Environmental isolation of actinomycetes from terrestrial and saline soil

Being part way through the awesome book Experiment Eleven has inspired me to get out into the field more as Schatz did and take more soil samples.  The Streptomyces are slow growing as compared to other bacteria and the production of secondary metabolites can be influenced heavily by growth media.  The plan is to start with selective or semi-selective growth media in the hopes of minimizing the unwated growth of gram negative bacteria, yeasts, and ascomycete fungi (molds).  Once Streptomyces are isolated, they will be subcultured onto different media like Soya Flour Mannitol, Tryptic Soy Agar, and Starch Casein Agar.   I have propionic acid and nalidixic acid to help with selection.

Actinomycetes Isolation Agar w/ Glycerol

Sodium Caseinate ……………..……………………………….2.0 g

Asparagine…..………..………..………..………………………0.1 g

Sodium Propionate…..………..………..………..………..….4.0 g

Dipotassium Phosphate………..………..………..………....0.5 g

Magnesium Sulfate …………..………..………..………..…..0.1 g

Ferrous Sulfate …………………………………………………..1.0 mg

Agar…..………..…………………………………………………15.0 g

Glycerol……………………………………………………………5g

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The pictures from a few weeks ago were of Streptomyces coelicolor and Streptomyces avermitilis on both PDA and NA (potato dextrose agar and nutrient agar, as those were the only plates I had ready that day).  I re-streaked them because I was going to do some inhibition testing but instead found myself taking pictures of their beautiful pigmentation and enjoying the smell of geosmin.

I did end up using a spare plate of the coeliclor for a small streak test against Staph.  The interesting thing you might note is the color change to a more reddish hue, which is due to a decrease in the pH of the local medium probably due to waste/metabolites.  The blue colored actinorhodin is interesting to read about, and pretty to look at!

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I’m also quite excited because the brand new UPLC-MS should be online within 2 weeks which will send natural product discovery as well as synthesis verification into light-speed.  I also spent $500 of my own money to finally get an iGEM kit, and am laying the seeds for the first iGEM team at SSU before I leave to grad school next year.  Lots of cool new things to do some hardcore science with!

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