scholarly journals The presence of two cytochromes b in the facultative methylotroph Pseudomonas AM1

1979 ◽  
Vol 180 (1) ◽  
pp. 237-239 ◽  
Author(s):  
C W Keevil ◽  
C Anthony
Keyword(s):  
Cytochrome C ◽  
Continuous Culture ◽  
Batch Culture ◽  
Growth Conditions ◽  
Redox Potentials ◽  
Deficient Mutant ◽  
Facultative Methylotroph

Two cytochromes b with absorption maxima at 555 and 562 nm and differing in their mid-point redox potentials are synthesized in Pseudomonas AM1 during growth on methanol or succinate in batch culture, or in NH4+-limited or carbon-limited continuous culture. Both cytochromes b were also present in a cytochrome c-deficient mutant in all growth conditions.

scholarly journals Effect of growth conditions on the involvement of cytochrome c in electron transport, proton translocation and ATP synthesis in the facultative methylotroph Pseudomonas AM1

1979 ◽  
Vol 182 (1) ◽  
pp. 71-79 ◽  
Author(s):  
C. William Keevil ◽  
Christopher Anthony
Keyword(s):  
Electron Transport ◽  
Cytochrome C ◽  
Proton Translocation ◽  
Atp Synthesis ◽  
Growth Conditions ◽  
Wild Type ◽  
Limited Growth ◽  
Bacterial Membranes ◽  
Facultative Methylotroph ◽  
Carbon Excess

The stoicheiometry of proton translocation, the amounts of cytochromes firmly bound to membranes, and cell yields with respect to succinate and O2 have been measured in the facultative methylotroph Pseudomonas AM1 and in the mutant lacking cytochrome c (mutant PCT76) during carbon-limited growth and carbon-excess growth. →H+/O ratios during endogenous respiration of about 4 were measured in wild-type bacteria grown in carbon-excess conditions, and in the mutant in all growth conditions. During methanol- or succinate-limited growth of wild-type bacteria the →H+/O ratio increased to about 6. Cell yields with respect to succinate and O2 were higher in wild-type than in the mutant lacking cytochrome c by an amount suggesting loss in the mutant of 30% of the ATP-generating capacity of wild-type bacteria. During carbon-limited growth on methanol or succinate some cytochrome c was tightly bound to bacterial membranes, whereas none was tightly bound in bacteria grown in batch-culture or in NH4+-limited conditions. It is proposed that the role of cytochrome c in Pseudomonas AM1 depends on growth conditions and hence on the ‘needs’ of the bacteria. During growth in carbon-excess conditions it is only required for methanol oxidation, mediating between methanol dehydrogenase and cytochrome a/a3. In these conditions oxidation of NADH and succinate by way of cytochrome b and cytochrome a/a3 occurs without the mediation of cytochrome c. This is the only route for oxidation of NADH and succinate in the cytochrome c-deficient mutant in all growth conditions. During carbon-limited growth the cytochrome c becomes bound to the membrane in such a way that it can mediate between cytochromes b and a/a3, hence becoming involved in proton translocation and ATP synthesis during NADH and succinate oxidation. An alternative possibility is that in wild-type bacteria the cytochrome c is always involved in electron transport, but that its involvement in measurable proton translocation only occurs in carbon-limited conditions.

Kinetic analysis of batch and continuous culture of Streptococcus cremoris HP

1978 ◽  
Vol 24 (4) ◽  
pp. 372-380 ◽  
Author(s):  
P. L. Rogers ◽  
L. Bramall ◽  
I. J. McDonald
Keyword(s):  
Lactic Acid ◽  
Steady State ◽  
Kinetic Analysis ◽  
Continuous Culture ◽  
Batch Culture ◽  
Lactic Acid Production ◽  
Streptococcus Cremoris ◽  
Lactose Utilization ◽  
State Growth ◽  
Batch Data

The growth of Streptococcus cremoris on a semidefined medium was studied at initial lactose concentrations of 0.2–5.0% in batch culture, and in lactose-limited chemostat cultures at 0.5% lactose. Kinetic analysis of the batch data, using statistical techniques, indicated the importance of lactose limitation and lactic acid inhibition of the growth of S. cremoris. A model for the biomass production, lactose utilization, and lactic acid production in batch culture was proposed. In continuous culture, it was found that steady state populations were maintained at higher dilution rates (D = 0.6–0.7 h−1) than the maximum predicted by batch culture (0.56 h−1). No evidence for a selection of fast-growing mutants was obtained. Copious growth adhering to the walls of the fermentor (i.e. wall growth) occurred very rapidly at higher dilution rates and this undoubtedly affected steady-state growth and wash-out and, as a consequence, the apparent maximum dilution rate.

scholarly journals The interaction between methanol dehydrogenase and the autoreducible cytochromes c of the facultative methylotroph Pseudomonas AM1

1980 ◽  
Vol 190 (2) ◽  
pp. 481-484 ◽  
Author(s):  
D T O'Keeffe ◽  
C Anthony
Keyword(s):  
Cytochrome C ◽  
Methanol Dehydrogenase ◽  
High Ph ◽  
First Order ◽  
Facultative Methylotroph ◽  
Cytochromes C ◽  
Pure Methanol

Cytochromes cH and cL were autoreduced at high pH (pK greater than 10) and the autoreduced cytochromes reacted with CO. The autoreduction was first-order with respect to oxidized cytochrome c and was reversible by lowering the pH. Pure methanol dehydrogenase reduced cytochrome c (in the absence of methanol) by lowering the pK for autoreduction to less than 8.5. A mechanism is proposed for the autoreduction of cytochrome c and its involvement in the reaction with methanol dehydrogenase.

Magnetochrome: a c-type cytochrome domain specific to magnetotatic bacteria

2012 ◽  
Vol 40 (6) ◽  
pp. 1319-1323 ◽  
Author(s):  
Marina I. Siponen ◽  
Géraldine Adryanczyk ◽  
Nicolas Ginet ◽  
Pascal Arnoux ◽  
David Pignol
Keyword(s):  
Cytochrome C ◽  
Iron Acquisition ◽  
Magnetic Domain ◽  
Redox Potentials ◽  
Protein Sequence Analysis ◽  
Biophysical Characterization ◽  
Domain Specific ◽  
New Family ◽  
Periplasmic Proteins ◽  
Field Lines

Magnetotactic bacteria consist of a group of taxonomically, physiologically and morphologically diverse prokaryotes, with the singular ability to align with geomagnetic field lines, a phenomenon referred to as magnetotaxis. This magnetotactic property is due to the presence of iron-rich crystals embedded in lipidic vesicles forming an organelle called the magnetosome. Magnetosomes are composed of single-magnetic-domain nanocrystals of magnetite (Fe3O4) or greigite (Fe3S4) embedded in biological membranes, thereby forming a prokaryotic organelle. Four specific steps are described in this organelle formation: (i) membrane specialization, (ii) iron acquisition, (iii) magnetite (or greigite) biocrystallization, and (iv) magnetosome alignment. The formation of these magnetic crystals is a genetically controlled process, which is governed by enzyme-catalysed processes. On the basis of protein sequence analysis of genes known to be involved in magnetosome formation in Magnetospirillum magneticum AMB-1, we have identified a subset of three membrane-associated or periplasmic proteins containing a double cytochrome c signature motif CXXCH: MamE, MamP and MamT. The presence of these proteins suggests the existence of an electron-transport chain inside the magnetosome, contributing to the process of biocrystallization. We have performed heterologous expression in E. coli of the cytochrome c motif-containing domains of MamE, MamP and MamT. Initial biophysical characterization has confirmed that MamE, MamP and MamT are indeed c-type cytochromes. Furthermore, determination of redox potentials for this new family of c-type cytochromes reveals midpoint potentials of −76 and −32 mV for MamP and MamE respectively.

scholarly journals ß-galactosidase production by Kluyveromyces lactis in batch and continuous culture

2011 ◽  
Author(s):  
◽  
Elaine C. Ram
Keyword(s):  
Carbon Source ◽  
Continuous Culture ◽  
Batch Culture ◽  
Shake Flask ◽  
Kluyveromyces Lactis ◽  
Shake Flask Culture ◽  
Lactose Hydrolysis ◽  
Strictly Aerobic ◽  
Fed Batch ◽  
Cell Lysates

Kluyveromyces sp. have adapted to existence in milk due to the evolution of permeabilisation and hydrolytic systems that allow the utilisation of lactose, the sugar most abundant in milk. Lactose hydrolysis, to equimolar units of glucose and galactose, is facilitated by a glycoside hydrolase, i.e., β-galactosidase (EC 3.2.1.23). The versatility of this enzyme allows its application in numerous industrial processes, amongst the most significant of which, is its role in the alleviation of lactose intolerance, one of the most prevalent digestive ailments, globally. In this study, β-galactosidase production by Kluyveromyces lactis UOFS y-0939 was initially optimised in shake flask culture with lactose as the sole carbon source, and thereafter, production was scaled up to batch, fedbatch and continuous culture. Shake flask studies revealed optimum conditions of 30°C, pH 7 and a 10% inoculum ratio, to be most favourable for β-galactosidase synthesis, producing a maximum of 0.35 ± 0.05 U.ml-1 when cell lysates were prepared by ultrasonication with glass beads. Batch cultivation in 28.2 and 40 g.L-1 lactose revealed that elevated levels of the carbon source was not inhibitory to β-galactosidase production, as maximum enzyme activities of 1.58 and 4.08 U.ml-1, respectively, were achieved. Cell lysates prepared by ultrasonication and homogenisation were compared and homogenised cell lysates were more than 3.5 fold higher that those prepared by ultrasonication, proving homogenisation to be the superior method for cell disruption. The lactose feed rate of 4 g.L-1.h-1 in fed-batch culture operated at ± 20.4% DO, appeared to be inhibitory to biomass production, as indicated by the lower biomass productivity in fed-batch (0.82 g.L-1.h-1) than batch culture (1.27 g.L-1.h-1). Enzyme titres, however, were favoured by the low DO levels as a maximum of 8.7 U.ml-1, 5.5 fold more than that obtained in batch culture, was achieved, and would be expected to increase proportionally with the biomass. Continuous culture operated at a dilution rate of 0.2 h-1, under strictly aerobic conditions, revealed these conditions to be inhibitory to the lactose consumption rate, however, the non-limiting lactose and high DO environment was favourable for β-galactosidase synthesis, achieving an average of 8 ± 0.9 U.ml-1 in steady state.

A Two-Layer Gold Surface with Improved Surface Enhancement for Spectro-Electrochemistry Using Surface-Enhanced Infrared Absorption Spectroscopy

2009 ◽  
Vol 63 (9) ◽  
pp. 1068-1074 ◽  
Author(s):  
C. Nowak ◽  
C. Luening ◽  
W. Knoll ◽  
R. L. C. Naumann
Keyword(s):  
Cytochrome C ◽  
Absorption Spectroscopy ◽  
Infrared Absorption ◽  
Gold Surface ◽  
Growth Conditions ◽  
Infrared Absorption Spectroscopy ◽  
Optimum Conditions ◽  
Self Assembled Monolayer ◽  
Surface Enhanced ◽  
Reversible Reduction

A two-layer gold surface is developed for use with surface-enhanced infrared absorption spectroscopy (SEIRAS) consisting of a conducting underlayer onto which Au nanoparticles (AuNPs) are grown by self-catalyzed electroless deposition. AuNPs are grown on protruding substructures of the 25 nm thin underlayer. The enhancement factor of the two-layer gold surface is controlled by the growth conditions. Cytochrome c adsorbed to a self-assembled monolayer of mercaptoethanol is used as a reference system. Under optimum conditions the absorbance of the amide I band is increased by a factor of 5 versus the classical SEIRAS surface. Reversible reduction/oxidation of cytochrome c on the two-layer gold surface is shown to take place by cyclic voltammetry.

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