Personal Blog - Weird Isolates

Wouldn't it be great if samples never got contaminated, or that if they were we could just streak the out once and they would be pure samples again? It would sure save everyone a lot of time. Unfortunately for us, a lot of bacteria seem to disagree with this sentiment.

The first time I Gram stained my isolate SP25-CBH-04, I knew there was no way it was clean. The stain was a mix of pink and purple across the slide, gorgeous on an abstract art piece, not as appreciated when on a bacteria colony. I knew my results weren't due to overstaining either, since all the purple gram-positive bacteria were medium-length bacilli, while all the pink gram-negative bacteria were short bacilli, arranged in chains. They looked like a traffic jam on a one way street in Barbieland. This was only the first time this isolate had been streaked, though, so it was ok and I would be able to isolate the two different bacteria the second time, right?

Wrong. I knew I was in for a treat with the Gram stain the second time around when I saw the second round of quadrant streaks where 04 looked identical to the first time. Sure enough, my stain revealed, to nobody's surprise but to my chagrin, purple gram-positive bacilli and short gram positive rods arranged in chains. Consistency is key, I guess. Though the color of the second bacteria was different this time, the fact that the morphology of the bacteria after being streaked was the same showed that these bacteria were the same two colonies as the first time. They just really did not want to be lonely. That's ok, I guess we all need to keep some friends around.

Because these two bacteria strains likely display some sort of symbiotic relationship and one doesn't seem to grow without the other, we decided to just let them exist in a mixed culture. This isn't ideal if I wanted to continue to purify this isolate, but for now, they can live happily ever after.