need to identify a contaminant in the cell culture

Sudheendra Rao N R via (by sudhee26 from
Wed Jul 29 14:07:45 EST 2009

Hi, all,I recently found this contaminant in one of the thawed vials..i want
to ID it.i dont know how to post pictures in this list..but i will give

1. macroscopically: it appears floating mass of myecilium: two
latyers..layer 1-close to cell surface sometimes sticking to cells..layer
two: surface of media..looks like oil has spilled in media..looks
greasy..very difficult to get rid of even after repeated PBS washings..layer
1: is clump of mycelia..layer 2: looks like broken mycelia floating..both
layer1 and layer 2 are not motile.

2. cell morphology does not seem to change a lot..cells look healthy.but
they die suddenly when the contaminant number flourishes. no change in media
color except media top looks greasy/oily..imagine oil spilled in
sea!!!..they grow in FBS+pen-strep, they are resistant to geneticin too..

3. i took the supernatant and plated on LB agar (thats the only thing i
have--i dont do microbiology :))..with ampicillin (since i found out that
this is penicillin resistant)..within 6 days i small colonies which
increased up to 3 mm diameter by 15 days..all colonies have same
morphology..i guess hence its not something spurious..and also on two
different plates i got same kind of colonies.

Form: Circular (grossly, but when looked at 10X magnification we can make
out that its not so)
Color: Cream
Margin: undulating
Elevation: umbonate
Surface: smooth. Macroscopically surface looks infrequently studdent with
cream colored spekles.
Opacity: Opaque

5. 40X magnification revealed very interestingly margin of this colony which
appeared on LB plate with ampicillin had Claw like projection
around..covering almost entire periphery (around) of the colony..probably
thats how colony spreads and becomes big..also at 40X the colony does not
look homogenous..its made of fine grains..

so what is it..I will try posting some pics to my blog..

meanwhile..i really appreciate the that I can get rid of it..i am
anyway ordering amphotericin B.


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