I am conducting DNA extraction experiments from K562 cells. For a reason unbeknown to me, the total mass of DNA extracted happens to be much larger than what I expect considering the number of cells I put inside my sample. Thus, I am trying to figure out, if perhaps my sample is contaminated by a bacteria giving rise to an increased extracted DNA. Looking through a 40x magnification under an upright microscope, I can clearly see there are some entities moving around inside my hemocytometer. But, I am not sure if the movement is due to Brownian motion or I am actually looking at a cluster of bacteria. Attached you can find the video I took using the brightfield mode: the two large cells are the K562 cells.
If the DNA you extracted is degraded or the RNA is not removed, the DNA quality measured by Nanodrop will be higher than the theoretical value. I recommend further confirmation by agarose gel electrophoresis and Compare the brightness of you DNA band to the DNA marker band comparison, and then consider bacteria contamination.
Here is an an idea, take a couple micro-liters of your suspicious sample and put it on a glass slide. Then dispense less a smaller volume of dilute 0.2 micron filtered or autoclaved glucose to edge of the droplet. If the organisms swim towards the edge then they are alive bacteria.
Something else you could try is a gram stain procedure. It should stain both gram positive and gram negative bacteria purple and pink.
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