Jensen's Medium (Nitrogen-Free Broth) Selective Liquid Medium for Free-Living Nitrogen-Fixing Bacteria | Cat: AS-1447
$139.00 AUD
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AuSaMicS Life Science™ · Dehydrated Culture Media · Soil & Agricultural Microbiology
Jensen's Medium (Nitrogen-Free Broth)
Selective Liquid Medium for Free-Living Nitrogen-Fixing Bacteria | Cat: AS-1447
The liquid (broth) format of Jensen's nitrogen-free medium, for enrichment and detection of free-living nitrogen-fixing bacteria, particularly Azotobacter species. As in the agar format, selectivity relies entirely on the absence of an added nitrogen source — only diazotrophic organisms capable of fixing atmospheric nitrogen proliferate. Ideal for enrichment culture, turbidity-based screening, and downstream plating or molecular work. Australian stock held in Epping, Melbourne — same-day dispatch with full COA documentation.
AS-1447 In Stock Australia Same-Day Dispatch Jensen's Formula (Broth)
Quick Specs
CatalogueAS-1447
Dissolution24.1 g/L
Final pH7.2 – 7.8
Sterilisation121°C / 15 min
ReferenceJensen, H.L. (1942)
Overview
Jensen's Medium Broth is the liquid form of Jensen's nitrogen-free formulation, used for enrichment, detection, and cultivation of free-living nitrogen-fixing bacteria, particularly Azotobacter species. Nitrogen-fixing organisms are free-living bacteria that grow well on a nitrogen-free medium, utilising atmospheric nitrogen gas for cell protein synthesis — cell protein that is subsequently mineralised in soil after cell death, contributing to nitrogen availability for crop plants.
As with the agar format (AS-1444), selectivity comes from what is absent: because no nitrogen source is added, only organisms capable of biological nitrogen fixation grow well, while non-fixing contaminants are suppressed by nitrogen limitation. The broth format is preferred for enrichment culture prior to plating, for turbidity-based screening of multiple samples, and for liquid-phase molecular or biochemical downstream work.
Historical Development
The formulation originates from Danish-Australian soil microbiologist H.L. Jensen's 1942 paper, "The Azotobacter of Danish agricultural soils," published in the Proceedings of the Linnean Society of New South Wales (57, 205\u2013212) — part of a series of studies by Jensen through the early 1940s on nitrogen-fixing and cellulose-decomposing soil bacteria. The medium remains in active use in current research: a 2023 study used Jensen's nitrogen-free medium to culture reference strain Azotobacter vinelandii (ATCC BAA-1303) for label-free imaging of diazotroph activity, underscoring the formulation's continued relevance more than eight decades after its original description.
Mode of Action
Sucrose acts as the sole energy source, supporting the high metabolic cost of nitrogen fixation. Sodium molybdate supplies molybdenum, an essential cofactor of the nitrogenase enzyme complex; ferrous sulfate provides iron, also required for nitrogenase function. Dipotassium phosphate buffers the medium; sodium chloride maintains osmotic equilibrium; calcium carbonate stimulates growth and, in the broth format, settles as a fine suspension that should be resuspended by mixing before inoculation and periodically during incubation.
Broth vs. Agar — Which Format Do I Need?
| Feature | AS-1447 (Broth) | AS-1444 (Agar) |
|---|---|---|
| Format | Liquid, no agar | Solid, 15 g/L agar |
| Total dissolution | 24.1 g/L | 39.1 g/L |
| Best for | Enrichment culture, turbidity screening, liquid-phase downstream work | Colony isolation, morphology observation, single-colony purification |
| Typical workflow | Enrich in broth first, then streak to agar for isolated colonies | Direct plating from soil dilutions for colony counts and isolation |
Applications
| Application | Notes |
|---|---|
| Enrichment of Azotobacter spp. from soil/rhizosphere | Liquid enrichment increases recovery of low-abundance diazotrophs prior to plating |
| Agricultural microbiology research | Study of biological nitrogen fixation and soil nitrogen cycling |
| Biofertiliser development | Liquid-scale screening and propagation of candidate nitrogen-fixing strains |
| Reference-strain maintenance | Culturing diazotroph reference strains (e.g. Azotobacter vinelandii) for downstream imaging, physiology, or genetic studies |
Intended use: For laboratory and agricultural research use only. Not intended for therapeutic, diagnostic, or food-safety testing applications.
Technical Data Sheet Summary
Formula — Per Litre
| Component | g/L | Role |
|---|---|---|
| Sucrose | 20.000 | Energy source |
| Calcium Carbonate | 2.000 | Growth stimulant |
| Dipotassium Phosphate | 1.000 | Buffering, phosphorus source |
| Magnesium Sulfate | 0.500 | Mg²⁺ ion source |
| Sodium Chloride | 0.500 | Osmotic equilibrium |
| Ferrous Sulfate | 0.100 | Nitrogenase cofactor |
| Sodium Molybdate | 0.005 | Nitrogenase cofactor |
Total: 24.1 g/L (no agar). Final pH 7.2–7.8 at 25°C. Due to calcium carbonate, the prepared broth forms a characteristic opalescent suspension with fine precipitate — this is expected and should be resuspended by gentle mixing before inoculation.
Preparation
| Dissolution | Suspend 24.1 g in 1 litre of distilled/purified water. Heat just to boiling to dissolve. |
| Dispensing | Dispense into flasks or tubes at the required volume before sterilisation. |
| Sterilisation | Autoclave at 121°C for 15 minutes. |
| Before Use | Mix well to resuspend the calcium carbonate precipitate before inoculation, and periodically during incubation to keep the suspension homogeneous. |
Quality Control (Growth Promotion Testing)
| Test Organism | Inoculum | Expected Result (48\u201372 h, 28\u201330°C) |
|---|---|---|
| Azotobacter chroococcum (reference strain) | \u2264 100 CFU | Good growth (visible turbidity) without added nitrogen source |
| Azotobacter vinelandii ATCC BAA-1303 | \u2264 100 CFU | Good growth (visible turbidity); reference strain used in current diazotroph research |
| Escherichia coli ATCC 25922 | \u2264 100 CFU | No growth to markedly inhibited growth (selectivity check \u2014 non-fixing organism) |
Storage
| Dehydrated Powder | Store below 30°C, tightly closed, protected from moisture and light. Hygroscopic. |
| Prepared Broth | 2–8°C. Discard if contaminated or discoloured. Use freshly prepared medium where possible. |
Literature / References
| # | Reference |
|---|---|
| 1 | Jensen, H.L. (1942). The Azotobacter of Danish agricultural soils. Proceedings of the Linnean Society of New South Wales, 57, 205\u2013212. |
| 2 | Subba Rao, N.S. (1977). Soil Microorganisms and Plant Growth. Oxford and IBH Publishing Co., New Delhi. |
| 3 | Label-free functional analysis of root-associated microbes with dynamic quantitative oblique back-illumination microscopy. PMC10635382 (2023) \u2014 Jensen's nitrogen-free medium used with Azotobacter vinelandii ATCC BAA-1303. |
Safety Data Sheet Summary
Full 16-section SDS prepared in accordance with the GHS and Australian WHS Regulations (Safe Work Australia).
| GHS Classification | Not classified as a hazardous substance or mixture |
| Signal Word / Pictograms | None required |
| Biosafety Note | Microbiological growth medium — treat inoculated cultures as potentially containing viable soil microorganisms; handle per AS/NZS 2243 series |
| Transport | Not classified as Dangerous Goods (ADG, IATA, IMDG); no UN Number applicable |
Full 16-section GHS-compliant SDS is available as a downloadable document — contact support@ausamics.com quoting catalogue number AS-1447.
Certificate of Analysis
Each batch of Jensen's Medium Broth (AS-1447) is released with a batch-specific Certificate of Analysis.
| Test Parameter | Specification |
|---|---|
| Dehydrated Appearance | Off-white, fine, free-flowing, hygroscopic powder |
| Prepared Appearance | Cream coloured, opalescent suspension with fine precipitate (resuspends on mixing) |
| pH (prepared, 25°C) | 7.2 – 7.8 |
| Productivity Test | Azotobacter chroococcum / A. vinelandii \u2014 good growth (visible turbidity) without added nitrogen |
Batch-specific COA is issued with every shipment. Contact support@ausamics.com quoting catalogue number AS-1447.