DNA

Difco Nutrient Agar (DNA)

Difco Nutrient Agar is a rich medium commercially available from BD and routinely used for cultivating many non-fastidious organisms. It contains beef extract and peptones; exact composition will vary between batches.

Many Streptomyces sp. grow well on DNA, but developmental and/or antibiotic production phenotypes may differ compared to growth on other media (e.g. SFM).

Preparation

Per Litre:

• 4g Difco Nutrient Broth Powder
• 10g Agar
• 1L dH₂O

Instructions

1. For solid medium, add 0.8g of DNB powder into each 250ml conical flask
2. Add 2g of Agar
3. Add 200ml dH₂O
4. Autoclave

Uses

• Streptomyces Colony PCR (see High GC PCR for instructions)
• Spore titres
• Re-isolation experiments
• Selection for resistance to salt-sensitive antibiotics
• Streptomyces Bacteriophage plaque assay

Notes

For growth in liquid culture, DNB can be made without the agar.

According to the recipe in Practical Streptomyces Genetics, it should be 8g of DNB per litre, however some groups choose to use 4g instead. This has little effect on the ability of Streptomyces to grow on the soild medium, DNA.