scholarly journals nifH Sequences and Nitrogen Fixation in Type I and Type II Methanotrophs

2001 ◽  
Vol 67 (9) ◽  
pp. 4009-4016 ◽  
Author(s):  
Ann J. Auman ◽  
Catherine C. Speake ◽  
Mary E. Lidstrom
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Freshwater Lake ◽  
Type I ◽  
Type Ii ◽  
Nitrogen Fixing ◽  
Protein Sequence Analysis ◽  
High Identity ◽  
Rice Roots ◽  
Methane Oxidizing Bacteria

ABSTRACT Some methane-oxidizing bacteria (methanotrophs) are known to be capable of expressing nitrogenase and utilizing N2 as a nitrogen source. However, no sequences are available fornif genes in these strains, and the known nitrogen-fixing methanotrophs are confined mainly to a few genera. The purpose of this work was to assess the nitrogen-fixing capabilities of a variety of methanotroph strains. nifH gene fragments from four type I methanotrophs and seven type II methanotrophs were PCR amplified and sequenced. Nitrogenase activity was confirmed in selected type I and type II strains by acetylene reduction. Activities ranged from 0.4 to 3.3 nmol/min/mg of protein. Sequence analysis shows that thenifH sequences from the type I and type II strains cluster with nifH sequences from other gamma proteobacteria and alpha proteobacteria, respectively. The translatednifH sequences from three Methylomonas strains show high identity (95 to 99%) to several published translated environmental nifH sequences PCR amplified from rice roots and a freshwater lake. The translated nifHsequences from the type II strains show high identity (94 to 99%) to published translated nifH sequences from a variety of environments, including rice roots, a freshwater lake, an oligotrophic ocean, and forest soil. These results provide evidence for nitrogen fixation in a broad range of methanotrophs and suggest that nitrogen-fixing methanotrophs may be widespread and important in the nitrogen cycling of many environments.

Comparative surface and ultrastructural views of methylotrophic bacteria by TEM, STEM, SE, and freeze-etch electron microscopy.

1987 ◽  
Vol 45 ◽  
pp. 792-793
Author(s):  
T.A. Fassel ◽  
M.J. Schaller ◽  
M.E. Lidstrom ◽  
C.C. Remsen
Keyword(s):  
Cytoplasmic Membrane ◽  
Structural Features ◽  
Methylotrophic Bacteria ◽  
Type I ◽  
Type Ii ◽  
Membrane Complex ◽  
Oxidation Of Methane ◽  
Methane Oxidizing Bacteria ◽  
Wall Structures ◽  
Methylomonas Albus

Methylotrophic bacteria play an Important role in the environment in the oxidation of methane and methanol. Extensive intracytoplasmic membranes (ICM) have been associated with the oxidation processes in methylotrophs and chemolithotrophic bacteria. Classification on the basis of ICM arrangement distinguishes 2 types of methylotrophs. Bundles or vesicular stacks of ICM located away from the cytoplasmic membrane and extending into the cytoplasm are present in Type I methylotrophs. In Type II methylotrophs, the ICM form pairs of peripheral membranes located parallel to the cytoplasmic membrane. Complex cell wall structures of tightly packed cup-shaped subunits have been described in strains of marine and freshwater phototrophic sulfur bacteria and several strains of methane oxidizing bacteria. We examined the ultrastructure of the methylotrophs with particular view of the ICM and surface structural features, between representatives of the Type I Methylomonas albus (BG8), and Type II Methylosinus trichosporium (OB-36).

Nitrogen fixation

1976 ◽  
Vol 274 (934) ◽  
pp. 341-358 ◽  
Keyword(s):  
Nitrogen Fixation ◽  
Metabolic Regulation ◽  
Higher Plants ◽  
Focal Point ◽  
Nitrogenase Activity ◽  
Nitrogen Fixing ◽  
Blue Green Algae ◽  
International Biological Programme ◽  
The 1960S ◽  
Biological Programme

The International Biological Programme served as a focal point for studies on biological nitrogen fixation during the 1960s. The introduction of the acetylene reduction technique for measuring nitrogenase activity in the field led to estimates becoming available of the contribution of lichens, blue-green algae, nodulated non-legumes and bacterial-grass associations, as well as of legumes. Other studies carried out on the physiology and biochemistry of the process led to the eventual purification and characterization of the nitrogenase enzyme. These studies, collectively, provided the springboard for current work, so essential in view of the present energy crisis, on how to increase the use and efficiency of nitrogen-fixing plants, on the metabolic regulation of the nitrogenase enzyme and on the genetics of the nitrogen-fixing process, both in higher plants and in free-living micro-organisms.

scholarly journals NODULE SENESCENCE AND BIOMASS COMPONENTS IN COMMON BEAN CULTIVARS

2008 ◽  
Vol 31 (3) ◽  
pp. 195
Author(s):  
Fabián Fernández-Luqueño ◽  
David Espinosa-Victoria ◽  
Antonio Munive ◽  
Langen Corlay Chee ◽  
Luis M. Serrano-Covarrubias
Keyword(s):  
Nitrogen Fixation ◽  
Common Bean ◽  
Nitrogenase Activity ◽  
Dry Weight ◽  
Type I ◽  
Fresh Weight ◽  
Symbiotic Relationships ◽  
Nodule Senescence ◽  
Biomass Components ◽  
Growth Habits

Most legumes establish mutualistic symbiotic relationships with atmospheric nitrogen-fixing bacteria (rhizobia), giving origin to nodules. Nodules exhibit natural or induced aging which coincides with the drop in nitrogenase activity at the flowering period or at the pod filling stage. In this research, the onset of nodule senescence (NS) was evaluated under greenhouse conditions in five common bean (Phaseolus vulgaris L.) cultivars of two growth habits, determined (Type I) and indeterminate (Type III), inoculated with Rhizobium etli CE-3. Weekly destructive samplings were taken to determine nitrogen fixation by the acetylene reduction assay, the number and fresh weight of nodules, as well as root and above ground biomass dry weight. It was found that NS in bean appears to be independent of host plant phenological stage (flowering or pod filling), the longer period the symbiotic system is fixing nitrogen the greater yield is obtained, and that the nodules number and fresh weight are reliable indicators of the nitrogen fixation capacity.

scholarly journals Medicago truncatulaFerroportin2 mediates iron import into nodule symbiosomes

2019 ◽  
Author(s):  
Viviana Escudero ◽  
Isidro Abreu ◽  
Manuel Tejada-Jiménez ◽  
Elena Rosa-Núñez ◽  
Julia Quintana ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Symbiotic Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Specific Gene ◽  
Nitrogen Fixing ◽  
Loss Of Function ◽  
Model Legume ◽  
Endosymbiotic Bacteria ◽  
Signal Transduction Proteins ◽  
Iron Delivery

ABSTRACTIron is an essential cofactor for symbiotic nitrogen fixation. It is required by many of the enzymes facilitating the conversion of N2into NH4+by endosymbiotic bacteria living within root nodule cells, including signal transduction proteins, O2homeostasis systems, and nitrogenase itself. Consequently, host plants have developed a transport network to deliver essential iron to nitrogen-fixing nodule cells. Model legumeMedicago truncatula Ferroportin2(MtFPN2) is a nodule-specific gene that encodes an iron-efflux protein. MtFPN2 is located in intracellular membranes in the nodule vasculature, and in the symbiosome membranes that contain the nitrogen-fixing bacteria in the differentiation and early-fixation zones of the nodules. Loss-of-function ofMtFPN2leads to altered iron distribution and speciation in nodules, which causes a reduction in nitrogenase activity and in biomass production. Using promoters with different tissular activity to driveMtFPN2expression inMtFPN2mutants, we determined that MtFPN2-facilitated iron delivery across symbiosomes is essential for symbiotic nitrogen fixation, while its presence in the vasculature does not seem to play a major role in in the conditions tested.

A comparison of carbon source utilization for growth and nitrogenase activity in two Frankia isolates

1986 ◽  
Vol 32 (4) ◽  
pp. 353-358 ◽  
Author(s):  
Mary F. Lopez ◽  
Patricia Young ◽  
John G. Torrey
Keyword(s):  
Nitrogen Fixation ◽  
Carbon Source ◽  
Oxygen Uptake ◽  
Acetylene Reduction ◽  
Nitrogenase Activity ◽  
Carbon Sources ◽  
Alnus Rubra ◽  
Nitrogen Fixing ◽  
Pure Cultures

The carbon source requirements for the growth and nitrogen fixation of two morphologically distinct Frankia isolates were examined. Isolate ArI3 (from Alnus rubra) grew well on propionate, malate, acetate, and trehalose, and isolate CcI2 (from Casuarina cunninghamiana) grew best on pyruvate, acetate, and propionate. In general, the same carbon sources that supported growth supported both the development of vesicles and nitrogenase activity in long-term induction experiments in both isolates. However, ArI3 cultures induced on proprionate had 7 to 26 times the activity of other carbon sources and ArI3 cultures induced on acetate did not develop any detectable acetylene reduction. In a parallel set of experiments, cultures of both isolates were induced for nitrogenase activity on propionate and the resulting nitrogen fixing cultures were washed free of the organic acid by centrifugation. The washed cultures were incubated in the presence of various carbon sources to determine the ability of a particular substrate to supply energy directly for nitrogen fixation when vesicles and nitrogenase were already present. As was observed in the long-term induction experiments, pyruvate, propionate, and acetate supported the greatest activity in CcI2. Succinate and malate supported the greatest activity in ArI3, and propionate had very little stimulation of acetylene reduction. The reason for the lack of stimulation by propionate for washed cells of ArI3 was unclear but may have been due to toxic concentrations of the organic acid. In an attempt to compare the carbon utilization of ArI3 in pure culture with that in the alder symbiosis, oxygen uptake in the presence of various carbon sources of vesicles clusters isolate from Alnus rubra nodules inoculated with ArI3 was compared with the oxygen uptake of nitrogen-fixing pure cultures of ArI3. The oxygen uptake of the isolated vesicle clusters was stimulated by sucrose, trehalose, and glucose, but not by a variety of organic acids. In comparison, nitrogen-fixing pure cultures of ArI3 readily oxidized sugars and organic acids.

Molybdenum enhancement of nitrogen fixation in a Mo-starved Azotobacter vinelandii Nif− mutant

1982 ◽  
Vol 28 (10) ◽  
pp. 1173-1180 ◽  
Author(s):  
William J. Page ◽  
S. Karen Collinson
Keyword(s):  
Molecular Weight ◽  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Polyacrylamide Gel Electrophoresis ◽  
Nitrogen Fixing ◽  
Wild Type ◽  
Cell Extracts ◽  
In The Wild ◽  
Dinitrogenase Reductase

Molybdenum (Mo)-starved wild-type and Nif− strains of Azotobacter vinelandii reduced acetylene (fixed nitrogen) in Mo-limited nitrogen-free medium. Vanadate enhanced this activity in all of the strains. Molybdate caused repression of nitrogenase activity in the Nif− mutants and enhanced the nitrogenase activity in the wild type. The nitrogenase activity in the Nif− mutant UW3, however, was enhanced by Mo, became maximal after 3 h, and then declined to zero after 10 h of incubation. The activation of nitrogenase by Mo followed a 5- to 10-min lag and was inhibited when streptomycin or rifampin was added with Mo. Examination of Mo-starved nitrogen-fixing UW3 cell extracts by two-dimensional polyacrylamide gel electrophoresis revealed molecular weight 57 000, 50 000, and 30 000 proteins that were Mo and NH4+ repressive. The molecular weight 30 000 protein appeared in the same position on the gel as the wild-type dinitrogenase reductase, although UW3 did not produce this protein under Mo-sufficient nitrogen-fixing conditions. Cell extracts prepared 3 h after Mo addition lacked the molecular weight 57 000 and 50 000 proteins but contained a new protein corresponding to the β subunit of dinitrogenase. When UW3 nitrogenase activity was lost, the dinitrogenase reductase-like protein also was absent. The results suggest that a complex active in nitrogen fixation may form between components of the traditional Mo-sufficient and alternative Mo-starved cell nitrogen fixation systems.

A new nitrogen-fixing Clostridium species from a high Arctic ecosystem

1979 ◽  
Vol 25 (8) ◽  
pp. 947-948 ◽  
Author(s):  
D. C. Jordan ◽  
Patricia J. McNicol
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
High Arctic ◽  
Undescribed Species ◽  
Nitrogen Fixing ◽  
Canadian High Arctic ◽  
Clostridium Species ◽  
Gram Negative ◽  
Arctic Ecosystem ◽  
Devon Island

A hitherto undescribed species of yellow-pigmented, Gram-negative Clostridium sp., possessing nitrogenase activity, has been isolated from a number of sampling sites on the Truelove Lowland of Devon Island in the Canadian high Arctic. This bacterium, tentatively designated Clostridium arcticum sp. nov., accounted for 19% of all isolates recovered which were capable of anaerobic nitrogen fixation.

scholarly journals Artificial activation of nif gene expression in nodule bacteria Ex Planta

2019 ◽  
Vol 17 (2) ◽  
pp. 35-42
Author(s):  
Andrey K. Baymiev ◽  
Roman S. Gumenko ◽  
Anastasiya A. Vladimirova ◽  
Ekaterina S. Akimova ◽  
Zilya R. Vershinina ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Nitrogenase Activity ◽  
Regulatory Protein ◽  
Inducible Promoter ◽  
Nitrogen Fixing ◽  
Nodule Bacteria ◽  
Free Living ◽  
Living State ◽  
Artificial Activation ◽  
Nifa Gene

Background. Rhizobia are the most effective nitrogen-fixing organisms that can fix nitrogen only in symbiosis with leguminous plants. The general transcriptional activator of nitrogen fixation genes in diazotrophic bacteria is NifA. In this work, the possibility of modifying the regulation of nitrogen fixation in the nodule bacteria Mesorhizobium, Ensifer and Rhizobium was studied by introducing an additional copy of the nifA gene into the bacterial genomes during the regulation of induced bacterial promoters. Materials and methods. A series of expression genetic constructs with NifA genes of nodule bacteria strains under the control of an inducible promoter Pm were created. The resulting constructs were transformed into strains of nodule bacteria. The obtained recombinant strains were investigated for the appearance of their nitrogen-fixing activity in the free-living state. Results. It was shown that the expression of nifA in recombinant cells of all three genera of bacteria leads to the appearance of insignificant nitrogenase activity. At the same time, the level of nitrogenase activity does not have a correlation with the level of expression of the introduced nifA gene, which, most likely, is a consequence of the multilevel regulation of nitrogen fixation. Conclusion. The possibility of artificial activation of nitrogenase activity in nodule bacteria in the free-living state by introducing the NifA regulatory protein gene into bacteria was shown.

scholarly journals Abundance, Activity, and Community Structure of Pelagic Methane-Oxidizing Bacteria in Temperate Lakes

2005 ◽  
Vol 71 (11) ◽  
pp. 6746-6752 ◽  
Author(s):  
Ingvar Sundh ◽  
David Bastviken ◽  
Lars J. Tranvik
Keyword(s):  
Fatty Acids ◽  
Bacterial Biomass ◽  
Transformation Method ◽  
Substantial Contribution ◽  
Type I ◽  
Type Ii ◽  
Temperate Lakes ◽  
Oxidation Activity ◽  
Methane Oxidizing Bacteria ◽  
Specific Oxidation

ABSTRACT The abundance and activity of methane-oxidizing bacteria (MOB) in the water column were investigated in three lakes with different contents of nutrients and humic substances. The abundance of MOB was determined by analysis of group-specific phospholipid fatty acids from type I and type II MOB, and in situ activity was measured with a 14CH4 transformation method. The fatty acid analyses indicated that type I MOB most similar to species of Methylomonas, Methylomicrobium, and Methylosarcina made a substantial contribution (up to 41%) to the total bacterial biomass, whereas fatty acids from type II MOB generally had very low concentrations. The MOB biomass and oxidation activity were positively correlated and were highest in the hypo- and metalimnion during summer stratification, whereas under ice during winter, maxima occurred close to the sediments. The methanotroph biomass-specific oxidation rate (V) ranged from 0.001 to 2.77 mg CH4-C mg−1 C day−1 and was positively correlated with methane concentration, suggesting that methane supply largely determined the activity and biomass distribution of MOB. Our results demonstrate that type I MOB often are a large component of pelagic bacterial communities in temperate lakes. They represent a potentially important pathway for reentry of carbon and energy into pelagic food webs that would otherwise be lost as evasion of CH4.

scholarly journals Molecular Characterization of Methanotrophic Isolates from Freshwater Lake Sediment

2000 ◽  
Vol 66 (12) ◽  
pp. 5259-5266 ◽  
Author(s):  
Ann J. Auman ◽  
Sergei Stolyar ◽  
Andria M. Costello ◽  
Mary E. Lidstrom
Keyword(s):  
16S Rrna ◽  
Methane Oxidation ◽  
Lake Sediment ◽  
Freshwater Lake ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Rrna Gene ◽  
Type I ◽  
Type Ii ◽  
Oxidation Potentials

ABSTRACT Profiles of dissolved O2 and methane with increasing depth were generated for Lake Washington sediment, which suggested the zone of methane oxidation is limited to the top 0.8 cm of the sediment. Methane oxidation potentials were measured for 0.5-cm layers down to 1.5 cm and found to be relatively constant at 270 to 350 μmol/liter of sediment/h. Approximately 65% of the methane was oxidized to cell material or metabolites, a signature suggestive of type I methanotrophs. Eleven methanotroph strains were isolated from the lake sediment and analyzed. Five of these strains classed as type I, while six were classed as type II strains by 16S rRNA gene sequence analysis. Southern hybridization analysis with oligonucleotide probes detected, on average, one to two copies of pmoA and one to three copies of 16S rRNA genes. Only one restriction length polymorphism pattern was shown for pmoA genes in each isolate, and in cases where, sequencing was done, the pmoA copies were found to be almost identical. PCR primers were developed formmoX which amplified 1.2-kb regions from all six strains that tested positive for cytoplasmic soluble methane mono-oxygenase (sMMO) activity. Phylogenetic analysis of the translated PCR products with published mmoX sequences showed that MmoX falls into two distinct clusters, one containing the orthologs from type I strains and another containing the orthologs from type II strains. The presence of sMMO-containing Methylomonas strains in a pristine freshwater lake environment suggests that these methanotrophs are more widespread than has been previously thought.

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