We have (had) these bugs too. They are sometimes a pain in the neck, 
especially when you do immunofluorescence.
Dicty grows ok in suspension culture and they sometimes eat them (we saw 
the bugs inside Dicty).
They seem to come from the medium but different charges had the same 
problem.
We actually made media the old way (from single components): same problem.

They are pretty esoteric: grow very slow, appear to need Dicty to grow 
(do not grow in LB or on LB plates, do not grow in HL5 when you dilute 
out the Dicty), are resistant to everything we tried - apparently even 
to autoclaving: we possibly saw a few in fresh media (difficult to 
identify, just little grey spots).
Sorry, we have no good advice. At some point (after a lot of 
unsuccessful work to get rid of them) they more or less disappeared the 
same way they came.
wolfgang

Am 08.11.2013 16:32, schrieb Damer, Cynthia Kay:
> Dear Colleagues,
>
> My lab is currently experiencing a culture contamination problem that I have not experienced previously.  We are culturing Dicty in HL-5 supplemented with penicillin and streptomycin on plastic sterile culture dishes.  The contaminant appears to be very small (less than a micron) and spherical and is not able to move.  In addition, it is very slow growing.  However, as the contaminant becomes more numerous, the Dicty cells become rounded and eventually die.  Unfortunately, even when we thaw out strains in new media, the contaminate appears again.  We've also tried centrifuging and washing many times and greatly diluting the cultures.  This seems to get rid of most of it, but it eventually grows up again.
>
> Any advice would be appreciated.
>
> Thanks,
>
> Cynthia
>
> Cynthia K. Damer
> Professor
> Biology Department
> Brooks Hall Room 229
> Central Michigan University
> Mount Pleasant, MI 48859
> (989) 774-3455
>