Bacterial DNA Extraction - possible of contamination? - (Apr/15/2011 )
I would like to ask if there is any possible that contamination will occur during bacterial DNA extraction. Just assume that the contamination did not occur during the culturing for overnight, thats mean no contamination from other bacteria.
The answer is: yes
But is very rare...
It might be from your dried skin, insect's leg (happened to my friend), carry over DNA from gloves or pipettor when using not filtered tips..
Insect leg???
Please tell us the story Adrian... 
Years back I was working with my friend in a lab where cockroaches were all around...nobody really cares the hygiene of that lab.
My friend did a plant DNA extraction: Grind with liquid nitrogen, phenol chloroform extraction..etc everything is just perfect... till one day, his PCR shows some unspecific bands, only in 1 sample... he was quite puzzled, troubleshoot and repeat PCR but still is same... till a senior told him to re-prepare his extraction buffer and reagent to re-proceed again... thats where he observed and found many traces of cockroaches's leg on his working benches and in some reagent bottle.
At first he couldn't believe it was contaminated with cockroaches's dna. That senior challenged him to spike some cockroaches legs in some plant sample and proceed the extraction again followed by PCR...and the unspecific band was "reproduced"...
So, during the following lab meeting, we were all decided to clean our lab throughly...
Actually, at some point... somehow I do feel that is the senior who was actually spiked the cockroaches leg in his sample in the first place... or else why would the senior suggest him to do that to investigate?...hahaha...
adrian kohsf on Mon Apr 18 07:18:56 2011 said:
Years back I was working with my friend in a lab where cockroaches were all around...nobody really cares the hygiene of that lab.
My friend did a plant DNA extraction: Grind with liquid nitrogen, phenol chloroform extraction..etc everything is just perfect... till one day, his PCR shows some unspecific bands, only in 1 sample... he was quite puzzled, troubleshoot and repeat PCR but still is same... till a senior told him to re-prepare his extraction buffer and reagent to re-proceed again... thats where he observed and found many traces of cockroaches's leg on his working benches and in some reagent bottle.
At first he couldn't believe it was contaminated with cockroaches's dna. That senior challenged him to spike some cockroaches legs in some plant sample and proceed the extraction again followed by PCR...and the unspecific band was "reproduced"...
So, during the following lab meeting, we were all decided to clean our lab throughly...
Actually, at some point... somehow I do feel that is the senior who was actually spiked the cockroaches leg in his sample in the first place... or else why would the senior suggest him to do that to investigate?...hahaha...
He was a senior, so maybe he allready noticed that problem before? If they have had that problem with cockroaches for years I can imagine they have had problems with that before.
Altough, you do wonder how just the leg got in and not the entire cockroach..
adrian kohsf on Mon Apr 18 07:18:56 2011 said:
Actually, at some point... somehow I do feel that is the senior who was actually spiked the cockroaches leg in his sample in the first place... or else why would the senior suggest him to do that to investigate?...hahaha...
Yes, it does look like the senior what to 'show off' how learned he was... and placed those legs in reagent bottles...
pito on Mon Apr 18 09:05:38 2011 said:
Altough, you do wonder how just the leg got in and not the entire cockroach..
gt_ameya on Mon Apr 18 11:58:37 2011 said:
Yes, it does look like the senior what to 'show off' how learned he was... and placed those legs in reagent bottles...
Hahahaha... exactly! Why is only the legs and not the wing or the entire cockroach?
I should have really become a part-time Sherlock Holmes last time and investigate the issue, but then it was many years back...
Great story adrian! 