Overview

Gifu Anaerobic Medium (GAM) is a rich, non-selective general-purpose broth for the cultivation and isolation of obligate and facultative anaerobic bacteria, developed by Tomotari Mitsuoka and colleagues at the University of Tokyo.

GAM combines a multi-peptone and digested-serum proteinaceous base with a dual L-cysteine + sodium thioglycollate reductant system, which together drive a low oxidation–reduction potential (Eh) and create the reducing conditions strict anaerobes require. The serum and liver components supply haem, growth factors and the peptide diversity that make GAM effective for fastidious clinical and gut anaerobes — including Bacteroides, Prevotella, Fusobacterium, Bifidobacterium, Clostridium and the more demanding streptococci.

This is the original GAM formulation, with glucose at 3.0 g/L — the broader-use, mild-fermentation profile preferred for clinical primary isolation and for Clostridium sporulation work. (For long-incubation maintenance and gut-microbiome culturomics, the lower-glucose Modified GAM, mGAM, at 0.5 g/L glucose is preferred.)

The GMExpression dehydrated base is supplied without hemin or Vitamin K₁ in the powder; both are offered as separate, freshly prepared stocks that are added after autoclaving. This design keeps the dry powder stable during storage and shipping, avoids hemin co-precipitation during autoclaving, and lets users who are working only with facultative organisms omit the supplements when they are not required.

We also have

  • Modified GAM (mGAM) — glucose reduced to 0.5 g/L for lower acidogenicity, long-incubation maintenance and fastidious gut-anaerobe / Bifidobacterium work.
  • Vitamin K₁ stock (0.5 mg/mL) and Hemin stock (1 mg/mL) — optional post-autoclave supplements for haem-auxotrophic Bacteroides and other fastidious anaerobes.
  • Complementary GMExpression anaerobic media: YCFA Medium (Modified), YCFA Medium (Full), Chopped Meat Broth (ATCC 1490) and PYG Broth.
  • Anaerobic Preparation Kit (Lite / Plus) — vacuum-deoxygenation tools for PRAS Hungate-tube workflows.

Package Contents

  • Dehydrated GAM base, 250 g — prepares approximately 5 L of medium at 49.0 g/L.
  • [Optional, order-based stocks] Vitamin K₁ solution (0.5 mg/mL) and Hemin solution (1 mg/mL), added after autoclaving (10 mL of each per litre).
  • [Optional] Anaerobic Preparation Kit (Lite or Plus) for pre-reduced (PRAS) Hungate-tube preparation.

Composition — per 1 L of prepared medium (dehydrated base 49.0 g/L)

Gifu Anaerobic Medium (Dehydrated base per 1L)

ComponentConcentrationFunction
Proteose peptone10.0 gPrimary peptide source
Soy peptone3.0 gSupplementary peptide; supports Bifidobacterium
Yeast extract5.0 gB-vitamins, NAD precursors
Beef extract2.2 gBeef-extract complex
Digestive serum powder (bovine)13.5 gSerum hydrolysate; haem and growth factors
Beef liver powder1.2 gReducing peptides and growth factors
D-Glucose3.0 gCarbohydrate source (original-GAM level)
Potassium dihydrogen phosphate (KH₂PO₄)2.5 gBuffer
Sodium chloride (NaCl)3.0 gOsmotic balance
Soluble starch5.0 gSlow-release carbohydrate
L-Cysteine0.3 gReductant
Sodium thioglycolate0.3 gReductant (dual system with cysteine)
Total dehydrated base49.0 g

Anaerobic supplements (post-autoclave additions)

ComponentFinal ConcentrationFunction
Vitamin K₁ (optional, post-autoclave: 10 mL × 0.5 mg/mL)5 mg/LSupports Bacteroides fumarate-reductase pathway
Hemin (optional, post-autoclave: 10 mL × 1 mg/mL)10 mg/LHaem source for haem-auxotrophic anaerobes

Final pH: 7.3 ± 0.1 at 25 °C.


Choose your GAM / anaerobic medium

GAM is non-selective and broad-spectrum. Use this quick-compare to position the original GAM against the other GMExpression anaerobic media:

Organism / use classGAM (original)mGAMYCFAChopped Meat
Clinical primary isolationPrimarySupportedLimitedPrimary
Clostridium sporulationPrimarySupportedLimitedPrimary
Long-incubation maintenanceSupportedPrimarySupportedPrimary (hold)
Bacteroides / PrevotellaPrimaryPrimarySupportedPrimary
BifidobacteriumSupportedPrimarySupportedPossible
Butyrate producers (F. prausnitzii)PossibleSupportedPrimary (SCFA)Possible

Rule of thumb: use original GAM for clinical primary isolation and Clostridium sporulation; mGAM for long-incubation and gut-microbiome work; YCFA for SCFA-dependent butyrate producers; Chopped Meat for long-term hold.

Use and Applications

GAM is a general-purpose anaerobic broth recommended for the cultivation and isolation of anaerobic bacteria and for susceptibility testing against antibiotics other than sulpha drugs. Because the base contains digested serum (a natural haem source), it also supports fastidious facultative organisms such as streptococci, pneumococci and meningococci, and is suitable for blood-culture applications.

  • Primary isolation and cultivation of obligate and facultative anaerobes from clinical, gut-microbiome and food specimens.
  • Antimicrobial susceptibility testing of anaerobes (non-sulpha agents).
  • Clostridium primary isolation and sporulation — the 3.0 g/L glucose level favours vigorous first-passage growth.
  • Semisolid / solid formats — add agar (3 g/L semisolid; 15 g/L solid) for transport-hold tubes or isolation plates.
  • Probiotic and food microbiology — Lactobacillus, Bifidobacterium and Clostridium identification.

Compatible Microorganisms

GAM is non-selective and broad-spectrum. Representative validated taxa:

  • Obligate anaerobes: Bacteroides fragilis (ATCC 25285), B. vulgatus (ATCC 8482), B. thetaiotaomicron; Prevotella, Porphyromonas; Fusobacterium nucleatum; Bifidobacterium spp.; Eubacterium spp.; Clostridium perfringens (ATCC 13124), C. sporogenes (ATCC 11437), Clostridioides difficile; Veillonella parvula.
  • Facultative / fastidious: Streptococcus pyogenes (ATCC 19615), other streptococci, pneumococci and meningococci; Lactobacillus / Lacticaseibacillus spp.; Enterococcus faecalis; Escherichia coli (no selective agent).
Taxonomy note: the 2020 Lactobacillus reclassification (Zheng et al. 2020, IJSEM 70:2782) split the historical genus into 25 new genera; current literature should use Lacticaseibacillus, Limosilactobacillus, etc.

Preparation

1
Weigh. 49.0 g of the dehydrated base per litre of medium.
2
Dissolve with heat. Add to distilled water and heat to dissolve completely. Heating is mandatory — skipping it causes white colloidal precipitate to form after autoclaving.
3
Adjust pH. Confirm pH 7.3 ± 0.1 at 25 °C.
4
Dispense. Aliquot as required; dispense under N₂ flush for pre-reduced (PRAS) Hungate-tube format.
5
Autoclave. 115 °C for 15 min (the low-browning cycle for serum/starch/cysteine blends).
6
Cool and supplement. Cool to ~50 °C; if using the optional stocks, add 10 mL of 0.5 mg/mL Vitamin K₁ and 10 mL of 1 mg/mL Hemin per litre (final 5 mg/L VK₁, 10 mg/L hemin); mix well.

For semisolid or solid medium: add agar before autoclaving — 3 g/L for a semisolid transport/hold format, 15 g/L for isolation plates (pour at ~50 °C).

Critical control points

  • Heat to dissolve. The starch and serum components must be fully dissolved by heating before autoclaving; otherwise a white colloidal precipitate forms on cooling.
  • 115 °C autoclave cycle. The lower cycle minimises Maillard browning of the serum + starch + cysteine blend; 121 °C produces visibly darker (still functional) medium.
  • Dual reductant system. The cysteine + thioglycollate combination gives a lower Eh than cysteine alone; do not omit either component.
  • Post-autoclave supplementation. Add Vitamin K₁ and Hemin stocks only after cooling to ~50 °C, to avoid hemin co-precipitation and Vitamin K₁ degradation during the sterilisation cycle.

Cautions

White colloidal precipitate. Forms after autoclaving if the powder was not fully heat-dissolved first. Always dissolve with heat before sterilisation.
Maillard browning. Over-autoclaving (121 °C) darkens the medium; prefer 115 °C × 15 min. Honey-amber colour is normal.
Soluble-starch settling. Mix thoroughly immediately before dispensing; the starch can settle as a fine sediment during refrigerated storage.
Animal-origin components. Contains digestive serum powder, beef extract and beef liver powder (bovine). Not suitable for animal-product-free workflows; bovine components carry standard TSE/BSE customs considerations — see Customs & Documentation.
Vitamin K₁ stock. The ethanolic Vitamin K₁ stock is light-sensitive; store protected from light and add fresh.

Storage and Expiry · Safety

Store the dehydrated base tightly closed in a cool, dry place away from light. Optional Vitamin K₁ and Hemin stocks are order-based (2–5 business days to prepare) and should be refrigerated and protected from light. Prepared medium is best held under an anaerobic, vacuum-sealed atmosphere with an oxygen absorber at 4 °C, which extends the functional shelf life to approximately six months. A lot-specific SDS is supplied and available under the Documentation tab.

Customs & Documentation

GAM contains bovine-derived components and is treated as a regulated product under most national biosecurity regimes. GMExpression supplies the documentation pack used across its anaerobic-media exports:

HS ClassificationHS 3821.00.90 — prepared culture media for micro-organisms.
USDA GuidelineUSDA Guideline 1114 compliance statement for animal-origin culture media.
DAFF EX188MAustralian zoosanitary export-certification pipeline for animal-derived components.
SDS & CoALot-specific Certificate of Analysis and Safety Data Sheet (SDS_GMNB-GAM01).
Australian biosecurity advantage. GMExpression sources animal-derived inputs from antibiotic-free South Australian supply and certifies exports through the Australian DAFF pathway — a biosecurity-grade alternative to incumbent Asia-Pacific GAM supply.

References

  1. Mitsuoka T, Sega T, Yamamoto S. (1965). Eine verbesserte Methodik der qualitativen und quantitativen Analyse der Darmflora von Menschen und Tieren. Journal of Bacteriology 89: 1556. (Original GAM publication.)
  2. Mitsuoka T. (1992). Intestinal flora and aging. Nutrition Reviews 50(12): 438–446.
  3. Nissui Pharmaceutical Co. Ltd. Product information: GAM Broth (05422), Modified GAM Broth (05426).
  4. Carroll KC, Pfaller MA, et al. (eds). (2019). Manual of Clinical Microbiology, 12th ed. Washington, DC: ASM Press.
  5. Zheng J, et al. (2020). A taxonomic note on the genus Lactobacillus. Int J Syst Evol Microbiol 70: 2782–2858.

Frequently Asked Questions

Q1. What is the difference between GAM and Modified GAM (mGAM)?
The principal difference is glucose: original GAM contains 3.0 g/L, whereas mGAM is reduced to 0.5 g/L. The higher glucose in original GAM favours vigorous first-passage growth, clinical primary isolation and Clostridium sporulation, while the lower-glucose mGAM is less acidogenic and better for long-incubation maintenance and fastidious gut-anaerobe / Bifidobacterium work.
Q2. Why are Vitamin K₁ and Hemin supplied as optional stocks rather than in the powder?
Adding them after autoclaving keeps the dry base stable in storage, prevents hemin from co-precipitating during the sterilisation cycle, and avoids thermal/oxidative loss of Vitamin K₁. It also lets users working only with facultative organisms omit the supplements when they are not needed. Haem-auxotrophic anaerobes such as Bacteroides benefit from both stocks (final 10 mg/L hemin, 5 mg/L VK₁).
Q3. Why does the prepared medium look darker than YCFA?
The digested serum, beef and liver components and soluble starch undergo mild Maillard browning during autoclaving, giving a honey-amber colour that is darker than the pale-yellow of YCFA. This is normal; excessive darkening indicates over-autoclaving — keep to 115 °C × 15 min.
Q4. How do I make a semisolid or solid (plate) version?
Add agar to the broth formulation before autoclaving: 3 g/L for a semisolid transport/hold format, or 15 g/L for isolation plates (pour at ~50 °C).
Q5. Why must I heat the powder to dissolve it?
Full dissolution by heating is required before autoclaving. If heating is skipped, the medium tends to form a white colloidal precipitate after the autoclave cycle on cooling.
Q6. Can I prepare pre-reduced (PRAS) Hungate tubes of GAM?
Yes. Dispense under N₂ flush and use the GMExpression Anaerobic Preparation Kit (Lite/Plus) vacuum-deoxygenation workflow, which is medium-agnostic. Note the standard GAM base contains no resazurin; add 1 mg/L resazurin if a visual oxygen indicator is wanted.
Q7. Does GAM contain animal-origin ingredients?
Yes — digestive serum powder (bovine), beef extract and beef liver powder. It is therefore not suitable for animal-product-free workflows, and the bovine components carry standard customs/biosecurity considerations (see Customs & Documentation).
Q8. Is there a CLSI standard equivalent for GAM?
GAM is not formally listed in CLSI M11/M22/M56-A but is recognised in the ASM Manual of Clinical Microbiology as an acceptable general anaerobic broth, and is the de-facto reference broth across Japan and the wider Asia-Pacific (Japanese Pharmacopoeia / Riken-JCM tradition).