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Ascospore Agar (Product Code: AS-1436) by Ausamics
$87.00 AUD
Ascospore Agar
Potassium Acetate Sporulation Medium for Ascosporogenous Yeasts | McClary Modification | Cat. No. AS-1436
Cat. No. AS-1436 pH 6.4 ± 0.2 43.5 g/L Agar 30.0 g/L Potassium Acetate 10.0 g/L ✓ McClary Modification ✓ HiMedia M162 Equivalent ✓ Oxoid CM0715 Equivalent 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch 📄 COA Every Batch
Cat. No.
AS-1436
pH (25°C)
6.4 ± 0.2
Dissolution
43.5 g/L
Incubation
25–30°C / 3–10 d
Sterilisation
121°C / 15 min
📄 Full DocumentationCOA, TDS & SDS every batch
🇦🇺 Australian StockNo import delays
⚡ Same-Week DispatchMelbourne warehouse
🔬 Technical SupportDirect from our team
Overview
Ascospore Agar (AS-1436) is a specialised sporulation medium formulated for the induction and detection of ascospore formation in ascosporogenous yeasts, particularly Saccharomyces cerevisiae and related species. It is the McClary modification of the original acetate sporulation agar — replacing sodium acetate with potassium acetate to achieve a higher and more consistent rate of ascospore production.
Unlike nutrient-rich propagation media, Ascospore Agar is intentionally nutrient-limited. The very low dextrose concentration (1.0 g/L), combined with potassium acetate as the primary carbon source and a mildly acidic pH (6.4), creates the specific physiological stress conditions that trigger Saccharomyces to abandon vegetative budding and undergo meiosis — producing the characteristic asci containing 1–4 ascospores that are the basis of yeast identification, taxonomy, and reproductive biology studies.
Which Yeast Medium Do I Need? — Decision Guide
▶ FOLLOW THE QUESTIONS TO FIND THE RIGHT MEDIUM
Q1: What is your primary goal?
↓ Induce sporulation / detect ascospores / confirm yeast identity by meiosis
↓
Q2: Is your yeast strain diploid?
YES — diploid strain
↓
✅ USE: Ascospore AgarAS-1436 — McClary modification
NO / UNKNOWN — haploid or unknown ploidy
↓
⚠️ Cannot sporulateConfirm ploidy first — haploid strains cannot produce ascospores on any medium
↓ Vegetative growth, isolation, enumeration, or biomass
↓
Q3: Application type?
Clinical / dermatophytes / cosmetic QC→ Sabouraud Dextrose Agar (AS-1341)
Brewery / fermentation / malt yeasts→ Malt Extract Agar (AS-1278)
Food mycology / mould sporulation→ Potato Dextrose Agar (AS-1330)
Yeast genetics / recombinant protein→ YPD Agar / YEPD (AS-1243)
Mode of Action — The Science of Sporulation Induction
Potassium Acetate (10.0 g/L) — Sporulation Trigger: Acetate is metabolised via the glyoxylate cycle in Saccharomyces cerevisiae, bypassing TCA cycle steps that require NAD⁺. This metabolic shift, combined with depletion of fermentable carbon, activates the IME1 (Inducer of Meiosis 1) transcription factor — the master regulator of meiotic entry. Potassium ions create a more favourable ionic environment for sporulation than sodium, improving ascospore formation rate and consistency.
Low Dextrose (1.0 g/L) — Glucose Repression Relief: High glucose activates the cAMP-PKA signalling pathway in Saccharomyces, strongly repressing sporulation. At 1.0 g/L, glucose repression is relieved and the sporulation programme can proceed. Increasing the dextrose — even slightly — will reduce or eliminate sporulation.
High Agar (30.0 g/L) — Firm Surface for Microscopy: The elevated agar concentration produces a very firm, dry gel with excellent optical clarity, allowing direct microscopic examination of ascospores. Colonies can be directly stained with Malachite Green-Safranin on the plate or lifted for wet mount preparation.
Mildly Acidic pH (6.4 ± 0.2): Optimal for Saccharomyces cerevisiae sporulation while suppressing many bacterial contaminants.
Low Dextrose (1.0 g/L) — Glucose Repression Relief: High glucose activates the cAMP-PKA signalling pathway in Saccharomyces, strongly repressing sporulation. At 1.0 g/L, glucose repression is relieved and the sporulation programme can proceed. Increasing the dextrose — even slightly — will reduce or eliminate sporulation.
High Agar (30.0 g/L) — Firm Surface for Microscopy: The elevated agar concentration produces a very firm, dry gel with excellent optical clarity, allowing direct microscopic examination of ascospores. Colonies can be directly stained with Malachite Green-Safranin on the plate or lifted for wet mount preparation.
Mildly Acidic pH (6.4 ± 0.2): Optimal for Saccharomyces cerevisiae sporulation while suppressing many bacterial contaminants.
Applications
🍻
Brewery QC
Yeast strain verification and sporulation confirmation
🍶
Fermentation Labs
Yeast culture maintenance and identity confirmation
🔬
Yeast Taxonomy
Ascospore morphology for species differentiation
🧬
Sporulation Studies
Meiosis research, reproductive biology, yeast genetics
📚
Teaching Labs
Yeast life cycle demonstrations, ascospore staining practicals
🧪
Food Microbiology
Spoilage yeast identification in food products
Ascospore Staining — Interpretation Guide
After incubation (25–30°C / 3–10 days), confirm ascospore formation by staining. Recommended method: Malachite Green – Safranin (modified Schaeffer-Fulton method).
💚 GREEN
AscosporesMalachite Green retained in heat-resistant spore wall
AscosporesMalachite Green retained in heat-resistant spore wall
🔴 RED / PINK
Vegetative yeast cellsCounterstained by Safranin after decolorisation
Vegetative yeast cellsCounterstained by Safranin after decolorisation
| Structure | Appearance | Notes |
|---|---|---|
| Ascospores | Round to oval; green; 1–4 per ascus | Heat-resistant wall retains Malachite Green after decolorisation |
| Ascus (spore sac) | Oval cell enclosing 1–4 ascospores | Parent cell that underwent meiosis |
| Vegetative cells | Pink to red (Safranin) | Cells that did not sporulate; budding may be observed |
💡 Tips for maximum sporulation: Use a young, actively growing culture (18–24h on rich medium). Transfer a heavy loopful to Ascospore Agar and spread thinly. Incubate loosely covered or uncovered to allow slight desiccation — this significantly improves sporulation rates. Check from day 3 and continue to day 10 for slow-sporulating strains.
Ascospore Agar vs Other Yeast Media
| Medium | Dextrose | Key Carbon | Purpose |
|---|---|---|---|
| Ascospore Agar (AS-1436) ★ | 1.0 g/L (low) | Potassium Acetate 10 g/L | Sporulation induction — meiosis trigger under nutrient limitation |
| Sabouraud Dextrose Agar (AS-1341) | 40.0 g/L (high) | Dextrose | Vegetative growth, yeast isolation, clinical diagnostics |
| Potato Dextrose Agar (AS-1330) | 20.0 g/L | Potato infusion + Dextrose | Vegetative growth; mould sporulation (not yeast meiosis) |
| Malt Extract Agar (AS-1278) | Malt | Malt extract | Brewery and fermentation yeast propagation |
| YPD Agar (AS-1243) | 20.0 g/L | Dextrose + YE + Peptone | Rich vegetative growth — actively suppresses sporulation |
⚠️ Important: Do not use Ascospore Agar as a general yeast growth medium. The low nutrient content and acetate-based carbon source are specifically designed to inhibit vegetative growth and trigger sporulation. For general yeast cultivation, use Sabouraud Dextrose Agar (AS-1341) or Malt Extract Agar (AS-1278).
Frequently Asked Questions
❓ Why is the dextrose concentration so low (1.0 g/L)?
This is intentional and critical. High glucose activates the cAMP-PKA signalling pathway in Saccharomyces cerevisiae, which powerfully represses the sporulation programme. At 1.0 g/L, glucose repression is relieved and the IME1-driven sporulation cascade can proceed. Increasing the dextrose — even slightly — will reduce or eliminate sporulation. The potassium acetate (10 g/L) provides the energy cells need to complete meiosis.
❓ Why potassium acetate rather than sodium acetate?
AS-1436 is the McClary modification. McClary replaced sodium acetate with potassium acetate because potassium ions provide a more favourable osmotic and ionic environment for Saccharomyces sporulation, resulting in higher and more consistent ascospore yields. This is the current standard referenced in most commercial media specifications including HiMedia M162 and Oxoid CM0715.
❓ Why is the agar concentration 30 g/L?
The higher agar level (standard media use 15 g/L) produces a firmer, drier surface that contributes to the nutrient-limited, slightly desiccated microenvironment promoting sporulation. It also improves optical clarity for direct microscopic examination and provides a stable surface for Malachite Green-Safranin staining applied directly to the plate.
❓ My yeast is not sporulating — what should I check?
(1) The strain must be diploid — haploid Saccharomyces cannot undergo meiosis. (2) Transfer a fresh culture from rich medium (YPD, Malt Extract Agar, 18–24h) — old or starved cultures sporulate poorly. (3) Incubate at 25–28°C, not 37°C — elevated temperature suppresses sporulation. (4) Allow up to 10 days — some strains are slow. (5) Do not seal plates — CO₂ release and slight desiccation improves sporulation rates.
❓ Is AS-1436 equivalent to HiMedia M162 and Oxoid CM0715?
Yes. AS-1436 follows the same McClary formulation: Potassium Acetate 10 g/L, Yeast Extract 2.5 g/L, Dextrose 1.0 g/L, Agar 30.0 g/L, pH 6.4 ± 0.2, dissolution 43.5 g/L. Equivalent to HiMedia M162, Oxoid CM0715, and Neogen 7138A. Full COA supplied with every batch.
Cross-Reference / Equivalents
| Manufacturer | Product Name | Cat. No. |
|---|---|---|
| HiMedia | Ascospore Agar (McClary's) | M162 |
| Thermo Scientific / Oxoid | Ascospore Agar | CM0715 |
| Neogen (Acumedia) | Ascospore Agar | 7138A |
| AuSaMicS | Ascospore Agar (McClary Modification) | AS-1436 |
Related Products
Product Specifications
| Product Name | Ascospore Agar |
| Catalogue Number | AS-1436 |
| Synonyms | McClary's Ascospore Agar; Potassium Acetate Sporulation Agar; Yeast Sporulation Agar; Ascosporogenous Yeast Medium |
| Formulation Basis | McClary modification — potassium acetate replaces sodium acetate for improved sporulation rate and consistency |
| Commercial Equivalents | HiMedia M162 | Thermo Scientific/Oxoid CM0715 | Neogen 7138A |
| Medium Type | Specialised sporulation agar — nutrient-limited, potassium acetate-based |
| Dissolution | 43.5 g/L in distilled or deionised water |
| Final pH at 25°C | 6.4 ± 0.2 |
| Sterilisation | Autoclave 121°C for 15 minutes |
| Appearance (powder) | Light beige, free-flowing homogeneous powder |
| Appearance (prepared agar) | Clear to slightly amber; very firm gel (30 g/L agar) |
| Incubation | 25–30°C for 3–10 days (loosely covered or uncovered for best results) |
| Storage (powder) | Tightly sealed, cool and dry, protected from moisture and direct sunlight |
| Storage (prepared plates) | 2–8°C; use within 2 weeks of preparation |
| HS Tariff Code | 3821.00.00 |
Formula — Per Litre (McClary Modification)
| Ingredient | g/L | CAS | Function & Rationale |
|---|---|---|---|
| Potassium Acetate | 10.0 | 127-08-2 | Primary carbon source via glyoxylate cycle; triggers IME1-driven sporulation; potassium ions enhance sporulation rate vs sodium acetate (McClary modification) |
| Yeast Extract | 2.5 | 8013-01-2 | Minimal vitamins, B-complex, amino acids, and growth factors sufficient for meiotic completion but insufficient to support vegetative growth |
| Dextrose (D-Glucose) | 1.0 | 50-99-7 | At 1.0 g/L relieves glucose repression of sporulation without activating cAMP-PKA suppression of meiosis; supplementary energy only |
| Agar | 30.0 | 9002-18-0 | High concentration — firm, dry surface promotes sporulation; excellent optical clarity for direct microscopy; stable for Malachite Green staining |
| Total | 43.5 g/L | pH 6.4 ± 0.2 at 25°C — Autoclave 121°C / 15 min | |
Preparation Protocol
1
Suspend 43.5 g of dehydrated Ascospore Agar (AS-1436) in 1 litre of purified or distilled water.
2
Heat with frequent agitation and bring to a gentle boil for 1 minute until completely dissolved. The high agar content (30 g/L) requires complete boiling for full dispersion.
3
Sterilise by autoclaving at 121°C for 15 minutes.
4
Cool to 45–50°C. Pour approximately 20 mL per 90 mm Petri dish. Allow to solidify fully — the high agar level produces a very firm gel.
5
Inoculate with a fresh yeast culture (from YPD or Malt Extract Agar, 18–24h growth). Spread thinly. Incubate at 25–30°C loosely covered or uncovered for 3–10 days.
6
Examine microscopically from day 3. Stain with Malachite Green – Safranin for confirmation. Ascospores = green; vegetative cells = red/pink.
⚠️ Critical: Start with a fresh, actively growing diploid yeast culture. Haploid strains cannot produce ascospores. Old or starved cultures may not sporulate reliably. Sealed plates reduce sporulation efficiency significantly.
Expected Results by Organism
| Organism | Sporulation | Incubation | Ascus Morphology |
|---|---|---|---|
| Saccharomyces cerevisiae (ATCC 9763) | Positive ✓ | 25–28°C / 3–5 days | Oval asci; 1–4 round ascospores; hat-shaped in some strains |
| Saccharomyces pastorianus | Positive ✓ | 25°C / 5–7 days | Oval asci; 1–4 ascospores; may be less uniform |
| Zygosaccharomyces spp. | Positive ✓ | 25°C / 5–10 days | Conjugating asci; 1–4 round/oval ascospores |
| Candida spp. | Negative ✕ | — | No ascospores — Candida is ascomycetous but non-ascosporogenous on this medium |
| Non-ascosporogenous yeasts | Negative ✕ | — | Vegetative growth only; no asci visible |
Literature & References
| # | Reference |
|---|---|
| 1 | McClary DO, et al. Factors affecting sporulation in Saccharomyces cerevisiae. J Bacteriol. 1959;78(3):362–368. [Original McClary modification paper — potassium acetate replacing sodium acetate] |
| 2 | Barnett JA, Payne RW, Yarrow D. Yeasts: Characteristics and Identification. 3rd ed. Cambridge University Press; 2000. [Standard yeast identification methods including ascospore agar protocol] |
| 3 | Kurtzman CP, Fell JW, Boekhout T (eds). The Yeasts: A Taxonomic Study. 5th ed. Elsevier; 2011. [Ascospore formation as taxonomic criterion for ascosporogenous yeast identification] |
| 4 | HiMedia Laboratories. Ascospore Agar (McClary's), Cat. M162. Technical specifications; current edition. [Reference commercial formula] |
| 5 | ISO 11133:2014. Culture media — Preparation, production, storage and performance testing. Geneva: ISO; 2014. |
📄 Full 16-section GHS SDS available (Australian WHS Regulations 2023 / GHS 7th Edition) — support@ausamics.com.au
Section 1 — Identification
| Product Name | Ascospore Agar |
| Catalogue No. | AS-1436 |
| Supplier | AuSaMicS Pty Ltd | ABN 56 676 640 467 |
| Address | 31 Longview CT, Thomastown VIC 3074, Australia |
| Emergency | Poisons Information Centre: 13 11 26 (24 hr) |
| Phone / Email | +61 412 520 598 | support@ausamics.com.au |
| Intended Use | Specialised sporulation culture medium for laboratory and research use. Induction and detection of ascospore formation in ascosporogenous yeasts. For laboratory use only. |
Section 2 — Hazard Identification (GHS 7th Ed / WHS 2023)
| GHS Classification | NOT classified as a hazardous substance under Australian WHS Regulations 2023 at intended use concentrations. |
| Signal Word | None required |
| Other Hazards | Combustible dry powder — avoid ignition sources when handling large quantities. Dust may cause mild respiratory irritation. No significant chemical hazard at normal laboratory handling quantities. |
Section 3 — Composition Summary
| Component | g/L | CAS | GHS Hazard Classification |
|---|---|---|---|
| Potassium Acetate | 10.0 | 127-08-2 | Not classified as hazardous at use level |
| Yeast Extract | 2.5 | 8013-01-2 | Not hazardous |
| Dextrose (D-Glucose) | 1.0 | 50-99-7 | Not hazardous |
| Agar | 30.0 | 9002-18-0 | Not hazardous |
PPE, Handling & Disposal Summary
| Respiratory PPE | P1 filter mask when weighing or handling bulk powder in quantity |
| Eye Protection | Safety glasses or spectacles when handling dry powder |
| Skin / Gloves | Nitrile gloves when handling inoculated cultures |
| Engineering Controls | Handle in well-ventilated laboratory environment |
| Waste — uninoculated medium | Dispose as non-hazardous solid/liquid waste per local EPA regulations |
| Waste — inoculated plates | Autoclave all inoculated plates (121°C / 15 min) before disposal as microbiological waste |
| Transport | Not classified as dangerous goods — ADG, IMDG, IATA |
| Regulatory | Australian WHS Regulations 2023 | GHS 7th Edition | AICIS compliant | HS 3821.00.00 |
⚠️ Biosafety Note: Saccharomyces cerevisiae is generally classified as BSL-1 (non-pathogenic). However, if Ascospore Agar is used for identification or handling of unknown yeast isolates from clinical specimens, apply appropriate BSL-2 precautions and consult your institutional biosafety policy.
Quality Control Specifications
| Parameter | Specification | Method | Result |
|---|---|---|---|
| Appearance (powder) | Light beige, free-flowing, homogeneous powder | Visual | Conforms |
| Appearance (prepared agar) | Clear to slightly amber; very firm gel (30 g/L agar) | Visual after dissolution | Conforms |
| pH (prepared, 25°C) | 6.4 ± 0.2 | pH meter (calibrated electrode) | Conforms |
| Dissolution | Complete at 43.5 g/L with boiling | Visual inspection | Conforms |
| Moisture Content | ≤ 5.0% (w/w) | Loss on drying (105°C) | Conforms |
| Sporulation — S. cerevisiae ATCC 9763 (positive control) | Ascospore formation confirmed within 5 days at 25–28°C; asci with 1–4 ascospores visible by Malachite Green staining | Microscopic examination + staining per standard protocol | Conforms |
| Sporulation — Candida albicans ATCC 10231 (negative control) | No ascospore formation observed | Microscopic examination | Conforms |
Batch Traceability — Sample Reference
📋 Example Batch Information (actual batch details on label and COA)
Product
Ascospore Agar
Catalogue No.
AS-1436
Batch No.
Stated on label
Manufacturing Date
Stated on label
Expiry Date
Stated on label
Storage
Cool, dry, sealed
Manufacturer
AuSaMicS Pty Ltd — Melbourne, Australia
COA
Included with every order
Packaging Options
| Standard Pack Sizes | 100 g · 250 g · 500 g · 1 kg |
| Bulk / Custom | Larger quantities and custom pack sizes available — contact support@ausamics.com.au |
| Packaging | Amber glass or food-grade HDPE container; hermetically sealed; labelled with batch number, expiry, storage conditions, and intended use |
Manufacturing & Quality Assurance
Manufactured by AuSaMicS Pty Ltd
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per McClary modification / HiMedia M162 reference specification
✓ Batch QC per ISO 11133:2014 — pH, sporulation performance (positive & negative controls), appearance, moisture
✓ COA, TDS, and SDS included with every order
✓ Australian stock — same-week dispatch, no import lead times
✓ Technical support directly from our microbiology team
31 Longview CT, Thomastown VIC 3074, Australia | ABN 56 676 640 467
✓ Formulated per McClary modification / HiMedia M162 reference specification
✓ Batch QC per ISO 11133:2014 — pH, sporulation performance (positive & negative controls), appearance, moisture
✓ COA, TDS, and SDS included with every order
✓ Australian stock — same-week dispatch, no import lead times
✓ Technical support directly from our microbiology team
⚠️ For laboratory, industrial, educational, and research use only. Not intended for food, drug, cosmetic, or therapeutic applications. AuSaMicS Pty Ltd accepts no liability for use outside the intended laboratory application.