Showing papers by "Douglas B. Kell published in 1981"
TL;DR: In this article, the authors studied the permeability of the cytoplasmic membrane of Clostridiumpasteurianum to weak acids and bases by an osmotic swelling method.
115 citations
TL;DR: The absence of respiration-driven 204Tl+ uptake indicates that P. denitrificans cells grown under the conditions specified in the present work do not possess K+-transport systems of either the Kdp or TrkA types that have been described in Escherichia coli.
Abstract: 1. Aerobic respiration by cells of Paracoccus dentrificans drives the uptake of the lipophilic cation butyltriphenylphosphonium. Anaerobiosis or addition of an uncoupler of oxidative phosphorylation (carbonyl cyanide p-trifluoromethoxyphenylhydrazone) results in efflux of the cation. Changes in the concentration of butyltriphenylphosphonium in the suspension medium were measured by using an ion-selective electrode, the construction of which is described. 2. If the uptake of butyltriphenylphosphonium is used as an indicator of membrane potential, then at pH 7.3 an estimate of about 160 mV is obtained for cells of P. dentrificans respiring aerobically in 100 mM-Hepes [4-(2-hydroxyethyl)-1-piperazine-ethanesulphonic acid/NaOH or 100mM-NaH2PO4/NaOH. This potential, however, is decreased by more than 20 mV in reaction media containing a high concentration of phosphate (100 mM) together with at least 1 mM-K+. 3. Anaerobic electron transport with NO3-, NO2- or N2O as terminal electron acceptor generates a membrane potential of about 150mV in described suspension media. The presence of these species under aerobic conditions, moreover, has negligible effect upon the extent of uptake of butyltriphenylphosphonium normally driven by aerobic respiration. These data indicate that none of these molecules exert a significant uncoupling effect on the protonmotive force. 4. No 204Tl+ uptake into respiring cells was detected. This adds to the evidence that 204Tl+ is not a freely permeable cation in bacterial cells and therefore not an indicator of membrane potential as has been proposed. The absence of respiration-driven 204Tl+ uptake indicates that P. denitrificans cells grown under the conditions specified in the present work do not possess K+-transport systems of either the Kdp or TrkA types that have been described in Escherichia coli.
60 citations
TL;DR: This article aims to develop the idea that energytransducing membrane systems normally contain a number of proteinaceous components whose role is to act co-operatively as conformationally switchable proton conductors, permitting fast, controlled lateral proton transfer along the surface of such energy- transducing membranes.
Abstract: The colicins are a heterogeneous group of proteinaceous bactericidal agents produced by a variety of bacteria and active against many strains of Escherichia coli; many other bacteriocins active against other bacterial species, and exhibiting broadly similar properties to some of the colicins, have also been described (for review see [1-3]). As Plate has recently pointed out in a short review [4], certain of the colicins, especially those of the El, K and Ia types, which are known to disrupt membrane energy transduction processes in sensitive bacterial strains, may prove' extremely useful as probes of the nature of membrane energy transduction processes themselves. The purpose of the present article is threefold. Primarily, to develop the idea that energytransducing membrane systems normally contain a number of proteinaceous components whose role is to act co-operatively as conformationally switchable proton conductors, permitting fast, controlled lateral proton transfer along the surface of such energy-transducing membranes, and acting as the major energetic links between the various protonmotive sources and proton-accepting sinks embedded in such membranes. Secondly, to draw together evidence that the elements of such a "protoneural" network are themselves the prime target of the membrane-active colicins, and, thirdly, to point out that the recognition that such a network is an important feature of proton-coupled energy-transducing systems in vivo both provides a ready explanation for a variety of data apparently at odds with most presently accepted schemes of protonmotive energy transduction and renders intelligible a number of experimentally observable features of such systems for which a unifying view has not previously been offered. As will be clear from the following, we make no claim to the originality of many of the ideas presented here; we do believe, however, that our attempt to meld the conclusions drawn from a variety of experimental approaches into a unifying model will be helpful to those concerned with membrane energy transduction processes, their physiological roles and their molecular mechanisms. We begin with an outline summary of current ideas concerning the nature of energy transduction processes catalysed by membrane-located proteins.
47 citations
01 Jan 1981
TL;DR: This chapter discusses the electron transport system and hydrogenase of paracoccus denitrificans, a respiratory “jack-of-all-trades” and a very good example of adaptation of the electron-transport chain to changing growth conditions.
Abstract: Publisher Summary This chapter discusses the electron transport system and hydrogenase of paracoccus denitrificans . One feature that characterizes bacteria is the ability to adapt to environmental changes and nutritional conditions. At the molecular level, the versatility of bacterial systems can be explained, at least in part, by adaptive changes in their respiratory chains. The Paracoccus denitrificans , formerly Micrococcus denitrificans Beijerinck, is a respiratory “jack-of-all-trades” and a very good example of adaptation of the electron-transport chain to changing growth conditions. The changes in bacterial respiratory chains occur most often at the level of the terminal oxidases, and this is exemplified in P. denitrificans . Although, it is an aerobic bacterium, P. denitrificans can use nitrate, nitrite, and nitrous oxide as terminal electron acceptors. However, it is unable to use organic compounds as electron acceptors for anaerobic growth, and so is nonfermentative. Besides utilizing a variety of terminal electron acceptor molecules, P. denitrificans can grow on a diverse range of carbon compounds from methanol to sucrose
40 citations
TL;DR: It was found that the compound was much more toxic to potentially sensitive bacteria in aerobic nutrient broth media containing 1% glucose than in the same medium lacking added glucose, suggesting that toxicity might be associated with aerobic respiratory metabolism.
Abstract: Tinopal AN, (1,1-bis(3,N-5-dimethyl benzoxazol2yl)methine p toluene sulphonate) (Fig. 1), is a cationic benzoxazole derivative present in the commercial product Uvitex AN (CibaGeigy Ltd., UK), which has been used as a fluorescent optical brightener in ultra violet light microscopy as a tool for the non-specific differentiation of bacteria and fungi from background plant material [1,2]. It was later realised that Tinopal A N was, in some cases, a potent bactericidal agent and more recently its selective toxicity was investigated [3] with particular reference to phytopathogenic pseudomonad and xanthomonad bacteria. It was found [3] that the compound was much more toxic to potentially sensitive bacteria in aerobic nutrient broth media containing 1% glucose than in the same medium lacking added glucose, suggesting that toxicity might be associated with aerobic respiratory metabolism. Thus it seemed appropriate to assess in greater detail the mode of inhibition of aerobic bacterial growth by Tinopal AN. For this purpose, the respiratory
13 citations
TL;DR: The cytokinins constitute one of the five groups of plant hormones, and are characterised by their ability to promote cell division in cultured plant callus tissue under appropriate conditions as discussed by the authors.