Energy Transduction in Chlorobium limicola: Role of Membrane-bound Adenosine Triphosphatase and the Proton Electrochemical Gradient

Abstract

Photophosphorylation in vivo by Chlorobium limicola was inhibited by lipophilic cations and the energy-transfer inhibitors diphenylphosphorylazide, Dio-9, 4-chloro-7-nitrobenzofurazan and chlorhexidene. Membrane-bound ATPase activity was also inhibited by these energytransfer inhibitors. The formation of a membrane potential was stimulated approximately 1 -7-fold on illumination, rising to a value between -1 10 and -150 mV. The sensitivity of the processes producing this membrane potential to uncouplers, energy-transfer inhibitors and 2-heptyl-4-hydroxyquinoline-N-oxide was measured in the light and the dark.

Electron transport in green photosynthetic bacteria

“…Light-induced ATP formation has been extremely difficult to demonstrate in the green bacteria, especially in cell-free preparations [14,80]. This may at least in part result from the structure of the membranes, which when the cells are broken tend to form sheets instead of the vesicles typical of the purple bacteria [11,74].…”

Mechanisms of Sugar Transport in the Rumen Bacterium Selenomonas ruminantium

“…We were unable to detect an accumulation of sucrose phosphate. However, previous workers were only able to detect the sucrose phosphate intermediate in mutants of Streptococcus mutans which lacked sucrose phosphate hydrolase (St Martin & Wittenberger, 1979).…”

“…In these experiments PEP-dependent phosphorylation of glucose was constitutive, while the phosphorylations of maltose and sucrose were inducible (Table 1). PTS-mediated transport of disaccharides (P-glucosides, lactose, sucrose) has been described in enteric bacteria (Postma & Lengeler, 1985), and an inducible maltose PTS has been observed in streptococci (St Martin & Wittenberger, 1979;Martin & Russell, 1987).…”

“…Sucrose hydrolase assay. Sucrose hydrolysis was determined by the enzymic method of St Martin & Wittenberger (1979). Each 1.0 ml reaction mixture contained 100 Mm-sodium/potassium phosphate buffer (pH 7*2), 5 mM-MgC12, 10 mM-ATP, 0.2 mM-NADP+, 6.4 U glucose-6-phosphate dehydrogenase, 2 U hexokinase, 2 U phosphoglucose isomerase (EC 5.3.1.9), 4 mM-Sucrose and 100 p1 of cell extract (final concentration of protein 585 pg ml-*).…”

Further Evidence for the Existence of a Membrane Potential in Trypanosoma brucei brucei

“…This was based on the measurement of accumulation ratios for 137Cs+, in the presence of valinomycin, or for labelled methyltriphenylphosphonium ion using a rapid filtration technique and principles previously described (Horan et al, 1978;Sissons & Midgley, 1981). The composition of the incubation medium was as follows: organism (-0.3 mg protein ml-l) in Na-HEPPS-glucose, 4.45 ml; radiochemical, either 0.05 ml 137CsCl (2.25 mM, 5 pCi pmol-l) or 0-045 ml [3H]methyltriphenylphosphonium bromide (7.2 p~, 2.8 pCi pmol-l) or 0.045 ml [14C]methyltriphenylphosphonium bromide (1-1 mM, 9 pCi pmol-l) [l pCi = 37 kBq]; valinomycin, 4-5 p1 of a 1 mg ml-I methanolic solution, if added.…”