title: [Proton cycles through membranes in bacteria: relationship between proton passive and active fluxes and their dependence on some external physico-chemical factors under fermentation].
abstract: This paper represents H+ circles through the bacterial membranes, their peculiarities and relationship with ATP synthesis or hydrolysis, utilization or accumulation of energy are considered. Data on passive and active proton (H+) fluxes through the bacterial membranes are analyzed and their relationship with membrane H+ conductance (Gm(H+)) and permeability for H+ (P(H+)) is discussed. Methods for determination of bacterial membrane Gm(H+) are presented and some difficulties in obtaining and interpreting data are pointed out. Different ways and mechanisms of passive and active H+ fluxes, including a role of membrane lipids in H+ transfer, importance of phase transitions in lipid bilayers, operation of protonophores as well as H+ translocation via the F0 factor of the F0F1-ATPase, are discussed. Dependence of Gm(H+) for Escherichia coli, Enterococcus hirae, Streptococcus lactis and other bacteria on some external physico-chemical growth factors, particularly, on pH and oxidation reduction potential as well as influence of osmotic stress on Gm(H+) and H+ active fluxes through the bacterial membrane under fermentation have been shown. The relationship between Gm(H+), P(H+) and active H+ fluxes through a membrane is proposed, possible mechanisms of relationship between their alterations depending on pH and oxidation reduction potential are discussed. The results are important for understanding the structural and functional properties of bacterial membranes determining H+ cycles operation and mechanisms of H+ fluxes essential in adaptation of bacteria to altered environment conditions.
authors.forename: K
authors.initials: K
authors.lastname: Akopian
authors.forename: A
authors.initials: A
authors.lastname: Trchuian
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis* / Q000737:chemistry; D002463:Cell Membrane Permeability; D004926:Escherichia coli / Q000201:enzymology; D005285:Fermentation; D017136:Ion Transport; D008051:Lipid Bilayers / Q000737:chemistry*; D008564:Membrane Potentials; D009997:Osmotic Pressure; D006180:Proton-Translocating ATPases / Q000737:chemistry; D011522:Protons
chemical_list: D008051:Lipid Bilayers; D011522:Protons; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases