Jensen's Medium (Nitrogen-Free): Selective Medium for Free-Living Nitrogen-Fixing Bacteria; Cat: AS-1444
$139.00 AUD
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AuSaMicS Life Science™ · Dehydrated Culture Media · Soil & Agricultural Microbiology
Jensen's Medium (Nitrogen-Free)
Selective Medium for Free-Living Nitrogen-Fixing Bacteria | Cat: AS-1444
A nitrogen-free selective medium for detecting and cultivating free-living nitrogen-fixing bacteria, particularly Azotobacter species. Selectivity relies on the absence of an added nitrogen source, so only organisms capable of atmospheric nitrogen fixation grow well. Australian stock held in Melbourne — same-day dispatch with full COA documentation.
AS-1444 In Stock Australia Same-Day Dispatch Jensen's Formula
Quick Specs
CatalogueAS-1444
Dissolution39.1 g/L
Final pH7.2 – 7.8
Sterilisation121°C / 15 min
ReferenceJensen, H.L.
Overview
Jensen's Medium is recommended for 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. This cell protein is subsequently mineralised in soil after cell death, contributing to nitrogen availability for crop plants.
Because no nitrogen source is added, this medium is inherently selective: only organisms capable of biological nitrogen fixation grow well, while non-fixing contaminants are suppressed by nitrogen limitation.
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 contributes to the medium's characteristic opalescent appearance.
Applications
| Application | Notes |
|---|---|
| Isolation and screening of Azotobacter spp. | Standard method for detecting free-living nitrogen-fixing bacteria from soil and rhizosphere samples |
| Agricultural microbiology research | Study of biological nitrogen fixation and soil nitrogen cycling |
| Biofertiliser development | Pre-screening of candidate nitrogen-fixing strains for biofertiliser formulation |
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 |
| Agar | 15.000 | Solidifying agent |
Total: 39.1 g/L. Final pH 7.2–7.8 at 25°C. Due to calcium carbonate, the prepared medium forms a characteristic opalescent solution with slight precipitate — this is expected.
Preparation
| Dissolution | Suspend 39.1 g in 1 litre of distilled/purified water. Heat just to boiling to dissolve. |
| Sterilisation | Autoclave at 121°C for 15 minutes. |
| Pouring | Cool to 45–50°C, mix well to resuspend the precipitate, and pour into sterile Petri plates. |
Storage
| Dehydrated Powder | Store below 30°C, tightly closed, protected from moisture and light. Hygroscopic. |
| Prepared Medium | 2–8°C. Discard if contaminated or discoloured. |
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-1444.
Certificate of Analysis
Each batch of Jensen's Medium (AS-1444) 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, slightly opalescent gel with slight precipitate |
| pH (prepared, 25°C) | 7.2 – 7.8 |
| Productivity Test | Azotobacter chroococcum — good growth without added nitrogen |
Batch-specific COA is issued with every shipment. Contact support@ausamics.com quoting catalogue number AS-1444.