BG -11 Medium Preparation,Composition,Principle

BG -11 Medium- Preparation,Composition,Principle

In today’s article we will discuss about the BG-11 medium, the culture media to grow blue green algae. At the beginning of this article, we will see the principle of this media. We will also be able to know about BG-11 medium composition and how to prepare. Let’s see information about BG11 Media.



To prepare growth medium for cyanobacteria or blue green algae


BG 11 is the growth medium for photoautotrophic blue green algae derived by by Allen and Stanier in 1968. This medium supports cyanobacteria from fresh water, soil and marine habitat, which contains high amount of nitrate and phosphate. As cyanobacteria are N2 fixer, a considerable amount of nitrogen source is being provided. This medium also contain several micro-nutrients like boron along with macro-nutrients and trace metals. EDTA or Ethylenediamine tetraacetic acid is present in the media as bond with metal ions MgNO2EDTA. Ferric citrate and citric acid combined to form stock solution which added with main medium after autoclave. Ammonium citrate is used for BG agar as carbon source which influence the production of CO2.


Ingredients Gm/L
Sodium Nitrate (NaNO3) 1.5
Dipotassium hydrogen phosphate(K2HPO4) 0.0314
Magnesium sulphate (MgSO4, 7H2O) 0.036
Calcium chloride dihydrate (CaCl2, 2H2O) 0.0367
Sodium carbonate (Na2CO3 )
Ferric ammonium citrate 0.006
Disodium magnesium EDTA


Citric acid 0.0056
Agar (if needed) 15g
Trace metal solution 1.0 ml
Distilled water
1000 ml
pH 7.4


  1. Media was prepared by reading all prescribed ingredients before autoclaving, after which agar powder was added
  2. Several source of BG agar where collected (freshwater, soil and marine water) and plated over BG 11 medium aseptically.
  3. Plates were incubated for overnight at 27 degree centigrade
  4. After specific incubation confluent growth was observed
  5. Colony wise they were separated and identified

Possible Result

After sufficient incubation plates were observed with numerous cyanobacterial colonies from each sample source

Appearance : Off white to cream homogeneous free flowing powder

Colour and Clarity of Prepared medium: Colourless clear to slightly opalescent solution forms in tubes (slight precipitate may occur)


  • Micro-nutrients are very much essential for growth of cyanobacteria, they should be added properly
  • Agar powder always should be added after autoclaving.
  • Store in a tightly closed container at 10-30°C
  • On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product.


Why BG-11 media is considered as best growth medium for cyanobacteria?


BG 11 is widely used for the micro algae and cyano bacteria. It shows many effective results after plating the sample. So BG 11 is a preferable media for general use for cyanobacteria

What is the full form of BG 11 medium?

In BG 11 Media BG stands for Blue Green Algae

What is the best medium for culture of cyanobacteria?

BG 11 media or modified BG 11 media is better media for growing Cyanobacteria, but it depends on the strains.

What is the best medium for culture of cyanobacteria except BG 11?

ASM-1 medium

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