Spot the antibiotics producer: STREPTOMYCES

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Antibiotics.

The human gets ill, goes downhill, forgets the dollar bill, takes a pill, regains will, re-feels the thrill.

It’s simply the recuperation cycle.

But, do you ever think about the fundamentals of having the chance of recuperation from infections?

Sure.

It’s thanks to the pill - the antibiotic.

Good job!

Now, zoom in deeper…

Do you actually know where this savior comes from?

Think no further than the soil.

Streptomyces.


ISOLATION OF STREPTOMYCES

1st step: Air dry the soil samples for 3-4 h at 45° for the selection of Actinomyces spores, considering that many other bacteria die during this pre-treatment

2nd step:Dilute 1-3g of soil in 10 ml saline solution (NaCl 0,9%) and let the solution stand for 15 min

3rd step: Prepare 3 dilutions (1:10, 1:100, 1:1000) out of it

4th step: Prepare the Mannitol Soy Agar (MSA) petri dishes

MSA RECIPE:

In a 250 mL conical flask mix:

  • 2g Agar
  • 2g Mannitol
  • 2g Soya flour (Holland and Barrett)
  • 10 mM CaCl2
  • 100 mL Deionised water

Medium alternative: Inorganic Salt Starch Agar (ISSA)

5th step: Plate an aliquot of 0.1ml of each dilution on the medium (MSA)

The loop used for spreading the solution on the medium (shown on the 2nd photo) is a DIY loop, created from paper clips

6th step: Incubate at 30° for 5-7 days

Important: Use parafilm to fortify the covers of each petri dish, in order to avoid evaporation, as it can lead to contamination.

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Optional: Supplementation with cyclohexamide (50 μg/ml) and nystatin (50 μg/ml) to further remove competing bacteria


3-DAY OUTCOMES

Observations: The no-dilution petri dish shows a tendency towards contamination. Other petri dishes seem on the right track by far. The small white powdery looks like a good sign.

6-DAY OUTCOMES

Observations: There has been overgrowing a hybrid of organisms, but assumingly the pinky/white powdery dots are streptomyces colonies.Such colonies are mostly to be found on the 1:100 and 1:1000 dilution plates. In this case, creating subcultures is the best solution, in order to get a unified-type of biotope in the petri dish!

Only one sample has been contaminated, as it was the first one to get done during the isolation process.

FINAL DAY MICROSCOPICAL VIEWS

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Insight

Streptomyces species are the most abundant source of antibiotics. More specifically, they produce the two-thirds of all existent antibiotics. Except that, this genus produces a rife scope of bioactive compounds. It usually inhabits the soil and plays a significant role in decomposing.

So, next time when you get ill, decide to take another pill, in order to re-feel the thrill...

...take a minute to think and praise the genus of good welfare.



Inspiration: http://annadumitriu.tumblr.com/ - Anna Dumitriu https://exploringtheinvisible.com/ - Dr. Simon Park