On the possible role of respiratory activity of Acholeplasma laidlawii cells in sugar transport

Abstract

1. Out of 20 exogeneous substrates only ethanol and, to a much lesser extent, lactate and pyruvate were shown to be capable of stimulating the respiration of Acholeplasma laidlawii cells. However, none of these substrates changed the initial rate of active transport of 3-O-methyl-D-glucose (3-O-MG). 2. From inhibitory analyses and spectroscopic data, it is apparent that the respiratory chain of A. laidlawii has no cytochromes and is probably not responsible for oxidative phosphorylation. 3. Valinomycin and nigericin stimulated cell respiration only in the presence of K+-ions, while monensin stimulated it in the presence of Na+-ions. 4. 3-O-MG transport was shown to be sensitive to uncouplers, ATPase inhibitors and arsenate are resistant to a majority of respiratory inhibitors tested. This suggested that there was no relationship between respiration and carbohydrate transport in the A. laidlawii cells. Further evidence was provided by the absence of respiratory stimulation during the transport of non-metabolizing carbohydrates.

Kinetics and distribution of alcohol oxidising activity in Acholeplasma and Mycoplasma species

“…This study has con¢rmed the observation of Tarshis et al [5] that A. laidlawii is able to oxidise ethanol. This ability was also demonstrated in a further six Acholeplasma species and it was additionally shown that, in those species tested, propanol, butanol and pentanol (but not isopropanol) were oxidised.…”

“…It was also considered possible that the enzyme was important in regulating NADP /NADPH ratio. However, such roles would not satisfactorily explain the high rate of ethanol oxidation in A. laidlawii, which exceeded that for pyruvate [5]. In addition, if the presence of alcohol dehydrogenase varies amongst Mycoplasma species, it might be a useful character in identi¢cation.…”

“…Tarshis et al [5] reported that ethanol (4 mM) caused a four-fold stimulation in the rate of oxygen uptake by Acholeplasma laidlawii cells suspended in a bu¡ered salts solution. This suggests the presence of alcohol deydrogenase activity which would result in the formation of acetaldehyde, a reactive and toxic intermediate.…”

Symport H+/carbohydrate transport into Acholeplasma laidlawii cells

“…It is well established that the flux of neutral substrates is mediated by H' symporters in response to the total protonmotive force [2][3][4]. We have demonstrated that the aerobic and anaerobic transport of 3-O-methyl-D-glucose (3-O-MC) into Acholeplasma Zaidlawii cells is sensitive to arsenate, inhibitors of glycolysis, uncouplers and DCCD [5,6]. We describe here the concomitant uptake of H* with 3-O-MG by Ach.…”

Kinetics and distribution of alcohol oxidising activity inAcholeplasmaandMycoplasmaspecies

“…Tarshis et al [5] reported that ethanol (4 mM) caused a four‐fold stimulation in the rate of oxygen uptake by Acholeplasma laidlawii cells suspended in a buffered salts solution. This suggests the presence of alcohol deydrogenase activity which would result in the formation of acetaldehyde, a reactive and toxic intermediate.…”