPase (unc) were constructed and tested for their ability to form a complex between sex pili and the filamentous phage fd under conditions where either the membrane potential or the cellular concentration of ATP was lowered. The uncoupler carbonyl cyanide m-chlorophenylhydrazone and the respiratory inhibitor cyanide, as well as valinomycin-K+ and colicin E1, all markedly diminished complex formation, indicating that the maintenance of a membrane potential, but probably not the pH gradient, is essential for the formation of the complex. Since complex formation with freshly centrifuged cells (which initially lacked sex pili) as well as with preincubated cells (in which pre-existing pili were available for complex formation) was inhibited by exposure to the inhibitors, energy seems to be required for both the reappearance (probably assembly) and the maintenance of sex pili on the cell surface. Brief exposure of freshly centrifuged cells to arsenate resulted in only partial inhibition of complex formation. However, marked inhibition of complex formation was observed following exposure to arsenate of preincubated cells possessing sex pili. This indicates that compounds such as ATP may also be required for maintenance of sex pili on the cell surface.

Topics: Adenosine Triphosphate; Arsenates; Carbonyl Cyanide m-Chlorophenyl Hydrazone; Colicins; Coliphages; Cyanides; Energy Metabolism; Escherichia coli; F Factor; Fimbriae, Bacterial; Membrane Potentials; Valinomycin

Experiments have been carried out to determine whether the active uptake of Ca2+ by sporulating Bacillus megaterium cells is driven by the pH gradient across the plasma membrane or by the membrane potential delta psi. Results from experiments using the ionophores nigericin and valinomycin which respectively dissipate the delta pH and the membrane potential, suggest that Ca2+ uptake during sporulation is driven by delta psi. It is further suggested that calcium is transported across the membrane via an antiport system in exchange for one or more protons. Arsenate and an inhibitor reported to be specific for membrane-bound ATPase, efrapeptin, have been used in other experiments to probe the role of ATP generation in calcium transport.

Topics: Adenosine Triphosphate; Anti-Bacterial Agents; Arsenates; Bacillus megaterium; Biological Transport, Active; Calcium; Hydrogen-Ion Concentration; Membrane Potentials; Nigericin; Oxygen Consumption; Peptides; Spores, Bacterial; Valinomycin