Use of Pankhurst tubes to assay acetylene reduction by facultative and anaerobic nitrogen-fixing bacteria

1969 ◽  
Vol 15 (11) ◽  
pp. 1342-1343 ◽  
Author(s):  
N. E. R. Campbell ◽  
Harold J. Evans
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Most Probable Number ◽  
Bacterial Isolates ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Probable Number ◽  
Density Measurements ◽  
Large Numbers ◽  
Root Surfaces

Pankhurst tubes are simple and inexpensive vessels in which to screen large numbers of bacterial isolates by the acetylene reduction test for nitrogen fixation. A modification is described which allows, in addition, optical density measurements of growth. The method is well suited to most probable number estimations of facultative and anaerobic nitrogen-fixing bacteria in soils and on root surfaces.

Asymbiotic N2-fixing bacteria associated with three boreal conifers

1984 ◽  
Vol 14 (4) ◽  
pp. 595-597 ◽  
Author(s):  
L. Z. Florence ◽  
F. D. Cook
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Seedling Root ◽  
Natural Stands

Azotobacter spp., Azospirillum spp., and Desulfovibrio spp., were identified as the predominant nitrogen-fixing bacteria associated with seedling root sections collected from natural stands of Pinusbanksiana Lamb., Piceamariana (Mill.) B.S.P., and Larixlaricina (Du Roi) K. Koch growing in Alberta. Samples from the sandy upland habitat of P. banksiana exhibited lower average rates of nitrogen fixation relative to the wet lowland occupied by P. mariana and L. laricina. Average nitrogen-fixing capacity (by acetylene reduction) was greater among bacteria isolates from L. laricina than those from P. mariana. Azospirillum spp. were strongly associated with P. mariana, while Azotobacter spp. were isolated more frequently from L. laricina.

scholarly journals Nitrogen Fixation in Pozol, a Traditional Fermented Beverage

2020 ◽  
Vol 86 (16) ◽  
Author(s):  
Jocelin Rizo ◽  
Marco A. Rogel ◽  
Daniel Guillén ◽  
Carmen Wacher ◽  
Esperanza Martinez-Romero ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Growth Promotion ◽  
Point Of View ◽  
Intestinal Microbiome ◽  
Acetylene Reduction Activity ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Free Living ◽  
Functional Perspective

ABSTRACT Traditional fermentations have been widely studied from the microbiological point of view, but little is known from the functional perspective. In this work, nitrogen fixation by free-living nitrogen-fixing bacteria was conclusively demonstrated in pozol, a traditional Mayan beverage prepared with nixtamalized and fermented maize dough. Three aspects of nitrogen fixation were investigated to ensure that fixation actually happens in the dough: (i) the detection of acetylene reduction activity directly in the substrate, (ii) the presence of potential diazotrophs, and (iii) an in situ increase in acetylene reduction by inoculation with one of the microorganisms isolated from the dough. Three genera were identified by sequencing the 16S rRNA and nifH genes as Kosakonia, Klebsiella, and Enterobacter, and their ability to fix nitrogen was confirmed. IMPORTANCE Nitrogen-fixing bacteria are found in different niches, as symbionts in plants, in the intestinal microbiome of several insects, and as free-living microorganisms. Their use in agriculture for plant growth promotion via biological nitrogen fixation has been extensively reported. This work demonstrates the ecological and functional importance that these bacteria can have in food fermentations, reevaluating the presence of these genera as an element that enriches the nutritional value of the dough.

scholarly journals Genomic characterization and computational phenotyping of nitrogen-fixing bacteria isolated from Colombian sugarcane fields

2019 ◽  
Author(s):  
Luz K. Medina-Cordoba ◽  
Aroon T. Chande ◽  
Lavanya Rishishwar ◽  
Leonard W. Mayer ◽  
Lina C. Valderrama-Aguirre ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Nitrogen Fixation ◽  
Plant Growth ◽  
Phosphate Solubilization ◽  
Bacterial Isolates ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
A Genome ◽  
Plant Growth Promoting ◽  
Growth Promoting

ABSTRACTPrevious studies have shown that the sugarcane microbiome harbors diverse plant growth promoting (PGP) microorganisms, including nitrogen-fixing bacteria, and the objective of this study was to design a genome-enabled approach to prioritize sugarcane associated nitrogen-fixing bacteria according to their potential as biofertilizers. Using a systematic high throughput approach, 22 pure cultures of nitrogen-fixing bacteria were isolated and tested for diazotrophic potential by PCR amplification of nitrogenase (nifH) genes, common molecular markers for nitrogen fixation capacity. Genome sequencing confirmed the presence of intact nitrogenase nifH genes and operons in the genomes of 18 of the isolates. Isolate genomes also encoded operons for phosphate solubilization, siderophore production operons, and other PGP phenotypes. Klebsiella pneumoniae strains comprised 14 of the 22 nitrogen-fixing isolates, and four others were members of closely related genera to Klebsiella. A computational phenotyping approach was developed to rapidly screen for strains that have high potential for nitrogen fixation and other PGP phenotypes while showing low risk for virulence and antibiotic resistance. The majority of sugarcane isolates were below a genotypic and phenotypic threshold, showing uniformly low predicted virulence and antibiotic resistance compared to clinical isolates. Six prioritized strains were experimentally evaluated for PGP phenotypes: nitrogen fixation, phosphate solubilization, and the production of siderophores, gibberellic acid and indole acetic acid. Results from the biochemical assays were consistent with the computational phenotype predictions for these isolates. Our results indicate that computational phenotyping is a promising tool for the assessment of benefits and risks associated with bacteria commonly detected in agricultural ecosystems.IMPORTANCEA genome-enabled approach was developed for the prioritization of native bacterial isolates with the potential to serve as biofertilizers for sugarcane fields in Colombia’s Cauca Valley. The approach is based on computational phenotyping, which entails predictions related to traits of interest based on bioinformatic analysis of whole genome sequences. Bioinformatic predictions of the presence of plant growth promoting traits were validated with experimental assays and more extensive genome comparisons, thereby demonstrating the utility of computational phenotyping for assessing the benefits and risks posed by bacterial isolates that can be used as biofertilizers. The quantitative approach to computational phenotyping developed here for the discovery of biofertilizers has the potential for use with a broad range of applications in environmental and industrial microbiology, food safety, water quality, and antibiotic resistance studies.

A Survey of Asymbiotic Nitrogen Fixation in the Rhizosphere of Weeds

Weed Science ◽  
1978 ◽  
Vol 26 (2) ◽  
pp. 148-150 ◽  
Author(s):  
A. R. Conklin ◽  
P. K. Biswas
Keyword(s):  
Thin Film ◽  
Nitrogen Fixation ◽  
Acetylene Reduction ◽  
Rhizosphere Soil ◽  
Soil Samples ◽  
Reduction Technique ◽  
Nitrogen Fixing ◽  
Weed Species ◽  
Nitrogen Fixing Bacteria ◽  
Asymbiotic Nitrogen Fixation

The occurrence of asymbiotic nitrogen fixing bacteria in the rhizosphere of twenty weed species has been investigated. Using the roll tube method root-rhizosphere soil samples were diluted and added to test tubes containing low N media. Tubes were flushed with nitrogen, stoppered, and rolled to form a thin film of media on the inner wall. After 7 days incubation the nitrogen fixation rates were estimated using the acetylene reduction technique. Rates ranged from 38 to 783 nmoles acetylene reduced per hour. Of twenty species tested, three showed high rhizosphere populations of asymbiotic nitrogen fixing bacteria.

scholarly journals Genomic characterization and computational phenotyping of nitrogen-fixing bacteria isolated from Colombian sugarcane fields

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luz K. Medina-Cordoba ◽  
Aroon T. Chande ◽  
Lavanya Rishishwar ◽  
Leonard W. Mayer ◽  
Lina C. Valderrama-Aguirre ◽  
...  
Keyword(s):  
Antibiotic Resistance ◽  
Nitrogen Fixation ◽  
Plant Growth ◽  
Phosphate Solubilization ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Promising Tool ◽  
A Genome ◽  
Plant Growth Promoting ◽  
Growth Promoting

AbstractPrevious studies have shown the sugarcane microbiome harbors diverse plant growth promoting microorganisms, including nitrogen-fixing bacteria (diazotrophs), which can serve as biofertilizers. The genomes of 22 diazotrophs from Colombian sugarcane fields were sequenced to investigate potential biofertilizers. A genome-enabled computational phenotyping approach was developed to prioritize sugarcane associated diazotrophs according to their potential as biofertilizers. This method selects isolates that have potential for nitrogen fixation and other plant growth promoting (PGP) phenotypes while showing low risk for virulence and antibiotic resistance. Intact nitrogenase (nif) genes and operons were found in 18 of the isolates. Isolates also encode phosphate solubilization and siderophore production operons, and other PGP genes. The majority of sugarcane isolates showed uniformly low predicted virulence and antibiotic resistance compared to clinical isolates. Six strains with the highest overall genotype scores were experimentally evaluated for nitrogen fixation, phosphate solubilization, and the production of siderophores, gibberellic acid, and indole acetic acid. Results from the biochemical assays were consistent and validated computational phenotype predictions. A genotypic and phenotypic threshold was observed that separated strains by their potential for PGP versus predicted pathogenicity. Our results indicate that computational phenotyping is a promising tool for the assessment of bacteria detected in agricultural ecosystems.

Use of Iron Milk Medium for Enumeration of Clostridium perfringens

1982 ◽  
Vol 65 (5) ◽  
pp. 1129-1133 ◽  
Author(s):  
William D St John ◽  
Jack R Matches ◽  
Marleen M Wekell
Keyword(s):  
Clostridium Perfringens ◽  
Incubation Time ◽  
Incubation Temperature ◽  
Egg Yolk ◽  
Most Probable Number ◽  
Biochemical Tests ◽  
Probable Number ◽  
Large Numbers ◽  
Whole Milk ◽  
Short Incubation Time

Abstract A simple iron milk medium was used for isolation and enumeration of Clostridium perfringens from soil, sludge, and water samples. The whole milk contained only iron powder as a reducing agent; no other inhibitors were added. The iron milk most probable number (MPN) procedure was compared with 4 plating media: sulfite-polymyxin-sulfadiazine, Shahidi-Ferguson perfringens, tryptose-sulfite- cycloserine (both with and without egg yolk), and tryptone-sulfite-neomycin. The selectivity of the iron milk relies solely on the rapid growth of C. perfringens at 45°C and the stormy fermentation reaction within 18 h. Isolates were confirmed as C. perfringens by standard biochemical tests. The iron milk MPN procedure compared very well with the 4 plating media tested. Selectivity of incubation temperature, short incubation time, and ease of identification by the characteristic stormy fermentation make this method ideal for enumerating C. perfringens from large numbers of samples.

Endophytic nitrogen fixation – a possible ‘hidden’ source of nitrogen for lodgepole pine trees growing at unreclaimed gravel mining sites

2019 ◽  
Vol 95 (11) ◽  
Author(s):  
Kiran Preet Padda ◽  
Akshit Puri ◽  
Chris Chanway
Keyword(s):  
Nitrogen Fixation ◽  
Lodgepole Pine ◽  
Nifh Gene ◽  
Control Treatment ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria ◽  
Mining Sites ◽  
Greenhouse Study ◽  
Gravel Mining ◽  
Pine Trees

ABSTRACT Lodgepole pine (Pinus contorta var. latifolia) trees have been thriving on unreclaimed gravel mining sites in British Columbia, Canada, with tissue nitrogen-content and growth-rate unaffected by extremely low soil nitrogen-levels. This indicates that pine trees could be accessing a hidden nitrogen source to fulfill their nitrogen requirements – possibly via endophytic nitrogen-fixation. Endophytic bacteria originally isolated from native pine trees growing at gravel sites were selected (n = 14) for in vitro nitrogen-fixation assays and a year long greenhouse study to test the overall hypothesis that naturally occurring endophytic nitrogen-fixing bacteria sustain pine tree growth under nitrogen-limited conditions. Each of the 14 bacteria colonized the internal tissues of pine trees in the greenhouse study and fixed significant amounts of nitrogen from atmosphere (23%–53%) after one year as estimated through 15N isotope dilution assay. Bacterial inoculation also significantly enhanced the length (31%–64%) and biomass (100%–311%) of pine seedlings as compared to the non-inoculated control treatment. In addition, presence of the nifH gene was confirmed in all 14 bacteria. Our results support the possibility that pine trees associate with nitrogen-fixing bacteria, capable of endophytic colonization, to survive at unreclaimed gravel mining pits and this association could potentially be utilized for effective reclamation of highly disturbed sites in a sustainable manner.

Changes in acetylene reduction activities and effects of inoculated rhizosphere nitrogen-fixing bacteria on rice

2005 ◽  
Vol 41 (5) ◽  
pp. 371-378 ◽  
Author(s):  
Zhe Piao ◽  
Zongjun Cui ◽  
Bin Yin ◽  
Jian Hu ◽  
Chunhong Zhou ◽  
...  
Keyword(s):  
Acetylene Reduction ◽  
Nitrogen Fixing ◽  
Nitrogen Fixing Bacteria

Bacterial Populations of Ground Beef, Textured Soy Protein and Ground Beef Extended With Soy Protein After 3 and 10 Days of Refrigerated Storage1,2

1978 ◽  
Vol 41 (8) ◽  
pp. 647-653 ◽  
Author(s):  
JAMES F. FOSTER ◽  
RICHARD C. HUNDERFUND ◽  
JAMES L. FOWLER ◽  
JOHN T. FRUIN ◽  
LINDA S. GUTHERTZ
Keyword(s):  
Soy Protein ◽  
Ground Beef ◽  
Microbial Populations ◽  
Plate Count ◽  
Most Probable Number ◽  
Bacterial Populations ◽  
Probable Number ◽  
Fecal Streptococcus ◽  
Large Numbers ◽  
Aerobic Plate Count

A survey of the microbial populations of 31 samples of ground beef (GB), textured soy protein (TSP), and ground beef extended with TSP (SGB) after 3 and 10 days of storage at 4 C was done. Analyses included aerobic plate count (APC), psychrotrophic plate count (PPC), coliform Most Probable Number (CMPN) and plate determinations (CPC), Escherichia coli MPN (EMPN) and plate determinations (EPC), Staphylococcus aureus MPN, and fecal streptococcus plate count. Statistical analyses of data from the enumeration procedures showed significant increases in the total microbial flora after 10 days of storage. PPCs were significantly higher than APCs. CMPNs were significantly higher than CPCs for GB and SGB. The EMPNs were significantly higher than EPCs in SGB only. These products contained a variety of microorganisms many in large numbers; however if properly handled and cooked before consumption, these products should present no public health problems.

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