is this contamination? (View forum version)



hl2409

Posted 05 February 2010 - 07:35 AM

Hi,

I grew gram-negative bacteria in Tryptic Soy Broth media. They should be non-motile rods according to papers. But under microscope, I found huge amount of dots moving very fast and some non-motile dots too (they look like exactly same). Meanwhile, the culture media has formed some flocs. However, if I put the culture in 4C fridge for 1h and check again, they are all non-motile.

Is this contamination? (I have been trying to grow the culture for 3 months, and the same thing happened again and again...)

pito

Posted 05 February 2010 - 09:27 AM

Can you take a picture of this?

And what bacteria are you growing

About the fridge: motile bacteria will become less mobile or non motile when you placed them in the fridge, so thats not something strange.

hl2409

Posted 05 February 2010 - 03:18 PM

They are Methyloversatilis universalis http://ijs.sgmjourna...full/56/11/2517
Two pictures and one video attached. thank you very much!

  • Picture1.gif
  • Picture2.gif

hl2409

Posted 05 February 2010 - 03:27 PM

link of video:




Can you take a picture of this?

And what bacteria are you growing

About the fridge: motile bacteria will become less mobile or non motile when you placed them in the fridge, so thats not something strange.


pito

Posted 07 February 2010 - 09:57 AM

The images are not that clear, but the movement doesnt seem to be because those are motile bacteria.
The movement is so fast , looks like you got some dancing or very speedy bacteria there.
I would rather think its because of heavy brownian movement or just the flluid that is moving because your are not using a stable microscope or something?

The flocks can indeed be some contamination or waste.
Did you see those flocks before you inocculated the samples? (eg: you make tubes with media, and put them in the fridge for a few weeks and then when you want to use them you see those flocks or?)
What you can do is: spread the media with the flocks on a petri dish and see what grows.
But most likely its contamination.

Did you obtain the culture you work with as a pure culture somewhere or?

hl2409

Posted 08 February 2010 - 11:40 AM

The video is not that typical. Usually more cells will move across the field of view (in all directions) within 2 seconds.

The flocs are there after 1 day growth and won't disappear at lower temperature. Under microscope, flocs are bunches of cells.

I will do petri dishes again, but according to previous experiment, uniform white small colonies will form. Thank you very much!!!

pito

Posted 11 February 2010 - 02:00 AM

The video is not that typical. Usually more cells will move across the field of view (in all directions) within 2 seconds.

The flocs are there after 1 day growth and won't disappear at lower temperature. Under microscope, flocs are bunches of cells.

I will do petri dishes again, but according to previous experiment, uniform white small colonies will form. Thank you very much!!!



The movement is indeed strange, but I dont think its because you have motile bacteria.


The flocs arent that special really: some bacteria are known to form flocs, so it might not be contamination.

You should try something about this in the literature or try to get in contact with one of the authors of that file you posted here, they might know more about it.