Marine Agar 2216 (Zobell Marine Agar)
Isolation, enumeration and maintenance of heterotrophic marine bacteria
Marine Agar 2216 is a non-selective medium whose salts reproduce the ionic composition of seawater, allowing marine bacteria that need sea salts to grow in the laboratory. It is based on the 2216 formulation of ZoBell (1941) and is one of the most widely used media in marine microbiology and aquaculture research. Dissolve in purified water; the sea salts are already included.
Also known as: ZoBell Marine Agar 2216, Marine Agar, ZMA, Marine Medium 2216.
Principle of the Medium
Many marine bacteria need sodium, magnesium, calcium and potassium at seawater concentrations and do not grow on ordinary laboratory media. Marine Agar 2216 supplies these major ions plus the trace ions of seawater. Peptone and yeast extract provide nitrogen, vitamins and growth factors, ferric citrate supplies iron, and agar allows colony isolation and counting.
Major and trace salts at seawater levels
6 g/L organics suit marine heterotrophs
Non-selective: supports diverse marine genera
Typical Marine Bacteria Recovered
| Genus | Growth | Notes |
|---|---|---|
| Vibrio | Good | Includes V. harveyi, V. alginolyticus; potential pathogens also grow |
| Aliivibrio, Photobacterium | Good | Some strains are bioluminescent |
| Pseudoalteromonas, Alteromonas | Good | Pigmented colonies are common |
| Shewanella, Marinobacter | Good | Some Shewanella strains are pink to salmon |
| Marine actinomycetes (e.g. Salinispora) | Variable | Slow-growing; extended incubation needed |
Related Marine and Aquatic Media
| Medium | Type | Best use |
|---|---|---|
| Marine Agar 2216 (AS-1289) | Non-selective agar | Isolation, counts and maintenance of marine bacteria |
| Marine Broth 2216 (AS-1290) | Non-selective broth | Enrichment and biomass of marine bacteria |
| TCBS Agar (AS-1080) | Selective differential agar | Pathogenic Vibrio such as V. cholerae |
| Alkaline Peptone Water (AS-1005) | Enrichment broth | Vibrio enrichment before TCBS |
| R2A Agar (AS-1341) | Low-nutrient agar | Oligotrophic freshwater bacteria |
For pathogenic Vibrio: enrich in Alkaline Peptone Water, then plate on TCBS Agar.
Comparable Products
| Supplier | Product | Relationship |
|---|---|---|
| AuSaMicS | Marine Agar 2216 (AS-1289), 52.4 g/L | — |
| BD Difco | Marine Agar 2216 (212185), 55.1 g/L | Comparable published formulation; uses MgCl₂ 8.8 g and sodium sulfate |
| HiMedia | Zobell Marine Agar 2216 (M384) | Comparable published formulation |
| BD Difco / Sigma-Aldrich | Marine Broth 2216 | Same salt composition, without agar |
Based on published formulations. Trademarks belong to their respective owners.
Advantages and Limitations
Advantages
- ✓ No seawater needed: consistent salinity every batch
- ✓ Standard reference medium for many marine type strains
- ✓ Broad recovery of marine heterotrophs
- ✓ Matching broth available (AS-1290)
Limitations
- ▲ Non-selective: dilute mixed samples
- ▲ Some marine bacteria need low-nutrient or special media
- ▲ Potential pathogens such as V. vulnificus can grow
- ▲ Fine precipitate is normal; swirl before pouring
Frequently Asked Questions
What is Marine Agar 2216 used for?
It is used to isolate, count, purify and maintain heterotrophic marine bacteria from seawater, sediments, marine organisms and aquaculture systems. Its salts reproduce the ionic composition of seawater.
Should Marine Agar 2216 be dissolved in seawater?
No. The powder already contains the sea salts. Dissolve 52.4 g in 1 L of purified water. Using seawater would roughly double the salinity and inhibit many marine bacteria.
Is a precipitate in Marine Agar 2216 normal?
Yes. A fine precipitate of calcium and magnesium salts forms during heating and autoclaving. It is normal and does not affect performance. Swirl the medium before pouring.
What temperature should Marine Agar 2216 plates be incubated at?
Most marine heterotrophs grow well at 20–25 °C for 24–72 hours. Use 10–15 °C for psychrophilic bacteria, and extend incubation for slow-growing isolates.
What is the difference between Marine Agar 2216 and TCBS Agar?
Marine Agar 2216 is non-selective and supports a broad range of marine bacteria. TCBS Agar is selective and differential, and is used to isolate pathogenic Vibrio species such as V. cholerae and V. parahaemolyticus.
Typical Formula (g/L)
Salt composition of Marine Broth 2216 with 15 g/L agar. Formula may be adjusted to meet performance requirements.
Incubation Guide
References
- ZoBell CE. Studies on marine bacteria. I. The cultural requirements of heterotrophic aerobes. J Mar Res. 1941;4(1):42–75.
- Zimbro MJ, Power DA, et al., eds. Difco & BBL Manual: Manual of Microbiological Culture Media. 2nd ed. BD Diagnostics; 2009. Marine Agar 2216 and Marine Broth 2216.
- ATCC. ATCC Medium 2: Marine Agar/Broth 2216. American Type Culture Collection.
- Gontang EA, Fenical W, Jensen PR. Phylogenetic diversity of gram-positive bacteria cultured from marine sediments. Appl Environ Microbiol. 2007;73(10):3272–3282.
Quality Control
Recommended Control Strains (25 °C, 24–72 h)
Safety
Not classified as hazardous under the GHS. Not Dangerous Goods for transport. Avoid breathing dust and wear gloves and eye protection when weighing. This non-selective medium can grow potential pathogens such as Vibrio parahaemolyticus and V. vulnificus, so handle cultures under appropriate biosafety conditions and autoclave inoculated plates before disposal. The full SDS is available for every lot.
Storage
Dehydrated medium: Store at 15–25 °C in a dry place with the container tightly closed. Hygroscopic. Use before the expiry date on the label.
Prepared plates: Store at 2–8 °C in sealed bags, protected from light. Validate the use period in your laboratory.