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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 🇦🇺 Made in Melbourne ⚡ Same-Week Dispatch
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.
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 the TCA cycle steps that require NAD⁺. This metabolic shift, combined with the depletion of fermentable carbon, activates the IME1 (Inducer of Meiosis 1) transcription factor — the master regulator of meiotic entry. The McClary modification uses potassium acetate specifically because 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 concentrations activate the cAMP-PKA signalling pathway in Saccharomyces, which strongly represses sporulation. By limiting dextrose to just 1.0 g/L, Ascospore Agar relieves glucose repression and allows the sporulation programme to proceed. This is why the dextrose level must NOT be increased — it would suppress the very response the medium is designed to induce.
High Agar (30.0 g/L) — Firm Surface for Microscopy: The elevated agar concentration (30 g/L vs the standard 15 g/L) produces a very firm gel with excellent optical clarity, allowing direct microscopic examination of ascospores on the agar surface. 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): Slightly below neutral, optimal for Saccharomyces cerevisiae sporulation. Yeast cells tolerate this pH well while many bacterial contaminants are suppressed.
Low Dextrose (1.0 g/L) — Glucose Repression Relief: High glucose concentrations activate the cAMP-PKA signalling pathway in Saccharomyces, which strongly represses sporulation. By limiting dextrose to just 1.0 g/L, Ascospore Agar relieves glucose repression and allows the sporulation programme to proceed. This is why the dextrose level must NOT be increased — it would suppress the very response the medium is designed to induce.
High Agar (30.0 g/L) — Firm Surface for Microscopy: The elevated agar concentration (30 g/L vs the standard 15 g/L) produces a very firm gel with excellent optical clarity, allowing direct microscopic examination of ascospores on the agar surface. 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): Slightly below neutral, optimal for Saccharomyces cerevisiae sporulation. Yeast cells tolerate this pH well while many bacterial contaminants are suppressed.
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 methods: Malachite Green – Safranin (standard method); modified Schaeffer-Fulton method; or equivalent ascospore staining technique.
💚 GREEN
AscosporesMalachite Green retained
AscosporesMalachite Green retained
🔴 RED / PINK
Vegetative yeast cellsCounterstained by Safranin
Vegetative yeast cellsCounterstained by Safranin
| Microscopic Structure | Typical Appearance | Notes |
|---|---|---|
| Ascospores | Round to oval; green with Malachite Green stain; 1–4 per ascus | Heat-resistant spore wall retains Malachite Green after decolorisation |
| Ascus (spore sac) | Oval cell enclosing 1–4 ascospores | Parent cell that underwent meiosis; wall may be visible |
| Vegetative cells | Pink to red with Safranin counterstain | 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 uncovered or loosely covered to allow slight desiccation — this 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, sporulation of moulds (not yeast meiosis) |
| Malt Extract Agar | Malt | Malt extract | Brewery and fermentation yeast propagation and enumeration |
| YPD Agar | 20.0 g/L | Dextrose + Yeast Extract + Peptone | Rich vegetative growth — 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.
FAQs
❓ 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 concentration — even slightly — will reduce or eliminate sporulation. The acetate carbon source (10 g/L potassium acetate) provides the energy the cells need to complete meiosis.
❓ Why potassium acetate rather than sodium acetate?
Ascospore Agar is the McClary modification of the original acetate sporulation medium. 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. The original sodium acetate formulation remains in use, but the potassium acetate version is the current standard referenced in most commercial media specifications.
❓ Why is the agar concentration so high (30 g/L)?
The higher agar level (standard is 15 g/L) produces a firmer, drier surface that contributes to the nutrient-limited, slightly desiccated microenvironment that promotes sporulation. It also improves optical clarity for direct microscopic examination of colonies and individual cells on the agar surface, and provides a stable surface for the Malachite Green-Safranin staining protocol applied directly to the plate.
❓ My yeast is not sporulating — what should I check?
Several factors affect sporulation efficiency: (1) The strain must be diploid — haploid Saccharomyces cannot undergo meiosis. (2) Transfer a fresh culture from a rich medium (YPD, Malt Extract Agar) — starved or very old cultures sporulate poorly. (3) Ensure incubation is at 25–28°C, not 37°C — elevated temperature suppresses sporulation in many strains. (4) Allow up to 10 days — some strains are slow. (5) Avoid sealed plates — some CO₂ release and slight desiccation improves sporulation rates.
❓ Is AS-1436 equivalent to HiMedia M162?
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. 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 |
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 of acetate sporulation medium — potassium acetate replaces sodium acetate for improved sporulation rate |
| 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) |
| Storage (powder) | Tightly sealed, cool and dry, protected from moisture and direct sunlight |
| Storage (prepared plates) | 2–8°C; use within 2 weeks |
| HS Tariff Code | 3821.00.00 |
Formula — Per Litre (McClary Modification)
| Ingredient | g / L | Function |
|---|---|---|
| Potassium Acetate | 10.0 | Primary carbon source via glyoxylate cycle; triggers IME1-driven sporulation; potassium ions enhance sporulation rate vs sodium acetate (McClary modification) |
| Yeast Extract | 2.5 | Minimal vitamins, B-complex, amino acids, and accessory growth factors sufficient for meiotic completion but insufficient to support vegetative growth |
| Dextrose (D-Glucose) | 1.0 | Minimal supplementary carbon; at 1.0 g/L relieves glucose repression of sporulation pathway without activating cAMP-PKA suppression of meiosis |
| Agar | 30.0 | 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.
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 |
Literature & References
| # | Reference |
|---|---|
| 1 | McClary DO, et al. Factors affecting sporulation in Saccharomyces cerevisiae. J Bacteriol. 1959;78(3):362–368. [Original McClary modification — 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 | +61 412 520 598 | support@ausamics.com.au |
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. Dust may cause mild respiratory irritation. Potassium acetate component: not classified as hazardous at use level. No significant chemical hazard at normal laboratory handling. |
Composition Summary
| Component | g/L | CAS | Hazard |
|---|---|---|---|
| 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 |
| Respiratory PPE | P1 filter when weighing bulk powder |
| Eye Protection | Safety glasses when handling dry powder |
| Skin / Gloves | Nitrile gloves when handling inoculated cultures |
| Waste (plain medium) | Autoclave all inoculated plates (121°C / 15 min) before disposal as microbiological waste |
| Transport | Not dangerous goods — ADG, IMDG, IATA |
| Regulatory | Australian WHS Regulations 2023 | GHS 7th Edition | AICIS compliant |
⚠️ Biosafety note: Saccharomyces cerevisiae is generally classified as BSL-1 (non-pathogenic). However, if Ascospore Agar is used for the identification or handling of unknown yeast isolates from clinical specimens, apply appropriate BSL-2 precautions and consult your institutional biosafety policy.
Quality Specifications
| Parameter | Specification | Method |
|---|---|---|
| Appearance (powder) | Light beige, free-flowing, homogeneous powder | Visual |
| Appearance (prepared agar) | Clear to slightly amber; very firm gel (30 g/L agar) | Visual after dissolution |
| pH (prepared, 25°C) | 6.4 ± 0.2 | pH meter (calibrated) |
| Dissolution | Complete at 43.5 g/L with boiling | Visual inspection |
| Moisture Content | ≤5.0% (w/w) | Loss on drying |
| Sporulation — S. cerevisiae ATCC 9763 | Ascospore formation confirmed within 5 days at 25–28°C; asci containing 1–4 ascospores visible by Malachite Green staining | Microscopic examination + staining per standard protocol |
| Sporulation — negative control | Non-ascosporogenous yeast (e.g. Candida albicans ATCC 10231) — no ascospore formation on Ascospore Agar | Microscopic examination |
| Batch COA | Available every production lot | 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 |
Manufacturing & Documentation
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, appearance
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch, no import delays
✓ Technical support 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, appearance
✓ COA, TDS, SDS included with every order
✓ Australian stock — same-week dispatch, no import delays
✓ Technical support from our microbiology team
⚠️ For laboratory, industrial, educational, and research use only. Not intended for food, drug, cosmetic, or therapeutic applications.