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1.
Michael Ringel Roland Gross Torsten Krafft Achim Kröger R. Schauder 《Archives of microbiology》1996,165(1):62-64
Wolinella succinogenes grows by anaerobic respiration with formate and polysulfide. Polysulfide forms spontaneously from sulfur and sulfide. Here
we report that this eubacterium also grows with formate and elemental sulfur under conditions that do not allow polysulfide
formation. With the appropriate amount of Fe2+ added to the medium, the concentration of polysulfide was calculated to be 0.4 nM, which is 1/400th of the concentration
that of dissolved elemental sulfur. At commensurable growth rates, the growth yield with sulfur was one quarter of that with
polysulfide as electron acceptor. The same low growth yield either with sulfur or with polysulfide as electron acceptor was
measured for a Δpsr mutant that lacks the genes encoding polysulfide reductase (Psr).
Received: 8 June 1995 / Accepted: 12 September 1995 相似文献
2.
Thiobacillus denitrificans strain RT could be grown anaerobically in batch culture on thiosulfate but not on other reduced sulfur compounds like sulfide, elemental sulfur, thiocyanate, polythionates or sulfite. During growth on thiosulfate the assimilated cell sulfur was derived totally from the outer or sulfane sulfur. Thiosulfate oxidation started with a rhodanese type cleavage between sulfane and sulfone sulfur leading to elemental sulfur and sulfite. As long as thiosulfate was present elemental sulfur was transiently accumulated within the cells in a form that could be shown to be more reactive than elemental sulfur present in a hydrophilic sulfur sol, however, less reactive than sulfane sulfur of polythionates or organic and inorganic polysulfides. When thiosulfate had been completely consumed, intracellular elemental sulfur was rapidly oxidized to sulfate with a specific rate of 45 natom S°/min·mg protein. Extracellularly offered elemental sulfur was not oxidized under anaerobic conditions. 相似文献
3.
4.
Christiane Dahl Gábor Rákhely A.S. Pott-Sperling Barna Fodor Mária Takács rás Tóth Monika Kraeling Krisztina Gyrfi Ákos Kovács Jennifer Tusz Kornél L. Kovács 《FEMS microbiology letters》1999,180(2):317-324
The dsr genes and the hydSL operon are present as separate entities in phototrophic sulfur oxidizers of the genera Allochromatium, Marichromatium, Thiocapsa and Thiocystis and are organized similarly as in Allochromatium vinosum and Thiocapsa roseopersicina, respectively. The dsrA gene, encoding the alpha subunit of 'reverse' siroheme sulfite reductase, is also present in two species of green sulfur bacteria pointing to an important and universal role of this enzyme and probably other proteins encoded in the dsr locus in the oxidation of stored sulfur by phototrophic bacteria. The hupSL genes are uniformly present in the members of the Chromatiaceae family tested. The two genes between hydS and hydL encode a membrane-bound b-type cytochrome and a soluble iron-sulfur protein, respectively, resembling subunits of heterodisulfide reductase from methanogenic archaea. These genes are similar but not identical to dsrM and dsrK, indicating that the derived proteins have distinct functions, the former in hydrogen metabolism and the latter in oxidative sulfur metabolism. 相似文献
5.
The reduction of elemental or sulfane sulfur to hydrogen sulfide by eubacteria was investigated. Spirillum 5175 had the most active sulfur oxidoreductase. It could be cultivated with fumarate (F), elemental sulfur (S) or nitrate (N) as electron acceptor. Maximum activity was found for Spirillum 5175S but activity was also present in Spirillum 5175F and Spirillum 5175N, i.e. the sulfur oxidoreductase is a constitutive enzyme. It was localized in the membrane, and no activity was found in the cytoplasm in contrast to Desulfovibrio baculatus. Different procedures were applied for the measurement of the sulfur oxidoreductase activity. In the manometric assay hydrogenase was coupled to the sulfur oxidoreductase, and the uptake of dihydrogen was measured in the presence of elemental sulfur. Alternatively, H2S was assayed directly or was trapped in 12% NaOH and determined by the methylene blue procedure. Using 35S sulfur and 35S-labelled compounds both the substrate and H2S could be measured. A further increase in sensitivity was achieved using phenosafranin. It was reduced photochemically, and served as the electron donor to the sulfur oxidoreductase, i.e. no hydrogenase was required. This was an important result in view of the fact that not all sulfur-reducing bacteria contain hydrogenase. However, in those cases the hydrogenase isolated from Clostridium pasteurianum could be coupled to the sulfur oxidoreductase. Among the different forms of elemental sulfur Janek sulfur gave the best results in terms of activity and reproducibility. The reduction of elemental sulfur to hydrogen sulfide had a pH optimum at pH 8.7–8.9. There was always a lag-phase which was pH-dependent. During this period the turbidity of the solution changed. Addition of thiols, such as GSH, shortened the lag-phase and caused an increase in activity of the sulfur oxidoreductase. In the presence of p-chloromercuribenzenesulfonic acid the reaction rate decreased significantly. Comparable reaction rates and activity values of the sulfur oxidoreductase in Spirillum 5175F were obtained with organic trisulfides, RS-S-SR. In contrast to elemental sulfur RS-S-SR are well-defined chemical compounds suitable for quantitative and mechanistic investigations. Labelling the central sulfur of RS-S-SR with 35S gave a satisfactory recovery of the total radioactivity in form of (35S) H2S in our assay. Trisulfides were shown to be formed as reactive intermediates in bacteria. This process required the sulfur transferase rhodanese which was present in Spirillum 5175, or other sulfur-reducing eubacteria.Abbreviations EPR
Electron Paramagnetic Resonance
- A
Absorbance
- PCMS
p-chloromercuribenzenesulfonic acid
- Sp. 5175F
Splrillum 5175 grown with fumarate
- Sp. 5175S
with sulfur
- Sp. 5175N
with nitrate
- SCE
Standard Calomel Electrode 相似文献
6.
7.
Abstract Among sulfur compounds, thiosulfate and polythionates are present at least transiently in many environments. These compounds have a similar chemical structure and their metabolism appears closely related. They are commonly used as energy sources for photoautotrophic or chemolithotrophic microorganisms, but their assimilation has been seldom studied and their importance in bacterial physiology is not well understood. Almost all bacterial strains are able to cleave these compounds since they possess thiosulfate sulfur transferase, thiosulfate reductace or S -sulfocysteine synthase activities. However, the role of these enzymes in the assimilation of thiosulfate or polythionates has not always been clearly established.
Elemental sulfur is, on the contrary, very common in the environmental. It is an energy source for sulfur-reducing eubacteria and archaebacteria and many sulfur-oxidizing archaebacteria. A phenomenon still not well understood is the 'excessive assimilatory sulfur metabolism' as observed in methanogens which perform a sulfur reduction which exceeds their anabolic needs without any apparent benefit. In heterotrophs, assimilation of elemental sulfur is seldom described and it is uncertain whether this process actually has a physiological significance.
Thus, reduction of thiosulfate and elemental sulfur is a common by incompletely understood feature among bacteria. These activities could give bacteria a selective advantage, but futher investigations are needed to clarify this possibility. Presence of thiosulfate, polythionates and sulfur reductase activities does not imply obligatorily that these activities play a role in thiosulfate, polythionates or sulfur assimilation as these compounds could be merely intermediates in bacterial metabolism. The possibility also exists that the assimilation of these sulfur compounds is just a side effect of an enzymatic activity with a completely different function. 相似文献
Elemental sulfur is, on the contrary, very common in the environmental. It is an energy source for sulfur-reducing eubacteria and archaebacteria and many sulfur-oxidizing archaebacteria. A phenomenon still not well understood is the 'excessive assimilatory sulfur metabolism' as observed in methanogens which perform a sulfur reduction which exceeds their anabolic needs without any apparent benefit. In heterotrophs, assimilation of elemental sulfur is seldom described and it is uncertain whether this process actually has a physiological significance.
Thus, reduction of thiosulfate and elemental sulfur is a common by incompletely understood feature among bacteria. These activities could give bacteria a selective advantage, but futher investigations are needed to clarify this possibility. Presence of thiosulfate, polythionates and sulfur reductase activities does not imply obligatorily that these activities play a role in thiosulfate, polythionates or sulfur assimilation as these compounds could be merely intermediates in bacterial metabolism. The possibility also exists that the assimilation of these sulfur compounds is just a side effect of an enzymatic activity with a completely different function. 相似文献
8.
Ectothiorhodospira halochloris grows photoheterotrophically with a variety of sulfur sources. During sulfide oxidation to elemental sulfur considerable amounts of polysulfides may be accumulated transiently. When grown on elemental sulfur no sulfate was produced by oxidation, but sulfide and polysulfide were formed by reduction. Only one soluble cytochrome c-551 was isolated and purified. It was a small acidic hemeprotein with a molecular weight of 6,300, an isoelectric point of 3.1 and a redox potential of-11 mV at pH 7.0. It showed three absorption maxima in the reduced state (=551 nm; =523 nm; =417 nm). The addition of various c-type cytochromes to a suspension of spheroplasts stimulated the velocity of sulfide oxidation. This stimulation was best with the small acidic cytochromes from E. halochloris or Ectothiorhodospira abdelmalekii. Sulfide oxidation was stopped by several uncoupling agents, ionophores and electron transport inhibitors. Antimycin A, rotenone and cyanide had no effect on sulfide oxidation.Dedicated to Prof. Dr. H. G. Schlegel on the occasion of his 60th birthday 相似文献
9.
Washed membranes prepared from H2+CO2- or formate-grown cells of Methanococcus voltae catalyzed the oxidation of coenzyme F420H2 and the reduction of the heterodisulfide (CoB–S–S–CoM) of 2-mercaptoethanesulfonate and 7-mercaptoheptanoylthreonine phosphate,
which is the terminal electron acceptor of the methanogenic pathway. The reaction followed a 1:1 stoichiometry according to
the equation: F420H2 + COB–S–S–CoM → F420 + CoM–SH + CoB–SH. These findings indicate that the reaction depends on a membrane-bound F420H2-oxidizing enzyme and on the heterodisulfide reductase, which remains partly membrane-bound after cell lysis. To elucidate
the nature of the F420H2-oxidizing protein, washed membranes were solubilized with detergent, and the enzyme was purified by sucrose density centrifugation,
anion-exchange chromatography, and gel filtration. Several lines of evidence indicate that F420H2 oxidation is catalyzed by a membrane-associated F420-reducing hydrogenase. The purified protein catalyzed the H2-dependent reduction of methyl viologen and F420. The apparent molecular mass and the subunit composition (43, 37, and 27 kDa) are almost identical to those of the F420-reducing hydrogenase that has already been purified from Mc. voltae. Moreover, the N-terminus of the 37-kDa subunit is identical to the amino acid sequence deduced from the fruG gene of the operon encoding the selenium-containing F420-reducing hydrogenase from Mc. voltae. A distinct F420H2 dehydrogenase, which is present in methylotrophic methanogens, was not found in this organism.
Received: 18 September 1998 / Accepted: 2 November 1998 相似文献
10.
Wolinella succinogenes can grow at the expense of sulphur reduction by formate. The enzymes involved in the catalysis of this catabolic reaction have been investigated. From the results the following conclusions are drawn: 1. The enzyme isolated as a sulphide dehydrogenase from the cytoplasmic membrane of W. succinogenes is the functional sulphur reductase that operates in the electron transport from formate to sulphur. 2. The enzyme (Mr 200,000) consists essentially of one type of subunit with the Mr 85,000 and contains equal amounts of free iron and sulphide (120 mol/g protein), but no heme. It represents the first functional sulphur reductase ever isolated. 3. The electron transport chain catalyzing sulphur reduction by formate consists merely of formate dehydrogenase and sulphur reductase. A lipophilic quinone which mediates the transfer of electrons between enzymes in other chains, is apparently not involved. This is the first known example of a phosphorylative electron transport chain that operates without a quinone. 4. The same formate dehydrogenase appears to operate in the electron transport both with sulphur and with fumarate as the terminal electron acceptor in W. succinogenes.Abbreviations DMN
2,3-Dimethyl-1,4-naphthoquinone
- DTT
dithiothreitol
- MK
menaquinone (vitamin K2)
- PMSF
phenylmethane sulfonylfluoride
- Tricine
N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]-glycine
- Tea
triethanolamine
- Hepes
4-(2-hydroxyethyl)-1-piperazineethane sulfonate
Dedicated to Professor F. Schneider (Philipps-Universität Marburg) on the occasion of his 60th birthday 相似文献
11.
In the phototrophic sulfur bacterium Allochromatium vinosum, sulfur of oxidation state zero stored in intracellular sulfur globules is an obligate intermediate during the oxidation of sulfide and thiosulfate. The proteins encoded in the dissimilatory sulfite reductase (dsr) locus are essential for the oxidation of the stored sulfur. DsrMKJOP form a membrane-spanning complex proposed to accept electrons from or to deliver electrons to cytoplasmic sulfur-oxidizing proteins. In frame deletion mutagenesis showed that each individual of the complex-encoding genes is an absolute requirement for the oxidation of the stored sulfur in Alc. vinosum. Complementation of the ΔdsrJ mutant using the conjugative broad host range plasmid pBBR1-MCS2 and the dsr promoter was successful. The importance of the DsrMKJOP complex is underlined by the fact that the respective genes occur in all currently sequenced genomes of sulfur-forming bacteria such as Thiobacillus denitrificans and Chlorobaculum tepidum. Furthermore, closely related genes are present in the genomes of sulfate- and sulfite-reducing prokaryotes. A phylogenetic analysis showed that most dsr genes from sulfide oxidizers are clearly separated of those from sulfate reducers. Surprisingly, the dsrMKJOP genes of the Chlorobiaceae all cluster together with those of the sulfate/sulfite-reducing prokaryotes, indicating a lateral gene transfer at the base of the Chlorobiaceae.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at . 相似文献
12.
The cyanobacterium Oscillatoria limnetica, capable of anoxygenic photosynthesis in the light with sulfide as electron donor can anaerobically break down its intracellular polyglucose in the dark. In the absence of elemental sulfur, the organism carries out lactate fermentation; in its presence, anaerobic respiration occurs in which sulfur is reduced to sulfide. Induction of anoxygenic photosynthesis or synthesis of new proteins is not necessary for either process. Cells adapted in the dark to sulfur reduction are capable of anoxygenic photosynthesis during a subsequent light period, unless protein synthesis has been inhibited during the dark incubation period.Abbreviations DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- FCCP
Carbonylcyanide p-trifluoromethoxyphenylhydrazone
- mgat
milligramatom
- OD
optical density 相似文献
13.
Methyl-coenzyme M reductase (MCR) catalyses the reduction of methyl-coenzyme M (CH3-S-CoM) with coenzyme B (HS-CoB) to methane and CoM-S-S-CoB. It contains the nickel porphyrinoid F430 as prosthetic group which has to be in the Ni(I) oxidation state for the enzyme to be active. The active enzyme exhibits an axial Ni(I)-derived EPR signal MCR-red1. We report here on experiments with methyl-coenzyme M analogues showing how they affect the activity and the MCR-red1 signal of MCR from Methanothermobacter marburgensis. Ethyl-coenzyme M was the only methyl-coenzyme M analogue tested that was used by MCR as a substrate. Ethyl-coenzyme M was reduced to ethane (apparent K
M=20 mM; apparent V
max=0.1 U/mg) with a catalytic efficiency of less than 1% of that of methyl-coenzyme M reduction to methane (apparent K
M=5 mM; apparent V
max=30 U/mg). Propyl-coenzyme M (apparent K
i=2 mM) and allyl-coenzyme M (apparent K
i=0.1 mM) were reversible inhibitors. 2-Bromoethanesulfonate ([I]0.5 V=2 µM), cyano-coenzyme M ([I]0.5 V=0.2 mM), 3-bromopropionate ([I]0.5 V=3 mM), seleno-coenzyme M ([I]0.5 V=6 mM) and trifluoromethyl-coenzyme M ([I]0.5 V=6 mM) irreversibly inhibited the enzyme. In their presence the MRC-red1 signal was quenched, indicating the oxidation of Ni(I) to Ni(II). The rate of oxidation increased over 10-fold in the presence of coenzyme B, indicating that the Ni(I) reactivity was increased in the presence of coenzyme B. Enzyme inactivated in the presence of coenzyme B showed an isotropic signal characteristic of a radical that is spin coupled with one hydrogen nucleus. The coupling was also observed in D2O. The signal was abolished upon exposure of the enzyme to O2. 3-Bromopropanesulfonate ([I]0.5 V=0.1 µM), 3-iodopropanesulfonate ([I]0.5 V=1 µM), and 4-bromobutyrate also inactivated MCR. In their presence the EPR signal of MCR-red1 was converted into a Ni-based EPR signal MCR-BPS that resembles in line shape the MCR-ox1 signal. The signal was quenched by O2. 2-Bromoethanesulfonate and 3-bromopropanesulfonate, which both rapidly reacted with Ni(I) of MRC-red1, did not react with the Ni of MCR-ox1 and MCR-BPS. The Ni-based EPR spectra of both inactive forms were not affected in the presence of high concentrations of these two potent inhibitors. 相似文献
14.
Effi Eisenmann Joachim Beuerle Klaus Sulger Peter M. H. Kroneck Wolfram Schumacher 《Archives of microbiology》1995,164(3):180-185
Sulfurospirillum deleyianum grew in batch culture under anoxic conditions with sulfide (up to 5 mM) as electron donor, nitrate as electron acceptor,
and acetate as carbon source. Nitrate was reduced to ammonia via nitrite, a quantitatively liberated intermediate. Four moles
of sulfide were oxidized to elemental sulfur per mole nitrate converted to ammonia. The molar growth yield per mole sulfide
consumed, Ym, was 1.5 ± 0.2 g mol–1 for the reduction of nitrate to ammonia. By this type of metabolism, S. deleyianum connected the biogeochemical cycles of sulfur and nitrogen. The sulfur reductase activity in S. deleyianum was inducible, as the activity depended on the presence of sulfide or elemental sulfur during cultivation with nitrate or
fumarate as electron acceptor. Hydrogenase activity was always high, indicating that the enzyme is constitutively expressed.
The ammonia-forming nitrite reductase was an inducible enzyme, expressed when cells were cultivated with nitrate, nitrite,
or elemental sulfur, but repressed after cultivation with fumarate.
Received: 13 March 1995 / Accepted: 29 May 1995 相似文献
15.
W. Hazeu W. H. Batenburg-van der Vegte P. Bos R. K. van der Pas J. G. Kuenen 《Archives of microbiology》1988,150(6):574-579
The intermediary production of elemental sulfur during the microbial oxidation of reduced sulfur compounds has frequently been reported. Thiobacillus ferrooxidans, an acidophilic chemolithoautotroph, was found to produce an insoluble sulfur compound, primarily elemental sulfur, during the oxidation of thiosulfate, trithionate, tetrathionate and sulfide. This was confirmed by light and electron microscopy. Sulfur was produced from sulfide by an oxidative step, while the production from tetrathionate was initiated by a hydrolytic step, probably followed by a series of chemical reactions. The oxidation of intermediary sulfur was severely inhibited by sulfhydryl-binding reagents such as N-ethylmaleimide, by the addition of uncouplers or after freezing and thawing of the cells, which probably damaged the cell membrane. The mechanisms behind these inhibitions have not yet been clarified. Finally, it was observed that elemental sulfur oxidation by whole cells depended on the medium composition. The absence of sulfate or selenate reduced the sulfur oxidation rate.Non-standard abbreviations NEM
N-ethylmaleimide
- CCCP
carbonyl cyanide m-chlorophenyl hydrazone 相似文献
16.
Methyl-coenzyme M reductase (MCR) catalyzes the methane-forming step in methanogenic archaea. It contains the nickel porphinoid F430, a prosthetic group that has been proposed to be directly involved in the catalytic cycle by the direct binding and subsequent reduction of the substrate methyl-coenzyme M. The active enzyme (MCRred1) can be generated in vivo and in vitro by reduction from MCRox1, which is an inactive form of the enzyme. Both the MCRred1 and MCRox1 forms have been proposed to contain F430 in the Ni(I) oxidation state on the basis of EPR and ENDOR data. In order to further address the oxidation state of the Ni center in F430, variable-temperature, variable-field magnetic circular dichroism (VTVH MCD), coupled with parallel absorption and EPR studies, have been used to compare the electronic and magnetic properties of MCRred1, MCRox1, and various EPR silent forms of MCR, with those of the isolated penta-methylated cofactor (F430M) in the +1, +2 and +3 oxidation states. The results confirm Ni(I) assignments for MCRred1 and MCRred2 forms of MCR and reveal charge transfer transitions involving the Ni d orbitals and the macrocycle orbitals that are unique to Ni(I) forms of F430. Ligand field transitions associated with S=1 Ni(II) centers are assigned in the near-IR MCD spectra of MCRox1-silent and MCR-silent, and the splitting in the lowest energy d–d transition is shown to correlate qualitatively with assessments of the zero-field splitting parameters determined by analysis of VTVH MCD saturation magnetization data. The MCD studies also support rationalization of MCRox1 as a tetragonally compressed Ni(III) center with an axial thiolate ligand or a coupled Ni(II)-thiyl radical species, with the reality probably lying between these two extremes. The reinterpretation of MCRox1 as a formal Ni(III) species rather than an Ni(I) species obviates the need to invoke a two-electron reduction of the F430 macrocyclic ligand on reductive activation of MCRox1 to yield MCRred1.Electronic Supplementary Material Supplementary material is available in the online version of this article at http://dx.doi.org/10.1007/s00775-004-0549-9Abbreviations F430
cofactor 430
- F430M
penta-methylated form of cofactor 430
- Ni(I)F430M
F430M with the nickel atom in the +1 oxidation state
- Ni(II)F430M
F430M with the nickel atom in the +2 oxidation state
- Ni(III)F430M
F430M with the nickel atom in the +3 oxidation state
- MCR
methyl-coenzyme M reductase
- MCRox1
MCR exhibiting the MCR-ox1 EPR signal
- MCRox1-silent
EPR silent form of MCR obtained from the MCRox1 form
- MCRred1
MCR exhibiting the EPR signals red1c and/or red1m
- MCRred1c
MCRred1 in the presence of coenzyme M
- MCRred1m
MCRred1 in the presence of methyl-coenzyme M
- MCRred2
MCR exhibiting both the red1 and red2 EPR signals
- MCRred1-silent
EPR silent form of MCR obtained from the MCRred1 form
- MCRsilent
EPR silent form of MCR 相似文献
17.
Pterin derivatives were extracted from formate dehydrogenase and from polysulfide reductase of Wolinella succinogenes and converted to 6-carboxypterin. The amounts of 6-carboxypterin were consisted with the molybdenum content of the enzymes. The bis(carboxamidomethyl) derivatives of the cofactors showed absorption spectra that were identical with that of the corresponding molybdopterin guanine dinucleotide derivative (cam MGD). After hydrolysis of the derivatives with nucleotide pyrophosphatase in the presence of alkaline phosphatase, guanosine was formed together with a compound showing the properties of dephospho-bis(carboxamidomethyl)-molybdopterin. It is conluded that both formate dehydrogenase and polysulfide reductase of W. succinogenes contain molybdopterin guanine dinucleotide.Abbreviations
MPT
molybdopterin
-
MGD
molybdopterin guanine dinucleotide
-
cam MPT
bis(carboxyamidomethyl)-molybdopterin
-
cam MGD
bis(carboxyamidomethyl)-molybdopterin guanine dinucleotide 相似文献
18.
D.A. Saffarini T.J. DiChristina D. Bermudes K.H. Nealson 《FEMS microbiology letters》1994,119(3):271-277
Abstract Pleiotropic respiratory mutants, incapable of growth on any electron acceptor other than oxygen, were isolated from two strains of Shewanella putrefaciens (MR-1 and sp200). All anaerobic respiratory functions were restored by complementation of the mutants with specific cloned DNA fragments. Southern hybridization experiments revealed that the fragment that complements the MR-1 mutant was localized on the megaplasmids of both strains, while the fragment that complements the sp200 mutant was chromosomal. Neither of these fragments hybridized with the anaerobic regulatory genes of S. putrefaciens ( etrA ) or E. coli ( fnr ). 相似文献
19.
20.
Takeno S Ohnishi J Komatsu T Masaki T Sen K Ikeda M 《Applied microbiology and biotechnology》2007,75(5):1173-1182
Oxygen limitation is a crucial problem in amino acid fermentation by Corynebacterium glutamicum. Toward this subject, our study was initiated by analysis of the oxygen-requiring properties of C. glutamicum, generally regarded as a strict aerobe. This organism formed colonies on agar plates up to relatively low oxygen concentrations
(0.5% O2), while no visible colonies were formed in the absence of O2. However, in the presence of nitrate (), the organism exhibited limited growth anaerobically with production of nitrite (), indicating that C. glutamicum can use nitrate as a final electron acceptor. Assays of cell extracts from aerobic and hypoxic cultures yielded comparable
nitrate reductase activities, irrespective of nitrate levels. Genome analysis revealed a narK2GHJI cluster potentially relevant to nitrate reductase and transport. Disruptions of narG and narJ abolished the nitrate-dependent anaerobic growth with the loss of nitrate reductase activity. Disruption of the putative
nitrate/nitrite antiporter gene narK2 did not affect the enzyme activity but impaired the anaerobic growth. These indicate that this locus is responsible for nitrate
respiration. Agar piece assays using l-lysine- and l-arginine-producing strains showed that production of both amino acids occurred anaerobically by nitrate respiration, indicating
the potential of C. glutamicum for anaerobic amino acid production. 相似文献